What happens to the current in the relay when current transformer-type overload relays are activated?

When a current transformer-type overload relay is activated, the circuit functions in such a way that it measures the load current using the current transformer. In an overload condition, the current transformer will produce a secondary current that is proportional to the primary current, specifically reflecting the higher load. As this overload condition is detected, the output to the relay may experience an increase in measured current.

This increase in current effectively signals to the relay that an overload condition exists, prompting the relay to respond appropriately, such as tripping a circuit or alerting operators to potential issues. Therefore, an increase in current to the relay is indicative of the overload situation being recognized and addressed, which demonstrates the operational principle behind these types of overload relays.