Attachment 8 – Effects of Low Voltage

(1)Electric Motors (Refrigerator)

Effects of low voltage. When you subject a motor to voltages below the nameplate rating, some of the motor’s characteristics will change slightly and others will change dramatically. To drive a fixed mechanical load connected to the shaft, a motor must draw a fixed amount of power from the line. The amount of power the motor draws has a rough correlation to the voltage to current (amps). Thus, when voltage gets low, the current must increase to provide the same amount of power. An increase in current is a danger to the motor only if that current exceeds the motor’s nameplate current rating. When amps go above the nameplate rating, heat begins to build up in the motor. Without a timely correction, this heat will damage the motor. The more heat and the longer the exposure to it, the more damage to the motor.



The answer is: it depends on the type of appliance, and occasionally the effort that the manufacturer put into protection against those conditions. Modern electronic devices such as PC’s or TV’s have switching regulators in them that compensate for variable supply voltage. Interestingly, if the supply voltage drops, those devices draw *more* current in order to automatically keep the device’s power level constant, unlike non-regulated appliances like incandescent lamps. In extreme conditions, though, these regulated devices also often have over and undervoltage lockouts to turn themselves off.





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