# VFD On Geared Head Lathe



## Chuck K (Jul 29, 2013)

I have been trying to power my Polamco TUM 35 geared head lathe.  I have tried my existing 5hp rotary phase converter.  Its a panel I bought from a supplier on Ebay hooked up to a 5hp idler motor.  It has worked well for me for a few years.  The lathe has a 5hp motor.  The rpc would power it ok in lower speeds, but when I tried to start it in the 1250 rpm range it wouldn't spin up to speed.  Actually it was kind of slow getting to speed at 900 rpm.  I next tried using the 5hp rpc that came with the lathe.  This unit seemed to be heavy duty.  The company that manufactured it is still in business in MN.  I called and talked with a tech there before trying it and he told me it probably wouldn't turn a 5hp geared head lathe at high rpm.  He suggested a 7 1/2 hp unit at a minimum.  I did try it and it worked better then the one I had but wouldn't even begin to spin it up @ 2500 rpm.  Tonight a friend stopped by with a mitsibishi vfd.  I don't know how many amps it was rated for but he told me it was a 7 1/2 hp unit.  Model 100 I think.  He wired the control side of the box to a 110v circuit and used the inverter to power the motor.  It wouldn't spin it at 1250 rpm.  It would start turning slow, after about 15 seconds it would just shut down.  The amperage never went above about 4 amps.  It worked fine at lower speeds.  He mentioned that  I might be able to power it with a constant torque vfd.  Realistically I don't need the higher rpm ranges for my use, but it's going to eating at me just knowing that I don't have it powered correctly.  Has anyone had problems similar to this with a geared head lathe?  I don't believe there is anything mechanically wrong with the gearbox that would cause extra drag on the motor.  It just runs too smooth to have a bad bearing or gear in it.  Any suggestions would be appreciated.  Thanks

Chuck


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## Ray C (Jul 29, 2013)

Chuck,

I'm not all that familiar with RPCs but as far as VFDs go, there are none that I know of that power above 3HP when wired with single phase input.  In other words, VFDs above 3 HP require three phase input.

Question:  Is this lathe new to you and did it ever spin-up properly before?

I once replaced a motor which could be wired for 220 or 440 volt operation.  I accidentally left it wired for 440 but supplied 220.  It had the same symptom as yours... It wouldn't get up to speed.  Maybe check the wiring of the motor.


Ray





Chuck K said:


> I have been trying to power my Polamco TUM 35 geared head lathe.  I have tried my existing 5hp rotary phase converter.  Its a panel I bought from a supplier on Ebay hooked up to a 5hp idler motor.  It has worked well for me for a few years.  The lathe has a 5hp motor.  The rpc would power it ok in lower speeds, but when I tried to start it in the 1250 rpm range it wouldn't spin up to speed.  Actually it was kind of slow getting to speed at 900 rpm.  I next tried using the 5hp rpc that came with the lathe.  This unit seemed to be heavy duty.  The company that manufactured it is still in business in MN.  I called and talked with a tech there before trying it and he told me it probably wouldn't turn a 5hp geared head lathe at high rpm.  He suggested a 7 1/2 hp unit at a minimum.  I did try it and it worked better then the one I had but wouldn't even begin to spin it up @ 2500 rpm.  Tonight a friend stopped by with a mitsibishi vfd.  I don't know how many amps it was rated for but he told me it was a 7 1/2 hp unit.  Model 100 I think.  He wired the control side of the box to a 110v circuit and used the inverter to power the motor.  It wouldn't spin it at 1250 rpm.  It would start turning slow, after about 15 seconds it would just shut down.  The amperage never went above about 4 amps.  It worked fine at lower speeds.  He mentioned that  I might be able to power it with a constant torque vfd.  Realistically I don't need the higher rpm ranges for my use, but it's going to eating at me just knowing that I don't have it powered correctly.  Has anyone had problems similar to this with a geared head lathe?  I don't believe there is anything mechanically wrong with the gearbox that would cause extra drag on the motor.  It just runs too smooth to have a bad bearing or gear in it.  Any suggestions would be appreciated.  Thanks
> 
> Chuck


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## Chuck K (Jul 29, 2013)

