Patent ID: 6863502
Filing Date: 2005-03-08
Classification: F04B

Abstract:
1. A variable speed hydraulic pump, comprising: a variable speed electric pump drive motor; a hydraulic pump unit coupled to the electric motor and a hydraulic fluid source for pumping hydraulic fluid when operated by the motor; and a motor controller electrically connected to the motor for supplying an electrical drive signal to the motor in response to an electrical motor load signal characteristic of said drive signal which varies dependent on the torque exerted by said motor, said electrical motor load signal characteristic being detected by said motor controller, and wherein said motor controller changes said electrical drive signal supplied to said motor so as to output a constant power from said motor to said pump over substantially the entire operating pressure range of said pump; wherein the motor controller is programmed to decrease the speed of the motor when the motor load signal characteristic corresponds to a maximum rated pump pressure so as to maintain essentially said maximum rated pump pressure.