Rated Capacity
The maximum continuous power output a transformer can deliver at specified conditions without exceeding temperature limits.
Rated capacity (nameplate rating) is the maximum continuous apparent power at specified conditions without exceeding temperature rise limits. Valid for rated voltage, frequency, cooling mode, max ambient (typically 40C).
Above design ambient requires derating (see altitude derating). Cooling failure reduces to ONAN rating.
Can temporarily exceed (overload) per emergency loading guides (IEC 60076-7, IEEE C57.91).
QDTB specifies rated capacity for all cooling stages and provides loading guides. See nameplate for full specifications.
Related Products
Related Terms
kVA Rating
The apparent power rating of a transformer in kilovolt-amperes, determining load-carrying capacity.
Nameplate Rating
Manufacturer's certified specifications on the transformer nameplate defining all critical parameters.
Temperature Rise
The temperature increase of transformer components above ambient at rated load, a key design parameter.
Cooling Class (ONAN/ONAF/ODAF)
Standardized codes describing transformer cooling methods: O=Oil, N=Natural, A=Air, F=Forced, D=Directed flow.
More Terms Starting with “R”
Reactor
An inductive device in power systems to limit current, absorb reactive power, or filter harmonics.
Rectifier Transformer
A transformer designed to supply rectifier/inverter loads with enhanced harmonic and DC magnetization handling.
Voltage Regulation
The change in secondary voltage from no-load to full-load as a percentage, indicating voltage stability.
Ring Main Unit (RMU)
A compact factory-assembled HV switchgear set for ring-type or radial distribution networks.
More in “Performance Parameters”
Core Loss
Power dissipated in the transformer magnetic core due to hysteresis and eddy currents, also called iron loss or no-load loss.
Copper Loss
Power lost as heat in transformer windings due to electrical resistance, proportional to the square of load current.
Efficiency Class (IE1-IE4)
International classification for transformer energy efficiency, IE1 (standard) to IE4 (premium) with progressively lower losses.
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