Electric Motor Capacitor Size Chart

These capacitors usually have capacitance values of over 70 µf.

Electric motor capacitor size chart.

Divide the start up energy requirement in joules of the motor by x to arrive at the capacitor size needed in farads. This is basically a question of motor design there is no straightforward regular relationship between capacitance and the motor size in. 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.

The capacitor size for an ac motor is calculated base on the amount of current required to start the motor. Designed for continuous duty the run capacitor always remains energized and connected in the motor s electrical circuit. Capacitors rated above 70uf are considered start capacitors and are generally removed from the circuit electrically during operation. Motor start and motor run capacitors start capacitors.

The run capacitor should have the exact microfarad uf that the motor is rated for. A typical run capacitor rating ranges from 2 µf to 80 µf and is either rated at 370 vac or 440 vac. The start up energy of the motor is found either in its documentation or written on the motor itself. Assuming a start up energy of 0 00033 joules you obtain 0 33 divided by 66 1 which equals 5 0 times 10 6 farads.

A good rule of thumb is 50 to 100 of the total load.