| Variable Speed Control of Motor
(Jul 3, 2001) |
Variable Speed Drives: AC, DC (May 4, 2003) |
| Teco Westinghouse VFD
model FM100-201-N1 (Nov 29, 2001) |
VSD's (May 18, 2003) |
| Speed Control for 9" (Oct
23, 2002) |
Reduced speed on single phase
motor? (May 23, 2003 |
| VFD drives (Dec 17, 2002) |
Speed Control on 14"
(Jan 1, 2004) |
| VFD drives (Jan 23, 2003) |
VFD on a SB 16" is great but...
(Apr 23, 2004) |
| VFD drives (Mar 31, 2003) |
VFD's (Mar 16, 2005) |
| |
| Variable Speed Control of Motor
|
| I believe one of
the recent postings mentioned how pleased the author was with a
variable speed control he had installed on the motor of his lathe.
That kicked my brain in gear after a day or two and I dug out the
variable speed control for routers, that I have had in the tool pile
for years, to look it over. It is rated at 15 amps and designed as a
variable control for routers. Can't remember what project I bought
it for now, but once I needed to slow down a wood working router for
a particular job. Question: What would be the pros and cons of
plugging this speed control into my SB9C lathe motor? The motor is
the original issue one from 1945 apparently with the condenser can
on the top front. Am I likely to burn out anything? Will fine tuning
the speed of my turning move me one step closer to Complete
Happiness in this World? Comments? Opinions? Bubba K (1009) |
| DON'T DO IT!!!! This question comes
up every once-in-a-while, so everybody PAY ATTENTION. Here's the
simple answer: If you are using an induction motor (60Hz
single-phase, starting capacitor...) you'll smoke the router speed
controller and maybe wreck the capacitor or overheat the motor
windings. An induction motor runs nearly synchronous to the line
frequency rather than varying its speed based upon line voltage.
Your speed control is ONLY good for AC/DC brush-type universal
motors (like in routers). If you want variable speed your two
options are a DC motor + speed control, or a 3-phase motor and a
variable frequency drive. I was tempted to get one of the treadmill
motor + controller setups from Surplus Sales for about $50.00, but I
hate the sound of brush motors, and since the motor is rated to 6000
RPM, you would not get best performance out of it when replacing a
3450 RPM induction motor. I'm holding out for a good used variable
frequency drive. When I find one of those, I'll pick up a good used
1 HP 3-phase motor and do the conversion on my 9" model A. Until
then, I'm quite happy with 12 speeds of belt-drive. Cheers, and save
the speed control for your router! Paul R. (1010) |
| Your router speed
control is only to be used with AC/DC "universal motors. They have
brushes and will run on AC or DC current. Your lathe motor is a
capacitor start split phase or induction tupy- totally incompatible
with the router speed control. One or the other or both will be
destroyed if you try it! Marty
(1011) |
| Here is one sweetheart part of having
a variable speed control on my 9" SBL . I weld a lot of pipe , axles
and shafts on my lathe. I always put the ground on the material
itself and farthest from my headstock and have lots of leather for
the ways. I've rigged up a tool post holder for my Profax Mig
welder. It took a lot of practice but well worth it . I never before
could manage very well to turn the chuck or the piece with one hand
and weld with the other .I'd go to fast or to slow, get slag
inclusions, porosity in my welds and have to grind out and re-weld
and cursing all the time. I found the biggest problem with stopping
a weld halfway through the weld was heat warp . This was especially
noticeable on the SS blow pipes I build for the glass people . They
are a very fussy customer and the pipe has to roll dead true when
blowing glass. I use my mobile R9 Lincoln for most of my lathe
welding . I have the remote heat control with it so I run it over to
the lathe and then I can , once everything gets going smoothly,
watch the weld going on and control lathe speed with one hand and
heat and wire speed with the other. Too much set up for a small job
but when you have a lot to do and a clock to beat it sure is the
cat's pajamas.
(1012) |
| Paul, firstly, I basically agree with
your conclusion, the 3-phase motor with variable frequency drive is
the preferred solution. As far as the 6000 RPM DC motor speed is
concerned, even if you couldn't get small enough driver pulleys or
have room to fit large enough driven pulleys in the first-belt drive
to adjust for the greater motor speed you could always have added an
additional stage of speed reduction before the original motor
position. Anthony
(1018) |
| Anthony, I just got
rid of an extra jack-shaft and belt. I don't want to go back there
again ;-) But seriously, I was moving to simplify and make more
efficient the power transmission system on my 9" SB. I just finished
turning a two-step 9" pulley for the counter shaft. That along with
an 1150RPM 3/4 HP GE motor gives me the equivalent of a stock setup.
My lathe was missing the standard big cast iron counter shaft pulley
and had a an extra jack-shaft and step-pulley arrangement. Extra
power loss, and inconvenient to change speeds. Plus, the lowest
speed was still too high. Again I'll wait for a VF drive and 3 phase
(or VF-specific) motor. Paul R. (1021) |
| In the newest issue
of Home Shop Machinist there is an ad from a company called Surplus
Center out of Lincoln NE for a "2 1/2 HP Variable Speed Motor Kit"
for $49.95. Per description: "New ARGORD permanent magnet DC motor
controlled by solid state motor controller", "Amps-18.5", "RPM
0-6750","Size 7 3/4 x 4 x 4", "Shipping 14#". Possibly someone who
knows more about DC motors than I can decipher the specs, but 18.5
amps doesn't sound like 2 1/2 HP. I can scan the ad if anyone
interested, but I'm still trying to figure out if this would be the
ticket for my lathe (or my future homemade mill or homemade shaper. Frank (1035) |
| This motor is out
of a tread mill and the 2.5 HP is misleading. The motor won't put
out the rating of 2.5 HP at other than its full speed. There was a
long dialog on this motor on one of the other lists. It would be
better to find a 90 volt permanent magnet motor and controller
which will put out constant torque which it what you want. This
motor would be more like a 1 HP motor. Yasmiin
(1036) |
| Kinda what I
thought, but just to play Devils Advocate would this power a 9" SB
(my belt can handle about a third of the 3/4 HP I'm giving it).
Small and variable speed for $49.95? Actually I have no intention of
ordering the setup for the lathe (I'm perfectly happy with the 3/4
HP I have strapped to it) but it sounds like just the thing for my
mill in progress (Phoenix Mill, HSM Jan/Feb 01 thru ?) What I guess
I don't understand is the drop-off of torque v RPM in a DC motor. I
know you said "more like a 1HP motor" but how does this compare to
the 3/4 HP AC I have on the lathe. The motor in the lathe is a beast
(ask my poor belt), if I can get the same performance from a $50
treadmill motor. Frank (1040) |
| 1 HP = 746 Watts. 2.5 x 746 =
1865 which, when divided by 18.5 (amps), = 100.810810 volts
required. Higher voltage will give higher horsepower. This ignores
inefficiencies but is at least a starting point for making judgments.
