PHASE CHANGERS, ETC. 



[Exp. 



Position of Bator 



of different values or of different phase. A form* of apparatus 

 in common use is essentially an induction motor with wound 

 secondary brought out to terminals, and any induction motor so 

 constructed can be used as an induction regulator. 

 Such an apparatus may be used : 



1. As a single-phase potential regulator; used on lighting 

 feeders. 



2. As a phase shifter; used in laboratory testing. 



3. As a polyphase potential regulator ; used on polyphase lines, 

 particularly in supplying current to synchronous converters. 



5. (i) Single-phase Potential Regulator. 

 Supply the primary (or one phase of the 

 primary if a polyphase induction motor is 

 used) with a constant single-phase voltage not 

 exceeding the normal voltage of the apparatus. 

 The secondary voltage may be varied by turn- 

 FIG. i. Use as ing the rotor by hand to any desired position, 

 single-phase trans- and current be drawn to the full _ load 



former ; secondary 



voltage for differ- rating of the secondary. The apparatus is 



ent positions of ro- usec i m two ways : (a) as a transformer with 



primary and secondary not connected together ; 



(b) as an auto-transformer with the two coils connected, as in 



Fig. 2. 



6. (a) Use as Transformer. Place a voltmeter across the 

 open secondary and revolve the rotor step by step, so that the 

 secondary potential changes between zero and a maximum. (On 

 open circuit the data for methods (a) and (b) can be taken 



* (4a). An earlier form of regulator had stationary primary and sec- 

 ondary coils located at right angles, and a movable iron core which formed 

 part of the magnetic circuit and permitted more or less of the primary 

 flux to pass through the secondary. This device is sometimes referred to 

 as a " magnetic shunt." 



For a description of different forms of regulators, see: "Alternating 

 Current Feeder Regulators," by W. S. Moody (a paper before the Toronto 

 Section, A. I. E. E., February, 1908) ; " Alternating Current Potential 

 Regulators," by G. R. Metcalfe, Electric Journal, August, 1908. 



