# motor start and run windings

Discussion in 'General Electronics Chat' started by bonkers, Dec 17, 2008.

1. ### bonkers Thread Starter Member

Dec 11, 2008
14
0
When doing a voltage test cross a run or start winding to common should the meter red o volts if the winding is closed and 120 if the winding is open or 120 in either case. Would it act the same as a switch or would the resistance of the windings make a difference.

2. ### mik3 Senior Member

Feb 4, 2008
4,846
63
It will be 120V either case. It is not the same a switch because windings have resistance and reactance (they are inductors). Even switches have a small resistance.

3. ### bonkers Thread Starter Member

Dec 11, 2008
14
0
Funny, I got a big laugh out of that one. Exactly what is a spectrum analizer, and thanks for answer on motor windings, but what if motor winding is open, wouldn't the reading on the meter read 120 volts instead of 0 volts. This is assuming that the motor is not running, and only current is going through the windings with one open and one closed. In another words, motor is only getting current through one winding and trying to start, while the other winding is open. Or is one winding having an effect on the other winding since they are both in paralel, would this be the inductance reactance your talking about.

4. ### c_h_a_r_l_i_e_ New Member

Dec 17, 2008
1
0
in all 3-phase motors all of the windings should have the same resistance and receive the same voltage. in some cases motors motors will have a cyntrifigul switch that kicks out at about 75% of it top rpm. so when the motor is running the start winding is kicked out thus it will not read voltage because the circuit is broken by the switch. if you need to figure out which winding is what on the termenal the run windings have the highest resistance, the run windings will have less. hope this helps

intellitec college student

Dec 11, 2008
14
0