Older 3 phase motor connections

[doctor_ratz]

I am re-locating an older lathe that was connected to 480 3 ph. The new location only has low voltage, 208 3ph. L1, L2, L3 are connected to the bottom row of terminals. The 6 terminals that are jumpered by the bars are marked X,Y,Z, along the top row, and U,V,W along the bottom row. As you can see in the picture, there are three jumper wires added to the system. How do I re-configure to operate on low voltage ?

 

[charlie b]

You are relocating this device? Is it at your home? Is this a work-related task or a personal task?

 

[Jraef]

With terminals marked UVW, XYZ, it is a European motor. Low and High voltage for them is not the same as it is for us. We use 230-460V dual voltage connections where there are two sets of wiring changed from series to parallel. They use 220-380V where the windings are connected Star or Delta. You can use a motor designed for 380V 50Hz on a system that is 480V 60Hz, because the ratio of voltage and frequency is the basically same. But it doesn't work that way for the lower voltage. If you reconnect that for LV, it becomes the equivalent V/Hz ratio of 277V, but you will only have 208V. Your motor will develop far less torque, the slip will be higher, it will pull more current under the same load conditions and over heat.

Your better choice is to go buy a 208-480V transformer for that machine, or replace that motor.

 

[Aleman]

We have a bunch of motors with that style wiring and built for 60hz. Does it have a nameplate?

I did a conversion on one machine by wiring for low voltage and using the 208. That motor was a 380V. I know it's
not exactly the right thing to do but it works fine so far. We opted to cheap out and not buy a transformer. This
machine doesn't run much and we felt it was an acceptable risk. Might not be good to do on a lathe. But since I'm a
cheap bastard I would at least try it and put a clamp on it and see how bad it was. It might work ok just wiring it for
low voltage. And it's possible it's a 60hz motor.

 

[Aleman]

Forgot to add this

 

[ActionDave]

I don't understand the jumpers in the OP's photo.

 

[Rampage_Rick]

X1 Y1 Z1
X2 Y2 Z2
U1 V1 W1
U2 V2 W2

Current configuration is L1-U2-Z1 L2-V2-X1 L3-W2-Y1 X2-U1 Y2-V1 Z2-W1 which is presumably high voltage delta.

To configure for low voltage delta, one would think the correct configuration would be L1-U2-X2-Z1-W1 L2-V2-Y2-X1-U1 L3-W2-Z2-Y1-V1

However if this is in fact a European motor then it might be expecting 380V Wye. A nameplate would be helpful.

 

[Rampage_Rick]

I made a pretty picture:



I'd still want to verify the windings with a meter first... And obviously you need to remove all the existing jumpers. :roll:

 

[Aleman]

View attachment 11140

Forgot to add this

Never mind. Didn't see the XYZ nomenclature. Not sure how that would translate to the diagram I posted.

 

[kwired]

Something tells me just looking at the jumper configuration in the OP that this is a delta wound motor with all twelve leads brought out to the connection box. If so it can be configured for 240 volts, and may or may not work out with 208 applied, maybe use buck/boost transformers if needed to get to 240.

 

[don_resqcapt19]

Something tells me just looking at the jumper configuration in the OP that this is a delta wound motor with all twelve leads brought out to the connection box. If so it can be configured for 240 volts, and may or may not work out with 208 applied, maybe use buck/boost transformers if needed to get to 240.

How is it "delta wound" if you have all 12 leads? You can wire a 12 lead motor for either delta or wye. Of course you do have to know what the voltage ratings of the windings are so you can make the correct connections.

 

[kwired]

How is it "delta wound" if you have all 12 leads? You can wire a 12 lead motor for either delta or wye. Of course you do have to know what the voltage ratings of the windings are so you can make the correct connections.

Good point, I didn't really consider that you could wire it either way if all 12 leads are available, but as you said applied voltage and rated voltage of the windings will matter. Most general purpose motors that I run into with all 12 available typically get delta connected. Motors that are wye connected generally only bring out 9 leads 10,11 and 12 get connected together for either hi or low volts with a wye so they have no real need to be accessible.

OP's motor is not big enough that it would likely need to use wye-delta starting method either.