Short-term power (KB) of a transformer

The short-time power (KB) of a transformer describes the maximum power that it can supply for a short period of time without unacceptable heating or voltage drops occurring.

It is particularly important for control transformers, as high power is required for a short time when contactors and relays are switched on (pick-up power of the coils).

The design is carried out under defined conditions, typically with a power factor (cos φ) of around 0.5 and a maximum permissible voltage drop of 5% compared to the rated output voltage.

The short-time power ensures that even brief switch-on processes are carried out reliably without impairing the function of the control circuit.