Ray, The lathe is new to me.  When I bought it, it was powered with the rpc that came with it.  I ran it in lower speeds and it sounded good enough that I wasn't worried about the headstock.  I don't know if it would have spun up to speed in  higher gears. The friend that stopped by with the vfd today was here trying to troubleshoot it last week.  His first thought was that it was wired for 440.  He works with motors and drives everyday, but the Polish motor on this lathe was kind of foreign to him.  He wired it the opposite way and it just tripped the breaker.  He felt pretty confident that it was wired correctly for 220 to start with.  I guess we kind of discounted that avenue from that point.  Might be something to investigate further.  The wiring diagram under the cover is kind of faded and it isn't like any I have seen before.  He seemed to understand it after looking at it.  I asked him if it would be better powering the vfd with the rpc and he didn't think that would make an improvement.  Might be different if I had true 3 phase.  I don't know much about rpcs or vfds.  My understanding on vfds from the little research I have done in the past is that if it doesn't say that it can't be powered with single phase, then you can use either single or 3 phase.  I had a 5 hp Hitachi vfd on a Leblond geared head lathe that I powered with single phase, but if I remember correctly that lathe was only 2 hp.  I'm thinking if I had a 10 hp rpc it would probably work fine.  I have always limited myself to machines 3 hp or less so I wouldn't have power issues.  I guess I should have stuck to my plan.

Chuck

- - - Updated - - -

Ray, I reread your post.  Do you mean that the 7 1/2 hp vfd powered by single phase will work but only deliver 3 hp?  If that's the case I don't think a vfd is an option for me on this machine unless I can benefit by powering it with the rpc.  I have just about enough knowledge about electricity to be dangerous.

Chuck


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## Ray C (Jul 29, 2013)

I don't suppose you have a spare motor hanging around...  I personally would toss a 3HP, 3Phase new motor in there and call it a day.  I suppose though, you could take the other one to a motor shop.  If you know for sure how to switch the leads from one voltage to the other, the 220V setup will have lower resistance (leg-to-leg) than the 440.  Comparing the two setups will at least tell you which one is which.  Now keep in mind, some industrial equipment is rated for 380 which complicates matters even more -and I have no idea what the standard/common voltages are in Poland.

If there's any writing on it, go to google translator and convert it to english.


EDIT:  I really don't know how a VFD behaves when driven with single phase beyond the 3 HP range... 



Ray


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## Chuck K (Jul 29, 2013)

I have a few motors, but this one is a flange mount and I don't have one of those.  Although this lathe was made in Poland and has a Polish motor, it was made for export to the USA.  It has a Square D control panel on it.  I don't think the 380 v is and issue.  I'll research the motor tomorrow and see if I can find some wiring diagrams I understand.  Thanks

Chuck


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## Ray C (Jul 29, 2013)

Hey Chuck, any chance you can post a picture of the lathe?  

Ray


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## Chuck K (Jul 30, 2013)

Ray, Here's some pics:


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## Chuck K (Jul 30, 2013)

As I look at this I'm beginning to believe that it's wired 440.....what do you think?

After staring at it and comparing it to other diagrams....it has to be wired correctly for 220


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## Ray C (Jul 30, 2013)

It has all the classic symptoms of being undersupplied of voltage and by looking at the terminal block, it no doubt can be rewired for different voltages.  Sadly though, I've only rewired a handful of motors for 120/220 operation and only one for 220/440; as such, I cannot tell by looking at the wiring how to change it.  I'd recommend that you go to the Electrical/VFD section and post a new call for help that references this thread.  Give the new thread a title like "Need help coverting 3PH from 440 to 220" and that will get the attention of folks who know motors better than I.


Ray


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## 8ntsane (Jul 30, 2013)

Your saying your lathe is 5 hp, and the RPC is also 5hp. Be that's the case, your RPC is too small. General rule of thumb is X2 on the RPC. You have been told 7.5 at min, but I would go the X2 route on the RPC. I have seen the problem many times when trying to start a lathe in hi gear. 

You also mention a VFD with 110 input. Is this VFD the type that needs to be derated? Some do, some don't. If it does, you may need to get a VFD to handle the job. 5 hp on up can get expensive. I have a 5hp lathe running on a 7.5 hp VFD, and my machine works fine with it, except when I use the clutch when the lathe is in hi gear. In that case, it will kick the VFD out. As long as I leave the clutch engaged, and let the VFD ramp up, then Hi gear is no trouble at all.

