Here is the schematic of an industrial mixer. M1 is a two speed motor. My question is what are the coil heads corresponding terminals. If x,y,z corresponds to u,v,w in order how does y and v end up on the same phase (L2) ? Am I missing something here? If you follow the path from L2 to Y to V you end up back on L2 resulting in no current flow as you are on the same phase. I am in Canada if that helps

 

Not sure of what you are asking, I don't see any issue unless I am missing something?

 

Not sure of what you are asking, I don't see any issue unless I am missing something?

Follow L2 on the delta contactor, if y is the coil head and v is the other end of the coil when the delta contactor energizes it seems you have no current going through that winding on the motor unless there’s somthing I’m not understanding.

 

Follow L2 on the delta contactor, if y is the coil head and v is the other end of the coil when the delta contactor energizes it seems you have no current going through that winding on the motor unless there’s somthing I’m not understanding.

I interpret that you have an understanding of 3 coils with the following endpoints:
X to U
Y to V
Z to W

And when KM1 and KM3 are both energized, the center coil would have no potential difference across it because the same phase would be applied to both ends of the coil.

If I interpret that correctly...

If your understanding were correct then you would be correct. But I think you are looking at this like a wye/delta starter when it is a bit different than that. KM1 and KM3 will never be energized at the same time. KM1 is ON for low speed while KM2 and KM3 are OFF. For high speed KM1 is OFF while KM2 and KM3 are both ON.

This scheme switches between series and parallel-wye. Substitute X,Y,Z in your drawing for 1U,1V,1W below and U,V,W in your drawing for 2U,2V,2W below. Hopefully this helps it make sense.





In the diagram on the left above, KM1 applies voltage to the outer leads of the wye configuration, with the two coils of each phase in series.

In the diagram on the right above, KM2 shorts the outer leads of the wye together, placing the outer coils in parallel with (and now in reverse polarity with) the inner coils. This results in the following:

• applies doubled voltage across each of the coils
• Halves the number of stator poles (making the motor faster). This is a bit counterintuitive at first (at least to me). It seems this should double the poles (making the motor slower) but if you think about the direction of current flow between the two scenarios, you will notice that the parallel configuration yields basically duplicate sets of coils in parallel which is effectively half the number of EM poles as the series configuration in which each coil is effectively a unique pole.
• The polarity reversal would ordinarily reverse the direction of the motor, hence the swapping of U,W in your drawing (and you can note the same phase swapping by terminal# in the diagrams I posted).