Single Phase Motors have a wide range of applications both domestic and industrial. They have two windings for Starting and Running purposes. Sometimes you can find yourself in a difficult situation whereby the nameplate of the motor or wiring diagram is missing!! Sometimes the motor itself is inaccessible like in the case of borehole pumps.
Usually, there are three wires that come out of the motor casing. The start winding is normally connected in series with a start capacitor. Some Motors have only the start capacitors while others have the start and run capacitors.
The start capacitor is only connected when starting the motor and its disconnected automatically by a centrifugal switch when the motor is up to speed.
If you open the single-phase motor, you will find out that your motor has two types of winding of which one is made from a thick wire gauge and one thin. The thick wire gauge winding is the main winding and the thin wire gauge winding is starting winding.
But this Identification can only be done by disassembling the motor. This is mostly not necessary because the wiring diagram is printed on the motor nameplate.
The start winding has a high resistance compared to the run winding
Its best to measure the ohms with a analog multimeter
Resistance between A+B=15
A+C=20
B+C=25
So the results are A=35, B=40, and C=45.
Which wires have been named A, B and C? Which winding is the COMMON winding?