Sunday, 22 February 2015

What should you do when your fan’s capacitor/condenser is not working?

What should you do when your fan’s capacitor/condenser is not working?
We all know that our fan is a single phase AC induction motor. As there is no rotating magnetic field in single phase, single phase motors are not self starting. To solve this problem we temporarily we convert it into a two phase induction motor during starting. For this purpose, the stator of a single phase induction motor is provided with an extra starting winding, called auxiliary winding. The starting winding and the running winding are spaced 90 degree electrically apart from each other. There is a phase difference between starting and running winding current, that is ideally 90 degree. Here capacitor mainly creates that phase difference.
Now suppose your fans capacitor is not working and you don’t have a new one in your lab. Then what should you do?
Method 1- in a split phase motor, running winding has less resistance and more reluctance and starting winding has high resistance and low reluctance. So you put a resistance of high wattage value in series with the starting winding. Then starting winding current lags the voltage with a small angle and running winding current lags with voltage by a large angle. So, a phase difference is created. The motor becomes self starting.
Note- if the wattage value is less the resistor may burnt out.