What occurs when the seal-in (holding) contact on a motor starter is opened?

When the seal-in (holding) contact on a motor starter is opened, the circuit that keeps the motor starter's coil energized is interrupted. This action causes the motor to lose its electrical supply, ultimately leading to the motor stopping.

The purpose of the seal-in contact is to maintain the contactor in an energized state after the start button has been released. When the start button is pressed, the coil gets energized, and the seal-in contact closes, allowing the current to continue flowing. However, if this contact opens, it breaks the circuit, and the motor control circuit is de-energized.

This mechanism ensures that the motor operates only when intended, providing safety and control in industrial applications. Hence, the effect of opening the seal-in contact is that the motor will stop.