Anthony (1042) |
| So 18.5A
is about 2.5HP. I wonder about torque. To make a short story
long, I'm looking at building the "Pheonix Mill" HSM Jan/Feb-?. But
his Dave Gingery derived belt drive system is about 4ft long, and
I'm looking for a way to conserve bench space. A variable speed
motor sounds like just the ticket, IF the torque is there. Frank
(1044) |
| Teco
Westinghouse VFD model FM100-201-N1 |
| Does any one have any experience with the Teco Westinghouse VFD model
FM100-201-N1 and 1hp motor combination that Dealers Electric is
offering on their website http://www.dealerselectric.com/ . I am
very seriously considering it for my South Bend 10L (heavy). Any
input would be appreciated. Rikard
(2274) |
| This looks like a
good deal. I would only question the 1 HP. If its replacing a 1/2 HP
motor then it should work great. The motor is fan cooled. It doesn't
say if the fan speed is independent of the motor speed. If it isn't
then you can go down to about 30 hz. If you go below 30 Hz then you
need to be sure that the motor has an independent fan as otherwise
the motor will over heat. Yasmiin (2275) |
| From an electrical
engineering standpoint - This looks a whole lot better than the DC
stuff from treadmills. You may need some basic electrical savvy but
this looks like a very competent package for use with machine tools.
I would suggest if you are putting it in a home or home shop, wiring
it up by itself as a 240V single phase input to a new breaker in
your electrical panel, (or cannibalize the dryer circuit and use
that) run all the wiring between the motor and the drive in MC cable
or greenfield metallic flex, the rest can be romex or whatever fixed
wiring( just not plug-in cable). You might possibly experience some
radiated noise from the drive -seen as noise on radios, snow on TV
screen, etc. which can be reduced by using all metallic conduit or
metallic sheathed cable and putting the drive in a metal grounded
enclosure. I think I need at least one of these for development
projects. (2276) |
| I recently ordered
one for my 9" Model A, as 1 HP should be great for it. For your 10L,
I'm not sure, but probably okay. Although the motor is rated for
1800 RPM (@60Hz), your lathe may take a 3600 RPM motor. Not sure if
windage heating is an issue with these motors at higher speed--
still looking for specs on it. Also since its a TEFC motor, could be
a problem at low RPM end as Yasmiin mentioned. One thing nice about
my setup is that I'm currently using a 1150 RPM motor (custom
pulleys), so 1800 should give a nice range with good torque. All in
all, too good to pass up. I think you'll find the same. I'd say go
ahead and order one. You can make custom pulleys as required to get
the best speed/torque performance. As in pjwizr's post, plan to do a
nice job with wiring, grounding and shielding for minimal RFI,
although you shouldn't be watching TV while you machine ;-). I'll
report to the group when I get to playing with mine. Paul R.
(2277) |
| I am going to try
and get one for the Seneca Falls that I am restoring. Like others
have suggested I will change the pulleys between the motor and the
counter shaft so that the motor runs at a higher speed for the same
spindle speed I get without the variable speed. Then the 30 Hrz to
what ever should give a give belt position on the spindle a wide
speed range without going to low or two high. A question for those
electrical engineers that still remember this stuff what is a realistic top
frequency for the control that won't fry the motor or the bearings?
Yasmiin(2278) |
| Generally an
inverter duty motor would have a curve showing derating for
continuous operation at reduced speeds, or a chart, or the like, to
indicate appropriate design loading so the fan-cooling issue should
be taken care of by judicious consciousness of that loading
limitation. The design duty rating of this motor should protect it
in general lathe service. Also there is the issue of a motor thermal
device ( "overload" in electrical jargon): this is not specified in
the drive or motor literature on the website and this protection is
needed on the drive side to the motor to protect motor from thermal
overload. There is no problem loading the 1 HP motor lightly at
rated speeds per the derating curve, so if the speeds are OK on the
lathe, it should be possible to set up the pulleys to turn the
spindle as fast as the bearings would permit at top speed, and then
gear everything else down from that. The motor doesn't care what the
ratio of the load speed is, it's torque and power ratings are only
based on it's rotor speed. Just be careful not to put too much
cutting load on the tooling when running the machine fast - it may
be possible to overload the mechanical parts of the machine if it is
designed for limited HP drive. The variable-speed drive is designed
to try to keep the motor turning at its speed setting and will
control voltage and current to keep the motor there, even if the
load varies, so it's possible to overload the machine and the motor
or drive won't know or care. Might be best to use a flat drive on
this for a safety mechanism. It also will take more information
about the motor and drive to set everything up copacetically, but
this looks like a good solid set of equipment to start with.
(2279) |
| I am going to try it (the price
is right and I was primarily looking for a phase converter anyways).
Now I just need to assemble the hundred or so pieces of the lathe
that are on my garage floor after having been
stripped/sandblasted/and painted. I should be able to report back in
a month or so on my experience. Rikard
(2333) |
| Just received my
TECO-Westinghouse VFD/Magnatek 1HP motor combo from Dealers Electric
Motor. Everything as advertised. Motor: Magnatek TEFC 143CT mount
7/8" shaft with key Rated 6-60 HZ, 1800 RPM @60HZ, 1HP, 3PH Brand
new! Inverter Drive: FM100-201-N1 Input: 1Phase or 3Phase, 200~230V,
50/60 Hz, 4.5A Brand new in original box with documentation. Both
items packed well enough to survive the UPS journey from coast to
coast w/o damage. I'm Jazzed! Currently my motor has a 5/8" shaft,
so I'll either have to bore out that pulley to 7/8", or make another
one. Caution, my drive configuration is CUSTOM, so your stock setup
will be different. With a rated top RPM of 1800 for the Magnatek
motor, you guys with a standard 3600 RPM setup will have problems.
My setup uses an 1150 RPM motor with custom 2-step pulleys to get me
to the standard counter-shaft speeds. The new motor will put that
nominal speed in the middle of the new motor's range (180-1800 RPM).
Very nice, indeed! More To Follow. Paul R. (2334) |
| The standard speed
for a South Bend drive motor is 1725 RPM, not 3600, according to
"How to Run a Lathe", so it seems this motor would match a standard
lathe quite well. Chris (2335) |
| Better still! My
lathe came with a 3600 RPM repulsion/induction motor that looked
original, so I figured that's what they came with. But then again,
my lathe was real funky. It had a non-back-geared headstock and an
extra jack-shaft. I still think 3600 RPM might have been standard
with such a large pulley on the counter-shaft, though. Doing some
rough calculations, I can leave my motor belt set on the lowest
speed and get the effective range of up to 1100 RPM spindle speed,
down to 30 RPM w/o going into back-gear. With back-gear, I can get
some ridiculously slow RPMs. Paul R. (2336) |
| Speed Control
for 9" |
| My dad is giving me
a 9" South Bend Model B that he bought new in 1948 or there
about.
