While calculating the rating capacity of a circuit breaker, $\frac{\text{ Making capacity }}{\text{ Breaking capacity }}$ = ________.

Relationship between making and breaking current capacity

The rated breaking capacity is the maximum fault current a circuit breaker can successfully interrupt without damage.

It is always expressed in KVA and the current corresponding to breaking capacity is known as the breaking current.

The breaking current is given by:

$I_b=\frac{MVA}{\sqrt{3}\times V_L}$

where, Ib = Breaking current capacity

MVA = Apparent power  

VL = Line-to-line voltage

The relationship between making and breaking current is:

$I_m=2.55\times I_b$

where, Im = Making current

Ib = Breaking current

$\frac{\text{ Making capacity }}{\text{ Breaking capacity }}=2.55$