Devices used in magnetic across-the-line motor controllers to prevent contact chatter are referred to as?

Devices used in magnetic across-the-line motor controllers to prevent contact chatter are known as shaded rings. Shaded rings are components made typically of copper that are installed on the poles of the relay or contactor to modify the magnetic field. This modification helps to stabilize the contact closure and prevents the rapid opening and closing, or "chattering," of the contacts. Such chattering can lead to excessive wear and tear on the components, creating reliability issues and potential failure in motor control applications.

Shaded rings work by creating a delay in the magnetic field's collapse, allowing for smoother operation of the contactor and ensuring that the motor is engaged or disengaged without abrupt interruptions or oscillations. In contexts where reliable motor operation is critical, particularly for across-the-line starters, these devices play an important role in maintaining system integrity and performance.