In the 7.5-HP motor example, what is the rated voltage?

• A. 208 V
• B. 240 V
• C. 480 V
• D. 600 V

Answer: (B)

The key idea here is that a motor’s rated voltage is the specific voltage value printed on its nameplate that the windings are designed to operate at continuously. For this 7.5‑HP motor example, the nameplate specifies 240 volts, so it should be powered by a 240 V supply to deliver its rated horsepower and full torque without overheating. If you feed it a lower voltage, the motor will struggle to develop torque and may draw more current, while a higher voltage can over stress the insulation and shorten the motor’s life. Some motors can be wired for different voltages, but you must follow the nameplate and wiring diagram to set the correct winding configuration. The other voltages listed would only be appropriate if the motor is designed for those voltages; otherwise they won’t provide the expected performance.