Electricity: motive power systems – Induction motor systems – Primary circuit control
Patent
1992-05-07
1993-12-14
Wysocki, Jonathan
Electricity: motive power systems
Induction motor systems
Primary circuit control
318811, H02R 700
Patent
active
052706320
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a driving system for variably controlling of the number revolutions per time of an induction motor, and more particularly, to a driving system featuring an excellent responsiveness to a speed command.
2. Description of the Related Art
It is well known that each switching device of an inverter which supplies the current for driving each phase of an induction motor is turned ON or OFF in accordance with a sinusoidal wave PWM driving signal generated in response to a speed command, thereby performing variable control of the revolution speed of the motor. It is known that, in the sinusoidal wave PWM driving method, the responsiveness to a speed command is improved by carrying out vector control which permits instantaneous torque control of a motor by controlling the phases of driving signals. However, there is limitation in the switching performance of the switching devices of the inverter. Thus, it is difficult for the sinusoidal PWM driving method to properly control a motor's speed when the motor is in operation at such a high-speed as 40,000 revolutions or more per minute.
It is also known to variably control the revolution speed of an induction motor with ON-OFF control of switching devices of an inverter, using a square-wave signal. According to the square-wave drive control method, a motor's speed can be properly controlled even in a high-speed revolution range of the motor. However, in the square-wave drive control method, the vector control, which permits the control of an instantaneous torque of a motor, cannot be performed; therefore, slip control is employed so that a slip frequency can be controlled according to a motor revolution speed and a speed deviation thereof from a speed command to permit control of the average torque of the motor. Thus, the square-wave drive control method is disadvantageous in that it has poor responsiveness to the speed command.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a driving system for an induction motor, which is not only capable of proper speed control in a high-speed revolution area of the induction motor but also features an excellent responsiveness to speed commands.
To fulfill this object, the driving system for an induction motor in accordance with the present invention is equipped with an inverter which includes switching devices related to the individual phases of the motor, a detector for generating a pulse output which represents the actual revolution speed of the motor, and a circuit means which generates a slip pulse and a phase shifting pulse according to a speed command received from a host control unit and output pulses received from the detector, corrects the number of output pulses by using the slip pulse and phase shifting pulse, and generates a square wave signal used for controlling the switching operation of a switching device in accordance with the corrected output pulse.
Preferably, the circuit means has a circuit for generating PWM signals used for controlling the switching operation of the switching devices, and a selector circuit for selectively sending out either a square wave signal or a PWM signal. The selector circuit sends out the PWM signal when the revolution speed of a motor is a specified speed or less, whereas the selector circuit sends out the square wave signal when the revolution speed of the motor exceeds the specified speed.
Further, the circuit means preferably corrects the number of output pulses from the detector by a phase shifting pulse so that the exciting current of each phase of the motor and the secondary current, which are generated as a result of the switching operation of the switching device based on the square wave signal generated according to the corrected output pulses, intersect orthogonally with each other.
As described above, according to the driving system of the present invention, detector output pulses are corrected using a slip pulse and phase shifting pulse which are generated i
REFERENCES:
patent: 4047083 (1977-09-01), Plunkett
patent: 4259628 (1981-03-01), Iwakane et al.
patent: 4266176 (1981-05-01), Fulton
patent: 4321518 (1982-03-01), Akamatsu
patent: 4358726 (1982-11-01), Iwakane et al.
patent: 4543520 (1985-09-01), Danz et al.
patent: 4672288 (1987-06-01), Abbondanti
patent: 4926104 (1990-05-01), King et al.
Hirota Mitsuhiko
Inoue Tadashi
Fanuc Ltd
Wysocki Jonathan
LandOfFree
Driving system for an induction motor having a circuit for gener does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Driving system for an induction motor having a circuit for gener, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Driving system for an induction motor having a circuit for gener will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1708454