CHAPTER XXIV 



SINGLE-PHASE REGULATORS 



The IRS, or single-phase induction regulator is built 

 for use with electric furnaces and for the control of single- 

 phase lighting feeders. It comprises a primary and a 

 secondary winding, the former being placed in slots 

 on a movable core and the latter in slots on a stationary 

 core. The regulator may be wound with two poles, four 

 poles, six poles, or with any even number of poles; it 

 may be cooled by an air blast, or it may be placed in a 

 tank and cooled by oil, or by oil and water. 



The voltage induced in the secondary winding depends 

 upon the relative position of primary and secondary 

 windings, the primary being in shunt and the secondary 

 in series with the circuit to be controlled. Single-phase 

 as well as polyphase regulators have a distributed wind- 

 ing for both primary and secondary, but the maximum 

 pole face which can be covered by an active winding in a 

 single-phase regulator, in order to produce the best 

 results, is approximately 60 per cent. In the neutral 

 position of the regulator, the secondary winding there- 

 fore encloses an area on the primary core not enclosed by 

 an active primary winding, and the impedance would be 

 extremely high if no auxiliary winding were provided. 

 The slots of the primary which are not used for an active 

 winding are therefore filled with a short circuited winding 

 so that in the neutral position of the regulator the cur- 

 rent in the secondary induces a current in the short 

 circuited winding, thus reducing the impedance. 



The tests required are cold resistances, "boost" and 

 "lower, " core loss, impedance, heat runs and insulation. 

 Cold resistance is measured as on transformers. The 

 "boost" and "lower" test is made at the full potential 

 of the regulator and therefore requires care, as the mag- 

 netic leakage is greater at normal potential than at a 



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