320 ELECTRICAL ENGINEERING 



the coil to remain in such a position that the required current 

 flows in it. Fig. 300 shows the flux in the core. 



If the resistance or impedance of the load circuit decreases due 

 to the cutting out of one or more arc lamps an increase of the 

 current in both secondary and primary follows and the repulsion 

 between the coils, which is proportional to the product of their 

 currents, increases. The secondary, therefore, rises and increases 

 the leakage reactances of both coils and so less of the primary 

 magnetism links with the secondary; its voltage is, therefore, 

 decreased and its current drops to the required value. The 

 moving arm must be designed to give the required regulation with 

 a fixed weight W. 



Such an arrangement regulates for constant current between the 

 limits of secondary voltage set by the two extreme positions of the 

 moving coil. 



Neglecting the primary exciting current, equation 289, Art. 181, 

 applies to the constant-current transformer. 



#1 = /' r, + fa + 2 (m + fa) +E 



Hi) Iz> TI and rz are constant and x\ and Xz increase as E decreases. 



199. Induction Regulator. Induction regulators are special 

 transformers used to vary the voltage of an alternating-current 

 distributing circuit or the voltage impressed on a rotary con- 

 verter. 



There are two types of induction regulators, single-phase and 

 polyphase. 



(1) The single-phase regulator is illustrated in Figs. 301 to 303. 

 The primary coil P is carried on a movable core built of laminated 

 iron and is connected across the line. The secondary coil S is 

 carried on a stationary core and is connected in series with the 

 line to raise or lower the voltage. (Fig. 304.) 



The primary exciting current produces an alternating flux, 

 which induces a voltage in the secondary. This secondary volt- 

 age varies with the position of the primary winding, but it is 

 always in phase with or in opposition to the impressed voltage or 

 line voltage. In Fig. 301 all the primary flux (neglecting leakage) 

 passes through the secondary coil and the secondary voltage is a 



