Advice on how to run this motor please

Ropata · May 18, 2016

Hi there,

I am currently doing a complete rebuild of my 1965 Colchester Student lathe and have no idea about electrics. I have attached photos of the motor and badge (hopefully). My understanding is that this is the original 3ph two speed motor which I need to run off my domestic 240v home supply. I'm willing to spend the money on a good VFD but am getting a bit confused about how to tie it all in with the levers for this model among other things. Does anyone run this model with a VFD?

Any help will be greatly appreciated.

Sorry for the upside down photos.

LKeithR · May 18, 2016

Ropata said:
...Sorry for the upside down photos.

From new Zealand? Perfectly normal...

Ropata · May 18, 2016

Ha ha. Yeah getting cold down here now and I feel I'm going to be spending plenty of time in my freezing garage.

Joe H · May 18, 2016

Hey Ropata,

I set up a similar lathe 20 + years ago. It is a 13x36 Clausing Colchester.
It has a similar 2 speed three phase motor. Mine is dual voltage so it can be wired for 240 or 440. I'm going from 240 single to 240 3ph. Yours is 440 only which will present a problem since you have 240 v (I assume single phase). My motor is 60 cycles, yours is 50.

Unless you can find a VFD that takes 440 single phase input you will have to use a 440 3phase unit and downgrade for single phase input. Transform the 240 single phase to 440 single phase then feed the 440 single to the VFD. You probably could use a 5hp 440 3phase VFD for your 3hp motor but I'm not sure. The other guys here are VFD experts and I'm sure can answer the question.

On mine the lever with the red ball turns the unit on and off. I wired the vfd so that the on-off lever powers up the vfd. The vfd is controlled from a remote station mounted on the lathe head. All the gear head controls and lathe functions remain as before. It is a very complicated controller so it is best not to mess with it. I've had no problems with the set up.

Joe

9100 · May 18, 2016

Note that the hp rating is 3 at high speed and 1.5 at half speed. Because hp is calculated by multiplying speed times torque, that says that the torque is the same at both speeds. A VFD running the motor on the high speed winding will also give the same torque at half speed, so you can dispense with the speed change switch and do all the speed control with the VFD without any penalty.

I recently set up some cylindrical grinders that way. The VFD can be controlled with a potentiometer and the display has a multiplier that allows you to make it read directly in RPM. That makes a very convenient system, just dial in the speed you want. You do want to add an on-off switch controllimg the VFD. You turn on the power with the original switch, then control on-off, speed and reverse with the VFD. On the grinders I added a timer to keep the VFD on for braking and set up everything to work from the original switches, but that is beyond the scope of the present issue. The grinders are in a large shop where anyone can use them so the owner wanted everything as simple as possible. For presumably a single operator, the way I outlined first would do fine.

Bill

Ropata · May 18, 2016

Thanks Bill, I had heard this before hence my desire to go for the VFD option. So my only problem seems to be as Joe said about feeding voltage to the VFD? I'll try sending a few questions to a couple of companies that supply them.

Ropata · May 18, 2016

This is the response I got from automation direct.

Reply:
Unless the motor can be rewired for 230 vac then we have no option for you. It would take a 460 volt drive for the current configuration and the drive would need 3 phase 460 Vac to operate properly.
Regards,

Joe H · May 18, 2016

Ropata,

Years ago I did find a VFD that could use single phase 440 and transform it to 440 3ph. I wired up a standard transformer up as an auto-transformer (only allowed to raise voltage) and fed the vfd to run a Hardinge 440v only lathe. Still running today. I tried to find a similar unit a few years ago but none were available.
As far as I know any 460 3ph input VFD will work with 440 single phase input but the rated HP has to be downgraded 50%. The problem is that most units have phase protection that will disable the VFD if it detects a loss of phase on the incoming line. On some units the phase protection can be disabled which is what you need, some units you can't.

Maybe some other Board members can chime in about their experience.

Joe

metalmagpie · May 18, 2016

As a general rule, it is difficult to run a machine with a 2-speed motor from a VFD and use all the machine's original controls. Possible, but complex. Your situation is quite a bit worse, since your machine is 440 3-phase (380 3-phase where you live).

