Work out motor full load current instantly with clear inputs, formula shown and shareable results.
Motor nameplate power is mechanical output at the shaft, so the electrical input is that divided by efficiency. Full load current then follows from the three-phase relation. Direct-on-line starting draws roughly 6-8 times full load current, which is what sizes the protection and the supply.
Motor full load current
I = (kW / efficiency) x 1000 / (sqrt(3) x V x pf); DOL start current is about 6.5 x FLC
Electrical results are planning estimates only. Verify against the applicable wiring rules (IEC 60364, BS 7671, NEC or local code) and have all installation work designed and checked by a qualified electrician.
Overload protection is set on full load current, but short-circuit protection must let the starting surge through, so the two are sized differently.
The voltage dip during starting can trip other equipment. Star-delta, soft starters and VFDs all exist to limit that surge.