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close this bookElectrical Machines - Basic vocational knowledge (Institut für Berufliche Entwicklung, 144 p.)
close this folder8. Transformer
close this folder8.2. Operational behaviour of a transformer
View the document8.2.1. Idling behaviour Idling features
View the document8.2.2. Short-circuit behaviour
View the document8.2.3. Loaded voltage behaviour
View the document8.2.4. Efficiency

8.2.4. Efficiency

Efficiency represents the ratio of power output to power input.

Efficiency is determined by the separate loss indication.

Pin = Pout + PVFe + PVW


rated power of the transformer given

cos j = 1 (resistive load)


metered winding losses in short-circuit trial


metered iron losses in no-load trial

The following equation applies for determining efficiency for partially inductive or capacitive load:



Sn = 100 kVA
PVFe = 570 W
PVW = 2.1 kW
cos j = 0.85

Sought: h