JPS627393A - Controller for induction motor - Google Patents

Abstract

PURPOSE:To enable to use an induction motor as a drive source of a winding machine by maintaining the DC side power of an inverter constant so that the relationship between the rotating force and the rotating speed is inversely proportional. CONSTITUTION:A multiplier 4 calculates the product VXI of the current I and the voltage V of the DC side of an inverter 2. A setter 5 outputs a set value for the power of the DC side of an inverter 2. An error amplifier 6 outputs a signal corresponding a deviation between the set value from the setter 5 and the power VXI from the multiplier 4. The output signal is applied to the inverter 2. When the DC side power of the inverter 2 is maintained constant, the effective power of an induction motor 1 is held constant. Accordingly, the rotating force and the rotating speed of the motor 1 becomes inversely proportional.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a control device for an induction motor that drives a winder or the like.

<Prior Art> There are two drive systems for the winding machine: a surface drive system as shown in FIG. 3, and a shaft drive system as shown in FIGS. 4 and 5. In this shaft drive method, tension control methods include an external detection method shown in FIG. 4 and an internal control method shown in FIG. 5.

In the internal control type, a DC motor is used as a driving motor to maintain a constant tension on the material to be wound, and control is performed to maintain its output constant. To wind up something that is fed out at a constant speed with a constant tension,
It is sufficient to control the motor so that its rotational force and rotational speed are inversely proportional to each other.

That is, if the rotational force is To1 and the rotational speed is N, then To
X pJ-may be set constant. Now the unit is Toksr-
When s/Nrpa+, the output Pw of the motor is 2πN Pw=9.8Tox − . Therefore, if the output of the electric motor is constant, the rotational force To and the rotational speed N have an inversely proportional relationship, and the winding tension can be kept constant.

Conventionally, a DC motor has been used to perform this constant output control as described above. The reason for this is that DC motors have the advantage that when the field magnetic flux is constant, the current flowing through the armature is simply proportional to the rotational force, so the rotational force can be easily controlled.

However, DC motors have disadvantages in that they are expensive and have consumable parts such as brushes, making maintenance complicated.

On the other hand, induction motors have the advantage of being less expensive and maintenance-free than DC motors, but they have a strongly constant speed with respect to frequency, making it difficult to control rotational force.

<Object of the invention> The present invention has been made in view of the above circumstances, and its object is to provide an induction motor control device that allows the induction motor to be used as a drive source for a winder. be.

<Configuration of the Invention> An induction motor control device according to the present invention includes an inverter that converts direct current to alternating current and supplies alternating current power to the induction motor;
control means for controlling the output frequency of the inverter so that the power on the DC side of the inverter is constant;
The invention is characterized in that the induction motor is controlled so that its rotational force and rotational speed are inversely proportional to each other.

<Principle of the Invention> The present invention utilizes the fact that when an induction motor is operated by an inverter, the power on the DC side of the inverter is not affected by the power factor of the induction motor and is proportional to the effective power of the induction motor. . Therefore, if the output frequency of the inverter is controlled so that the power on the DC side of the inverter is constant, the rotational force and rotational speed of the induction motor will have an inversely proportional relationship.

<Example> An embodiment of the present invention will be described below.

FIG. 1 shows a first embodiment. The AC side of an inverter 2 is connected to the induction motor 1, and the DC power supply 3 is connected to the DC side of the inverter 2. The inverter 2 converts the direct current of the direct current power supply 3 into alternating current, and supplies the alternating current power to the induction motor 1 . The induction motor 1 drives a winder (not shown).

The multiplier circuit 4 calculates the current l and voltage V on the DC side of the inverter 2.
The product Vxl is calculated. The setting device 5 outputs a setting value for the DC side power of the inverter 2. error amplifier 6
is the set value from the setting device 5 and the power VX from the multiplier circuit 4.
A signal corresponding to the deviation from I is output. This error amplification 06
The output signal of is given to the inverter 2.

The setting device 5, the error amplifier 6, the inverter 2, and the multiplication circuit 4 constitute a closed loop control system that controls the DC side power of the inverter 2 to be kept constant. Keeping the DC side power of the inverter 2 constant means keeping the effective power of the induction motor 1 constant, and therefore, the rotational force and rotation speed of the induction motor I have an inversely proportional relationship.

A signal corresponding to the deviation between the DC power calculated by the multiplier circuit 4 and the setting value from the setting device 5 is given from the error amplifier 6 to the inverter 2, and the inverter 2 supplies AC power at a frequency corresponding to this signal to the induction motor. Supply to 1. The closed loop control system controls the frequency of the AC power supplied to the induction motor R1 so that the deviation between the DC side power of the inverter 2 and the set value of the setting device 5 becomes zero, that is, the DC side power becomes the set value. Control. As a result, the effective power of the induction motor 1 is constant, and since the rotational force and rotational speed of the induction motor 1 are inversely proportional, the tension applied to the material to be wound by the winder driven by the induction motor 1 is held constant.

FIG. 2 shows a second embodiment. In the first embodiment described above, since the voltage of the DC power supply 3 fluctuates, the DC side power of the inverter 2 is calculated by multiplying the current and the voltage. On the other hand, in this second embodiment, since the voltage fluctuation of the DC power supply 7 is negligible, the DC side power of the inverter 2 is controlled to be kept constant. Hold constant. The setter 8 outputs a set value for the DC side current of the inverter 2, and a signal corresponding to the deviation between this set value and the actual DC side current I is given to the inverter 2 from the error amplifier 9.

Inverter 2 supplies AC power with a frequency corresponding to this signal to induction motor 1. Then, the AC power supplied to the induction motor 1 is controlled so that the DC side current {circle around (2)} of the inverter 2 becomes the set value. As a result, the effective power of the induction motor I becomes constant.

<Effects of the Invention> As explained above, in the present invention, the output frequency of the inverter is controlled so that the DC side power of the inverter that supplies AC power to the induction motor is constant. The rotational force and the rotational speed have an inversely proportional relationship, and therefore an induction motor can be used as the motor for driving the winding machine, making it possible to reduce costs and eliminate the need for maintenance. In other words, inverters have been technologically established in recent years and are manufactured at low cost.
Induction motors are cheaper and more reliable than control devices for DC motors, which have not been widely used.
The price is 6. Furthermore, induction motors are maintenance-free because they do not have consumable parts such as brushes of DC motors.

Furthermore, by using an induction motor in the winder, the efficiency of the induction motor is higher than that of a DC motor, so there is less loss during the process that causes errors. Loss compensation and taper tension control can now be performed in the cylinder, improving the operating accuracy of the winder. Furthermore, by simply adjusting the maximum frequency of the inverter, it is possible to handle from high-speed weak tension to low-speed strong tension without changing the type of motor.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram showing a first embodiment of the present invention, FIG. 2 is a block circuit diagram showing a second embodiment of the present invention, and FIG.
4 and 5 are diagrams showing the drive system of the winding machine. 1... Induction motor 2... Impark 3.7... DC power supply 4... Multiplier circuit 5.8... Setting device 6.9... Error amplifier Patent applicant Nippon Inverter Co., Ltd. person
Patent Attorney Nishi 1) New Figure 2 2 Figure 3

Claims (1)

[Claims] An inverter that converts direct current into alternating current and supplies alternating current power to the induction motor, and a control means that controls the output frequency of the inverter so that the power on the direct current side of the inverter is constant, and the control means controls the rotation of the induction motor. A control device for an induction motor characterized by controlling the force and rotation speed so that they have an inversely proportional relationship.