Patent ID: 9334864
Filing Date: 2016-05-10
CPC Classification: F04B,F04C

Claim Text:
1. A method of operating a pumping system comprising a pumping mechanism, a motor for driving the pumping mechanism and a variable frequency drive unit having an input for receiving alternating current of relatively high power and first frequency from a power supply and an output coupled to an input of the motor for supplying alternating current of relatively low power and second, variable frequency to the motor, the second frequency having a maximum greater than the first frequency, the method comprising: supplying alternating current to the pump via the variable frequency drive unit; reducing the frequency of the alternating current supplied by the variable frequency drive unit to produce a reduced frequency alternating current in response to an increase in a magnitude of the alternating current drawn by the motor from the variable frequency drive unit; determining that the frequency of the reduced frequency alternating current is below the first frequency and in response, coupling the motor input directly to the power supply for the supply of said relatively high power alternating current to the motor.