Generator Sizing for Motor Starting

Required generator kW / kVA from running load and motor-starting kVA at the 30% voltage-dip criterion.

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Formula and source

Steady kW = Σ running_kW + non_motor_kW. Worst starting kVA = max over motors of starting_kVA(motor); starting_kVA = HP × code_kVA_per_HP from the NEMA MG-1 code letter, OR LRA × V × √phases / 1000 if the user supplies LRA. Required gen kVA = worst_starting_kVA / dip_factor (0.30 default per the 30% voltage-dip criterion). Required kW = max(steady, required_starting_kVA × 0.8).

NEMA MG-1 (Motors and Generators) by name; engineering-practice 30% voltage-dip criterion for transient motor starts.

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