Free calculator estimate AC motor rating current.
Motor starting current
Motor starting current or locked-rotor current relies on motor design. In NEMA motor design, locked-rotor current specify by design letter (i.e. B, C and D etc.) and voltage level. If a motor complies with IEC 60034, starting current shall be:
- SC/FLC = 7 for LV motors
- SC/FLC = 5 for HV motors
Motor rating again mechanical load
Motor rating shall be selected with sufficient motor torque for all speeds and operating modes (start-up, extreme condition etc.). For general guidance it is possible to choose the kW rating of the motor on a ‘rule-of-thumb’ basis by using table (extracted from API 610) below: