Thinking SCK Inrush Limiters

A Surge Current Killer (SCK) is an NTC power thermistor that can prevent a temporary, dangerously high inrush current surge from damaging electrical equipment when it’s first switched on. These current limiters are most commonly used in switching power supplies, low-voltage lighting transformers, LED driver circuits and DC motors.

The SCK series limiters operate by offering a high resistance when the equipment is first switched on, but then gradually reduce their resistance to a much lower value as they heat up – through I2R self-heating. This protects slow charging capacitors (e.g. in switch-mode power-supplies) or can help to bring electric motors or transfomers up to full operation (i.e. soft-start) by keeping the initial surge current within safe limits.

The SCK series offers diameters from 5mm to 30mm and continuous (solid-state) through current values of upto 30A.  By selecting the correct combination of cold (R25) resistance value and suitable disc diameter, a very effective surge protection device can be achieved.

Applications

• Switch mode power supplies
• Electric motors
• Lighting transformers
• LED driver circuits
• Halogen lamp circuits

Features