It is going to make a great addition to my shop set up of 7x12 and
mini-mill. I am wondering if anyone has ever put some kind of DC
Motor control on one of these and if so, how? ian
(6770) |
| The things usually
come with a single phase 110V AC motor. The only way that you can
add a speed control is by changing the motor to a DC motor with a
speed control. WW Grainger is a good source for this kind of stuff.
It could be kinda expensive to convert. Tom
(6771) |
| Ian; I'm using a
2 HP treadmill motor on my SB13. I made a pulley for the motor that
provides a 5:1 speed reduction so fairly slow speeds are well into
the torque band of the motor, and if opened up all the way will
avoid overspeeding the spindle by very much. This is a '29 unit with
bronze 2 piece bearings so 1000 RPM is pushing things, 700 RPM is
about the highest you really want to run. The motor is mounted to a
plate that in turn is secured to a pair of clamps that go on the
rear ways, much as a micrometer stop mounts. There is a piece of 3/4
inch shaft between the clamps, the plate has a block mounted to the
underside bored .751 through that the shaft goes through. This
allows the motor plate to swing for belt tension while keeping the
belt in alignment. The holes in the plate are slots rather than just
close fitting holes, this allows fine alignment adjustments of the
belt and motor. Stan (6772) |
| Not true. A
Variable Frequency Drive (VFD) can be used to give you any speed you
want with the OEM motor. Not that you'd want to run it at 3000
rpm. Tom (6774) |
| A simple but
slightly expensive solution would be to install a VFD. This can be
used to drive a single phase or a 3 phase motor. All the advantages
inherent in 3 phase such as good starting torques, true reversing
can be achieved. There are some motor/VFD sets available on eBay. But
you should also be able to just get the VFD and use the motor you
already have. One advantage of a VFD over a DC motor/controller is
that you can easily switch it between different motors so you can
drive/control all the other AC motors you have in shop. John
(6775) |
| I got my DC motor
and controller off eBay for around 100.00 Clint
(6776) |
| After mounting
a 1 hp treadmill motor on my bandsaw, I plan to do the same thing on
my lathe. Old treadmills are a dime a dozen. I found this one dumped
on the side of the road. Everything you need is right on the
treadmill. I did have a jackshaft on the saw that was used for the
old motor, so I ran the DC motor through it also. Sure is a nice
setup for any machine that you need to control the speed of. John (6805) |
| VFD drives |
| I just purchased a Model A. Unfortunately, the
existing motor is 3 phase (1/2 HP) and I don't have access to this
service. I am debating between replacing the motor with a single
phase 1/2 to 3/4 HP instant reversing or installing a VFD. Can
someone comment on the pros and cons of these alternatives? Denny (8043) |
| Denny, After
installing VFD/3ph motors on my 9" SBL and my Mill/Drill, I would
recommend a VFD if you can swing it. The only reservations I would
have are the size of your existing motor and the fact that it is
probably not really rated for variable frequency. That being said, a
good 1/2 hp 3-phase motor will probably outperform a cheap 1-phase,
and for the most part, a 1/2 hp motor will probably be sufficient. I
bought a 1hp package for my lathe, and a 2hp package for my
Mill/Drill from www.dealerselectric.com and am quite happy. Lots of
folks pick up a VFD on eBay for small bucks also. Paul R.
(8045) |
| Denny I changed
both my SB lathes over to 3/4 HP 110 volt with no problems what so
ever. I am planning to change out a little longer to DC motor, I
have them just have not had a chance to do it yet. There is really
no reason for a reversing motor when running a chuck. The only time
you would use one is if you run collets and threading If you have a
110volt 1/2-3/4 HP Reversing motor, then yes, by all means use it
and you will not have any problems. Clint (8047) |
| It's been a while
since I've work with one of these lathes, but I thought that reverse
is important. Don't you need to be in reverse when using the back
gears? Denny (8049) |
| Your using a 1HP
VFD package? That's not too big for a 9" lathe? Also, it looks like
the cost of an instant reversing single phase motor (not including
the new switch I'll probably need) is more than a comparable VFD
package. Is that right? Denny(8050) |
| You will need
reverse for metric threading or any threading if you don't have a
thread dial. Ed (8051) |
| Denny, I had
the original SBL motor on mine for many years. When it bagged out I
bought a 1 HP DC Motor and a Penta Variable speed control / reverse.
The Penta control was about $400 CDN but I picked up a brand new
motor off e-bay for $50 US so all told it cost me around $500 CDN or
say $350 US. I do a lot of small threading jobs so it really shines
for this. I have since bought the same set-up for my ML7 Myford so
you see I think it works just excellent for what I do. I find that
if you have it sometime you'll need it. When you are threading a
very small piece it really is nice to be able to run extra slow and
be able to stop in ample time without giving yourself a heart
failure in the process. I also build up shafts on my lathe with the
Mig welder fitted on the tool post. The variable speed is a real
winner for this job. Anyway just another fellows opinion for you to
mull over. (8053) |
| Yes. Instant
reversing single phase motors are expensive. c (8055) |
| A consideration
when obtaining VFDs to operate 3 phase motors from single phase
input; a derating factor is usually given for the VFD, sometimes as
much as 40% (depending on load). A 1 hp rated VFD, with single phase
power input, is a conservative rating to drive a 1/2 horse 3 phase
motor. Fred (8060) |
| The 1 and 2 HP Teco/Westinghouse
VFD's I got are full-rated for 1- or 3-phase. Paul R. (8064) |
| Paul, The VFD I got
from Allen Bradley was derated. Stands to reason that 3 phase at
220V constitutes more power delivered than single phase at the same
voltage. I wonder if the TECOs are already "derated". Fred (8066) |
| A review of what this involves might be
useful here. From what I've seen, the VFDs rated for full horsepower
on either 1 or 3 phase supply are not "derated" per se - they have
been designed with single phase parameters and get 3 phase ability
for little added cost. The VFDs I'm familiar with all rectify the
incoming AC and place it on a DC "bus" that has a storage capacitor
or two placed across it. One way of looking at it is that the
capacitor "smooths" the incoming pulses from the power line, and in
single phase you get 120 of these pulses per second. With three
phase, you get 360 pulses per second, so the capacitor can be
significantly smaller in value for a 'three phase only' unit and
still sustain the bus voltage high enough under load to supply the
full motor rating when it's needed. With the smaller cap using
single phase input, the bus voltage will droop further under load
than with 3 phase input, and may drop below proper operating values
for the VFD. What the manufacturers must do for a dual supply unit
is to enlarge the filter capacitor and (sometimes) install rectifier
diodes with higher peak current ratings. I mention "sometimes"
because solid state rectifiers with large ratings are so inexpensive
that they don't always do this. They often use two caps, a smaller
one directly across the rectifier output and a larger one across the
DC bus, with the bus separated from the rectifiers by a surge
resistor (a thermistor whose resistance goes down as it heats up
under load). That effectively reduces the starting current
requirement rating on the rectifiers, as well as being easier on the
bus capacitor(s) as well. So, can you do the same thing to a used 3
phase VFD you pick up on the side of the road? Possibly...though
automatic protection circuitry may get in your way - it depends on
the sophistication of the design. You need to consider two things -
the size of the existing capacitor(s) and the current rating on the
rectifier diodes. On many of the models I've looked at, the DC bus
is brought out to a couple of terminals on the interconnection
strip, so it may be possible to put some additional computer grade
capacitors in a safety enclosure and just wire them in, especially
if there is a surge thermistor in the line. Capacitor values for a
220v 3 phase unit are typically in the 800uF per rated hp range, but
single phase will do better with twice that value. My ancient 3ph to
3ph 220v Emerson uses 1200uF for the 2hp model and 2100uF for the
3hp model, along with a 420uF primary cap across the rectifiers.
