Inspite of best efforts, no state electricity board can ensure constant voltage to the customer because of long and inadequate distribution lines and irregular load pattern on distribution transformers. Generally Voltage is low during day time and high during night hours. Moreover on holidays, peak hours, rainy days and when agricultural and Industrial load is switched off, the voltage rises sharply which is more dangerous.
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 cause premature failure of winding.
- These higher losses of electric motors also increase the losses of cables, switches, transformers and other associated equipment.
- 3. For smooth continuous operation of motors, over load relays are usually set at 20% higher setting.
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 motors can withstand the high current for this period and will be safe. Also, the relays, contactors, switchgears, etc. incorporated with the motor will be safe.
|The table below compares the behaviour of 5 H.P. motor at different voltages:|
|425||11% More||18% More||0.7|
|435||19% More||28% More||0.60|
|445||265 more||38% More||0.57|
|The table below compares the behaviour of 60 watt lamp at different voltage:|
|Voltage||Current||Watts||Luminous Intensity||Life in Hours|
|240||0.27||65 W-8.3% More||820||575|