VFDs can be set to ramp up, slow, or fairly fast. That's a good thing in that respect. I would be willing to bet you would have better luck starting your lathe in hi gear with your RPC, if it was a 10 hp.


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## Chuck K (Jul 30, 2013)

Paul, I'm on the same page as you with the 10 hp rpc.  At some point I will do that, but for now I won't miss the high spindle speeds. The vfd was powered with single phase 220.  The 110v I mentioned was just an extension cord that he wired into the control panel to power everything but the motor ( and possibly the spindle brake....not sure about that).  I think wiring up a vfd for this lathe is a little bit out of my league.  Of course if a 10 hp unit comes down the pike I probably wont pass it up.)

Chuck


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## Codered741 (Jul 31, 2013)

I'm not familiar with this particular lathe, so I'm guessing here. I once used a Clausing lathe that would start the motor, and you would engage the spindle via a clutch. Does your lathe work that way? 

We had a nearly identitical problem when our clutch wore out. The increased resistance makes the clutch slip, before the spindle gets to speed. Low speeds were no problem, due to the mechanical advantage. At medium speeds the clutch would slip when cutting. 

If your lathe has a clutch, I would check this first. 

-Cody


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## Chuck K (Jul 31, 2013)

Cody, What your saying makes a lot of sense, but this machine doesn't have a clutch.  It's either off or on.  I really think I have a power issue...at least that's the avenue I'm going down until I prove myself wrong.  Thanks for the input. 

Chuck


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## rdhem2 (Aug 1, 2013)

Mr. Chuck;

Your Polish lathe is wired for 480 v or high voltage.  The picture of the jumpers in the pecker head gives it away.  Change to the alternate arrangement per the label which will give you a "Y" connection in parallel.  The motor has two windings, each capable of dropping 240 volts across them.  Wired in parallel, side by side, they each drop 240 volts and you read the amperage of each doing so so it is twice the amperage of the high voltage connection.  Wired in series, as they are now, they are connected end to end.  With each dropping 240 v,    240 v + 240 v = 480 v.

You will also have to change the heaters in the magnetic starter as they will (or should be) only capable of carrying the 1/2 the amperage necessary for a 240 v connection.  If you do not change them your starter will trip out due to overload when there is none.  The heaters are the gizmos held in by two screws just above where the motor leads leaving the panel are connected to the overload block.  They are spring loaded so when they jump out and it clicks, don't be alarmed!  Look in the phone book for Square D, call the supplier and give them the rating of the motor, (3 kw) they should at least tell you where you may purchase them.  If you have a *CED* (Consolidated Electrical Distributors) in your town I would start there.  They are nation wide and the local guys at least are great.  Just no guarantees that branch house handles the Sq "D" brand.

Nice control panel.  The magnetic starter on the lower right with two contactors and only one overload block is the reversing starter for the lathe drive motor.  I have no idea what the left hand starter is for, coolant pump maybe?  Also check the control transformers for the proper connection for the voltage supplied.  Control transformers may also be wired for 240 or 480 volts.

The largest VFD I am aware of that will operate on 240 v single phase is 7 1/2 hp.  The largest on 120 v single phase is indeed 3 hp.  But go to your industrial supplier and ask.  They come out with new stuff almost daily and you have to keep up with it.  Or at least I used to when I was in the biz!  VFD's do have timers that allow you to program start up and shut down times to reduce and control inrush current.  The terminology is usually "ramp up" and "ramp down times".  This is where inductive breaking enters the picture, by injecting current spikes into the motor if needed to control the stopping time.  Else it just slows the frequency to zero at the rate set.  These spikes are what break down motors that are non inverter duty rated.  This is why they are so touchy about guarantees unless your motor is rated for such use.  And if it is an older motor, it is not.

