Induction motor driving system

• US 4,680,525 A
• Filed: 05/02/1985
• Issued: 07/14/1987
• Est. Priority Date: 12/30/1980
• Status: Expired due to Term

• Current Assignee: Fanuc Ltd (Fanuc Corporation)
• Original Assignee: Fanuc Ltd (Fanuc Corporation)
• Inventors: Ishida, Hiroshi, Kobari, Katsuo
• Primary Examiner(s): Smith, Jr., David
• Application Number:
  US06/728,467
• Time in Patent Office: 803 Days
• Field of Search: 318/798, 318/806, 318/803, 318/807-811
• US Class Current: 318/798
• CPC Class Codes: H02P 21/00 Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation

Abstract

The drive system of an induction motor wherein the exciting current command value I_o of the induction motor (14) is held constant and the rotational speed thereof is caused to quickly respond to a command speed by the vector control circuit the induction motor (104) has exceeded a predetermined speed, an exciting current amplitude-controlling circuit (51) increases the exciting current command value in accordance with the rotational speed. The level of the driving supply voltage of the induction motor is sensed by a supply voltage output circuit (52), whereupon the exciting current amplitude-controlling circuit (51) is controlled so that the predetermined speed serving as a threshold value for changing the exciting current command value may be increased in accordance with the sensed level.

Claims

1. An induction motor driving system operatively connected to an induction motor generating a rotational speed signal and a driving supply voltage and operatively connected to receive an exciting current command signal, said induction motor driving system comprising:

exciting current amplitude controlling means, operatively connected to the induction motor, for receiving the rotational speed signal and outputting an amplitude signal;

means, operatively connected to said exciting current amplitude controlling means and the induction motor, for receiving the amplitude signal and increasing the current amplitude of the induction motor in dependence upon the amplitude signal;

detecting means, operatively connected to the induction motor, for receiving and detecting the level of the driving supply voltage of the induction motor and varying the rotational speed signal in accordance with the level of the driving supply voltage;

a supply voltage output circuit providing a supply voltage; and

a level changer, operatively connected between said supply voltage output circuit and said exciting current amplitude controlling means, for receiving and level changing the supply voltage and providing the level changed supply voltage and the rotational speed signal to said exciting current amplitude controlling means.

2. An induction motor driving system according to claim 1, further comprising:

a supply voltage output circuit for providing a supply voltage; and

a level changer, operatively connected between said supply voltage output circuit and said exciting current amplitude controlling circuit, for receiving and level changing the supply voltage and providing the level changed supply voltage and the rotational speed signal to said exciting current amplitude controlling circuit.

3. An induction motor driving system operatively connected to an induction motor generating a rotational speed signal, and operatively connected to receive an exciting current command signal, comprising:

exciting current amplitude controlling means, operatively connected to the induction motor, for receiving the rotational speed signal and outputting an amplitude signal;

means, operatively connected to said exciting current amplitude controlling means and the induction motor, for receiving the amplitude signal and increasing tnhe current amplitude of the induction motor in dependence upon the amplitude signal, thereby increasing the rotational speed of the induction motor;

a supply voltage output circuit providing a supply voltage; and

a level changer, operatively connected between said supply voltage output circuit and said exciting current amplitude controlling means, for receiving and level changing the supply voltage and providing the level changed supply voltage and the rotational speed signal to said exciting current amplitude controlling means.

4. An induction motor driving system according to claim 3, further comprising:

a supply voltage output circuit for providing a supply voltage; and

a level changer, operatively connected between said supply voltage output circuit and said exciting current amplitude controlling circuit, for receiving and level changing the supply voltage and providing the level changed supply voltage and the rotational speed signal to said exciting current amplitude controlling circuit.