Which types of interlocking are commonly used in motor control circuits?

In motor control circuits, interlocking is a crucial safety and operational feature that ensures certain conditions are met before a machine can operate or a motor can start. The correct answer is the combination of auxiliary contact and mechanical interlocking.

Mechanical interlocking provides a physical barrier that prevents two devices from operating at the same time, which is essential in applications where simultaneous operation could cause damage or create unsafe conditions. For example, in a system where two motors cannot run together due to overload risks, mechanical interlocking would ensure that if one motor is engaged, the other is automatically disengaged.

Auxiliary contacts are additional contacts found on relays and contactors that can be used to provide additional control logic for the circuit. They help in signaling and interlocking functions by providing feedback about the state of the primary device (like whether a motor is on or off). When wired together with mechanical interlocks, they enhance the overall safety and functional logic of the motor control system.

By employing both types of interlocking, the system gains robustness, as mechanical interlocking provides fail-safe physical separation, and auxiliary contacts allow for more complex control and feedback within the electrical circuit. This combination is widely recognized as best practice in motor control design for ensuring both reliable operation and safety.