Simulation of induction motor overload protection

S.A Utanan, A.S. Glazyrin.

Department of Electric Power System, National Research Tomsk Polytechnic University, Tomsk, Russia

Abstract

In this paper a simulation of induction motor overload protection is presented. The technique provides a simple model construction and visualization.

Key words: induction motor, overload, visualization, simulation.

Introduction

Overload occurs when the motor starts and protracted self, due to congestion driven mechanisms. For motor only is stable dangerous overload. Overcurrent due to start-up or self-motor, short-lived and self-destruct when the normal speed.

A significant increase in motor current can also be obtained at phase failure. At rated load, depending on the parameters of the motor stator current increase in the phase loss will be about (1.6 - 2.5) Ir. This overload is sustained. Also, sustained overcurrent is caused by mechanical damage or rotated by the motor mechanism and they overload mechanism. The main danger of over-current is the accompanying increase in the temperature of their individual parts, and first of all windings.

Relay has an definite time curve, which determines the response time of protection

The principle of protection

The scheme of the majority of the relay can be represented in the form of several basic blocks. There are converter, rectifier, low pass filter, comparator.

Fig.1 Block diagram of the relay

This principle of construction can be realized in Simulink.

Fig. 2 Simulink model of induction motor overload protection

The operation of definite time curve implemented in the block subsystem.

Fig. 3 Scheme element of subsystem

Checking the operation of the model

Relay starts with increasing current up to 1.1 of rated (I_im) value of the delay time is determined by the level of current. The delay time at a 1.1I_im equal to 5 s.

Fig.4 Transient response of induction motor overload protection: a) 1.1 of rated current b) significant overload c) inrush current

The figures show the operation the relay when the changing current.

Conclusion

The result of this work was confirmed by efficiency of the variant of relay protection. The main features include a way to implement a time delay.