Views: 6 Author: Site Editor Publish Time: 2023-10-25 Origin: Site
1. Look: Check whether the capacitor is bulging or swelling;
2. Listen: Connect the motor and listen to see if there is a buzzing sound from the motor. Turn the rotor by hand to rotate slowly and weakly;
3. Smell: Some capacitors are burnt due to excessive current and have a burning smell on the surface (limited to capacitors with plastic shells);
4. Use the capacitance scale of a multimeter to measure.
The single-phase current flowing through the motor cannot generate a rotating magnetic field, so a capacitor is needed to separate the phases. The purpose is to produce a phase difference of nearly 90゜ in the currents in the two windings to generate a rotating magnetic field.
Capacitive induction motors have two windings, the start winding and the run winding. The two windings are 90 degrees apart in space.A capacitor with a large capacity is connected in series to the starting winding. When the running winding and the starting winding pass through single-phase alternating current,due to the action of the capacitor, the current in the starting winding is 90 degrees ahead of the current in the running winding and reaches the MAX value first.Two identical pulse magnetic fields are formed in time and space, causing a rotating magnetic field to be generated in the air gap between the stator and the rotor.Under the action of the rotating magnetic field, an induced current is generated in the motor rotor. The current interacts with the rotating magnetic field to generate electromagnetic field torque, which causes the motor to rotate.
To make the single-phase motor rotate automatically, we can add a starting winding to the stator. The starting winding and the main winding are 90 degrees apart in space. The starting winding must be connected in series with a suitable capacitor so that the current of the starting winding is within the range of the main winding. The phase difference is approximately 90 degrees, which is the so-called phase separation principle.In this way, two currents that are 90 degrees different in time are passed into two windings that are 90 degrees different in space, and a (two-phase) rotating magnetic field will be generated in space.Under the action of this rotating magnetic field, the rotor can start automatically. After starting, when the speed rises to a certain level, the starting winding is disconnected with the help of a centrifugal switch or other automatic control device installed on the rotor. During normal operation, only the main winding work.Therefore, the starting winding can be made to work in a short time. But many times, the starting winding is not disconnected. We call this kind of motor a capacitive single-phase motor. To change the direction of this kind of motor, it can be achieved by changing the position of the capacitor in series.