Simulation of induction motor under-voltage lockout 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 under-voltage lockout protection is presented. The technique provides a simple model construction and visualization.

Key words: induction motor, under-voltage lockout protection, visualization, simulation.

Introduction

Induction motor is unacceptable to leave the operation in the long deep voltage drops in order to avoid overheating, especially if the motor is fully loaded.

In another case in more frequent cases of short-term disappearance or drastic reduction of voltage to the motor due to short circuits in the power line and off their network of relay protection. The most critical motors must not turned off when power interruptions of up to 10 seconds.

When a break in the supply longer than 0.5 seconds, turn off non-critical motors to facilitate the possibility of starting critical motors. Self-starting of a large number motors is associated with a large decrease in voltage. In addition, the motors of many mechanisms should not operate in the self-starting due to various conditions.

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 under-voltage lockout protection

Checking the operation of the model

The relay has two stages. The first stage has a time delay setting, and 0.5 s voltage equal to 0.7 of nominal. The second stage is triggered when the voltage drops to 0.5 rated voltage (Un) with a time delay of 5 s.

Fig.4 Transient response of induction motor under-voltage lockout protection: a) 1-st stage, b) 1-st and 2-st stage

The figures show the operation of stages the relay when the voltage drops.

Conclusion

The result of this work was confirmed by efficiency of the variant of relay protection.