Motor efficiency is defined as the ratio of what?

Motor efficiency is defined as the ratio of what?

• A. The percent of input power converted to heat in the windings
• B. The percent of input power used to drive the pump
• C. The ratio of mechanical output power to input electrical power
• D. The percent of energy lost to magnetic losses

Answer: (C)

Motor efficiency is the ratio of the useful mechanical power the motor delivers at the shaft to the electrical power it draws from the supply. In formula terms, efficiency equals Pout divided by Pin. Pout is the shaft power, torque multiplied by angular speed. Pin is the electrical input power, which for DC is voltage times current, and for AC is voltage times current times the power factor. This ratio shows how effectively electrical energy is converted into useful motion. The rest of the energy is lost as heat through copper losses in windings, core losses in the magnetic material, and mechanical losses like bearings and windage. So the defining idea is the mechanical output power relative to the electrical input power.

Motor efficiency is the ratio of the useful mechanical power the motor delivers at the shaft to the electrical power it draws from the supply. In formula terms, efficiency equals Pout divided by Pin. Pout is the shaft power, torque multiplied by angular speed. Pin is the electrical input power, which for DC is voltage times current, and for AC is voltage times current times the power factor. This ratio shows how effectively electrical energy is converted into useful motion. The rest of the energy is lost as heat through copper losses in windings, core losses in the magnetic material, and mechanical losses like bearings and windage. So the defining idea is the mechanical output power relative to the electrical input power.