Current Sensitive Devices - these include circuit breakers, fuses, motor starter heaters of all types and instantaneous current relays.
There are three basic methods of protecting a motor from winding failure.ġ. Ventilation Failure - blocked air openings, broken fans, or anything which may disrupt the normal ventilation system on a motor to open when the motor is running will cause abnormally high winding temperatures resulting in failure. High or Low Voltage - depending on winding design, high or low voltage can cause excessive currents and permanent winding damage.ħ. Voltage Unbalance - since the winding temperatures increases by a percentage equal to 2 times the square of the voltage unbalance, this can easily cause excessively high winding temperatures resulting in permanent winding damage.Ħ. Abnormally High Temperatures - an environmental condition where the motor is exposed to abnormally high temperatures can cause the total winding temperature to reach a point where permanent damage can occur.ĥ. This will permanently damage the motor winding.Ĥ. Running Overload - an abnormal condition which overloads the motor when it is running causing it to draw higher current then designed for. Starting Overload - an excessively high overload due to increased friction or inertia on the drive system can cause excessive temperature on the winding and permanent damage.ģ. Locked Rotor - a mechanical failure of some type which locks the rotor and prevents it from turning when power is applied to the motor.Ģ. A complete protection system for a winding is designed to remove the motor from the line when any of the following conditions occur:ġ. Down time in many motor applications are prohibitive and a good monitoring system is essential to minimize costs which can be incurred. Excessive winding temperature can permanently damage the winding, greatly reducing winding life and can cause complete winding insulation breakdown and failure. Winding protection is providing protection against excessive temperature.
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