Overload Relays
Many industries rely on their electronic motor to power their machinery and otherwise aid in their production processes. This critical component needs protection from faults and failure to ensure a long part life and less lost time. Overload relays are designed for protecting a motor from damage from overcurrents and overloads, input phase loss and phase imbalance.
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Allen-Bradley592-TPD630: Allen-Bradley NEMA Overload Relay
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Allen-Bradley592-TPD200: Allen-Bradley NEMA Overload Relay
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Allen-Bradley592-KOV16: Allen-Bradley NEMA Overload Relay
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What Are Overload Relays?
An overload relay is a device that protects an electric motor from overloads and failure. It can sense when the motor is being overloaded and will stop the power flow to mitigate damage. It will also protect motors from phase loss, failures and imbalance. The current will flow through its three poles. If it is interrupted at one of the poles, the current will increase at the other two poles. This increase causes the overload relay to trip.
One variety of overload relay — thermal overload relays — use electrothermal properties to detect overcurrent. The current flows through its poles, heating a bimetallic strip. If the flow exceeds the limits, the strip will bend. This bending activates the tripping mechanism that halts the power supply to the contactor coil and the current flow to the motor.
Uses for Overload Relays
Overload relays are crucial in any application that requires motor protection, such as manufacturing and robotics. Overload relays are incorporated in a circuit that contains contactors. It’s positioned in line with the motor, so the current flows through the overload relay first. Many contactors use overload relays in motor control centers.
Common Problems and Questions With Overload Relays
Though overload relays may seem similar to circuit breakers, they are quite different. Overload relays do not provide the same protection as a circuit breaker, as these devices do different things. The overload relay interrupts the current to the motor to protect the motor, whereas the circuit breaker protects the power distribution to the motor. Both are necessary for comprehensive protection.
Overload relays also do not protect against short circuits, so short circuit protection devices should also be incorporated into your company’s protective machinery.