A lathe starting with nothing in the chuck (no load condition) should start and run regardless of what gear they are in.  If they don't, you have a problem, as you know!  Motors are hard to start and may draw up to or over ten times the nameplate data, but only for a short time.  A motor, electrically speaking, is a dead short.  Until the rotor starts to turn, creating counter electromotive force, the resistance in the windings is virtually nil.  The slip in a motor is how much the rotor lags behind the sine wave in a 3 phase sine wave.  This slip is due to bearing resistance and physical weight of the rotor itself, and the load imposed upon the motor.  The farther it lags, the more current it draws and the less efficient it becomes.  This lag from synchronicity speed is also what causes heat and poor power factor which messes with your rpc also.  Basically creating watt-less un-measurable current that shows its self as heat, harmonics and other undesirable electrical noises.  Humming, buzzing, rattling, etcetera.

Are you glad you ask?


Edit---Check your RPC also for proper voltage hook up.   An added thought!


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## Ray C (Aug 1, 2013)

Excellent information there and I'm sure that will help Chuck out a lot!

BTW:  Just want to mention that you don't absolutely need to oversize a VFD.  If you have a 1 HP motor, a 1HP rated VFD will work fine etc...  There's nothing wrong with getting one oversized, it won't hurt anything but, it's not necessary unless you plan to really drive the motor hard on a very regular basis.  In that case, the VFD might last a little longer since it's not being stressed to it's maximum output.  The motor only uses up what it's capable of putting out when the situation calls for it.

It might be a different story with RPCs but I'm not familiar with them so someone else can possibly clarify.

Ray


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## Chuck K (Aug 1, 2013)

rdhem2 said:


> Mr. Chuck;
> 
> Your Polish lathe is wired for 480 v or high voltage.  The picture of the jumpers in the pecker head gives it away.  Change to the alternate arrangement per the label which will give you a "Y" connection in parallel.  The motor has two windings, each capable of dropping 240 volts across them.  Wired in parallel, side by side, they each drop 240 volts and you read the amperage of each doing so so it is twice the amperage of the high voltage connection.  Wired in series, as they are now, they are connected end to end.  With each dropping 240 v,    240 v + 240 v = 480 v.
> 
> ...




I'll have to look at this again.  I had assured myself that it was wired correctly for 220v.  The diagrams on the cover were confusing to me so I did a web search and compared the current wiring to the diagrams I found online.  It looked right to me.  Now as I think about it....when we changed the wiring and tried starting it, it just made a loud click and then nothing.  If it has the wrong heaters in it, that would explain why it didn't work wired the other way.  I really appreciate your explanation.

Chuck


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## bloomingtonmike (Aug 3, 2013)

Ray C said:


> Chuck,
> 
> I'm not all that familiar with RPCs but as far as VFDs go, there are none that I know of that power above 3HP when wired with single phase input.  In other words, VFDs above 3 HP require three phase input.
> Ray



That is the old way of thinking. There are lots of large single phase VFDs on the market these days - 10hp and beyond even if you have the amperage to supply them. They will cost you though. A 5hp rated 1ph in VFD will deliver the full 5hp. Here is a good one - SpeedStar:

http://www.driveswarehouse.com/p-2123-pc1-50.aspx


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## Ray C (Aug 3, 2013)

Thank You!  I've been looking for a unit like that for a while and it eases my decision on the next lathe which has a 5HP motor.

Thank you!


Ray



bloomingtonmike said:


> That is the old way of thinking. There are lots of large single phase VFDs on the market these days - 10hp and beyond even if you have the amperage to supply them. They will cost you though. A 5hp rated 1ph in VFD will deliver the full 5hp. Here is a good one - SpeedStar:
> 
> http://www.driveswarehouse.com/p-2123-pc1-50.aspx


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## Chuck K (Aug 3, 2013)

Ok....I took the cover back off the motor and rewired it the opposite way shown on the diagram.  The thing that confused me is that the terminal block is upside down.  Once I took off a wire and used U1 as a reference point the diagram made sense to me.  It's wired the same way as every dual voltage motor I've dealt with.  I put power to it (5hp rpc) and hit the lever for forward spindle rotation @ 630 rpm.  The relays clicked in and out and the spindle jerked each time the relays clicked...then nothing.  This is the same thing that happened when my friend wired it this way the first time he was trying to troubleshoot it.  At that point he looked at everything in the control panel and said that it was all set up for low voltage and although it didn't make sense to him, he thought that european motors might be wired differently than anything he works with.  So at that point he wire the motor the way it was originally and made plans to power it with a vfd to see if that would make it run at the higher rpm ranges. The vfd wouldn't power it either and that brings me up to where I am with it today.  At this point he's convinced that there is something in the control panel that isn't right. I took more pics of everything and I'll try to put captions with them as I post them, but I've had problems doing that in the past.

