Voltages must be within ______% of the motor rating.

• A. 5%
• B. 10%
• C. 15%
• D. 20%

Answer: (B)

Motor voltage tolerance is about how much the supply can vary from the motor’s rated voltage while it still runs safely. In practice, motors are designed to operate well when the applied voltage stays within about ±10% of the rated voltage. This range accounts for normal utility and feeder fluctuations, ensuring the motor develops enough torque to start and run without overheating. If voltage falls more than about 10%, the motor may struggle to start or deliver full torque, potentially overheating or tripping. If voltage climbs above that range, winding current and heat can increase, risking insulation damage. Therefore, the acceptable variation is around 10%.