Patent ID: 6124697
Filing Date: 2000-09-26
Classification: H02P

Abstract:
An improved drive for controlling the operative condition of an AC induction motor, the stator winding of which is energized by a variable frequency, variable voltage power supply, the power supply providing a voltage to the stator winding of the motor, the magnitude of which is determined by a characteristic of a first input signal to the power supply, the power supply causing the voltage to be applied to the stator winding at a frequency determined by a characteristic of a second input signal to the power supply, the energization of the stator winding causing a rotating field to be established in the motor, slip appearing in the motor as the difference between the speed of the rotating field and the speed of a rotor of the motor, said drive comprising:a first conductor means (131) couplable to the power supply for supplying the first input signal to the power supply;a second conductor (133) couplable to the power supply for applying the second input signal to the power supply;a speed sensor (134) couplable to the motor rotor for providing a signal indicative of the speed of the motor rotor;a speed reference signal source providing a signal corresponding to a desired speed of the motor;a speed regulating amplifier (110) receiving the signals from said speed sensor and said speed reference signal source and having an output providing a speed error signal;slip determining means (126) responsive to the speed of the motor rotor and the energization frequency of the stator winding for providing a signal indicative of the slip appearing in the motor;a slip regulating amplifier (118) receiving the speed error signal from said speed regulating amplifier and the slip signal from said slip determining means and providing a first output signal; andsumming means for receiving and summing said motor rotor speed signal from said speed sensor and said first output signal of said slip regulating amplifier and providing a second output signal forming said first input signal in said first conductor means and comprising said second input signal in said second conductor.