Contactor Sizing (DOL Motor)

Full-load and direct-on-line starting current, AC-3 making/breaking capacity and contactor selection with overload-relay setting.

Inputs

Motor power P kW

Supply voltage U V

Power factor cos φ —

Efficiency η —

Starting-current factor × Iₛ

Contactor Iₛ (AC-3) A

Results

Note — AC-3 contactors must carry Iₛ continuously and make ≥10×Iₛ / break ≥8×Iₛ (IEC 60947-4-1). De-rate for duty cycle, ambient temperature and frequent switching. Verify against the manufacturer's utilisation-category curves and a certified engineer.