🔍 Key Concepts

• Compare the schematic symbols in figures 1, 2, and 3 and note which type of trip element is present or missing. • Recall how thermal (overload) versus magnetic (short-circuit) trip elements behave in time: inverse-time vs instantaneous. • Think about which protection is normally used for sustained overloads versus short-circuit faults in molded-case circuit breakers.

💭 Think About

• What kind of element is shown in figure 2’s schematic: is it representing a thermal overload element or an instantaneous magnetic element? • Which type of element (thermal or magnetic) is designed to respond slowly to moderate overcurrents, and which one reacts very quickly to very high fault currents? • Looking at the answer choices, which ones pair the correct time characteristic with the type of fault that this element is intended to protect against?

✅ Before You Answer

• Verify whether figure 2 shows only one type of trip element (thermal or magnetic), unlike figure 3 which combines both. • Match inverse-time delay with the type of fault current it is normally used to protect against (overload vs short-circuit). • Match instantaneous trip with the type of fault current it is normally used to protect against (overload vs short-circuit).