I want to know why the starting winding of (2 ton) reciprocating compressor's motor have high voltage than running winding? I have attached the voltage that I have captured from oscilloscope.
This reciprocating compressor has potential relay with start capacitor and also have run capacitor. Start capacitor provide the start torque, but what is the purpose of running capacitor? I could see that, starting winding have high starting current. But when the starting capacitor is disconnected from potential relay, the voltage at starting winding to common become 275 V, which is very high but the point that is triggering the start winding current. Start winding current reduced to 0.1 A or more less. Why and how this can that the is high but current is almost zero? In this picture, you can see that the yellow is the starting voltage which is high. Blue the running voltage with respect to common. RMS voltage of starting winding is 276 V and RMS voltage of running winding is 226 V.
The current through starting is 0.1 A and the current through running winding is 12 A.