Specifying the Making Current of a Circuit Breaker

Introduction:
The making current of a circuit breaker is the maximum current that the breaker can safely interrupt when closing onto a fault. It is important to specify this value accurately to ensure the proper functioning of the breaker and to prevent damage to the electrical system.

Method of Specification:
The normal practice to specify the making current of a circuit breaker is in terms of peak value. This means that the maximum peak current that the breaker can safely interrupt is specified.

Reason for Peak Value:
The reason for specifying the making current in terms of peak value is that the peak value of the current is the value that causes the most stress on the breaker's contacts. The peak value occurs at the instant of contact closure, and it is this value that determines the ability of the breaker to interrupt the fault current.

Alternative Values:
While peak value is the normal practice for specifying making current, it is possible to specify the value in other ways as well. For example, RMS value and average value are two other possible methods of specification. However, these values are less commonly used and may not accurately reflect the breaker's ability to interrupt a fault.

Conclusion:
In summary, the making current of a circuit breaker is normally specified in terms of peak value. This is because the peak value is the value that causes the most stress on the breaker's contacts and determines the breaker's ability to interrupt a fault. While other values such as RMS and average value may be used, they are less commonly used and may not accurately reflect the breaker's ability to interrupt a fault.