The overload protection device in the motor starter detects excessive over-current conditions in the motor by measuring the motor current through the contactor’s power circuit. When an overload condition exists, the overload contacts in the lower power motor control circuit de-energizes the contactors.
What is the purpose of an overload device for a motor?
Overload relays protect the motor, motor branch circuit, and motor branch circuit components from excessive heat from the overload condition. Overload relays are part of the motor starter (assembly of contactor plus overload relay). They protect the motor by monitoring the current flowing in the circuit.
What is an overload device?
Overload protection is a protection against a running overcurrent that would cause overheating of the protected equipment. … Some devices provide both overcurrent and overload protection. A thermal-magnetic circuit breaker has both thermal (overload) and magnetic (overcurrent) elements.
What must be done before a motor overload can be reset?
the overload relay cannot be reset until the overload heater has cooled. The overload relay is reset by first turning the starter all the way off and then turning it back on.
What is the difference between a breaker and an overload?
More specifically, circuit breakers and fuses are designed to detect when there is too much current in the circuit, while overload relays are designed to detect if a motor is overheating and will open the circuit if the motor gets too hot.
Is an overloaded circuit dangerous?
Overloaded electrical outlets, or circuits that supply power to several outlets, is a major cause of residential fires. Overloaded outlets and circuits carry too much electricity, which generates heat in undetectable amounts. The heat causes wear on the internal wiring system and can ignite a fire.
Do all motors need overload protection?
EVERY motor needs overload protection of some type. Some small motors are impedance protected by design. Some motors can be overload protected by breakers or fuses. Some motor have internal temp probes that shut down the motor starter.
How do you check motor overload?
Overload Protection Test:
- Measure the normal motor running current (i motor).
- Turn off the motor and let it cool for about 10 minutes.
- Calculate the following ratio: i (motor) / i (overload min FLA). …
- Set the overload to its minimum FLA and turn on the motor.
- Wait for the overload to trip.
What is a overload protector?
The overload protector sits near the condenser by the current start relay and ensures the condenser does not overheat while working. If the overload protector senses that the compressor is approaching failure from overheating, it will temporarily shut the compressor down to allow it to cool.