JP2001339975A - Three phase motor regenerative power drive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that when making power running and regenerative control of a three-phase AC drive motor, capacitance of its capacitor increases since a regenerative power is controlled on its DC voltage. SOLUTION: A PWM converter which sends and receives power from a power source by controlling a PWM inverter for motor control and the DC voltage is controlled on a detected signal from a motor operation state judgment circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention is used for driving a three-phase AC motor.

[0002]

2. Description of the Related Art Conventionally, a three-phase AC inverter has been used for controlling a three-phase AC motor such as an induction motor or a synchronous motor used as an AC servomotor accurately and at a high speed. According to the state of the load, the motor powering and the regenerative operation are repeatedly performed. The power regeneration operation corresponding to this is performed by a method such as Japanese Patent Publication No. 61-37864. However, since these methods are performed regardless of the motor driving state by detecting the DC side voltage, the DC voltage value that is controlled to be constant expects the voltage fluctuation of the AC power supply, and the regenerative energy of the motor due to control delay or the like. Is temporarily set to a high voltage. For this reason, equipment connected to the DC side power supply must use a product with a high maximum rated voltage, increasing the cost. Large-capacity electrolytic capacitors of the same rated voltage have a short life when used at a high voltage. Furthermore, during regeneration, large energy is returned from the motor to the DC power supply, so a large-capacity capacitor is required for temporary storage. This increases the cost and installation area.

[0003]

The DC voltage is maintained at a constant high voltage irrespective of the operation state of the three-phase AC motor. To solve the need for a large-capacity capacitor to store the regenerative energy of the motor.

[0004]

When the power running operation and the regenerative operation of the three-phase AC motor are driven by the PWM inverter,
At the time of motor power running, the PWM converter is driven by the state determination circuit at the time of regeneration to control so as to have the minimum DC side voltage.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a PWM for driving a motor.
It is composed of a PWM converter that controls the DC voltage by transmitting and receiving power to and from an inverter and a power supply, and a motor operating state determination circuit.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, reference numeral 1 denotes a servo motor which drives a power running operation and a regenerative operation. 2 is a PWM inverter. 4 is a PWM converter. 3 is a DC circuit for converting the power of each AC motor. Has a capacitor to temporarily store the energy difference during DC and AC voltage conversion. Power is transferred between the 6 AC power supplies and 1 motor by the control operation. 5 is an AC impedance limiting reactor. 7
Is a motor operation state determination circuit. 10 is a power driver. The powering or regenerative operation of the motor is performed by ten drivers that drive the power circuit. The driver performs feedback calculation of the commanded forward rotation and reverse rotation speed commands and the motor speed detected by the encoder of 8,
A forward rotation acceleration / deceleration command and a reverse rotation acceleration / deceleration command are generated, and the motor is driven so as to follow the command speed by controlling the current of the power circuit as a torque command. At this time, the motor performs the powering operation and the regenerative operation only by the acceleration command and the deceleration command regardless of the forward and reverse rotation directions of the motor. The inverter supplies power from the DC power supply to the motor during power running and returns power to the DC power supply during regeneration. At this time, the DC voltage decreases and the converter supplies power to and from the 6 AC power supplies and performs regeneration to perform DC power supply. To process. The power running and the regenerative operation are originally determined by the operation state of the motor irrespective of the DC voltage, and are determined by a torque command and a rotation direction in control. The operations of the inverter and the converter perform the same operation.

From the above relationship, if the operating state of the motor is detected by the discriminating circuit 7 and the inverter and the converter are simultaneously controlled without delay, the power can be returned to the AC power supply without storing the regenerative energy of the motor in the DC circuit. become,
Except for conversion between AC voltage and DC voltage, the DC side capacitor for storing large-capacity regenerative power is not required. The power at the time of power running and regeneration is calculated from the torque command position and the number of rotations of the motor, and the power transfer to and from the AC power supply is controlled.

[0008]

According to the present invention, it is possible to lower the withstand voltage of the equipment to be used by making the DC voltage constant at the minimum voltage, and it is not necessary to store the motor regenerative energy in the DC side power supply circuit. It can be configured by the capacitor capacity.

[Brief description of the drawings]

FIG. 1 shows an embodiment of a regenerative operation.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 3-phase AC servo motor 2 PWM inverter 3 DC power supply circuit 4 PWM converter 5 Reactor 6 AC power supply 7 Motor operation state determination circuit 8 Motor speed detection encoder 9 Motor current detector 10 Power circuit driver

Claims (1)

[Claims] The present invention has a PWM (pulse width modulation control) inverter for driving a three-phase motor, a PWM converter for generating a DC voltage from an AC power supply, and a circuit for judging an operation state of the motor. , A regenerative operation), and drives the converter and the inverter under the same conditions, thereby minimizing the DC voltage and minimizing the capacitance of the capacitor connected to the DC power supply.