What are criteria to calculate nominal power (kW) of an electrical motor?
The nominal power is the mechanical power available at the motor’s shaft and it is done: • for three phases motors: P2 = (1.73 * V * I * cosr * η)/1000 (kW) • for single phase motors: P2 = (V * I * cosr * η)/1000 (kW) Motor nominal power have to be equal – or higher – than power requested from manufacturing machine. A motor over sizing means: • higher starting current; • bigger electrical protection and supply wires dimensions; • more expensive service because power factor (cosr) and, in certain condition, the efficiency for partial load are worse than at full load.
