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An Introduction To Motor Capacitors

December 29, 2021by vasudev_falcon0


A capacitor is a component of electronic equipment that has the property of storing electrical energy in an electrical field. It consists of two terminals and is a passive component. The effect of a capacitor is known as capacitance.

Motor Capacitors

A motor capacitor is an electrical capacitor that tends to alter the current to one of the windings of a single-phase AC motor to create a magnetic field, which can rotate. Generally, motor capacitors are of two types-

Run Capacitors

Start Capacitors

Applications of Motor Capacitors– Air conditioners, jacuzzi spa pumps, powered gates, heat-furnaces, or large fans.

Start Capacitors

Start capacitors are used to increase motor starting torque, through which the motor can be cycled on and off instantly. A start capacitor stays for a long time in a circuit and brings the motor up to a predetermined speed, which is 75% of its full speed. Then, it is removed from the circuit through a centrifugal switch.

After this, a run capacitor is required for a motor to work more efficiently.

Start capacitors work on ratings above 70 micro-F. Start capacitors, which work on ratings above 20 micro-F, are said to be non-polarized aluminum electrolytic capacitors. They consist of non-solid electrolytes, so; they are applicable only for short motor starting times.

The centrifugal switch is the most important component. The motor will not work properly if the switch is damaged or broken. If the centrifugal switch is always on, the motor will not start, and the capacitor is not part of the circuit. If the centrifugal switch is always off, the motor windings will burn out, and the capacitor will be inside the circuit.

Run Capacitors

Run capacitors are used in single-phase AC electric motors, to energize the second-phase windings so that a rotating magnetic field can be created while running the motor.

These capacitors are specially designed for continuous working while the motor is powered, and that’s why electrolytic capacitors are not used.

Usually, run capacitors are polypropylene film capacitors, which are energized throughout the working of the motor. They are rated from 1.5 to 100 micro F. If the capacitance value of the installed capacitor is wrong, then an uneven magnetic field will be created around the rotor. It can lead the rotor to cause hesitation at uneven points, which further leads to irregular rotation. The hesitation of the rotor causes the motor to become noisy, the energy consumption of the motor is increased. Therefore, the overall performance of the motor is dropped and leads the motor to overheat.

Safety Issues Of Motor Capacitors

Heat– The motor capacitor can overheat if it is defective because it is a component of a hot tub circulating pump. In this case, a fire hazard can be seen.

Toxic– Most of the capacitors are made of polychlorinated biphenyls. These are toxic chemicals that possess many long-lasting negative human and wildlife health effects. So, there is a need for replacing these types of capacitors.



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