JPH0583965A - Method for starting rotation-sensorless permanent magnet motor - Google Patents

Abstract

PURPOSE:To start a permanent magneto motor even when the motor is in a rotating state like a free run, by providing a voltage with the same phase as the terminal voltage so that the motor is started through power factor control in a current-phase motor control method. CONSTITUTION:A starting instruction causes a voltage detecting circuit 9 to detect an inductive voltage in a motor 2. When the inductive voltage is higher than a reference voltage, the rotor of the motor 2 is in a rotating state, and then a voltage wave forming circuit 10 generates a voltage with the same phase and slightly higher amplitude as compared to the terminal voltage in the motor 2. At the same time, a transistor in an inverter unit 4 is switched through a driving circuit 7, and thereby a voltage with the same phase as the inductive voltage is provided to the motor 2. Since the amplitude of the voltage is slightly larger than that of the inductive voltage, a small current is generated. Then, the current detected with a current sensor 8 is provided as an input to a power factor control circuit 6 so that the motor is driven through power factor control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for starting a permanent magnet motor drive circuit using a control system for driving a permanent magnet motor without using a rotation sensor.

[0002]

2. Description of the Related Art Conventionally, as a method of driving a permanent magnet motor without using a rotation sensor, there is Japanese Patent Application No. 1-294685 as a method of controlling the phase of current. This method
It has the configuration shown in FIG. The main circuit comprises a converter section 3 formed of a diode bridge, an inverter section 4 formed of a transistor bridge, and a smoothing capacitor 5. The current flowing through the main circuit is detected by the current sensor 8, and the power factor of the motor 2 is controlled by the power factor control circuit 6 based on this output. The drive circuit 7 is
The transistor of the inverter unit 4 is switched by the signal of the power factor control circuit 6.

[0003]

However, when the above method is used for control, the motor current is passed and the power factor control is performed by detecting the current. Therefore, when the motor is started, a low frequency voltage is applied to the motor. After the motor is supplied and the motor is rotated, the current is detected and the power factor is controlled. Therefore, when the motor starts during the free-run stop or when it is being rotated from the outside, the frequency of the motor and the supplied frequency do not match, so the motor vibrates or overcurrent flows and the overcurrent protection function is activated. It works, and the start may stop halfway. We propose a method that solves the above problems and allows the motor to be started in any state, such as during free running or when the motor is being rotated from the outside.

[0004]

In a control method for driving a permanent magnet motor by controlling the phase of a current flowing through the motor without using a rotation sensor, the terminal voltage of the motor is detected and the same voltage as this voltage is detected. A method for starting a rotation sensorless permanent magnet motor, characterized in that the motor is driven by power factor control after the phase voltage is supplied to the motor.

[0005]

The transient current flowing in the motor can be suppressed by detecting the terminal voltage of the motor before supplying the electric power to the motor and supplying the voltage having the same phase as that.
Further, since a current flows, power factor control can be performed by detecting this current, and it is possible to shift from open loop control to current phase control.

[0006]

EXAMPLE An example of the present invention will be described below.
FIG. 1 shows the configuration of an embodiment of the present invention. The control device 1 is
Converter unit 3, inverter unit 4, and smoothing capacitor 5
And a current sensor 8 flowing in the main circuit and control circuits 6 to 10. Reference numeral 6 is a power factor control circuit for detecting the current and controlling the voltage and frequency supplied to the motor.
Is a drive circuit for switching the transistors of the inverter section. Reference numeral 9 is a voltage detection circuit that detects the terminal voltage of the motor 2 and detects the magnitude of the induced voltage. When the detected voltage is lower than the standard voltage, it gives a signal to the power factor control circuit. When the voltage is higher than the standard voltage, the signal is sent to the voltage waveform forming circuit 10 that forms a voltage having the same phase as the terminal voltage. With the above configuration, the operation will be described below according to the flow of FIG.

The motor induced voltage is detected from the voltage detection circuit 9 according to the operation command. When this voltage level is lower than the reference voltage level, the rotor of the motor is in a stopped state and the same power factor control as in the conventional case is performed. When the voltage level is higher than the reference value, it means that the rotor of the motor is rotating, and the voltage waveform forming circuit creates a voltage whose amplitude is slightly larger than that of the motor terminal voltage. Switching the transistors of section 4. As a result, a voltage in phase with the induced voltage is supplied to the motor.
At this time, since the amplitude of the voltage is slightly larger than the induced voltage, some current flows. By detecting this current, power factor control becomes possible, and thereafter, the motor is driven by power factor control.

In this embodiment, since the voltage in phase with the induced voltage of the motor is supplied to the motor, torque pulsation does not occur or oscillates when the voltage is applied to the motor. Further, by slightly increasing the amplitude of the voltage by the induced voltage, the overcurrent does not flow and the motor start does not stop midway. Further, since the power factor can be controlled by detecting the current flowing due to a slight voltage difference, it is possible to smoothly shift from the voltage supply to the power factor control. Furthermore, since the frequency of the voltage supplied to the motor matches the frequency of the rotor, there is no vibration or overcurrent due to step-out. (Other embodiments)
Although the description has been given above regarding the start-up of the motor, a smooth restart can be performed by the same method even when the instantaneous interruption of the current occurs.

[0009]

According to the method of starting a permanent magnet motor without a rotation sensor of the present invention, the rotational position of the rotor can be grasped by the induced voltage even when the rotor is in the course of free running at the time of starting or is being rotated by a rotational force from the outside. By flowing a current in the same phase as the induced voltage, overcurrent, vibration, torque ripple, step out, etc. can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram of a control circuit of the present invention,

FIG. 2 is a flow chart of a control method of the present invention,

FIG. 3 is a block diagram of a conventional control circuit.

[Explanation of symbols]

1 ... Control device 2 ... Motor 3 ... Converter unit
4 ... Inverter section 5 ... Smoothing capacitor 6 ... Power factor control circuit 7 ... Drive circuit 8 ... Current sensor 9 ... Voltage detection circuit 10 ... Voltage waveform forming circuit

Claims (1)

[Claims] 1. A method for driving a permanent magnet motor by controlling the phase of a current flowing through the motor without using a rotation sensor, the terminal voltage of the motor is detected, and a voltage in phase with this voltage is detected by the motor. A method for starting a rotation sensorless permanent magnet motor, characterized in that the motor is driven by power factor control after being supplied to the motor.