This is why a 3hp unit is often desirable for, say, a 2hp motor if
it was designed as only a 3 phase input VFD...it already has a
higher capacitor value built into it. Bus voltage for a 220v unit is
normally 300-340vdc, so you'll need 400vdc or 450vdc capacitors. If
you need a surge thermistor, places like Digikey carry those at very
reasonable prices. Model number will depend on load rating of your
VFD. All this assumes that you have already run into problems with
using the unit at full rated power. I have a 1HP 460v 3 phase in VFD
I have been running on my Hardinge HLV-H with single phase input for
almost 2 years now and never had the 1HP motor noticeably slow down,
even on the heaviest cuts I've demanded of it. Same with the
Bridgeport, using the old Emerson. If you have the luxury of buying
what you want, then either a single phase rated unit or ~50% extra
capacity in a 3 phase input unit is the easiest way to go. But if
you happen on a good deal in a smaller VFD, you might want to simply
try it before you start adding capacitors and all that it entails.
Mike (8080) |
| Mike, You mentioned that you use a 460V VFD on your Hardinge using
single phase input. Are you using a Buck/Boost transformer set-up? I
have been curious about whether one could use a VFD that was rated
for 370 or 460 volt and adapt it to the lower voltage of 230.
without using set-up and then set-down transformers. Probably not
but it couldn't hurt to ask. I have been wanting to put a VFD on my
mill but finances are tight. Also,
could one power a 3 phase input VFD from a rotary phase converter?
Or would the VFD balk at the third leg not being properly balanced? Webb
(8082) |
| Webb. The first transformer in the chain is a small
480/240 lighting transformer I picked up at a hamfest for $20,
though I do see them on the bay occasionally. It's used in reverse,
which gives me between 470v and 500v on the output with my line - a
bit high for my liking, considering the replacement cost of this
'high end' GE VFD (a $135 eBay purchase - the smaller 440-480v VFD's
on eBay seem to go for very reasonable amounts.) At any rate,
because the GE specs stated a 506v max input spec, I put a 24v
control transformer secondary in series to buck the voltage down by
24vac. Overkill perhaps, but the VFD seems quite happy with that.
Wish it were that easy. In theory you should be able to change the
operating design center of the output side to use the lower bus
voltage, but there are so many different designs out there, many of
them using embedded or single purpose chip sets, that a redesign
would be a significant task. I wouldn't even attempt it unless I had
a detailed maintenance manual on the unit. The older 1970s and 80s
VFD's like my Emerson are probably more amenable to that kind of
conversion since they tend to use discrete components and you can
diddle with values and pulse timing, but I wouldn't recommend trying
it unless you had some experience in the area. Like 'they' say, it
all depends. It's not clear to me why one would *want* to, if a
simple 240/460v single phase transformer would do the job. The only
reasons I can foresee why you would want to are: 1) if the
particular VFD protection functions were inflexible and you couldn't
work around them somehow while using a single phase input (happens
with some sophisticated VFD's), or 2) if the VFD protection functions
were inflexible and weren't capable of tolerating the 'wild' leg
voltage excursions one occasionally sees from an otherwise tuned
rotary converter that is forced to serve a number of machines with
widely varying horsepower, or 3) if you had other machines you
wanted to run simultaneously off of the rotary converter. Now, all
of those are valid reasons and may fit your case, but it's generally
simpler for a home shop to settle on one or two VFD's (220v and 440v)
and switch them between machines, given their low cost. My 220v unit
powers the Bridgeport, vertical bandsaw, and Baldor grinder (not all
at once), while the 440v is dedicated to the Hardinge. Remote
start/stop buttons are paralleled for the 220v version, but I *do*
have to remember to throw the primary switch on for whichever
machine I'm using. Mike
(8090) |
| Mike, The reason
I asked about using a Rotary-Phase converter in combination with a 3
phase input VFD is so I could get the full rated output of the VFD
that would otherwise be de-rated by about 40 to 50% when connected
to single phase. I thought of a couple of other questions (while I
have your attention). My mill has a drum switch. Would I bypass this
when using a VFD (relying on the start/stop and forward/reverse
built into the VFD unit)? Or just throw the drum switch on (forward
say) and then activate the VFD? What about if your equipment uses a
push button station and contactor motor starters? Webb
(8098) |
| Lots of
variables in there, Webb. The VFD isn't a highly inductive load like
the drive motor slaved to an idler motor, so it's not clear to me
that all the phase relationships will support each other as is the
case with a straight rotary system with two motors. The conventional
wisdom would have us believe that would happen, but I haven't tried
it so I can't say for sure. If you already had a 3 phase converter,
there's absolutely no reason you couldn't hook it up and give it a
go. On the other hand, I would try the VFD on single phase by itself
first, as I mentioned in my first note. If that wasn't satisfactory,
then you can move on to the other options like a larger capacitor or
an idler motor. It all depends on what you have on hand to start
with. I realize that may sound unsatisfactory to someone who has to
order everything from scratch, but the incredible variety of VFDs
out there force us into this step by step mode, or risk
disappointment in the end. *IF* the VFD is sufficiently oversized
(and I'm talking about perhaps a 5hp unit for a 1hp load, then you
can generally keep the old method of powering up. It all depends on
the sophistication of the VFD, as many of them will protectively
shut down when faced with a sudden increase in load like that. It
also depends on the value of that capacitance I mentioned, as it has
to sustain the bus voltage high enough to avoid shutdown from that
mode as well. Having said that, using a VFD in this mode isn't
really getting the maximum out of the unit. It will baby your motors
in a number of different ways if you use the VFD to start and stop
them, which means leaving the drum switch on all the time and then
using a small independent pushbutton station to control the VFD. For
example, the GE/Fujitsu unit on my Hardinge went through a "motor
measurement" cycle when I first turned it on, measuring all of the
motor parameters to a high degree of precision, and uses that to
constantly monitor the health of the motor while it's running -
including temperature. It also has adjustable starting and stopping
ramps to ease the motor up to speed and down to a stop. I think
that's typical of all the later units. I just use the Hardinge
control circuitry to set up the contactors in "on" condition and
then use the VFD for the rest. It also solved another nagging
concern for me - over the years I've had and seen more than one
heavy workpiece get loose from the chuck or faceplate. Since I stand
to the right of the plane of possible ejecta to operate the
carriage, etc., that forces me to reach across that plane to hit the
off control. Sometimes scary, not to mention the coolant stripes I
used to get on my shirt. I mounted a new pushbutton station
for the VFD under the right coolant tray lip - pointing up at a 45
degree angle - and now I don't have to look like Don Knotts,
reaching in front of a vibrating workpiece. Lot more convenient, as
well. Mike
(8104) |
| Webb, I'm pretty
much in agreement with Mike. Bottom line, modern full-rated inverter
drives (VFD's) for small motors (2HP or less) can be had for
single-phase 220 (home shop) readily. It just makes no sense to
string together static or rotary phase converters ahead of the
drive, unless you have old-technology stuff laying around that you
want to attempt to use. Also, static phase converters cause you to
derate your motor output anyway. As far as using the drum switch is
concerned, NOTHING should go between the VFD and the motor (for 2HP
or less motors and cabling under a meter in length). I rewired my
drum switch to provide the control signals to the VFD so I would
retain the same "user interface." One draw-back with VFD's is that
they are dedicated to a particular machine. With a rotary phase
converter, you can set one up in the corner of the shop and run
several machines (typically, one at a time) while a VFD should not
be shared or moved from machine to machine (needs to be
reprogrammed). Yes, smooth start/stop are very cool to have, and may
keep you from spinning your chuck off. Also make sure you don't
configure an E-Stop brake that will stop the spindle dead in its
tracks. That will surely launch your work-piece across the room. No
more dimming house lights with the programmed
acceleration/deceleration from your VFD. When first shopping for big
iron, I was hesitant about considering machines with 3-phase motors.
