The large main motors on rolling mills are air cooled and have a heat exchanger supplied with cooling water. The cooling fan runs continuously at constant speed using large amounts of energy, even when the motor is lightly loaded. A variable frequency drive is used to power the fan motor so that the speed can be reduced when motor loading is low and cooling is not required, thereby considerably reducing energy consumption.
The cooling system optimizer determines the speed of the motor cooling fan so as to obtain the required main motor cooling air flow. To do this the optimizer estimates the temperature rise of the main motor based on the real-time current, winding temperature, inlet temperature and outlet temperature, and then adjusts the speed of the fan motor to produce the desired cooling flow.
Actual tests on rolling mill motors have shown that energy savings of up to 80% can be achieved with this control method.
