SWITCHBOARDS AND SWITCHBOARD APPLIANCES. 331 



switch for closing the circuit and a fuse for opening the circuit in 

 case of excessive over-load or short-circuit, and these simple 

 accessories are usually mounted on the wall conveniently near to 

 the motor. Large induction motors are usually provided with an 

 autotransformer for delivering current at reduced voltage at start- 

 ing, as explained on page 267, and it is usual to provide an auto- 

 matic oil switch, or circuit-breaker, and an ammeter, and these 

 accessories are usually mounted on a switchboard panel as shown 

 in Fig. 281. The diagram of connection for a three-phase induc- 

 tion motor and starting compensator is shown on page 268. 

 Figure 282 shows front and side views of the panel shown in 

 Fig. 281. 



Fig. 282. 



Synchronous converter panels. Figure 280 shows a six-phase 

 synchronous converter (AHR 2,300 V 300 K.W.) with an oil 

 switch, current transformer and ammeter, synchronizing recepta- 

 cle, potential transformer, and three step-down transformers which 

 are delta-connected to the supply mains and which supply six- 

 phase currents to the converter through an induction regulator. 

 The regulator is operated by a small motor, and the field winding 

 of the rotary converter is broken up into sections to avoid the 