No more! With the price of VFD's so low, and competitive with phase
converters, I'll never dismiss a machine because of its motor. When
the motor on my mill/drill started failing, that was all I needed to
install a new VFD/inverter-duty-motor combination. I'm hooked. I
like the smooth start/stop and variable speed so much I'm
considering VFD/motor retrofits for my big Rockwell wood lathe and
my delta table saw should I ever need to replace those motors (dream
on...). Paul R. (8110) |
| One of the enormous
values of this group is that you get different perspectives to fill
in a more complete picture of the issues involved in any particular
subject. This is especially true of the more complex technical
questions that seem to abound in our interest area. Paul's comments
are 'right on', and are essential elements for consideration in
making decisions in the VFD arena. I couldn't agree more, Paul. The
eternal economic conundrum is the number of permutations that I left
out of the equation. A person with an existing rotary will have a
different perspective than one having a 460/230 transformer sitting
in his garage, and so forth. That may change the ideal goal of
having one VFD per machine, which is obviously Nirvana. This is
certainly the ideal. Pragmatically, one may wish to leave the drum
switches in place and relegate certain functions to the VFD and
others to the drum switch. For example, it may be more trouble or
cost to add a switch for the VFD to perform the reversing function,
than to leave the drum switch for that function and add a separate
on/off station for simple VFD power on/off. The variations to
consider can get complex fairly quickly and of course depend on the
particular VFD remote options available and what remote switches you
have available in the junk box. Absolutely! Ummm, well, I take that
back...maybe not true for all of them. The earlier VFD's don't use a
computer to program functions tailored to a specific motor, so they
are more easily used with more than one motor connected to them. The
1985 model Emerson Accu-spede (sic) that I use for several machines
is one example of a VFD that is so lacking in sophistication that it
doesn't care *what* you have connected to it as long as it is within
its power rating. :-) Of course, it was only $75, so I can't
complain too much. It has a single programmed ramp up/ramp down rate
that is not instantly adjustable to connected motor needs, but
that's no worse than developing a compromise tuning setup for a
rotary converter used with several machines. Really excellent points
for a threaded chuck, or one which has a large rotational inertia! I
have yet to understand why instant reversing motors are considered a
good idea, even for a threading function on a mill. I've come around
to that view myself. Of course, it also has a large dependence on
one's hobby budget. Thanks for inserting those missing pieces, Paul
- really helps fill out the picture. Mike
(8121) |
| VFD Drives |
| I understand that many members of this
group use VFD's to power their lathes by converting single-phase
power to three-phase power. Is this 230V single-phase to 230V
three-phase? Or is it possible to use 110-120V single-phase
converted to 110-120V three-phase? I have a 9" S.B. model A with a
110V, single-phase, 1.0 HP Emerson motor (which uses nearly all 15
available amps when running, BTW, and when someone turns on a light
to one of the bathrooms, poof goes the circuit breaker, followed by
screams from me and the fellow in the bathroom). Second question: To
use a VFD, I assume I'll have to replace this motor with a
three-phase motor. Is is possible to acquire 110-120V three-phase
motors? Bilal (8866) |
| VFD's are normally
meant for 230v 3-phase 60 Hz to 230v 3-phase 0-120 Hz (or
thereabouts). Most can do 230v 1-phase to 230v 3phase with some
reduction in maximum power (usually can operate at 2/3 of rated
power) this is a function of the size of the caps in the VFD. I have
never seen 3-phase power at 120v, I have only seen it at 230v or
460v. c (8867) |
| A VFD will
convert 220 single phase to 220 3 phase. I am not aware of a 110
volt option, but it might be available, just not sure. If your 1
phase motor is 110/220 you might be able to wire it for 220 (if you
have 220 available) and you will draw less current (amps). I am
keeping my eye out for a 1 HP motor to power my 10L, I'd be willing
to trade straight up my 1/2 HP motor for your 1 HP motor and that
would reduce your current load to the affected circuit. I don't live
but 15 miles from you (Gaithersburg). Contact me offline if
interested. My mill is powered by a VFD so you are welcome to come
by and see that also. Mark (8871) |
| There are two
variants of "low" voltage 3 phase. 120/208 star(Y) and 230 open
delta. 120/208 can be thought of in terms of the letter Y. The
central point of the Y is grounded. The voltage from the ground to
any end of the Y is 120 Volts. The voltage between any two ends of
the Y is 208. 110 V single phase loads are connected between the
ground point and any of the 120 V ends. The best description I have
for 230 open delta is to think of it in the shape of the letter L.
The voltage on each leg of the letter is 230 V. It is also 230 V
between the ends of the two legs. One of the legs is grounded in the
center giving 115 V between the ground and the two ends of that leg.
