Motor Protection – Different protection units are used for the safeguard of the electric motors. Motors are used at various levels in various applications. Induction motors are hugely used at the domestic level as well as industrial or commercial level. Different categories of induction motors are used in industrial units. The big industrial motors are costly, thus the protection of a motor is an important parameter. Different motor protection units are used for the protection of motors. The motor protection can be divided into various categories depending upon the operation of the motor. The different protection categories for a motor are discussed below.
Overload protection is the type of protection which is against the mechanical overload conditions. The mechanical overload conditions can occur in a motor due to various reasons when a motor is in a running state. The overload situations can result in the increased temperature of the motor which can damage the motor. The protection used for the overload conditions can disconnect the motor in overload conditions from the main power supply. When the motor is overload due to any circumstance the windings of the motor arphote subjected to fire as the temperature of the motor is increased in overload conditions and as a result, the windings of the motor can be damaged. Similarly, if the outlets of the motor are covered and there is no point for the heat emission than the temperature of the motor is also increased as the motor keeps on running this can also result in the damaged windings of the motor. The overload protection units are tripped in case of an overload condition and the supply of the motor is cut-off and the motor is protected from further damage.
Whenever an excessive amount of current is passed through the motor, the motor protection unit is tripped. Circuit breakers and the fuses are used as protection units for the different motors. Overcurrent protection can protect personnel from electric shock, the control equipment of the motor, the conductors of the motor branch circuits and the motor itself from high currents.
Low Voltage Protection:
The protection unit or the device is used to disconnect the motor from the voltage source or the power source in case the voltage drops down below the rated value for the motor. The motor operates again whenever the voltage is balanced to the normal value. Different protection units have their own resetting points. Some protection units are manually reset. Some protection units are automatically reset to normal following different algorithms. Some protection units are reset to normal after some predefined interval of time. Some units can be reset to normal when the voltage stabilizes to its normal value.
Phase Failure Protection:
Phase failure protection is used to protection of motor in case of any phase failure during the operation of the motor. It is normally used in three-phased motors and upon failure, in any phase, the motor is disconnected from the power supply. A motor without phase failure protection keeps on running even if a phase is failed in the circuit which can damage the motor or it can affect the operation of the motor. If one phase is failed the other phase starts to deliver more current to the circuit which can burn the motor or the circuit it is attached with.
Phase Reversal Protection:
Phase reversal protection is a protection technique that is used to protect a motor from the phase reversal condition. Phase reversion in a motor can occur due to numerous reasons which can cause safety and operational problems. If two connections out of three connections of a motor are reversed somehow the motor starts rotating in the opposite direction. Upon detection of the opposite rotation of the motor, the protection unit for phase reversal disconnects the motor from the mains supply.
Ground Fault Protection:
Ground fault protection is used to protect the motor from different short circuit conditions. An excessive amount of current flows through the motor or the circuit in case of the short circuit. Ground fault protection is used to disconnect the motor in case of any ground fault.