Method of starting a permanent-magnet synchronous motor equipped with angular position detector and apparatus for controlling such motor

• US 5,801,509 A
• Filed: 09/27/1996
• Issued: 09/01/1998
• Est. Priority Date: 01/27/1995
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Yaskawa Denki
• Original Assignee: Kabushiki Kaisha Yaskawa Denki
• Inventors: Fujii, Syuuichi, Yamamoto, Eiji, Sawa, Toshihiro, Sonoda, Sumitoshi
• Primary Examiner(s): Sircus, Brian
• Application Number:
  US08/714,078
• Time in Patent Office: 704 Days
• Field of Search: 318/700-724, 318/661, 318/729, 318/652-660, 318/600-605
• US Class Current: 318/705
• CPC Class Codes: H02P 2205/01 Current loop, i.e. comparison of the motor current with a current reference
• CPC Class Codes: H02P 6/16 Circuit arrangements for detecting position
• CPC Class Codes: H02P 6/17 and for generating speed information
• CPC Class Codes: H02P 6/20 Arrangements for starting H02P6/08 takes precedence

Abstract

An angular position detector for generating trains of A- and B-phase pulses which are 90° out of phase with each other and a C-phase pulse per rotation are mounted on a permanent-magnet synchronous motor such that a magnetic pole origin of permanent magnets and a position where the C-phase pulse is generated agree with each other. After a power supply voltage is applied and in an initial stage before the permanent-magnet synchronous motor is operated normally, a motor control apparatus operates a current control loop with an alternating current command having a constant amplitude and a low frequency to supply an alternating current having a low frequency to the permanent-magnet synchronous motor for thereby rotating the rotor of the permanent-magnet synchronous motor from a stop at a low speed. The motor control apparatus then detects arrival at a magnetic pole reference when a C-phase pulse is detected, and detects an angular displacement of the magnetic poles of the rotor using counts of the A- and B-phase pulses counted in synchronism with the rotation of the rotor after the C-phase pulse is detected.

Claims

1. A method of starting a permanent-magnet synchronous motor in a permanent-magnet synchronous motor system which includes the permanent-magnet synchronous motor which has a rotor having permanent magnets as magnetic poles for driving the rotor, and an angular position detector mounted on a rotatable shaft of the permanent-magnet synchronous motor and having an A- and B-phase pulse train generating means for generating a number of A- and B-phase pulses per rotation which have respective electrical angles that are 90°

out of phase with each other and a C-phase pulse train generating means for generating a C-phase pulse per rotation, and a motor control apparatus having a speed control loop and a current control loop for energizing the permanent-magnet synchronous motor said angular position detector being installed such that a magnetic pole reference of the permanent magnets of the rotor and a position where the C-phase pulse is generated agree with each other, said method comprising the steps of;

when a power supply voltage is applied and in an initial stage before the permanent-magnet synchronous motor is operated normally, for starting to operate the permanent-magnet synchronous motor, supplying an angular displacement signal for a current command to the current command loop at a predetermined angle in each preset unit time, operating the speed control loop with a speed signal, which represents an angle change in said each preset unit time, as a command for a speed controller, for thereby controlling an amplitude of said current command, causing said motor control apparatus to supply an alternating current having a low frequency to the permanent-magnet synchronous motor for thereby rotating the rotor of the permanent-magnet synchronous motor from a stop at a low speed; and

detecting arrival at the magnetic pole reference when a C-phase pulse is detected, switching the angular displacement signal for the current command to an angular displacement signal for the current command which is produced using counts of the A- and B-phase pulses counted in synchronism with the rotation of the rotor with the position of the C-phase pulse being used as an origin, and switching the command for the speed controller to a predetermined speed command for the speed control to a predetermined speed command for thereby operating the permanent-magnet synchronous motor.

2. A method according to claim 1, wherein said rotor starts being rotated in the initial stage in response to the application of an alternating current power supply.

3. A method according to claim 1, wherein said rotor starts being rotated in the initial stage in response to an external command signal.

4. A method according to claim 1, wherein a direct current is supplied for a given period of time at an optional angle at the time of starting to detect the magnetic pole reference, thereafter an alternating current having a low frequency is supplied to the permanent-magnet synchronous motor based on an angular displacement signal from an angle signal generator in the permanent-magnet synchronous motor, and the permanent-magnet synchronous motor is stably rotated until a C-phase pulse from the angular displacement detector is detected.

