VFD On Geared Head Lathe

[Chuck K]

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

 

[Ray C]

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

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

 

[Chuck K]

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

 

[Ray C]

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

 

[Chuck K]

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

 

[Ray C]

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

Ray

 

[Chuck K]

Ray, Here's some pics:

 

[Chuck K]

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

 

[Ray C]

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

 

[8ntsane]

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.