Why is an inverse-time circuit breaker used with motors?

Why is an inverse-time circuit breaker used with motors?

• A. To trip instantly on overload
• B. To start the motor slower
• C. To allow high starting current and trip on overload
• D. To provide ground fault protection

Answer: (C)

An inverse-time circuit breaker is used with motors because motors need a large inrush current when starting, but still must be protected from sustained overloads. The inverse-time characteristic means the higher the overcurrent, the faster the breaker will trip. This lets the motor take full advantage of a brief startup surge without immediately tripping, and, once the motor reaches speed and the current settles to normal running levels, the breaker remains closed. If the motor experiences an overload or stalls and the current stays high, the breaker trips after a short delay, protecting the motor and wiring. It’s not about starting the motor slower, and it’s not specifically for ground-fault protection.

An inverse-time circuit breaker is used with motors because motors need a large inrush current when starting, but still must be protected from sustained overloads. The inverse-time characteristic means the higher the overcurrent, the faster the breaker will trip. This lets the motor take full advantage of a brief startup surge without immediately tripping, and, once the motor reaches speed and the current settles to normal running levels, the breaker remains closed. If the motor experiences an overload or stalls and the current stays high, the breaker trips after a short delay, protecting the motor and wiring. It’s not about starting the motor slower, and it’s not specifically for ground-fault protection.