TRANSFORMERS 



319 



live of the load. The transformer is used to obtain a constant 

 current for series arc-light circuits. 



When the secondary coil is close to the primary there is very 



Constant 

 Voltage 



FIG. 299. Constant-current transformer. 



little leakage and most of the flux produced by the primary links 

 with the secondary and the secondary voltage is, therefore, a 

 maximum. Primary and secondary currents are in opposite 



FIG. 300. Flux in the core of a constant-current transformer. 



directions and the two coils repel one another. The weight W 

 is so adjusted that the pull due to it together with the force of 

 repulsion of the coils just balances the weight of S and allows 



