Inverter control method and apparatus

• US 5,744,927 A
• Filed: 01/19/1995
• Issued: 04/28/1998
• Est. Priority Date: 01/28/1994
• Status: Expired due to Term

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Hayashida, Takahiro
• Primary Examiner(s): Sircus, Brian
• Application Number:
  US08/374,873
• Time in Patent Office: 1,195 Days
• Field of Search: 318/599, 318/807-811, 388/805, 388/812, 388/814, 388/820, 388/832, 388/804, 388/811
• US Class Current: 318/599
• CPC Class Codes: H02P 21/0003 Control strategies in general, e.g. linear type, e.g. P, PI, PID, using robust control

Abstract

An inverter control apparatus and method for a motor driven by an inverter circuit. The primary current of the motor is detected by a detector circuit and is used in combination with a primary current command value to provide pulse-width modulation of the inverter circuit. The inverter is controlled by a switching circuit that can change the PWM frequency based on any one or more factors, including motor speed, motor speed or position control mode, equivalent load factor and detected temperature.

Claims

1. An inverter control apparatus comprising a current detector for detecting the primary current of a motor driven by an inverter circuit, a speed detector for detecting the speed of said motor, and a pulse width modulation circuit for pulse-width-modulating said inverter circuit in accordance with the primary current detection value of said current detector and a primary current command value, said inverter control apparatus comprising constant torque-constant output PWM switching means for judging whether the motor speed detected by said speed detector is in a constant torque region or in a constant output region to switch the PWM frequency of said pulse width modulation circuit and to set the PWM frequency with the function of the motor speed in said constant output region.

2. The inverter control apparatus as set forth in claim 1, wherein said inverter control apparatus further comprises heat sink-ambient temperature difference PWM switching means for detecting the heat sink temperature and ambient temperature of said inverter apparatus to switch the PWM frequency of said pulse width modulation circuit according to a temperature difference.

7. The inverter control apparatus as set forth in claim 1, wherein said inverter control apparatus further comprises switching means for selecting between fixing and varying the PWM frequency of said pulse width modulation circuit.

14. The inverter control apparatus as set forth in claim 7, wherein said switching means is a user switching means which allows a user to make a selection.

3. An inverter control apparatus comprising:

a current detector for detecting the primary current of a motor driven by an inverter circuit;

a pulse width modulation circuit for pulse-width-modulating said inverter circuit in accordance with the primary current detection value of said current detector and a primary current command value; and

a speed-position PWM switching means for judging whether the motor is in a speed control mode or in a position control mode to switch the PWM frequency of said pulse width modulation circuit.

10. The inverter control apparatus as set forth in claim 3, wherein said inverter control apparatus further comprises heat sink-ambient temperature difference PWM switching means for detecting the heat sink temperature and ambient temperature of said inverter apparatus to switch the PWM frequency of said pulse width modulation circuit according to a temperature difference.

4. An inverter control apparatus comprising:

a current detector for detecting the primary current of a motor driven by an inverter circuit;

a pulse width modulation circuit for pulse-width-modulating said inverter circuit in accordance with the primary current detection value of said current detector and a primary current command value; and

a heat sink-ambient temperature difference PWM switching means for detecting the heat sink temperature and ambient temperature of said inverter apparatus to switch the PWM frequency of said pulse width modulation circuit according to a temperature difference.

5. An inverter control apparatus comprising:

a current detector for detecting the primary current of a motor driven by an inverter circuit;

a pulse width modulation circuit for pulse-width-modulating said inverter circuit in accordance with the primary current detection value of said current detector and a primary current command value;

an acceleration/deceleration-steady state PWM switching means for judging whether the motor is executing an acceleration/deceleration operation or a steady-state operation to switch the PWM frequency of said pulse width modulation circuit; and

a heat sink-ambient temperature difference PWM switching means for detecting the heat sink temperature and ambient temperature of said inverter apparatus to switch the PWM frequency of said pulse width modulation circuit according to a temperature difference.

6. The inverter control apparatus as set forth in claim 5, wherein said inverter control apparatus further comprises speed-position PWM switching means for judging whether the motor is in a speed control mode or in a position control mode to switch the PWM frequency of said pulse width modulation circuit.

8. An inverter control apparatus comprising:

a current detector for detecting the primary current of a motor driven by an inverter circuit;

a pulse width modulation circuit for pulse-width-modulating said inverter circuit in accordance with the primary current detection value of said current detector and a primary current command value;

an acceleration/deceleration-steady state PWM switching means for judging whether the motor is executing an acceleration/deceleration operation or a steady-state operation to switch the PWM frequency of said pulse width modulation circuit;

switching means for selecting between fixing and varying the PWM frequency of said pulse with modulation circuit; and

a speed-position PWM switching means for judging whether the motor is in a speed control mode or in a position control mode to switch the PWM frequency of said pulse width modulation circuit.

9. The inverter control apparatus as set forth in claim 8, wherein said inverter control apparatus further comprises switching means for selecting between fixing and varying the PWM frequency of said pulse width modulation circuit.

11. A method of controlling the operation of an inverter circuit for driving a motor comprising:

providing a primary current command value;

detecting the value of the primary current of the motor driven by said inverter circuit;

pulse-width-modulating said inverter circuit in accordance with said detected primary current value and said primary current command value;

judging a state of said motor operation; and

switching the PWM frequency of said pulse width modulation step according to said judged state;

wherein said judging step comprises judging whether said motor is in a position control mode or a speed control mode.

12. A method of controlling the operation of an inverter circuit for driving a motor comprising:

providing a primary current command value;

detecting the value of the primary current of the motor driven by said inverter circuit;

pulse-width-modulating said inverter circuit in accordance with said detected primary current value and said primary current command value;

judging a state of said motor operation;

shutting off gates of said inverter circuit at a beginning of a predetermined period of time TG;

switching the PWM frequency of said pulse width modulation step according to said judged state at a time TG/2; and

turning on the gates of said inverter circuit at the end of the predetermined period of time TG.

13. An inverter control apparatus comprising:

a current detector for detecting the primary current of a motor driven by an inverter circuit;

a pulse width modulation circuit for pulse-width-modulating said inverter circuit in accordance with the primary current detection value of said current detector and a primary current command value; and

a user switching means for allowing a user to select between fixing and varying the PWM frequency of said pulse width modulation circuit.

15. An inverter control apparatus comprising:

a current detector for detecting the primary current of a motor driven by an inverter circuit;

a pulse width modulation circuit for pulse-width-modulating said inverter circuit in accordance with the primary current detection value of said current detector and a primary current command value;

an acceleration/deceleration-steady state PWM switching means for judging whether the motor is executing an acceleration/deceleration operation or a steady-state operation to switch the PWM frequency of said pulse width modulation circuit; and

a user switching means for allowing a user to select between fixing and varying the PWM frequency of said pulse with modulation circuit.