Difference between circuit breaker and isolator

The circuit breakers and isolators serve a common purpose of circuit interruption. The primary difference between them lies in their behavior during faults in the circuit. In this article, let’s discuss the difference between a circuit breaker and an isolator.

Isolator/ Disconnectors

An isolator or disconnector, as the name indicates, is a switching or isolation device, intended to disconnect equipment or electrical Circuit from the supply. It is an offload device, which means it can be operated only when the current passing through it is zero. Unlike circuit breakers, it lacks a built-in arc suppression system. It can be operated only during offload conditions.

Difference between circuit breaker and isolator: Isolator

The main purpose of using an isolator is to ensure safety during maintenance. Before operating an isolator it is made sure that the current flowing through it is zero or within safety limits. The Breaking capacity of isolators is very less.

Circuit Breaker

Circuit breakers are protection devices. The main function of a circuit breaker is to protect equipment or circuit from overload and short circuit faults. Circuit breakers sense such faults and interrupt the power flow to the equipment/ circuit, hence preventing further damage to the equipment. The higher the intensity of the fault faster shall be the interruption of power.

Difference between circuit breaker and isolator: Circuit breaker
Circuit breaker

Circuit breakers are also equipped with a built-in arc quenching system. It enables them to be used during load and fault conditions. Various factors are taken into account while selecting a circuit breaker for a particular application.

Comparison of Isolator and circuit breaker

IsolatorCircuit Breaker
The isolator is meant only for interrupting the power during maintenance or repair.Circuit breakers are meant for the protection of a circuit or equipment from short circuit and overload faults while they are in operation.
Isolators can be operated only during offload.Circuit breakers can be operated during both on-load and offload.
The breaking capacity of isolators is very less.The breaking capacity of circuit breakers is high.

Summarizing the difference between circuit breaker and isolator

An isolator is an offload device meant for interruption of power flow to equipment or circuit during maintenance whereas, circuit breakers are protection devices, similar to fuses, that protect the equipment from overload and short circuit faults throughout its operation.

Other related comparisons

12 thoughts on “Difference between circuit breaker and isolator”

    • Switch disconnector is not same as an isolator. Switch disconnectors is an on-load isolation devices, meaning that it can be used to isolate the circuit even when there is power flow to the load. but isolators are off-load devices.

  1. Thanks for the simple explanation.
    Is it possible to combine both dc isolators and dc breakers in the same circuit as they function differently?

  2. What significance does the wattage have on an isolator? I.e if I have a 63amp 22kw 3 pole isolator on say a 30kw motor that’s rated at 60 amps say will that isolator be ok to use?

    • 60A is the maximum current your isolator is designed to carry. If the current exceeds 60A, the isolator could be damaged.

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