502 



ELECTRICAL EQUIPMENT 



contacts are provided. These carry the greater part of the 

 current flowing through the switch and obviate the necessity of 

 having large currents to pass within the oil vessel. These main 



contacts are outside the oil ves- 

 sel but inside the fireproof com- 

 partments of the cell, and so 

 placed as to secure the maxi- 

 mum radiation. In opening the 

 breaker they break contact be- 

 fore the contact rod, which opens 

 the circuit and ruptures the con- 

 sequent arc under oil. The main 

 contacts are of the laminated 

 brush type or of the ordinary 

 wedge-shaped finger type. 



To prevent throwing oil, a 

 baffle is used in each oil vessel. 

 By the baffle, the movement im- 

 parted to the oil by the expan- 

 sion of the gases formed by the 

 arc when the circuit is opened 

 under load is checked and di- 

 verted in such a manner as to 

 allow the gases to separate from 

 the oil and escape through the 

 vent in the cover of the oil ves- 

 sel, while the oil itself is forced 

 back into the region of the break- 

 ing arc under pressure, thus 

 shortening the time of breaking 

 the arc, confining the disturbance 

 or explosive effect on short cir- 

 cuit and practically eliminate 

 flashes due to hot gases and the 

 oil from the oil vessels. The 

 movement of the oil away from 

 and towards the center of the oil 

 vessel on the breaking of the cir- 

 cuit and also the movement of 

 the gases, are indicated in Fig. 309. The oil loses its velocity 



FIG. 309. Oil Vessel for High- 

 capacity Oil Circuit Breaker 

 Showing Oil Baffle Arrangement 

 and Contacts. 



