Star-delta conversion

[Maker]

I've taken the 415V motor from my mill apart so I can run it off my 230V inverter

I found all the connections between poles, and the star point (lower right) and multimetered everything to find each pole is about 1.5Ω and 6Ω from any of the supply lines to the star point with no weird cross connections so I'm happy its a functional motor.


I cut the star point and got all 6 ends of the required connections tinned, then went in for lunch. Now I can't remember which wires came from the supply and which from the star. Is there a way I can test which is which?

 

[Maker]

Oh hang on, does it even matter which end goes to which, as long as they're connected into a triangle?

 

[Newlands]

Why are there so many wires? Is it a two speed motor? When I did my 3 phase motor I had 6 wires in total, i.e. 3 coils with one wire from each end.

 

[Maker]

Why are there so many wires? Is it a two speed motor? When I did my 3 phase motor I had 6 wires in total, i.e. 3 coils with one wire from each end.

Its a 4 pole motor so there's a total of 12 coils in it, I had to strip all the insulated connections to find the star point, the other 9 just need to be re-insulated and tucked away.

 

[Seadog]

If you reverse some windings you'll end up with a motor that won't run, or sits and hums. It's important to have the star end of one coil going to the start of the next. The order you connect them doesn't matter. If the motor runs in the wrong direction you just reverse two phases.

I think you need to identify which way the end plate was fitted so that you can then see which of the ends reach the connector strip. Once you've done that it's simple. There is usually something that you can use as a witness mark to orientate it correctly.

Thought - it doesn't matter which way round the coils are, just so long as they're all in phase. there are two sets of wire you could group as the star point, therefore pick one set, they become the star end and the others are the phases. As before, if it rotates in the wrong direction reverse two of the phases

 

[Pete.]

I disagree I think it doesn't matter. So long as you identify each coil and don't join both ends of the same one, you're good.

 

[Seadog]

I disagree

With which bit?

 

[Maker]

I think you need to identify which way the end plate was fitted so that you can then see which of the ends reach the connector strip. Once you've done that it's simple.

I've already desoldered the original leads but they were quite long anyway so that wouldn't have helped.

 

[Seadog]

Looking at your photos again I would hazard a guess that the star was formed from the 2nd, 4th and 6th wires counting from the left. Two wires seem to have a fabric insulation whereas the remaining four look like PVC or similar. If that is the case it's the only combination that would match the first photo. Meter them first to make sure they are all independent before reconnecting.

 

[Maker]

Looking at your photos again I would hazard a guess that the star was formed from the 2nd, 4th and 6th wires counting from the left. Two wires seem to have a fabric insulation whereas the remaining four look like PVC or similar. If that is the case it's the only combination that would match the first photo. Meter them first to make sure they are all independent before reconnecting.

Don't know how I missed this post first time around (Or missed my original picture) but I connected it as you described, put heatshrink over all the joins and tie wrapped it down.

It runs off my inverter perfectly, now to stick it back in the mill, easier said than done.

 

[Seadog]

I'm glad it all worked out as hoped. Well done