408 



ALTERNATING CURRENTS 



disturbances occur; the induction motor does not require direct- 

 current excitation; it is very rugged. Its principal disadvantages 

 are that it takes lagging current and at light loads its power- 

 factor is low. 



FIG. 373(a). Switch assembly with cells, mechanism, etc. 



The advantages and disadvantages of the synchronous con- 

 verter as compared with motor-generator sets have already been 

 discussed in Par. 137, page 342. 



175. Oil Switches. With an ordinary air-break switch, it 

 is practically impossible to break a high-voltage circuit sup- 

 plying any considerable amount of power. Special air-break 



