RPC Balance Caps for two speed motor?

I'm setting up a second 5hp RPC in the basement. Actually been using it in "rope start" mode for several months, and now time to configure a start cap and contactors. I have balance caps on the one in the garage which for now only runs the milling machine and it is pretty well balanced phase-phase. I like the idea of balanced phase voltages but understand it isn't a requirement. The twist here is the lathe that will run off the one in the basement has a two speed motor. Before I wrap myself around the axle, I thought I'd inquire as to whether you can effectively balance the RPC for the two winding sets? Everything is a compromise, but is the outcome worth the effort? I have a decent selection of run caps on hand.

I'm not sure it will be worth the effort to try and balance for two speeds. Some two speed motors have almost the same amp draw on both speeds.What does the name plate on motor show?Balancing motors is only correct at a given load on a motor and lathe loads can be from lightly loaded to max if drilling a big hole.I have found some motors from Europe can be hard starting in high speed and you may need to add caps to help with that.The size of the converter and the size of lathe motor also has a bearing on the need for caps or their sizing.

The lathe is an EMCO Super 11 (from Austria). I'm not sure if it is related to running off the RPC, but it does start very slowly in the top gear ranges for both high and low speed, 1000 and 2000 rpm. It takes at least five - ten seconds to get up to 2000. Almost like it has a built in soft start. Works fine from 50-600rpm or plug reversing in the lower mid ranges. It won't take much to see how it reacts with some caps and it will be interesting to see of the high speed operation will be affected.

Why not put the caps downstream of the speed selector switch ?

You could install a current sensing relay to connect more capacitance for the higher speed.
Jim.

Jim Kennedy said:

You could install a current sensing relay to connect more capacitance for the higher speed.
Jim.

Click to expand...

If you read up about this:
Voltage Regulation

Watch the manufactured leg voltage when starting. Slow starts are often associated with low torque due to low volts on the 3rd wire.

Putting the caps downstream:
Small Motor