🔍 Key Concepts

• Thermal overload relay operation and purpose • Difference between test button and reset button on protective devices • How overload relays change state between normally closed (NC) and normally open (NO) auxiliary contacts when tripped

💭 Think About

• Look at what the nearby reset button already does; how would the function of the test button need to be different so both are useful? • Think about how you could safely check that an overload relay will trip without actually overloading the motor or changing the real current. • Consider whether the test button would realistically change the trip setpoint (amps value) or just change the relay’s contact position temporarily.

✅ Before You Answer

• Identify which device part in figure A actually performs the reset function and which one is labeled test button. • Decide whether a test you perform from the front of the relay can measure exact current or only simulate the tripped condition. • Confirm in the choices which options describe simulating a trip versus changing contact state after a real trip or measuring current value.