Troubleshooting single-phase compressors requires a technician to have a proficient understanding of capacitors. The run capacitor is one of two types of capacitors that could be found on single-phase compressors.
The run capacitor is used to improve the running efficiency of a compressor’s motor. The run capacitor is placed in series with the start winding of the compressor and will remain in the circuit as the motor operates. As current flows through the run capacitor and the start winding, it causes a phase shift of the motor’s current, thus improving the power factor of the motor. Since the run capacitor remains in the circuit, it needs to be able to dissipate the heat generated by being in continuous operation. This is done by its design. The run capacitor is oil-filled to allow the capacitor to dissipate the heat generated.