| 摘要 |
A pumping system has a motor (32) for driving a pumping mechanism (30). A variable frequency drive unit (36) has an input for receiving electrical energy of relatively high power and first, fixed frequency from a power supply, and an output coupled to an input (46) of the motor for supplying electrical energy of relatively low power and second, variable frequency to the motor. This second frequency preferably has a maximum value greater than the first frequency. A control circuit (50) is provided for selectively coupling the motor input (46) directly to the power supply for the supply of said relatively high power energy to the motor to maximise the torque that can be produced by the pumping mechanism. After a period of time the control circuit terminates the direct coupling of the motor input to the power supply for the supply of said relatively low power energy to the motor.
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