JPS63240391A - Speed controller for motor - Google Patents

Abstract

PURPOSE:To improve the handling property of a speed controller for a motor by using a power factor improving stepup chopper in a low voltage system of an AC power source and controlling a speed by a conducting angle control by a power converter in a high voltage system. CONSTITUTION:A speed controller for a brushless DC motor 5 converts the voltage 16 of an AC power source 1 through a rectifier 2 and a power factor improving stepup chopper 3 to a DC voltage Ed to drive the winding 5-1 of a motor 5 through an inverter 4. The controller for controlling the speed of the motor 5 consists of a microcomputer 6, a position detector 8 of a rotor 5-2, an inverter control unit 9, a DC voltage control unit 11 for controlling the chopper 3, a DC voltage comparator 25, and a DC current detector 26. Thus, the comparator 25 judges whether the voltage 16 of the power source 1 is of a low voltage system or a high voltage system, the speed is controlled by the chopper 3 at the time of the low voltage system, the output of the chopper 3 is held at a predetermined value at the time of high voltage system, and the inverter is controlled through its conducting angle to control the speed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a speed control device for an electric motor, and particularly to a speed control device for an electric motor that is compatible with two types of AC power supply voltage systems.

[Conventional technology]

a step-up chopper circuit that boosts a voltage obtained by rectifying an AC power supply voltage; a power conversion circuit that controls the conduction angle of the output voltage of the step-up chopper circuit and applies it to a three-phase AC motor;
A speed control device for an electric motor including the step-up chopper circuit and a control circuit for controlling the power conversion circuit is disclosed in Japanese Patent Laid-Open No. 61-1.
It is described in Publication No. 0968. The control circuit of this speed control device controls the boost chopper circuit and the power conversion circuit so as to keep the ratio of frequency and voltage constant in order to efficiently operate the motor at variable speeds.

[Problem that the invention seeks to solve]

By the way, the applications of the electric motor whose speed is controlled in this manner are various, and therefore the AC power source used may be a low voltage system or a high voltage system. If the voltage systems of the AC power sources differ in this way, it is necessary to prepare and use different motors and speed control devices depending on the voltage systems, resulting in a lack of productivity and ease of handling.

Therefore, an object of the present invention is to improve productivity and ease of handling by allowing one type of speed control device and electric motor to be used for two types of voltage systems.

[Means for solving problems]

In order to solve this problem, the present invention includes a power supply voltage detection circuit that detects the magnitude of the AC power supply voltage, and a power conversion circuit that maintains the conduction angle at a predetermined angle when the AC power supply voltage is a low voltage system. control the speed of the motor by changing the output voltage of the step-up chopper circuit in the current state, and if the AC power supply voltage is a high voltage system, change the conduction angle of the power conversion circuit while keeping the output voltage of the step-up chopper circuit at a predetermined value. A speed control circuit is provided to control the speed of the electric motor.

[For production]

When this motor speed control device is operated using a low voltage system as a power source, the power conversion circuit is controlled to maintain the conduction angle at a predetermined value and supplies power to the motor, but the voltage is controlled by the step-up chopper circuit. to control the speed. When operated using a high-voltage system as a power source, the boost chopper circuit is controlled to maintain its output voltage at a predetermined value, but the voltage supplied to the motor is controlled by the conduction angle in the power converter circuit to speed up the operation. Control.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 8.

FIG. 1 shows a block diagram of a speed control device for a brushless DC motor according to an embodiment of the present invention. The AC voltage 16 of the AC power supply 1 is converted to a DC voltage E4 via the rectifier circuit 2 and the power factor improving ambient pressure chopper circuit 3, and supplies DC power to the inverter 4, which in turn controls the windings of the brushless DC motor 5. Drive line 5-1.

The control circuit that controls the speed of the brushless DC motor 5 is
Microcomputer 6, position detection circuit 8 for detecting the magnetic pole position of rotor 5-2 of brushless DC motor 5 from motor terminal voltage 7. Inverter control section 9 for transistors Q and -Q6 forming inverter 4. A DC voltage control unit 11 that controls the boost chopper circuit 3 with reference to the waveform and magnitude of the power supply current IO. A DC voltage comparator 25 for determining whether the voltage system of the AC power supply 1 is a low voltage system or a high voltage system. It consists of a DC current detection section 26 that detects the DC current Id flowing through the inverter 4.

The microcomputer 6 is a brushless DC motor 5.
For example, speed control processing, position detection signal 1 from the position detection circuit 8, etc.
2. Speed command signal 13. Processing to take in the DC voltage comparison signal 30 and the detected DC current 23.

Inverter drive signal 14 and the DC voltage control section 11
The configuration is configured to execute a process of outputting a current command signal 15 to the inverter control section 9 and a voltage signal 24 to the inverter control section 9.

