Generators (Article 445) and Transformers (Article 450)

"Generators" is the second sub-topic of Motors & Generators. Transformer overcurrent protection (Table 450.3(B)) is the other classic Class II-exam calculation in this neighborhood, so it lives here too. Written from the 2023 text.

1. Generators — Article 445

• 445.6: stationary generators shall be listed (one-of-a-kind/custom units may be field labeled). 445.10: generators are of a type suitable for the location and also meet the 430.14 motor location rules (ventilation, maintenance).
• 445.11 nameplate: manufacturer, rated frequency, phases, rating in kW or kVA, power factor, normal volts and amperes, rated ambient temperature; whether or not the neutral is bonded to the frame (field changes get additional marking); generators over 15 kW also provide reactances, power rating category (prime/standby/continuous), temperature rise and insulation class, overload protection method, and available fault current (inverter types).
• 445.12 overcurrent: constant-voltage generators protected from overload by inherent design, breakers, fuses, protective relays or other identified means; two-wire dc generators — one OCPD actuated by the entire generated current (not in the shunt field); generators ≤ 65 V driven by individual motors — the motor OCPD suffices if it operates at ≤ 150 % of the generator's full-load current. Vital generators may alarm instead of trip.
• 445.13(A) conductors, no overcurrent protection at the generator: ampacity from the generator terminals to the first distribution device containing overcurrent protection ≥ 115 % of the nameplate current (100 % where the design prevents overloading). (B): with a listed OCPD or CT/overcurrent relay at the generator, conductors may be tapped from the load side per 240.21(B) (not for portable generators ≤ 15 kW with inaccessible field terminals). Still inside 445.13(A) in 2023: the neutral may be sized per 220.61, and conductors that must carry ground-fault current are no smaller than 250.30(A) requires.
• 445.14: live parts over 50 V ac / 60 V dc guarded. 445.17: terminal housings per 430.12, sized from the hp in