560 



ELECTRICAL EQUIPMENT 



of instruments required. Also, for making the necessary connec- 

 tions at the time of synchronizing. The contact elements are of 

 brass and come through the panel to the front, but are counter- 

 sunk in a hard rubber escutcheon plate, which makes accidental 

 contact very unlikely. The plugs have brass contacts supported 



,____ by a hard rubber shield, which 



also serves as a protection to 

 the hand. 



As will be noted from the 

 diagram of connections (Fig. 

 345), eight-point voltmeter 

 receptacles are provided for 

 the A.C. generator so that 

 the voltage across all the three 

 phases can be read in turn 

 when the plug is inserted. 



With the synchronizing 

 scheme, as shown in Fig. 345, 

 the synchronizing is actually 

 done between the machines. 

 For this reason two plugs are 

 required, one of which is in- 

 serted in the receptacles of one 

 of the machines which is run- 

 ning and the other in the re- 

 ceptacles of the machine 

 which is to be started and 

 synchronized. 



Ammeter Transfer Recep- 

 tacles. These are for reading 

 the current in any of three 

 phases on one ammeter by 

 changing the connections from 



the front of the panel. Each unit of a group consists of a brass 

 plug switch receptacle with fiber insulation, with contacts back 

 of the panel and with a molded bushing on the front. For read- 

 ing the current, the transfer plug is inserted in rotation in each 

 of the three receptacles of a group. Between such readings the 

 plug can be left inserted in one receptacle, thus giving a continu- 

 ous indication on that phase. 



FIG. 350. Automatic Throw-over 

 Switch. 



