Miniature circuit breaker

The S200 range of miniature circuit breakers (MCBs) has been increased so that five different tripping characteristics are available across the full range, which incorporates standard short circuit capacities of 6, 10 and 15-25 kA.

Where long cable runs need protection, a B-curve MCB will provide the best protection. The C-curve provides general-purpose protection for many light and power applications. For motor-starting and transformer protection, the D-curve is often utilised due to the high inrush or start-up currents of this type of load.

A K-curve characteristic for motor starting and transformer loads, offers improved protection to these circuits due to the better thermal characteristics of this curve (1.05-1.2 times rated current). In the short-circuit range of the K-curve, the protection level is 10-15 times rated current which also matches the characteristics of most inductive loads more closely than a D-curve MCB.

A Z-curve protects semiconductor electronics due to the instantaneous trip values at 2-3 times rated current and the thermal characteristics of 1.05-1.2 times rated current.