Start with the operating duty
Emergency operation during a utility outage differs from daily long-hour operation. Prime power (PRP) generally serves variable loads over extended operation; emergency standby power (ESP) serves utility outages. Constant-load continuous operation involves a separate continuous power (COP) rating.
Compare more than the largest number
Confirm the rating category, kW, kVA, frequency, voltage and applicable conditions. Annual hours, average loading and overload permission depend on the specific manufacturer rating. Do not derive every standby rating as prime × 1.1 or assume overload is always allowed.
A practical selection example
Suppose equipment needs 80 kW continuously during operation. A label of “100 kVA standby” alone does not establish suitability for daily long-hour service. Confirm the duty first, then the relevant rated kW, operating load, starting needs and derating for temperature and altitude.
Information to include in an inquiry
Send the application, daily hours, utility availability, simultaneously running equipment, site altitude and ambient temperature. Catalogue products are references for published specifications; the final configuration needs a review of actual conditions.
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Technical reference: Caterpillar