The electrical power issues that most frequently affect industrial plants include voltage sags and swells, harmonics, transients, and voltage and current unbalance.
Most problems with single-phase motors involve the centrifugal switch, thermal switch, or capacitor(s). If the problem is in the centrifugal switch, thermal switch, or capacitor, the motor is usually serviced and repaired. However, if the motor is more than 10 years old and less than 1 HP, the motor is usually replaced. If the motor is less than 1/8 HP, it is almost always replaced.
How to measure output voltage from a VFD to a motor