Ans. The damaged windings should be separated electrically from the other coils.
The pressure winding of the damaged phase should be short circuited upon itself and the corresponding low pressure winding should also be short circuited upon itself. The winding thus short circuited will choke down the flux passing through the portion of the core surrounded by them without producing in any portion of the winding a current greater than a small fraction of the current which would normally exist in such portion at full load.
Transformer Losses.—As previously mentioned, the ratio between the applied primary voltage and the secondary terminal voltage of a transformer is not always equal to the ratio of primary to secondary turns of wire around the core.
The commercial transformer is not a perfect converter of energy, that is, the input, or watts applied to the primary circuit is always more than the output or watts delivered from the secondary winding.
Fig. 1,938.—Interior of General Electric oil cooled 500 kva. 33,000 volt outdoor transformer showing lifting arrangement.
This is due to the various losses which take place, and the difference between the input and the output is equal to the sum of these losses. They are divided into two classes:
- 1. The iron or core losses;
- 2. The copper losses.
The iron or core losses are due to
- 1. Hysteresis;
- 2. Eddy currents;
- 3. Magnetic leakage (negligibly small).