This leg of the circuit is exactly the same as the typical 120/240 V
single phase supply. All single phase loads 115 V loads can be
connected to that leg. Any 230 V single phase loads can be connected
across either of the legs or between the ends of the two legs. As
far as I know the small 3 phase motors are always connected to the
ends of the legs regardless of whether you have 208 supply or 230
supply. Likewise they are rated to run on both voltage ranges. So
although there is no 120 V 3 phase motor you can run a 208 V 3 phase
motor off 3 120 V phases. You would have to check the suppliers but
I think some converters will work with a 110-120 Volt single phase
supply. They might not be able to deliver the full 110 volts on each
phase though so it would be de-rated. Using a 220-240 V supply will
require less current and electrically it is easier to supply the
rull rated voltage. Sorry about the mix and match of voltages but
110, 115 and 120 are really the same thing. Same thing for 230 and
240. 208 is different and only comes from the Y connection. Hope
this helps. If not hit delete. John (8876) |
| Anybody stuck with
a 3ph motor should just make a converter- really easy stuff, just
get your caps from McMaster and a surplus 3ph motor. Tom (8880) |
| I'm replying from
British Columbia Canada. You are requesting info on Variable
Frequency Drives, but the context of your question indicates that
you are talking about Phase converters. I would first take a look at
the size of the breaker that in on the line. If it is only a 15 amp
breaker, it is not large enough to handle your one HP motor. Check
this out with your local electrician. I suggest that the motor you
are using is adequate for your 9" SB and does not merit the
hassle
of 3 phase conversion. I had two lathes in my shop until I sold
them. They each had 1 HP single phase motors on them which were
completely satisfactory. Now having said that I also have a 16"
Colchester lathe which is my pride and joy. It has a 7 1/2 HP three
phase motor driving it. Being in a domestic situation, the shop
behind the house, I have had to go to a Phase converter. I am using
a ten HP three phase older type motor which I picked up for $50.00
complete with a start up motor mounted atop of it. With this in
place I am now able to power all the machines in my shop, lathe,
mill, press, punch, and air compressor. It has worked well for close
to 20 years now with complete satisfaction. If you would like to
have a look at this situation, and have access to the "Home Shop
Machinist" magazine out of Michigan, I have a writeup in May/June
1997 complete with pictures of my shop. Desmond (8881) |
| VFD drives |
| I've
installed three VFD controllers made by KB electronics, sold by B B
motor controls of Long Island NY. 1/2hp units sell for 150 dollars,
a 1hp sells for 200. They are bare chassis, and must be installed in
a protective enclosure. I use a plain electrical pull box, without
knockouts, and drill my own conduit holes as needed. I just put a
1/2hp unit on my 9" model A, and couldn't be happier. Also changed
over to a vee belt pulley set, driving a 46" type 5L cogged belt. I
set minimum motor speed to about 60 RPM, acceleration and
deceleration at about 1-1/2 seconds so that chucks won't unscrew.
Actually at low speed, reversing is almost instantaneous. This makes
power tapping and die threading simple. On my mill, I set the accel
and decel for almost nil, as the inertial loads on the spindle are
insignificant. Dave
(10029) |
| Better deal here I
think. Hey If you are looking for a VFD try this link these guys are
great and you get a nice unit that needs nothing but wired in and
your ready to go. I got mine last week and it works great!
http://www.dealerselectric.com
Frank (10033) |
| Maybe, but
I prefer to mount a knob actuated speed potentiometer near my on off
switch. I wouldn't care to fumble with touch pad switching when
speed needs to change urgently. Dave
(10036) |
| Dave it is
very easy to put a remote complete with speed control pot, and fwd
rev switch , and on off switch. The whole thing fits just great in a
single box mounted on the original switch pad on my SB 13x40 I can
email you pic's if wanted. Dee (10037) |
| I see your point!
However that is a feature you wouldn't have on a milling machine
(without adding it yourself) If you had 3 phase power and didn't
need to convert it! Would you ? I put a E STOP button between my VDF
and the panel for just that reason. I didn't want to have to try and
hit that small key pad button in a real emergency! (10038) |
| The Teco unit allow
remote controls and the manual explains how! (10040) |
| Right to all. There
is no absolute answer, and everyone is going to stand behind their
own product! I made a new control box that is similar to a Cutler
Hammer drum switch housing- bent up of two pieces of 14 gage steel.
On the model A, it mounts on the left hand gear guard, just like
south bend standard! On the front of the box, I mounted a three
position maintained switch- 22 mm industrial type with two NO
contact blocks in back. That controls stop-forward-reverse. On top
of the box I mounted the speed potentiometer. The power on-off is
only operated once a day, so I mounted it out of the way on the side
of the junction box enclosure. That hangs off the back of the rear
drive motor mount casting. Both my mill and lathe are set up the
same way, and with the same electronics, both the switches flip and
operate the same way. Dave (10042) |
| Variable Speed
Drives: AC, DC |
| Two questions about
variable speed: How many of you have a variable speed drive of some
type and do you find it very useful? For those of you with some
experience with variable-speed motors, what kind of system would you
recommend: AC PWM (pulse-width modulated), DC PWM DC SCR ....and for
the DC, shunt-wound or permanent-magnet?
(10795) |
| I had
one of the "tread-mill" motors on a 9" lathe and it worked, but not
that well at low speeds. I also have a VFD on my mill drill and love
it, but again at real low speeds, it just doesn't have the torque.
Between the two, I like the VFD best. (10799) |
| I had to convert a
Swedish miller from 460VAC 50Hz 3ph., and used a PMDC motor with a "BAV"
(Big-Assed Variac) speed control. Has worked very well for several
years, and am glad I converted. For the story see
http://www/gearloose.com I am seriously toying
with the idea of doing the same with my Model A, because the product
I make appears to machine best _between_ two of the fixed belt
speeds. Besides, there's a guy on here who needs my AC Motor!
(10800) |
| I have a 1HP
VFD/motor setup on my 9" model A and LOVE IT! Most of the time I
leave the flat belt on slowest speed and use the VFD to set the
desired speed. Granted, the only way you can get real low-speed
torque is to use the back-gears, so don't expect to do heavy
threading or large diameter heavy cuts w/o back-gear. Personally, I
would not use a DC brush motor on my lathe. They are too whiny and
the slow-speed performance lacks. I also installed a 2HP VFD/motor
setup on my mill drill. You can check out some of the pictures in
the mill_drill Yahoo group's Photos section,
http://photos.groups.yahoo.com/group/mill_drill/lst
under "PaulH's VFD Installation". Paul R. (10809) |
| I will be getting
one for my mill here in another month or two, to run a 2HP 3phase
which is one of there big advantages. 3phase motors are like $10 per
HP used and there is nothing to them compared to single phase
capacitor motors with all the junk inside them. Plus 3 phase pull
less amps per HP and a $250 drive will power a 3HP 3Phase no sweat.