I recently rebuilt a machine that had a 440-only 2-speed motor. I have a rotary phase converter that makes 220 3-phase already. I put 3 single phase transformers inside the base of the machine and connected them like a 3-phase transformer and just fed the machine 440 3-phase power. I suggest you buy or make a rotary phase converter. Thousands of guys have made their own, it isn't that hard to do and lots of guys will help you with the hard parts. Let the rotary phase converter make you 240 volt 3-phase power. Then connect a step-down transformer in reverse to step the voltage up to 440, and just connect your lathe to that. The *only* tricky bit is you have to keep track of which leg of the 3 that comprise your 3-phase power was generated by the RPC. Some guys call this the wild leg, or just phi3 or T3 if you like. The control electronics of your lathe should not be connected to the wild leg.

Good luck.

metalmagpie

moonlight machine · May 18, 2016

metalmagpie said:
As a general rule, it is difficult to run a machine with a 2-speed motor from a VFD and use all the machine's original controls. Possible, but complex. Your situation is quite a bit worse, since your machine is 440 3-phase (380 3-phase where you live).

I recently rebuilt a machine that had a 440-only 2-speed motor. I have a rotary phase converter that makes 220 3-phase already. I put 3 single phase transformers inside the base of the machine and connected them like a 3-phase transformer and just fed the machine 440 3-phase power. I suggest you buy or make a rotary phase converter. Thousands of guys have made their own, it isn't that hard to do and lots of guys will help you with the hard parts. Let the rotary phase converter make you 240 volt 3-phase power. Then connect a step-down transformer in reverse to step the voltage up to 440, and just connect your lathe to that. The *only* tricky bit is you have to keep track of which leg of the 3 that comprise your 3-phase power was generated by the RPC. Some guys call this the wild leg, or just phi3 or T3 if you like. The control electronics of your lathe should not be connected to the wild leg.

Good luck.

metalmagpie

metalmagpie is correct, easy to do a rpc and a transformer. Most of my machines are 220 3 ph but I have a few that like the 440, I just use a transformer for those. Easy peasy.

Ropata · May 19, 2016

Thanks Magpie, It's looking more like the way to go now that It seems to be getting quite complicated. I'm really hoping to leave this lathe as original as possible because It's in such good shape internally.

swarfless · May 19, 2016

Hi Ropata, don't want to give you false hope but it might be worth getting a motor rewinder or a good industrial sparky (not a house wirer) to have a look at your motor. If the gods are smiling on you it MAY be that your motor is star connected & could be reconnected in delta thus converting it to 240V 3 phase. I'm only saying this coz it is possible, however unlikely because of two-speed complication. Still possible nevertheless. Brook motors were pretty good back in the day. Good luck with it.

Ropata · May 19, 2016

Thanks Swarfless, I've already sent the photos to a re-winder close by just waiting for a reply. Fingers crossed.

9100 · May 19, 2016

The windings are probably connected in star for high speed and delta for low. You could have the motor completely rewound for 240V, but I can guarantee that you will not like the price.

dahlander - Google Search

Bill

Joe H · May 19, 2016

Ropata,

You can see from the responses you have two possible ways to go if a rewind is not in your future, a 230 v RPC with step up transformers to 460v or a derated 460 v VFD. If a rewind looks possible make sure the rewind configuration will work with your controller if you want to use the original lathe controls. I'm pretty sure you have the same type of motor as mine, a six lead, constant torque 2 speed motor. Mine is also 3/ 1.5 hp and the speeds are consistent with the difference in cycles (50 vs 60).

I've attached my wiring diagram if it may be of some use to you.

I've also attached some VFD info on how to use 1 phase input on a 3hase vfd.
As far as your correspondence with Auomation-Direct you are talking to salesman not somebody who knows the engineering properties of their product (at least that's my opinion).

