electronic Motors operating at low voltage tend to burn out because
Answers
Why are the coils in motor get damaged while it is operating in low voltage?
It is obvious that the question is relevant to Induction motors.
For almost all types of electrical loads, current increases as the supply voltage increases. However in case of induction motors, for a given mechanical load, the motor current is approximately inversely proportional to the supply voltage.
When supply voltage reduces to say 0.8 times the rated, current increases to approximately 1/0.8 time i.e. 1.25 times the rated. Copper loss in the motor increases to 1.25^2 times i.e. 1.56 times. This results in damage to the motor, if over-current/overload protection is not provided.
Why the motor current increases at reduced supply voltage? For almost all types of loads, current is expected to reduce at reduced voltage. However in case f induction motor, it is not so, because speed of the motor is constant, independent of the supply voltage and therefore motor draws constant power for a given mechanical load torque. As the power is constant and current is proportional to"power divided by voltage", current rises with the drop in supply voltage.
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