What is the voltage ratio for dual-voltage motors?

• A. 1 to 2
• B. 2 to 1
• C. 4 to 1
• D. 1 to 1

Answer: (B)

Dual-voltage motors are designed to run on two common line voltages by reconfiguring the windings: in the low-voltage setting the windings are wired in parallel, while in the high-voltage setting they’re wired in series. This setup means the high voltage is twice the low voltage—for example, 240 V vs 120 V. So the voltage ratio is 2 to 1, with the high-voltage operation being double the low-voltage operation.