44 COMMERCIAL ELECTRICAL TESTING 



In starting, the switches A are closed and the motor 

 M allowed to come up to speed, until the speed of the 

 motor running as a generator is above synchronism. 

 The alternator field is opened momentarily, whilst the 

 switches B are closed. The circuit in the alternator 

 field is then closed again, and full load current flows 

 through the two machines. No changes in load can 

 be made without changing the pulley ratio and it is 

 absolutely necessary that this ratio be correct in order 

 to obtain full load. 



