Electricity: motive power systems – Synchronous motor systems – Synchronization systems
Patent
1996-09-27
1998-09-01
Sircus, Brian
Electricity: motive power systems
Synchronous motor systems
Synchronization systems
318603, H02P 146
Patent
active
058015094
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method of starting a permanent-magnet synchronous motor equipped with an angular displacement detector, which comprises 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.degree. out of phase with each other and a C-phase pulse train generating means for generating a C-phase pulse per rotation.
BACKGROUND ART
Heretofore, permanent-magnet synchronous motors for use as AC servomotors rotate a rotor by supplying a stator winding with a drive current which has a certain phase relationship to magnetic fluxes produced by permanent magnets mounted on the rotor depending on their position. Before the rotor is rotated, it is necessary to detect the position of the permanent magnets. To meet this requirement, a magnetic pole detector and an encoder which serves as an angular position detector are mounted on the permanent-magnet synchronous motors.
FIG. 1 is an elevational view of a permanent-magnet synchronous motor having an encoder and a magnetic position detector, and FIG. 2 is a block diagram of a motor control apparatus for controlling the permanent-magnet synchronous motor.
An encoder (angular position detector) 300 and a magnetic pole detector 400 are mounted on a permanent-magnet synchronous motor 200. The encoder 300, the magnetic pole detector 400, the permanent-magnet synchronous motor 200, and a motor control apparatus 100A jointly make up a permanent-magnet synchronous motor system. The encoder 300 is attached to the rotatable shaft of the permanent-magnet synchronous motor 200 and generates A- and B-phase pulses per rotation that are 90.degree. out of phase with each other and a C-phase pulse per rotation.
The motor control apparatus 100A comprises a main circuit 110 and a control circuit 120A.
The main circuit 110 comprises a converter 111 for converting an alternating current into a direct current and outputting the direct current, a smoothing capacitor 112 for smoothing the direct current outputted from the converter 111, and an inverter 113 for energizing the permanent-magnet synchronous motor 200 based on a control signal from the control circuit 120A.
The control circuit 120A comprises a speed detector 121 for converting a signal from the encoder 300 into a speed signal, a speed controller 122 for controlling the speed of rotation of the permanent-magnet synchronous motor 200 based on an output signal SR from the speed detector 121 and a speed command SS, an angular signal detector 123A for detecting the signals from the encoder 300 and the magnetic pole detector 400 to generate an angular signal for a current command, a current command generator 124 for generating a current command from an output signal from the speed controller 122 and an output signal from the angular signal detector 123A, a current detector 125, and a current controller 126 for controlling a current of the inverter 113 based on the current command and a detected signal from the current detector 125.
If the permanent-magnet synchronous motor is incorporated in a spindle drive unit of a machine tool or an electric vehicle, it is necessary to reduce the size of the angular position detector due to limitations imposed on the location where the motor is installed. However, the conventional system requires two position detecting means, i.e., the encoder and the magnetic pole detector, and many signal lines to interconnect the inverter and the encoder and also the inverter and magnetic pole detector, resulting in a complex arrangement.
Attempts have been made to dispense with the magnetic pole detector. Japanese Patent Laid-open No. 197586/1994 discloses a motor control apparatus from which a magnetic pole detector is omitted. However, since the difference between the origin of the enc
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Fujii Syuuichi
Sawa Toshihiro
Sonoda Sumitoshi
Yamamoto Eiji
Kabushiki Kaisha Yaskawa Denki
Sircus Brian
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