Alarm contacts are sometimes used with machines that are associated with continuous processing, and are used to signal _____?

• A. Power outages
• B. A normal stop
• C. An overload condition
• D. Scheduled maintenance

Answer: (C)

Alarm contacts in machines used for continuous processing are there to alert the control system to conditions that could harm the equipment or affect product quality. An overload condition is exactly that kind of abnormal situation: the load or current is beyond safe limits, which can cause overheating, motor damage, or unsafe operation. When overload occurs, the protective relay activates and the alarm contact changes state, signaling the controller or operator to stop the machine or take action before damage occurs.

Power outages, a normal stop, and scheduled maintenance are expected or planned events and aren’t the kinds of fault conditions that an alarm contact is meant to signal.