Looking closely, we can see an interesting phenomenon with the hot motor curve. As the motor temperature rises, the no-load speed also increases. This is due to the effect heat has on the magnets. As the motor cools down, the speed will return to normal. The same concept applies to the other end of the curve where stall torque is reduced for a “hot” motor. Notice the efficiency curve and how under ideal circumstances the motor’s peak efficiency will occur near the motor’s operating torque.

DC Motor Characteristics

• Runs on DC power or AC line voltage with a rectifier
• Operating speeds of 1,000 to 5,000 rpm
• 60-75% efficiency rate
• High starting torque
• Low no-load speeds