Why does a single-phase motor start weakly

Release Time：

2025-06-11

From the perspective of a single-phase motor, it has coils, bearings, starting capacitors, and centrifugal switches, all of which can cause the motor to start weakly. For example, a short circuit or even burnout between coil turns can be measured with a multimeter. Due to factors such as poor working environment, foreign objects may enter the bearing and deteriorate its lubrication quality, causing wear or deformation. The centrifugal switch of a single-phase motor should be open when the motor is running normally and closed when it is not working. It may be due to other reasons that the centrifugal switch remains in an open state.

Why does a single-phase motor start weakly
Why does a single-phase motor start weakly? This article will analyze it for everyone.

Malfunctions in single-phase motor capacitors are very common, either due to a decrease in the leakage capacitance or the use of capacitors with excessive capacity after maintenance. Why does choosing too large a capacitance here cause the motor to start weakly or burn out?

Sometimes it is believed that a larger starting torque is better, and that using a large capacity capacitor is sufficient. In fact, this approach appears to increase the starting torque on the surface, but it also depends on its starting current. At this point, the rate of increase in motor starting current is greater than before, which is very detrimental to the motor.

For example, the capacitor connected in series with the starting winding of a single-phase capacitor starting motor only doubles, and the starting torque increases by 50%. Although the starting torque is indeed much larger than before, the starting current increases by about 200%. If the capacitance increases by two times during the operation of a single-phase motor, the starting torque also increases by nearly twice, but the motor efficiency will decrease by 50%. Such low efficiency cannot drive the load with the motor.

If the problem is not solved and the motor continues to work, the consequence is that the motor will be overloaded for a long time and eventually burn out the winding. So it is important to remind everyone to pay attention to these issues.