I couldn't figure out how to add captions so here's how the pics go:

The first pic is how I rewired the motor.  I switched the metal jumpers from the bottom to the top and added wire jumpers on the bottom to effectively link the the 3 wires together.

The second pic is the relays

The 3rd pic is the tag on the relays

The 4th pic is the starters

The 5th pic is the starter tag

The 6th pic is the heater

The 7th pic is the heater tag

The 8th pic is the transformers

The 9th pic is the panel tag


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## bloomingtonmike (Aug 3, 2013)

Chuck, Here are my initial thoughts.

Typically you only power the motor with a VFD - you do not have any contactors/relays or control circuits on the output side of the VFD. In fact it is not advisable to do that AT ALL. Try this. Wire the motor directly to the VFD T1,T2,T3 (or whatever the motor outputs are) and try power testing it only using controls on the VFD. You will do all your machine control from intelligent inputs/outputs on the VFD. You will use external switches to change input configuration settings on the VFD.

Also you said you had a 5hp and 7.5hp VFD. Are you using single phase in and are your VFDs rated for that? If your VFD is a 5hp 3 phase in VFD you typically derrate it by half. So that 7.5hp is not rated for 5hp single phase. It may work but you may error out the VFD under load. Hopefully it is sized and rated correctly. Guessing this was the case with the 7.5vfd not running fast enough. 

Also in one of the pic specs it says control is 120V - that typically means your coils may be 120V. Your VFD is sending 120V to each side of the coil (two hots total) and not just one side and neutral to the other. Verify the coil type in each contactor. Again I would bypass all of these anyway.


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## Chuck K (Aug 3, 2013)

My friend Duane stopped over once again this morning armed with a bag of test devises and other tools of the trade.  He solved the problem but we're still kind of confused as to why the machine was set up the way it was.  Basically the whole control panel was set up to run on low voltage but the motors were wired for high voltage.  The reason I couldn't get it to run on 220v after changing the motor over to low voltage was because the voltage at start up when fed from my 5hp rpc was too low for the transformers in the control panel.  It caused the relays to chatter and drop out.  Duane once again wired a 110v extension cord to the control panel to power everything except the motor starters and motor which were powered by the rpc.  That allowed the relays to hold and the motor ran perfectly.  I still can't run in high speeds but only because I don't have enough power to do it.  If I had a 10hp rpc I'm pretty sure it would do everything it's supposed to do. For now I'm going to mount a seperate box for a 110v circuit to power the controls and use the rpc I have to run the motor.  Duane seems to believe that now that he understands what was going on he could probably power it with his 7 1/2 hp vfd and get it to run in high gear.   Now all I have to do is decide where I'm going to put the machine, finish wiring it, and get it leveled up so I can take some true test cuts with it. Thanks for all the help.

Chuck


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## rdhem2 (Aug 4, 2013)

Congratulations on finding the problem with the drive motor on your lathe.  You done did it my man.  Stayed with the problem until it was resolved.

I too was puzzled about your remarks about the contactors clicking then everything coming to a halt.  It did not dawn on me at the time that it was due to voltage drop on start-up.  Makes sense though if you are hurting for size on the power supply.

You will need to consult a heater chart to see if the B22 heaters are correct for your application at 240 volts.  I don't know what the B1.03 units supply but they need to be verified also.

My experience with RPC's is limited and the few I have seen never impressed me.  I do not care how fancy the label is or how professional the construction, it is still just Hokus Pokus Brewhaha for the real meal deal and the alternate choices are many.

Again, CONGRATULATIONS!  Your *"JUNIOR ELECTRICIAN"* card is on it's way!  You have earned it.


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## Chuck K (Aug 4, 2013)

"Again, CONGRATULATIONS! Your *"JUNIOR ELECTRICIAN" card is on it's way! You have earned it."


*I think you better hold off on the JE card.  All I did was observe Duane while he did all the troubleshooting.  I did learn a few things
 while watching him though.  The first thing he did when he first opened the control panel was check the number on the heaters to see what they were rated for.  They are the correct heaters.  Again, that's what confused us.  Everything in the machine was set up for low voltage but the motors were wired for high voltage.  I guess it shouldn't surprise me.  I have seen "fixes" done on used machines that just make you ask yourself, "what was he thinking?".  

