The overload relay is the heart of motor protection and may be used instead of overcurrent protective equipment.

• A. True
• B. False
• C. Sometimes true
• D. Only for AC

Answer: (B)

Overload protection and short-circuit protection are separate functions in motor protection. An overload relay protects the motor from overheating by tripping when current stays high for too long, which safeguards windings during normal operation faults or extended overloads. But it isn’t designed to respond instantly to a severe fault or short circuit, and it won’t reliably interrupt fault currents fast enough to prevent damage. That’s the role of an overcurrent protective device, such as a fuse or circuit breaker, which is required to disconnect the circuit during a short circuit or severe fault. Because you need both types of protection—thermal (overload) and instantaneous (short-circuit)—you can’t rely on an overload relay alone to meet motor protection requirements. Hence the statement is not correct.