What is Electric Motor ?

is running.[3]

Run capacitors are designed for continuous duty while the motor is powered, which is why electrolytic capacitors are avoided, and low-loss polymer capacitors are

used. Run capacitors are mostly polypropylene film capacitors (historically: metallised paper capacitors) and are energized the entire time the motor is running.[1] Run

capacitors are rated in a range of 1.5 to 100 µF, with voltage classifications of 370 V or 440 V.[1]

If a wrong capacitance value is installed, it will cause an uneven magnetic field around the rotor. This causes the rotor to hesitate at the uneven spots, resulting in

irregular rotation, especially under load. This hesitation can cause the motor to become noisy, increase energy consumption, cause performance to drop and the motor

to overheat.[3]

Dual run capacitors

A dual "run capacitor" supports two electric motors, such as in large air conditioner or heat pump units, with both a fan motor and a compressor motor. It saves space

by combining two physical capacitors into one case. The dual capacitor has three terminals labeled "C", "FAN", and "HERM", which stand for the Common, Fan, and

HERMetically sealed compressor.[5]

Dual capacitors come in a variety of sizes, depending on the capacitance (µF), such as 40 plus 5 µF, and also the voltage. A 440 volt capacitor can be used in place of

a 370 volt, but not a 370 in place of a 440 volt.[2] The capacitance must stay the same within 5% of its original value.[2] Round cylinder-shaped dual run capacitors are

commonly used for air conditioning, to help in the starting of the compressor and the condenser fan motor.[2] An oval dual run capacitor could be used instead of a

round capacitor, but the mounting strap should be changed to better fit the oval shape.[2]

A faulty run capacitor often becomes swollen, with the sides or ends bowed or bulged out further than usual: it can be clear to see that the capacitor has failed because

it is swollen or even blown apart causing the capacitor's electrolyte to leak out. Some capacitors are built with a "Pressure Sensitive Interrupter" design that causes

them to fail before internal pressures can cause serious injury. One design causes the top of the capacitor to expand and break internal wiring.[6]