| Introduction Voltage fluctuation is a common phenomenon in every part of the country. The industrial units running round the clock, usually face the problem of low and high voltage. 90% of industrial load motors . Electric motors draw considerably high current at low & high voltage. This higher current affects the electrical motors ( particularly smaller capacity motors upto 7.5 H.P.) in three ways: |
- Higher current produces higher losses in electrical motors which causes premature failure winding.
- These higher losses of electric motors also increase the losses of cables, switches, transformers and other associated equipments.
- For smooth continuous operation of motors, overload relays are usually set at 20% higher setting.
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| Adverse Effects of Single Phasing |
- The line current increases by 1.5 times.
- If the relay setting is at 15-20% higher than actual operating current then the relay will take 4-6 minutes to trip.
- The motor ( particularly smaller capacity motors upto 7.5 H.P) cannot withstand this high current for such a long time and in most of the cases it burns out before the relay trips.
- Heavy short circuit current flows through the relays, contactors, cable etc.
- Under this condition when the relay, contactor trips, they produce sparks and some times burst.
- This further damages the switch gear and in some of the cases may cause fire also.
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| with the installation of the stabilizer and maintaining 390/400 volts, the motor will operate smoothly drawing 15-20% lesser current and correspondingly the relay setting can be reduced by 15-20% In case single phasing occurs, the relay will trip in 40-50 seconds. The motor can withstand the high current fot this period and will be safe. Also, the relays, contactors, switchgears, etc. incorporated with the motor will be safe |
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Faridabad, Haryana, India