5. An apparatus having a speed control loop and a current control loop, for controlling a permanent-magnet synchronous motor having a rotor having permanent magnets as magnetic poles for driving the rotor, and an angular position detector mounted on a rotatable shaft of the permanent-magnet synchronous motor and having an A- and B-phase pulse train generating means for generating a number of A- and B-phase pulses per rotation which have respective electrical angles that are 90°

out of phase with each other and a C-phase pulse train generating means for generating a C-phase pulse per rotation, the angular position detector being assembled so as to output a C-phase pulse when a magnetic pole reference of the rotor reaches a predetermined angle of a stator, said apparatus comprising;

a main circuit and a control circuit;

said main circuit comprising a converter for converting an alternating current into a direct current and outputting the direct current, a smoothing capacitor for smoothing the direct current outputted from the converter, and an inverter for energizing the permanent-magnet synchronous motor;

said control circuit comprising speed detecting means for converting a signal from said angular position detector into a speed signal and outputting the speed signal, speed control means for controlling a speed of the permanent-magnet synchronous motor with said speed signal and a speed command, angle signal detecting means for generating an angular displacement signal for a current command which is produced using counts of the A- and B-phase pulses counted in synchronism with the rotation of the rotor with the position of a C-phase pulse from the angular position detector being used as a magnetic pole reference of the rotor when the C-phase pulse is outputted, first current command generating means for generating a current command based on an output signal supplied from said speed control means and an output signal supplied from said angle signal detecting means, detecting an angular displacement of the magnetic poles of the rotor of the permanent-magnet synchronous motor using counts of the A- and B-phase pulses subsequently counted in synchronism with the rotation of the rotor when a C-phase pulse is thereafter detected during rotation of the permanent-magnet synchronous motor, and thereafter outputting a magnetic pole reference detection completion signal, second current command generating means for outputting an alternating current command having a constant amplitude and a low frequency, current command switch means for switching between outputting the current command outputted from the first current command generating means and outputting the current command outputted from the second current command generating means, magnetic pole detection command generating means for starting said second current command generating means and switching said current command switch means to said second current command generating means in an initial stage before a normal operation command is given to the permanent-magnet synchronous motor after a power supply voltage is applied to the permanent-magnet synchronous motor, and switching said current command switch means to said first current command generating means when said magnetic pole reference detection completion signal is outputted, current detecting means for detecting a current outputted from said inverter to the permanent-magnet synchronous motor, and current control means for controlling a current of said inverter with the current command supplied from said current command switch means and a detected signal from said current detecting means.

6. An apparatus having a speed control loop and a current control loop, for controlling a permanent-magnet synchronous motor having a rotor having permanent magnets as magnetic poles for driving the rotor, and an angular position detector mounted on a rotatable shaft of the permanent-magnet synchronous motor and having an A- and B-phase pulse train generating means for generating a number of A- and B-phase pulses per rotation which have respective electrical angles that are 90°

out of phase with each other and a C-phase pulse train generating means for generating a C-phase pulse per rotation, the angular position detector being assembled so as to output a C-phase pulse when a magnetic pole reference of the rotor reaches a predetermined angle of a stator, said apparatus comprising;

a main circuit and a control circuit;

said main circuit comprising a converter for converting an alternating current into a direct current and outputting the direct current, a smoothing capacitor for smoothing the direct current outputted from the converter, and an inverter for energizing the permanent-magnet synchronous motor;

said control circuit comprising speed detecting means for converting a signal from said angular position detector into a speed signal and outputting the speed signal, speed control means for controlling a speed of the permanent-magnet synchronous motor with said speed signal and a speed command, angle signal detecting means for generating an angular displacement signal for a current command which is produced using counts of the A- and B-phase pulses counted in synchronism with the rotation of the rotor with the position of a C-phase pulse from the angular position detector being used as a magnetic pole reference of the rotor when the C-phase pulse is outputted, angle command generating means for generating an angular displacement signal at a low frequency and a speed signal representing an angle change in each preset unit time of the angular displacement signal, angle command switch means for switching between outputting the angular displacement signal outputted from said angle signal detecting means and outputting the angular displacement signal outputted from said angle command generating means, speed command switch means for switching between outputting a speed command supplied to said apparatus and outputting a speed command outputted from said angle command generating means, magnetic pole reference detecting means for outputting a magnetic pole reference detection completion signal and outputting a reset signal to reset the angular displacement signal to zero to said angle signal detecting means when a C-phase pulse from said angular position detector is detected, magnetic pole detection command generating means for switching said angle command switch means and said speed command switch means to said angle command generating means in an initial stage before a normal operation command is given to the permanent-magnet synchronous motor after a power supply voltage is applied to the permanent-magnet synchronous motor, and switching said angle command switch means and said speed command switch means to said angle signal detecting means and the speed command supplied to said apparatus, respectively, when said magnetic pole reference detection completion signal is outputted, current command generating means for generating a current command from a current amplitude signal supplied from said speed control means and the angular displacement signal supplied from said angle command switch means, current detecting means for detecting a current outputted from said inverter to the permanent-magnet synchronous motor, and current control means for controlling a current of said inverter with the current command supplied from said current command generating means and a detected signal from said current detecting means.