The power factor improvement boost chopper circuit 3 includes a reactor 3-1.
．． Transistor Q7. It is composed of a diode 3-2 and a smoothing capacitor 3-3, and a drive signal for this transistor Q7 is created in the DC voltage control section 11, and by changing the on time and off time of the transistor Q, the power supply current 10 is changed. The configuration is such that the instantaneous magnitude can be changed.

FIG. 2 shows the relationship between the power supply voltage 16 and the power supply current 1o, and the waveform of the power supply current 1o is adjusted to have the same phase as the power supply voltage 16 by the boost chopper circuit 3 for power factor correction controlled by the DC voltage control section 11. The power factor of the power source is set to approximately 1.0 by making it a sine wave and controlling its effective value in accordance with the current command signal 15 output from the microcomputer 6.

The power supply current control unit 11 converts the output voltage of the rectifier circuit 2 into a voltage signal I having a full-wave rectified waveform synchronized with the power supply voltage I6.
7, a power supply voltage detection circuit 11-1 generates a synchronous current command signal 1, which is an analog signal by multiplying and combining this voltage signal 17 with the current command signal 15, which is a digital signal.
D/A converter 11-2 with multiplication to create 8, power supply current 1
A power supply current amplifier 11-3 detects and amplifies the full-wave rectified waveform of 0 by converting it into a voltage with a resistor R1, a detected power supply current signal 19 which is the output of this power supply current amplifier 11-3, and the synchronous current command signal 18. A current control amplifier 11-4 operates so as to make the difference voltage O, an error signal 20 which is the output of this current control amplifier 11-4, and a triangular wave signal 21 which is the output of the triangular wave oscillator 11-5. It is comprised of a comparator 11-6 that compares the signals and creates a chopper signal 22 for the transistor Q, and a chopper driver 11-7 for the transistor Q. .

The inverter control unit 9 includes a D/A converter 9-4 that converts the digital voltage control signal 24 output from the microcomputer 6 into an analog signal, and a voltage signal that is the output of the D/A converter 9-4. 27 and triangular wave oscillator 9-3
a comparator 9 for generating a chopper signal 29 for the inverter 4 by comparing the triangular wave signal 28 which is the output of the inverter 4;
-2 and an inverter driver 9-1 for the inverter 4.

The DC current detection unit 26 connects the DC current (■) to a resistance R.

DC current amplifier 2 that converts into voltage, detects it, and amplifies it.
6-1, and an A/D converter 26-2 that converts the output of the DC current amplifier 26-1 into a digital signal.

The DC voltage comparator 25 includes a set voltage amplifier 25-1 that amplifies the DC set voltage Ede, and this set voltage amplifier 25-1.
The comparator 25-2 compares the output of the DC voltage E4 detected by the resistors R3 and R4.

In this configuration, the reason why different control methods are used when the AC power supply 1 is a low voltage system and when it is a high voltage system, and the method of switching between them will be explained below.

The speed of the brushless DC motor 5 is controlled by changing the output voltage of the inverter 4.
There are two methods: one is to change the DC voltage E4 using the power factor improving boost chopper circuit 3, and the other is to change the voltage applied to the brushless DC motor 5 through PWM control using the inverter 4. In the former method, since the step-up chopper circuit 3 for power factor correction is used, when the DC voltage Ed is made lower than the peak value of the power supply voltage 16 of the AC power supply l, the power factor is improved near the peak value of the power supply voltage 16. The boost chopper circuit 3 remains off and does not operate, making it impossible to control the power supply current 10 into a sine wave. In order to perform speed control in such a region, it is necessary to perform PWM control using the inverter 4, which is the latter method.

Furthermore, if the same control method is used for the low-voltage system and the high-voltage system, the voltage applied to the motor 5 will change by half, so in order to obtain the same characteristics, it is necessary to use two types of motors with different applied voltages. Requires 5.

Therefore, different control methods are used for the low voltage system and the high voltage system in the method described below.

Fig. 3 shows the capacitor charging voltage E4 before starting the brushless DC motor 5, and the capacitor voltage Ed is Ed in a low voltage system and E6□ in a high voltage system.
is maintained. When the set voltage Edc of the DC voltage comparator 25 is set to a value greater than E□ and smaller than E6□, the output signal 30 of the comparator 25-2 changes to a high level when the system is a low voltage system and to a low level when the system is a high voltage system. do.

FIG. 4 shows the processing contents of the microcomputer 6, which takes in the output signal 30 of the DC voltage comparator 25 to determine whether the initial charging voltage E4 of the capacitor 3-3 is from the low voltage system or the high voltage system. In the case of a low voltage system, the inverter 4 is controlled to be energized at 120 degrees, and the speed of the motor 5 is controlled by varying the DC voltage E4 output from the power factor improving boost chopper circuit 3. In the case of a high voltage system, the DC voltage E4 output from the boost chopper circuit 3 for power factor improvement is controlled at a constant level, and the inverter 4 is
The speed of the electric motor 5 is controlled by 0 degree energization + PWM control.