Chuck


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## Ray C (Aug 4, 2013)

Good going, Chuck -to you and your friend.

I'm sorry I couldn't help much but, as soon as you mentioned heaters etc, it was out of my immediate realm of knowledge...


Ray


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## Jeephead (Aug 4, 2013)

Just a note for those of you about the heaters, if you did not have to push the reset buttons, not an overload or heater problem. just for future reference.


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## Chuck K (Aug 4, 2013)

Heaters are definitely not going to be an issue now.  I am the proud owner of a Mitsubishi 7 1/2 hp constant torque vfd.  I moved the lathe to it's permanent location and leveled it today.  I was in the process of setting it up for a test cut to get the tailstock dialed in when Duane showed up.  He did a temporary hook up to test the vfd and for the first time I got to see the lathe work in all speeds.  I removed the chuck from the spindle before going 2500.  I want to research a little and find out what speed it's rated for before I turn it that fast.  We did a little horse trading and I own the vfd which he's going to wire up for me.  It should be pretty straight forward except for the spindle brake.  He has some ideas for that, but his explanation was kind of going over my head.  Anyway....all I have to do is the no brain mounting work and he's going to take care of all the wiring and switches.  Life is good!

Chuck


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## Codered741 (Aug 4, 2013)

Chuck K said:


> Heaters are definitely not going to be an issue now.  I am the proud owner of a Mitsubishi 7 1/2 hp constant torque vfd.  I moved the lathe to it's permanent location and leveled it today.  I was in the process of setting it up for a test cut to get the tailstock dialed in when Duane showed up.  He did a temporary hook up to test the vfd and for the first time I got to see the lathe work in all speeds.  I removed the chuck from the spindle before going 2500.  I want to research a little and find out what speed it's rated for before I turn it that fast.  We did a little horse trading and I own the vfd which he's going to wire up for me.  It should be pretty straight forward except for the spindle brake.  He has some ideas for that, but his explanation was kind of going over my head.  Anyway....all I have to do is the no brain mounting work and he's going to take care of all the wiring and switches.  Life is good!
> 
> Chuck



Congrats!  Its always nice to see the machine working as it should.  

What is the model number on the drive?  I work with Mitsubishi drives all the time.  Constant torque drives are usually used to drive fans, not so great for machine tools.  Will probably work just fine though.  

-Cody


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## Chuck K (Aug 4, 2013)

Hmmmmmmmmmm.....I was under the impression that constant torque vfds were used for things like conveyors where you needed the same torque at all speeds.  Maybe I should research this a little.

Chuck

- - - Updated - - -



Codered741 said:


> Congrats!  Its always nice to see the machine working as it should.
> 
> What is the model number on the drive?  I work with Mitsubishi drives all the time.  Constant torque drives are usually used to drive fans, not so great for machine tools.  Will probably work just fine though.
> 
> -Cody




Cody, After googling the term "constant torque vfd"  I have to believe that you have your info wrong.  Fans are usually run with variable torque vfds.

Chuck


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## Codered741 (Aug 4, 2013)

Chuck K said:


> Hmmmmmmmmmm.....I was under the impression that constant torque vfds were used for things like conveyors where you needed the same torque at all speeds.  Maybe I should research this a little.
> 
> Chuck



Hey Chuck, 

Please disregard what I just said.  Eyes saw constant, brain said variable.  Never mind.  Evidently I need either more coffee or more sleep...

Sorry.  Constant torque drives ARE what you want for machine tools, Variable torque drives are for fans, etc.  

I would still like to know the model number if you have it handy.  

-Cody


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## Chuck K (Aug 4, 2013)

I'll have to get it for you tomorrow.  It was 200...but there was a letter in the model number that I don't remember right off hand.  It's an older model but it's never been used.  It's a lot bigger than the ones I've had in the past.  Must be close to 12" tall.  I'm assuming that with the newer technology they have shrunk things down a lot. I'm sure it will do everything I need it to do.

Chuck


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## Chuck K (Aug 4, 2013)

The model is Freqrol A200.


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