JPH04131199U - Power control device for induction motor - Google Patents

Abstract

(57) [Summary] [Purpose] The present invention constantly maintains the optimum efficiency against load fluctuations based on the voltage-current pattern formed by finding the relationship between the input voltage value and the input current value at the optimum efficiency point of the induction motor. This is characterized by the power control device that is maintained. A rectifier circuit of an inverter device is provided with a DC current detection section and a voltage detection section, and this current-voltage signal is inputted as an inverter adjustment command signal based on the input current-voltage relationship indicating optimum efficiency.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

The present invention relates to a device for controlling power supplied to an induction motor, and has special features. The relationship between the input voltage value and input current value at the optimum efficiency point of the induction motor is determined and formed. The input voltage and input current are controlled based on the voltage-current pattern determined, and the input voltage and current are controlled to respond to load fluctuations. This invention relates to a power control device that always maintains optimum efficiency.

0002

[Conventional technology]

(Background of the idea) Induction motors can easily achieve high-speed rotation even with commercial power, so they can be used for pumps, fans, etc. Although it is widely used in industrial machinery, it has the disadvantage that speed control is difficult. The rotational speed N of the induction motor is determined by the motor's peak as p, the slip as s, and the frequency of the applied voltage. When the wave number is f, it is generally given by equation 1.

0003

[Math 1]

0004 Speed control of an induction motor is performed by changing its torque characteristics. Maximum torque Tm is expressed as a function number 2 of frequency f and terminal voltage V.

[0005]

[Math 2]

[0006] In this way, constant torque is achieved by keeping (V/f) constant, but as shown in Fig. 2. As shown in Figure 3, efficiency decreases at low torque. (Conventional technology) Conventionally, for induction motors, the input voltage value and the optimum efficiency point at each load point were calculated. The input voltage and input are determined based on the voltage-current pattern formed by determining the relationship between the input current values. A device disclosed in Japanese Patent Application Laid-Open No. 2-51359 was proposed as a power control device for controlling current. It is.

[0007]

[Problem that the idea aims to solve]

Conventional power control equipment allows induction motors to achieve optimal efficiency regardless of the load power factor. Although it is possible to save power by controlling the input voltage of the induction motor, The power control circuit to control the AC phase control circuit and the phase control signal to this phase control circuit. This requires a phase control signal generation circuit that outputs If the phase control circuit and phase control signal generation circuit do not work properly, the power control device will not function correctly. Because the configuration is such that it does not always operate, the circuit structure is complex and the reliability of the device is poor. It is also a power control method by detecting alternating current (or voltage), In particular, there is a problem that alternating current detection cannot always be performed smoothly. there was.

[0008] The present invention has been made in view of these problems of the prior art. The purpose of is to detect the current and voltage of the DC section of the inverter and perform power control. The device is highly reliable and practical, and power control is smooth and easy. An object of the present invention is to provide a power control device for an induction motor.

[0009]

[Means to solve the problem]

This invention consists of a rectifier circuit that converts AC power into DC power, and a circuit connected to the rectifier circuit. a smoothing circuit which is connected to the smoothing circuit and receives direct current supplied through the rectifier circuit; A power control device comprising a voltage source inverter that performs reverse conversion into alternating current, the power control device comprising: A DC current detection section and a voltage detection section are provided in the current circuit, and the current detection section and voltage detection section The signal from the section is input to the processing unit, which calculates the input voltage and the optimum efficiency of the induction motor. As a voltage signal corresponding to a reference voltage based on a pattern that gives the relationship of the input current and input this to the inverter as an adjustment command signal. This is a power control device for electric motors.

0010

[Effect]

In order to operate the induction motor with high efficiency, the driving frequency of the induction motor is set as a parameter. The voltage-current characteristics of the applied voltage (driving voltage) and the current flowing through the induction motor are is obtained by collecting characteristic data due to the load, and the optimal voltage-current pattern is determined. get the tone. Then, optimal efficiency operation control is performed according to that pattern. Besides that Detects the direct current and voltage flowing through the rectifier circuit and responds to that current and voltage. based on a pattern that gives the relationship between input voltage and input current that exhibits optimal efficiency. Convert it to a voltage signal corresponding to the reference voltage, input it to the inverter, and output it. Adjust and control power.

