Overload relays are designed to imitate (on a much smaller scale) the heating patterns of the electric motor it is installed in, and interrupt the current once the heat sensing mechanism in the relay reaches a certain temperature.
An overload relay is made up of a heater paired with normally-closed contacts that open once the heater gets too hot. The overload contacts are connected in series and located between the contactor and the motor itself to prevent the motor from restarting once the overload trips.
Thermal Overload Relay
Thermal overload relay is a protective device, and that is mainly designed to cut the power whenever the motor uses too much current for an extended time period.
To achieve this, these relays include an NC (normally closed) relay. Once extreme current supplies throughout the motor circuit, then the relay gets open because of the improved temperature of the motor, a temperature of the relay, otherwise detected overload current, based on the type of relay.
Magnetic Overload Relay
Magnetic overload relay can be operated by detecting the magnetic field strength which is generated by the flow of current toward the motor. This relay can be built with a variable magnetic core within a coil that holds the motor current. The flux arrangement within the coil drags the core up. As the core increases far enough, then it trips a set of connections on the summit of the relay.
- An Overload relay is extensively used to protect the motor.
- An overload relay can be utilized for detecting both overload conditions as well as fault conditions & then declare trip commands for a protective device.
- Overload relay has developed into microprocessor systems as well as solid-state electronics.
- Overload relays deactivate the device whenever it pulls extreme current.
• Phase-loss sensitivity
• Adjustable tripping current
• Tripping class 10
• Auxiliary contacts 1NO and 1NC
• Hand/Auto/Reset button
• Temperature compensation from -4°F to +140°F
• Standards and Approvals: IEC 60947, VDE 0660, cULus listed, CE Marked, Marine
Source : Temcoindustrial, Elprocus
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