Electric Motor Capacitor Size Chart

These capacitors usually have capacitance values of over 70 µf.

Electric motor capacitor size chart.

The capacitor size for an ac motor is calculated base on the amount of current required to start the motor. Capacitors rated above 70uf are considered start capacitors and are generally removed from the circuit electrically during operation. This is basically a question of motor design there is no straightforward regular relationship between capacitance and the motor size in. Divide the start up energy requirement in joules of the motor by x to arrive at the capacitor size needed in farads.

The start up energy of the motor is found either in its documentation or written on the motor itself. Motor start and motor run capacitors start capacitors. A good rule of thumb is 50 to 100 of the total load. An electric motor capacitor is a device that first stores then releases an electrical charge to help start an electrical motor starting capacitor or to keep it spinning run capacitor the electrical charge or potential energy stored in the capacitor is used to give a power boost to the motor to help it overcome inertia to start rotating.

This is where the rule of 10 of the rating came from for start capacitors only. When install a motor using capacitor for starting or running methods we must sizing the rated of capacitor suitable with motor to get correct starting torque and avoid winding from overheating and can cause a damage. A properly sized run capacitor will increase the efficiency of the motor operation by providing the proper phase. Motor start capacitors are used during the motor startup phase and are disconnected from the circuit once the rotor reaches a predetermined speed which is usually about 75 of the maximum speed for that motor type.

Designed for continuous duty the run capacitor always remains energized and connected in the motor s electrical circuit.