Joe

Ropata · May 19, 2016

Joe H said:
Ropata,

You can see from the responses you have two possible ways to go if a rewind is not in your future, a 230 v RPC with step up transformers to 460v or a derated 460 v VFD. If a rewind looks possible make sure the rewind configuration will work with your controller if you want to use the original lathe controls. I'm pretty sure you have the same type of motor as mine, a six lead, constant torque 2 speed motor. Mine is also 3/ 1.5 hp and the speeds are consistent with the difference in cycles (50 vs 60).

I've attached my wiring diagram if it may be of some use to you.

I've also attached some VFD info on how to use 1 phase input on a 3hase vfd.
As far as your correspondence with Auomation-Direct you are talking to salesman not somebody who knows the engineering properties of their product (at least that's my opinion).

Joe

View attachment 171680 View attachment 171681
View attachment 171685

Thanks Joe. The RPC route looks quite full on for someone with my experience. So you're telling me that you run the same motor through an VFD and that you're pretty sure the automation direct guy might be unaware of the possibility to do this?

Joe H · May 20, 2016

Ropata,

I'm pretty sure my motor is identical to yours except that mine is possibly dual voltage and it is 60 cycle for USA, in any case it is wired for 230v. Yours will only work with 440v.

I use a 230v single phase input VFD, 230v 3phase output. When I got the VFD my planned wiring set up to use all the original controls was by popular misconception not possible. I was somehow able to talk to someone on Teco's engineering staff that told me my setup would work and not harm the VFD as long as I wasn't switching under full load which is really not possible on a gear head lathe. I posted the Yasakawa info to show that downgrading the capacity to use single phase 460v input is possible. I can't remember all the details of my installation but my point is - If you are really interested in a VFD, do your homework,It probably can be made to work.

Of course the bottom line is your comfort level with the electrical part of phase conversion and the resources that are available to you.

Good Luck,

Joe

johansen · May 20, 2016

9100 said:
The windings are probably connected in star for high speed and delta for low. You could have the motor completely rewound for 240V, but I can guarantee that you will not like the price.

Bill

Perhaps, but that also requires 6 windings that are connected in star for the high voltage, high speed option.

Connecting them in delta for the low speed isn't really delta in the normal sense of the word.. its funny trickery where the two windings are opposing each other.... Inside the motor all the coils are all oriented the same way making all "north" poles and the "south" pole of the winding is in between the coils. how they get away with this i'm not sure, as it implies that any standard 9 wire motor can be run at half speed, but perhaps lower voltage is required to prevent saturation.

reversing the polarity of half of the coils in the "delta" "low speed" winding will get you a motor that is looking for 277/480volts, (or 254/440) which is sufficiently close to what you can get from a 240volt vfd, and will run just fine on the slightly lower voltage.

And you should be able to rewire it for 240vac star "high speed" as well.

9100 · May 20, 2016

johansen said:
Perhaps, but that also requires 6 windings that are connected in star for the high voltage, high speed option.

Connecting them in delta for the low speed isn't really delta in the normal sense of the word.. its funny trickery where the two windings are opposing each other.... Inside the motor all the coils are all oriented the same way making all "north" poles and the "south" pole of the winding is in between the coils. how they get away with this i'm not sure, as it implies that any standard 9 wire motor can be run at half speed, but perhaps lower voltage is required to prevent saturation.

reversing the polarity of half of the coils in the "delta" "low speed" winding will get you a motor that is looking for 277/480volts, (or 254/440) which is sufficiently close to what you can get from a 240volt vfd, and will run just fine on the slightly lower voltage.

And you should be able to rewire it for 240vac star "high speed" as well.

I will have to think about that one a bit. High speed has adjacent coils in the same polarity, making one pole of two windings. Low speed reverses one set, making twice as many poles. Come to think of it, I doubt that the world could handle twice as many poles. We don't have a lot of them around St. Louis, but Chicago is oversupplied already.

Bill

JST · May 20, 2016

The wiring diagram posted states that motor as being two speed constant torque, consequent pole. presumably this one is like that. If so, it starts oit with the coils forming opposite poles, and at slow speed shifts all to one polarity to double the pole count. The opposite poles then re-appear in the space between wound poles, essentially "if it ain't actively being a north pole, it''s a south pole".

Chicago? How's about Cleveland?

Advice on how to run this motor please

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