Fig. 1,983.—General Electric air cooled constant current transformer. View showing external appearance with case on.
The regulation is said to be "good" or "close," when this change is small. In the design of a transformer, good regulation and low iron losses are in opposition to one another when the best results are desired in both. A well designed transformer, however, should give good results, both as to regulation and iron losses, the relative value depending upon the class of work it has to do, and size.
Transformer Connections.—The alternating current has the advantage over direct current, in the ease with which the pressure and current can be changed by different connections of transformers.
On single phase circuits the transformer connections can be varied to change current and pressure, and in addition on polyphase circuits the phases can also be changed to almost any form.
Single Phase Connections.—The method of connecting ordinary distributing transformers to constant pressure mains is shown by the elementary diagram, fig. 1,984, where a transformer of 10 to 1 ratio is indicated with its primary winding connected to a 1,000 volt main, and a secondary winding to deliver 100 volts.
Fig. 1,984.—Single phase transformer connection with constant pressure main.
Fig. 1,985.—Usual method of single phase transformer connections for residence lighting with three wire secondaries. A balancing transformer is connected to the three wire circuit near the center of distribution as shown.