CHAPTER VI. 

 THE TRANSFORMER. 



The Transformer. One of the greatest advantages of alternat- 

 ing over direct currents is the ease with which an alternating 

 current may be converted from a low current at high pressure 

 to a high current at low pressure of approximately equal 

 power, and vice versa, without the employment of rotating 

 machinery. 



The transformer is the means by which this transformation 

 is accomplished. The principles underlying its construction 

 and behaviour are illustrated in the experiments which 

 follow. 



General Principles. Fig. 59 represents a rectangular 

 frame consisting of a number of soft-iron stampings of the 

 shape shown, placed side by side, so that the section of the 

 frame is approximately square. This forms a magnetic 



FIG. 59. PRINCIPLE OF THB TRANSFORMER. 



circuit of very high permeability without any air gap. Two 

 separate windings of insulated wire are indicated as being 

 wound upon this magnetic circuit, one winding being con- 

 nected to an alternator. A current sent through either 

 winding will produce a magnetic flux in the core, which is 

 the name usually applied to the magnetic circuit of a trans- 

 former. The general direction of this flux is indicated in the 

 diagram by a dotted line. An alternating current flowing 

 in the coil connected to the alternator will produce an alter- 

 nating field in the magnetic circuit as indicated in the diagram, 

 where the upper arrows show the direction of current and 



