JPS61288784A - Induction motor with winding for brake - Google Patents

Abstract

PURPOSE:To enable to stop a motor in emergency when a variable frequency controller is out of order by winding a brake winding on a rotor in addition to a squirrel-cage winding, and supplying a DC current to the brake winding to generate a brake torque. CONSTITUTION:A main switch 2 is closed, and an auxiliary switch 7 and an exciting switch 10 are opened in a normal operation. When a variable frequency controller 1 becomes defective, the switch 2 is opened, and a power switch 13 and the switch 10 are then closed to supply a DC current by a transformer 12 and a rectifier 11 through a brush 6 and a slip ring 5 to a brake winding 4. The rotor can be stopped in emergency by connecting a load resistor 8 with a stator winding 3 by the voltage induced in the winding 3 and closing the switch 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an induction motor and a control device thereof, and particularly to a configuration and circuit system of an induction motor suitable for performing emergency braking.

[Background of the invention]

Recently, variable alternating current (AC) has been developed in the main machinery of rolling mills, and a representative example is a drive system that combines a squirrel cage induction motor and a variable frequency control device (for example, a cycloconverter). By the way, if you want to make an emergency stop of the squirrel cage induction motor for some reason, there are various braking methods (for example, regenerative braking and two-phase braking) when there is no abnormality in the variable frequency control device, but if the variable frequency control device is malfunctioning, When this happens, there is no way to make an emergency stop, and when the above drive system is used, it has the disadvantage of having a large negative impact on the product. The braking method for induction machines is specified in Induction Machines (University Course of the Institute of Electrical Engineers of Japan) K.

[Purpose of the invention]

The purpose of the present invention is to eliminate the above-mentioned drawbacks and to provide a structure and a circuit system for a squirrel-cage induction motor for emergency stop of the squirrel-cage induction motor when a variable frequency control device fails. be.

[Summary of the invention]

In order to achieve the above object, the present invention winds a brake winding i in addition to the squirrel cage winding around the rotor of a squirrel cage induction motor.
If the variable frequency control device fails, the output of the control device is disconnected, a resistive load is connected to the stator winding, and DC current is supplied to the brake winding from an external power source to obtain braking torque. This is how it was done.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. Second
The figure shows a sectional view of a rotor of a squirrel cage induction motor suitable for performing an emergency stop according to the present invention. In the figure, 1 rotor core 14
A conductor 16 of KFi squirrel cage winding is inserted into the slot 15 of . Furthermore, the characteristic feature is that the same slot 150
A brake winding 18 is wound around the lower part with an insulator 17 interposed therebetween. FIG. 1 shows a circuit diagram of a variable frequency control device suitable for performing an emergency stop according to the present invention. In the figure, 1 is a variable frequency control device, 2 is a main switch,
3 is a stator winding, 4 is a rotor winding in which the brake winding 18 is connected in three phases (the squirrel cage winding is not shown), 5 is a slip ring, 6 is a brush, 12 is a transformer, 13 is the power switch.

In this configuration, the present invention will be described in detail.

During normal operation, main switch 2 is closed, auxiliary switch 7,
When the excitation switch 10 is opened, a voltage is applied to the stator winding 3 by the variable frequency control device 1, and the rotor is synchronized with the power supply frequency by the action of the rotor squirrel cage winding (not shown). and rotate. In addition.

The variable frequency control device IFi operates in response to the output signal of the position detector 9 directly connected to the rotor shaft, and controls the entire speed of the motor to an appropriate value.

Next, if the variable frequency control device 1 breaks down, it is desirable that it can be stopped immediately from the perspective of the load side. For this reason, in the configuration of FIG. 1, when the variable frequency control device 1 fails, the main switch 2 is first opened, and then the power switch 13.
By closing the excitation switch 10, a direct current from the transformer 12 and the rectifier 11 is supplied to the break/key winding 4 via the brush 6 and the slip ring 5. In this case, DC magnetic flux is generated by the rotating brake winding 4, and a voltage is induced in the stator winding 3. Therefore, by closing the auxiliary switch 7 and connecting the load resistor 8 to the stator winding 3, a load current flows through the stator winding 3.
It is possible to absorb the inertial torque generated on the rotor shaft and to make an emergency stop of one rotor.

〔Effect of the invention〕

According to the present invention, even if the variable frequency control device fails, the squirrel cage induction motor can be safely and urgently stopped. As a result, it is possible to minimize the adverse effects on the load device driven by the variable frequency controlled squirrel cage induction motor and the products produced thereby.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the drive and emergency stop of a squirrel-cage induction motor according to an embodiment of the present invention, and FIG. 2 is a sectional view of a main part of its rotor. 1... Variable frequency control device, 2... Main switch, 3
... Stator winding of squirrel cage induction motor, 4... Rotor winding by brake winding of squirrel cage induction motor, 5...
・Slip ring, 6... Brush, 7... Auxiliary switch, Death... Load resistance, 10... Excitation switch, 1
1... Rectifier, 12... Transformer, 13... Power switch.

Claims (1)

[Claims] 1. In a squirrel-cage induction motor driven by a variable frequency control device, a brake winding is wound around the rotor of the squirrel-cage induction motor in addition to the squirrel-cage winding. An induction motor with a brake winding, characterized in that rotational torque is obtained by a squirrel cage winding during operation, and control torque is obtained by a brake winding during an emergency stop. 2. In claim 1, a main switch that opens each phase is provided between the variable frequency control device and the squirrel cage induction motor, and after opening the main switch, the brake winding is connected to the external power supply. A wire-wound induction motor for brakes is equipped with an excitation switch for supplying direct current and an auxiliary switch for connecting the stator winding to a resistive load, thereby making it possible to emergency stop a squirrel-cage induction motor. Electric motor. 3. The induction motor with a brake winding according to claim 1, characterized in that the brake winding is provided at the lower part of the slot into which the squirrel-cage winding is inserted, with an insulator interposed therebetween.