[0011]

【Example】

The present invention will be explained below along with examples. Figure 1 is a block diagram showing the basic configuration of the present invention. It is a lock diagram. In FIG. 1, a power control device 1 integrates AC power at a commercial frequency. It consists of a rectifier circuit 11 for converting DC power into DC power, and a smoothing capacitor 14. a smoothing circuit 13 connected to the rectifier circuit 11; A voltage source inverter that converts direct current supplied through the rectifier 11 back into alternating current, e.g. For example, it is equipped with a PWM inverter 15. 18 is a detection unit for the direct current flowing through the rectifier circuit 11, and 19 is a detection unit for both sides of the rectifier circuit. A voltage detection section 22 is a microcomputer processing unit MPU; A pattern that provides the relationship between input voltage and input current that indicates the optimal operating efficiency of the induction motor 25 is pre-stored. The MPU includes the current detection section 18 and the voltage The signal from the detection unit 19 is inputted via amplifiers 20 and 21, and is further input to the induction motor. Set the speed setting 23. The signal output from MPU22 is input via pulse width modulator PWM24. It is input as an adjustment command signal for the inverter 15. Figure 4 shows the motor drive frequency f (in This shows the voltage-current characteristics when the inverter frequency) is taken as a parameter. The turn is stored in advance in the MPU. In this invention, the current and voltage of the DC power supply section of the inverter are detected. By controlling the power of the induction motor, highly efficient operation control with a constant power factor is possible. Detection of AC current and AC voltage of conventional induction motor drive AC power supply It is possible to achieve the same effect as power control using This allows for easy flow detection.

0012

[Effect of the idea]

The present invention is constructed as described above and produces the following effects. Detects the DC current and voltage of the rectifier circuit, converts this signal, feeds it back, and inverts it. Since the configuration adjusts the output of the controller, power control can be performed smoothly and easily. Wear.

[Submission date] March 4, 1992

[Procedural amendment 1]

[Name of document to be amended] Specification

[Correction target item name] 0006

[Correction method] Change

[Correction details]

[0006]Thus, by keeping (V/f) constant, constant torque is achieved, but as shown in FIGS. 2 and 3, efficiency decreases at low torque. (Prior art) Conventionally, electric power is used to control the input voltage and input current of an induction motor based on a voltage-current pattern formed by determining the relationship between the input voltage value and the input current value that indicates the optimal efficiency point at each load point. As a control device, a device disclosed in Japanese Patent Application Laid-Open No. 2-51395 has been proposed.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the basic configuration of a power control device according to the present invention.

FIG. 2 is an efficiency characteristic diagram of V/f control and V-1 pattern control.

FIG. 3 is a power factor characteristic diagram of V/f control and V-1 pattern control.

FIG. 4 is a voltage-current characteristic diagram using motor drive frequency as a parameter.

[Explanation of symbols]

1 Power control device 11 Rectifier circuit 13 Smoothing circuit 15 Inverter 18 Current detection section 19 Voltage detection section 22 MPUs 24 PWM 25 Induction motor

Claims (1)

[Scope of utility model registration request] 1. A rectifier circuit that converts alternating current power into direct current power, a smoothing circuit connected to the rectifier circuit, and a smoothing circuit connected to the smoothing circuit that converts the direct current supplied through the rectifier circuit back into alternating current. A power control device comprising a voltage source inverter, wherein the rectifier circuit is provided with a direct current detection section and a voltage detection section, and signals from the current detection section and the voltage detection section are input to an arithmetic processing device, It outputs a voltage signal corresponding to a reference voltage based on a pattern that gives the relationship between input voltage and input current that indicates the optimum efficiency of the induction motor, and this is
A power control device for an induction motor, which inputs an adjustment command signal to the inverter.