Kerry (10818) |
| VSD's |
| Some
people add "chokes" (copper wire wrapped around a steel donut) to
handle voltage transients with VFD's. ah, the good old days... I
remember them well. the Graham 6 step drives, the Parametrics and
Reliance PWD drives.... for some time the pwm drives have been using
IGBT's. the high frequency offers signals that are actually better than
the 3 phase sine wave from the wall. A simple PWM drive will power the
motor for a normal application, a Vector drive will start a motor at
higher torque AND can be used for synchronous motor speeds, very good
speed regulation. A DC drive can deliver 150% of starting torque. A lot
of people de-rate drives and use a 3hp for 2hp motor. but that is
usually because they have the wrong drive. Often the drives are
selected for cost rather than performance as from what I have gathered,
E-Bay is one of the suppliers. you get what is available. And then
there are those who figure that running a drive at 3/4 of it's rating
will just increase it's life. All the drive manufacturers have sales
and engineering sheets that will help in the selection of a drive. some
time spent reading will pay off in the long run. http://www.reliance.com/prodserv/standriv/appnotes/d7725.pdf
Dave (11194) |
| Dave and Kerry,
I looked at your link and I guess you missed this part... C. The
speed regulator section provides gate pulses to the continually
alternating Insulated Gate Bipolar Transistors (IGBTs). The relative
on-to-off times for pulses to be successively fired is continually
alternating so as to create a sinusoidal voltage pattern at the IGBT
output. The wave frequency is altered to produce variable speed
outputs. As I read this description, "gate pulses" and "sinusoidal"
still means that there is a stair step ramp up and down (albeit very
fine steps). I didn't mean to imply that VFD's aren't good. On the
contrary, I believe they are the way to go. I just meant to point
out that the signal output from a VFD is different from the signal
provided by your power company in regards to 3 phase. As to your
friend that builds rota-phases for a living; has he put an
oscilloscope on his rota-phase and an ampere meters on all leads? I
doubt it. If he did, he would find it doesn't produce true 120
degree 3 phase output. The simplest test I can think of is to take a
volt meter and measure the three phase-to-neutral voltages. Most
rota-phases will put out relatively good phase-to-phase voltage but
their phase-to-neutral voltage of the generated third leg will be
off. If he puts an autotransformer in his rota-phase, then you can
get full HP but it has to be tuned to a particular load. No good for
a shop that has varying loads (i.e. different pieces of equipment
being turned on and off). Webb (11197) |
| Reduced speed
on single phase motor? |
| Is it something
that should be tried. I have a 3600 1HP motor that I would like to
have at 1700 RPM now because it's a polisher and has dual shaft I
don't want to gear it down. and go through pulley's and all that. if
it is something that can't be done or would not be cost effective
I'll just gat a 1HP 3 ph and another AC drive. Which is what I plan
on doing to my 9" junior except I think I'll go with 1/2 or 3/4 in
3PH because of the added torque from the better motors. Can ya tell
I like the AC drive. I don't know what I would do with out it. Maybe
hand crank the Mill? Or do the make a AC drive for single phase
motors? Kerry (11350) |
| Single phase motors
don't lend themselves to variable speed
operation due to the fact that they have a set of windings in them
that only operate during starting. These windings are switched out by
a centrifugal switch. As long as the motor stays at or near its
operating speed the start windings are out of the picture. If you try
to slow it down you will cause the start windings to be
activated. These coils draw excessive current in order to get the
motor up to speed. If they are kept connected for an extended period
of time the motor will overheat. 3 phase motors are superior in many
ways to single phase motors, if you can use em do so. Rob
(11353) |
| Kerry, Would you
like to sell that 1HP, 3600 rpm polishing motor? I think I can get
you just about any kind of lathe motor you need. Let me know what
your motor needs are and if possible, please send me a couple of
pics of that 3600 motor you have. Maybe you would be interested in a
trade? I live in Rhode Island so shipping may be calculated.
(11360) |
| Kerry, The only
way I know of getting an induction motor to run at a slower speed is
to use a VFD. The RPM. of an induction motor depends on the number
of "poles" inside the motor (windings) and of course the cycle rate
of your power. Here in the U.S., all power is at 60 cycles per
second (at least what you get out of your service panel - I'm not
talking about long distance transmission). Therefore, the RPM of a
motor (no load) is 7200/(# of poles). A 2 pole motor is 3600; a 4
pole motor is 1800; etc. But if you change the cycle rate coming
into the motor, you change the RPM of the motor (remember that we're
talking about induction motors). That is what a VFD will do. Now
with all that "blather" aside, I'm curious why you want a slower
buffer? Buffing, like most forms of metal working, is about SFM
(surface feet per minute). I'll admit I don't know a lot about
buffing but what I do know from the gunsmithing field is a 1 HP 3600
RPM buffer turning a 6 or 8 inch buffing wheel would work just fine.
Webb (11381) |
| Yep you're right
you can run a 6" wheel on a 3600 rpm motor but an eight inch wheel
to me is pushing it and I don't like the speed. I set up our shop at
work with a 3/4 HP 1700 RPM Baldor buffer and a full set of 8"
wheels from brownells after I brought my setup in and sold them on
the idea. but after using the bigger wheels at a slower speed I feel
I get more control and it takes longer to burn up a part. Kerry
slower speed is to use a VFD. The RPM. of an induction motor depends
on the number of "poles" inside the motor (windings) and of course
the cycle rate of your power. Here in the U.S., all power is at 60
cycles per second (at least what you get out of your service panel -
I'm not talking about long distance transmission). Therefore, the
RPM of a motor (no load) is 7200/(# of poles). A 2 pole motor is
3600; a 4 pole motor is 1800; etc. But if you change the cycle rate
coming into the motor, you change the RPM of the motor (remember
that we're talking about induction motors). That is what a VFD will
do. slower buffer? Buffing, like most forms of metal working, is
about SFM (surface feet per minute). I'll admit I don't know a lot
about buffing but what I do know from the gunsmithing field is a 1
HP 3600 RPM buffer turning a 6 or 8 inch buffing wheel would work
just fine. (11409) |
| Speed Control
on 14" |
| Anyone familiar
with the variable speed control on a 70's vintage 14"? This is the
one with the increase and decrease buttons and an analog meter for
readout. From seeing it disassembled, it looked like the speed was
varied by a pair of variable diameter pulleys. I'm hoping this is
the case so that I can use a static phase converter to power the
lathe. If it is actually a VFD, I don't think I can put a static
phase converter in front of it. Wally (16126) |
| Even if it is a VFD the static converter should be ok. Sounds
like its what is known as a reeves drive, If it has the double cone
pulleys. Those things are rugged and smooth operating. Just make sure
the spindles are clean and well lubricated, but not over lubricated.
RC
(16177) |
| VFD on a SB
16" is great but... |
| I just finished
installing a Variable frequency drive on a older 16" SB lathe. It
uses 230VAC single phase power in and puts out variable frequency /
voltage from 3 - 60HZ and 12 - 203V 3 phase. I installed an older 3
HP, 3 phase motor so I would still have great power even down at
lower motor speeds. It's fabulous! I set the min speed to 3 Hz and
it just crawls making it easy to center using a dial indicator. I am
having trouble with the 2" woven flat belt slipping a lot, though.
