Nola Energy Savers for Induction Motors - How they work

The Nola energy saver system for induction motors relies on the correlation between the power factor of the motor and the efficiency of the motor in that as the power factor falls, the efficiency of the motor also falls.

Reducing the voltage applied to the motor will reduce the iron loss of the motor, but it can also increase the copper loss of the motor. A net reduction in the power consumed by the motor will only occur when the work current of the motor is less than the magnetising current. This will occur when the power factor is significantly less than cos(45) = 0.7

The Nola patent describes monitoring the power factor of the motor and when this power factor is less than a preset value, reducing the voltage applied to the motor. As the voltage is reduced, the magnetising current is reduced, the iron loss current is reduced, and the work current is increased.
Voltage reduction continues until the power factor is equal to the preset value. If load is applied to the motor, the power factor increases and so the voltage is increased. The controller adjusts the voltage in a manner to try to keep the measured power factor equal to the preset value.

Voltage reduction is achieved by the use of a phase controlled triac or phase controlled reverse parallel connected SCRs.