Energy storage motor circuit breaker size

What size circuit breaker for a 5 horsepower motor?

A 70-amp circuit breaker is a standard size so the correct size for the maximum overcurrent protection device for this 5 horsepower motor. If a calculation for the protective device does not match a standard circuit breaker size, then the next higher overcurrent protection device rating can be used.

What does a circuit breaker do?

Circuit breakers are designed to trip (or break the motor circuit from the main supply) when motor circuit current exceeds the circuit breaker rating, preventing motor damage. Consider a scenario where a 40 amp circuit breaker was specified for an electric motor circuit.

Is an oversized breaker better than an undersized breaker?

An oversized breaker is just as bad (or even worse) than an undersized circuit breaker: it won't protect the motor circuit from fault currents and may burn and damage the motor. The National Electrical Code (NEC) Article 430 specifies rules and considerations for correctly sizing overload protection devices.

What is a 40 amp circuit breaker?

Consider a scenario where a 40 amp circuit breaker was specified for an electric motor circuit. It means that the circuit breaker will trip at 40 amp regardless of the type of load the motor is subjected to. From this example, it would make sense to use a 100 A circuit breaker for a 40 A motor circuit, right? Wrong!

What is a circuit breaker in an electric motor?

Engineers mitigate these risks by including circuit breakers in electric motor circuits, which simply makes (or breaks) the electric motor circuit under normal (or fault) conditions.

Can an instantaneous trip circuit breaker be used?

An instantaneous trip circuit breaker can only be used if it is adjustable and part of a listed combination motor controller, 430.52 (C) (3). The second exception concerns whether or not the selected protective device can carry the starting current of the motor.