I've used belt dressing which has helped, but I still have the
slipping problem with even moderate cuts. If I replace the belt,
what is the best material to use that just won't slip? Has anyone
found a great solution to belt slipping on the larger lathes?
(18592) |
| Leather belts need
a minimum diameter pulley based upon the thickness of the belt. All
flat belts should be run on a crowned sheave. Too much belt dressing
is counterproductive. You may have multiple minor issued adding up.
Urethane flat belts grip fairly well and are tough. JP (18594) |
| I use a nitrile
rubber coated polyester belt on my 16/24 with a 5hp baldor motor.
The grip is very strong and sticky. Works great . If the bearing
throws oil on it I just wash it off with ivory soap and clean the
cones. It never needs dressing. (18904) |
| It sounds good,
but what about the clip? I'm concerned about it making noise when it
runs. Ed P (18911) |
| Yeah, it ticks as
it hits the cones, but not very loud at all. it doesn't slap like
you'd think. after a little while I didn't notice the ticking
anymore, but I also didn't hear my old, useless, soggy-ass leather
belt sliming all over the cones in a heavy cut as the rpms drooped,
especially on the highest speed with the small end of the cone! (my
machine runs a 5hp Baldor motor, with a 5-1/2" motor pulley so
I get
about 1200rpm in high "gear" ) c.m. (18927) |
| VFD's |
| Thanks, Jim B, Gabe,
Bernard R and all VFD informed members for the VFD info. I just
finished packing the guns and rigging equipment for my trip to
Maryland. My cloths are still in the dryer, but the trailer is
hitched to the truck with all lights working and the tires aired up.
From what you guys have said about these VFD s ; they look like they
are affordable, work well when set up correctly, vary the speed well
without loosing much, if any, power when run nearest to 60 Hz (for
heavy work). And I can keep the old motor, while ditching the rotary
phase converter. If you can set it up like Bernard said with a
simple pot controlling output frequency it would be great, as the
ones on the ships required pushing small buttons in the correct
sequence to change the output. I have the old drum switch on the
pipe mount coming off of the lathe bed, a very stout unit. Would it
be possible to mount a box with the forward/reverse switch being a 3
position toggle switch, the pot for speed control, a digital readout
for spindle speed, motor speed or output frequency, and maybe a big
red non-returning emergency stop button to be located remotely from
the box that houses the VFD, say on the old stout pipe mount? When I
get back I am getting one of these VFD s. I did not know the prices
were affordable. BTW, if you want to get a rear T. A. screw (cross
feed screw) out of a 13 SB lathe with a taper attachment, do not put
the end of this screw 4 away from the wall behind the lathe. Put it
at least 8 away from the wall with 10 being better. I am going to
have to move my lathe when I get back as I want to overhaul the
apron / saddle / cross feed next. I have a small 25 by 35 shop that
has no extra room in it (the machine tool hobby must share space
with a Jaguar hobby, motorcycle hobby, welding hobby and my
ammunition), 4 was not worth all the rigging that I am going to have
to do to move the lathe 6 away from the wall (zoning does not permit
moving the wall). I like this users group. You guys are knowledge
rich and other than a certain powerful lawyer, gentlemen. I wish you
all well in my absence, as we do not have a computer in Maryland.
Maybe one of my shooting friends, a computer sciences professor, at
the University of Maryland can get me on line up there, after all,
he talked me through getting this computer working to do what I want
it to do. Nick
(26113) |
| Nick, When it comes
to buying the switches, you need light duty. preferably gold plated,
instrument types. The signal to the VFD are likely 24Volt at about
10milliAmp, (the VFD provides the voltage source all you need is the
wire and the switches) at these levels normal house hold switches do
not provide reliable switching. My own preference is illuminated
push button switches, one for motor ON/OFF and another for motor
reverse, www.mouser.com has a wide selection. All the
VFD's I've used
have a digital readout which can be set to show different parameters,
I normally leave mine showing output frequency. A chart showing VFD
frequency with corresponding RPM at your normal gearing and back
gearing is easier than doing the conversion in your head. The way I
would wire it up would be, incoming ac line to the main switch, then
to the emergency shut down, mounted on on near the machine and then
to the VFD. In use, the existing Fwd/Stop/Reverse switch is
permanently left Fwd, then put tape or lock it in some way to
prevent operation, only use your push button switches to operate. (VFDs
don't like having their motors disconnected when running.) Bernard R (26124) |
| Nick, VFDs just
recently became affordable. About 5 years ago, a VFD rated for 1HP
was close to $1000. Now, you can get the "basic" type for around
$200, new. There is now a "vector flux" type that has good torque
throughout the range, but they aren't cheap. To run a 250W motor
with a VFD I was given the following price for VFDs rated at 1/3 HP.
"basic VFD" 115V input/230 3 ph output constant torque 15 to 60 Hz no
provision for tachometer based feedback or add-ons $160-$200 "Vector
flux" 230 V 1 ph input/ 230 V 3ph output constant torque from 0 to 60
Hz ability to use tach feedback and other neat add-ons $500 (just the
controller) $300 for Tach feedback module I went with a speed pot on
my mill setup. After you setup your SB to run with a VFD, you won't
want to run it any other way. A VFD/3 ph setup is my preferred way to
make something that isn't variable speed, variable speed. It beats
DC and old mechanical pulleys hands down, which is why they spec AC
drives on today's CNC machines. Gabe
(26133) |
| Gabe, Try
www.automationdirect.com , a Hitachi sensorless vector drive for 1/2 HP
is listed at $269, I'm using the 2HP unit for my mill @ $399 (less
when I got mine). Bernard R (26137) |
| Nick, I purchased a
3HP Hitachi VFD from Drives Warehouse on eBay. I have been
absolutely pleased with it thus far. I love this VFD. Jim
(26147) |
| They certainly have
excellent prices. I'll go there when I eventually make my lathe
variable speed. I did my mill because 440 RPMs was not a desirable
slow speed, coupled with the fact it took a metric frame motor, made
VFD/3-phase the only way to go. Unless my VFD breaks or something,
it won't ever have a single phase motor on it again. My lathes have
acceptable low range speeds and single phase motors, so it is hard
to justify doing them immediately, though converting them to is high
on my wish list. -Gabe (26148) |
| Nick I think you
have made the correct decision for your situation, I installed a VFD
for a friend's wood lathe a couple of years ago when prices were
higher. there are a couple of wrinkles to optimizing the package. In
my case I even had the single phase motor rewound to 220V,3ph.
because of a European flange mounting and long shaft. Expect rated
torque from minimum speed to about 1800RPM and constant
HP (decreasing torque) from about 1800 up to 2700 speeds above that
are impractical even though they may be theoretically possible the
usual motor would probably shake itself into oblivion. Jim
(26182) |
