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 is of 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 of 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.
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, cables etc.
- Under this condition when the relay, contactor trips, they produce sparks and some times bursts..
- This further damages the switchgear and in some of the cases may cause fire also.
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 for this period and will be safe. Also, the relays, contactors, switch gears, etc. Incorporated with the motor will be safe.
Plot No. 195, Sector-24, Faridabad, Haryana, 121005, India