How can I identify the main and auxiliary windings of a single phase induction motor which has only three terminals (1.Red, 2. Yellow & 3. Black) out of the device? How to connect capacitor and power supply to it?
Measure the winding resistances. Auxiliary windings are often thinner and therefore have a higher resistance (even if it's just a little bit higher).
Once you know which terminals are used for each of the two windings, you can connect them to the power supply and the capacitor as shown in the following picture:
The picture was taken from the book "R. Fischer: Elektrische Maschinen, 15.Auflage, Hanser Verlag München"
Apply a (small) DC voltage step to a test circuit, consisting of a resistor and one of the windings in serial combination. Capture the current with an oscilloscope. Measure the time constant of the system and calculate the inductance L of the winding. Repeat this process for the second winding. The winding with the higher inductance value should be the main winding.
- If the direction of rotaion of motor is shown or known then ther is a solution except exact value of capactitor ( however the norms says.. loking at shaft end motor should generally rotate in clock-wise direction. I am not sure of your motor).
- connect a capacitor as suggested by Simon and connect supply between common terminal and capacitor ( winding) termnal and if motor runs in opposite direction then the shift the connection to other treminal of capacitor . Now the motor will rotate in the specified direction. the motor terminal which is connected directly to supply is main winding and the one connected through capacitor is aux. winding. vtingole
first of all identify common terminal by checking resistance. and connect the capacitor b/w main and aux terminal. and connect the terminal of common and main or aux as per required direction of rotation.
The aux winding should have the greatest resistance as this is what puts it out of phase with main winding to give an apparent rotating magnetic field. This is achieved by using thinner wire or alternately resistance wire.