Electrical Machines - Basic vocational knowledge (Institut für Berufliche Entwicklung, 144 p.): 8. Transformer: 8.2. Operational behaviour of a transformer: 8.2.4. Efficiency

Electrical Machines - Basic vocational knowledge (Institut für Berufliche Entwicklung, 144 p.)

8. Transformer

8.2. Operational behaviour of a transformer

		8.2.1. Idling behaviour Idling features
		8.2.2. Short-circuit behaviour
		8.2.3. Loaded voltage behaviour
		8.2.4. Efficiency

Efficiency represents the ratio of power output to power input.

Efficiency is determined by the separate loss indication.

P_in = P_out + P_VFe + P_VW

P_out	rated power of the transformer given
	cos j = 1 (resistive load)
P_VW	metered winding losses in short-circuit trial
P_VFe	metered iron losses in no-load trial

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

Example:

Given:

S_n = 100 kVA
P_VFe = 570 W
P_VW = 2.1 kW
cos j = 0.85

Sought: h

Solution: