202 COMMERCIAL ELECTRICAL TESTING 



shows e.m.f. induced in secondary coils directly in phase 

 with the primary impressed e.m.f. This is the position 

 of maximum boost. Positions CCC represent the neutral 

 position, and DDD the maximum lower position. EEE 

 represents a position between neutral and maximum 

 lower. 



By changing the position of the armature with respect 

 to the field the secondary voltage may be made to assume 

 any phase relation with respect to the primary e.m.f.; 

 it can be in series with it or directly opposed to it. This 

 movement of the armature is obtained by means of a 

 segment on the shaft which meshes with a worm on the 

 small operating shaft. The regulator may be arranged 

 for hand operation only, or can be motor operated. 

 Either a direct current or an induction motor may be 

 used. The motor is controlled by a small double-pole 

 double-throw switch on the switchboard, by means of 

 which the voltage is raised or lowered as desired. 



To stop the regulator on reaching the limits of regula- 

 tion when moving in either direction, a limiting switch is 

 provided which opens automatically. If properly con- 

 nected, however, this automatic cut-off does not interfere 

 with movement in the opposite direction, which can be 

 obtained by the double-pole double-throw switch. 



The winding of the primary and secondary is similar 

 to that of a Form M induction motor the primary being 

 placed on the movable core. For a three-phase or six- 

 phase regulator the primary may be Y- or delta-con- 

 nected; for an IRH six-phase regulator, the primary may 

 be connected diametrically. The secondary or station- 

 ary winding is placed on the stationary core and is an 

 open winding, each section or phase being connected in 

 series with the corresponding phase of the line to be 

 controlled. 



The tests required are cold resistance, boost and lower, 

 core loss, impedance, heat run, hot resistance, double 

 potential for one minute, one and one-half potential for 

 five minutes, and high potential test. If the regulator 

 is motor operated, the motor should be tested during the 

 heat run to save rewiring. Air readings should be taken 

 on the air blast regulators. 