To give a specific example, in the case of a low voltage system, as shown in Fig. 5, the boost chopper circuit 3 changes the DC voltage E4 from E0 to Ea+a (maximum value) in response to the speed command signal Nd~NZ''. Figure 6(a), Tb) shows one phase of the line voltage of the motor 5, and the inverter 4 is
Since the control is fixed to 0 degree energization, the voltage applied to the electric motor m5 is controlled by the boost chopper circuit 3, and the boost chopper circuit 3 controls the speed of the motor 5.

In the case of a high voltage system, as shown in FIGS. 7(al) and (b), the step-up chopper circuit 3 is controlled so that the DC voltage Ea becomes constant Eda (maximum voltage in the case of a low voltage system),
Since the inverter 4 is subjected to 120 degree energization + PWM control, the average voltage E1 changes by PWM control, and the inverter 4
Speed control of the electric motor 5 is performed.

As a result, the voltage applied to the brushless DC motor m5 is the same regardless of whether the AC power supply 1 is a low voltage system or a high voltage system, and one type of brushless DC motor 5 can be used regardless of the power supply voltage 16. can.

FIG. 8 shows another embodiment, and the difference from FIG. 1 is that the judgment as to whether the AC power supply voltage 16 is a low voltage system or a high voltage system is made based on the output voltage of the rectifier circuit 2. Since the output signal 30 of the DC voltage comparator 25 has a pulse waveform, a latch circuit 25-3 is provided, and its output is input to the microcomputer 6. According to this configuration, it is possible to take in this output signal at any time and determine whether the power supply voltage Ed is a low voltage system or a high voltage system.

〔Effect of the invention〕

According to the present invention, the voltage of the AC power supply is detected and the speed of the motor is controlled using a step-up chopper circuit for power factor correction in the low-voltage system, and the DC voltage is kept constant by the step-up chopper circuit in the high-voltage system. By configuring the power conversion device to perform speed control using conduction angle control, one type of speed control device and electric motor can handle two types of power supply voltages, improving productivity and ease of handling. effective.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the circuit configuration of an embodiment of the present invention, Fig. 2 is a waveform diagram of AC power supply voltage and power supply current, Fig. 3 is a diagram of initial charging voltage characteristics of a capacitor, and Fig. 4 is a microcomputer Speed control switching processing flowchart, fifth
The figure is a DC voltage characteristic diagram for speed command value, Figure 6 is a voltage waveform diagram applied to the motor during speed control by the boost chopper circuit for power factor improvement, and Figure 7 is the voltage applied to the motor during speed control by inverter 4. The voltage waveform diagram and FIG. 8 are block diagrams showing the circuit configuration of another embodiment. DESCRIPTION OF SYMBOLS 1... AC power supply, 2... Rectifier circuit, 3... Boost chopper circuit, 4... Inverter, 5... Brushless DC electric motor i, 6... Microcomputer, 9...
Inverter control section, 11... DC voltage control section, 25.
...DC voltage comparison section. Fig. 2 Fig. 3 d M Fig. 4 Fig. 5 d it, ltn cold Fig. 6 Fig. 7

Claims (1)

[Scope of Claims] 1. A step-up chopper circuit that steps up a voltage obtained by rectifying an AC power source voltage, a power conversion circuit that controls the conduction angle of the output voltage of this step-up chopper circuit and applies it to a motor, and In a speed control device for a motor that includes a chopper circuit and a control circuit that controls a power conversion circuit, the control circuit includes a power supply voltage detection circuit that detects the magnitude of the AC power supply voltage, and a power supply voltage detection circuit that detects the magnitude of the AC power supply voltage. In this case, the speed of the motor is controlled by changing the output voltage of the step-up chopper circuit while keeping the conduction angle of the power conversion circuit at a predetermined value, and when the AC power supply voltage is a high voltage system, the speed of the step-up chopper circuit is controlled. A speed control device for an electric motor, comprising a speed control circuit that controls the speed of the electric motor by changing the conduction angle of the power conversion circuit while maintaining the output voltage at a predetermined value. 2. In claim 1, the speed control circuit has a predetermined conduction angle of the power conversion circuit as a maximum value when the AC power supply voltage is a low voltage system, and a predetermined conduction angle of the power conversion circuit when the AC power supply voltage is a high voltage system. A speed control device for a motor, characterized in that the output voltage of a step-up chopper circuit is set to a value equal to the maximum output voltage in the case of a low voltage system.