HOW A MOTOR STARTER WORKS
A Motor Starter is an electrical control and protection device designed to safely start, stop, and protect electric motors from overload and phase failure. It combines a switching mechanism with a Bi-Metal Thermal Overload Relay to ensure reliable motor operation and long service life.
Working Principle
When the START button is pressed, the contactor coil is energized, causing the main contacts to close. This allows electrical current to flow through the contactor and thermal overload relay to the motor, enabling it to start and operate normally.
During normal operation, the Bi-Metal Thermal Overload Relay continuously monitors the motor current. As long as the current remains within the rated limit, the relay keeps the circuit energized and the motor runs safely.
If the motor draws excessive current due to overload, the bi-metal strips inside the thermal relay heat up and bend. This activates the trip mechanism, opening the control circuit and de-energizing the contactor coil. As a result, the main contacts open and disconnect the motor from the power supply.
The 25A Thermal Overload Relay provides adjustable overload protection within its specified current range, ensuring accurate tripping according to the motor's rated current while preventing overheating and winding damage.
Protection Mechanism
Normal Condition: The contactor remains energized, allowing power to flow through the overload relay to the motor for continuous operation.
Overload Condition: The bi-metal relay detects excessive current, heats up, bends, and trips the contactor, disconnecting the motor automatically.
Manual Reset: After the fault is removed and the relay cools down, the overload relay can be reset manually before restarting the motor.
Result
The Motor Starter automatically controls motor operation while protecting it against overload conditions. Its integrated 25A Bi-Metal Thermal Overload Relay helps prevent overheating, extends motor life, and ensures safe, reliable, and efficient performance in industrial and commercial applications.
