20 STANDARDIZATION RULE.^ Of 1'IIE A.I.E.E. 



202 In a HVDKAI in ! t RHINE or OTHER WATER-MOTOR, the regulation is 

 the ratio of the maximum variation of speed in passing slowly from rated- 

 load to no-load (at constant head of water; i.e.. at constant difference of 

 level between tail race and head race), to the rated-load speed, 

 variation and pulsation see Sees. 59-64. 



203 In a GENERATOR-UNIT, consisting of a generator united with a prime- 

 mover, the regulation should be determined at constant conditions of the 

 prime-mover; i.e pressure, head, etc. It includes the 

 inherent speed variations of the prime-mover. For this reason the regu- 

 lation of a generator-unit is to be distinguished from the regulation of 

 either the prime-mover, or of the generator contained in it, when taken 

 separately. 



(II) CONDITIONS FOR AND TESTS OP REGULATION. 



204 SPEED. The REGULATION OF GENERATORS is to be determined at con- 



.t speed, and of alternating apparatus at constant impressed frequency. 



205 N ON INDUCTIVE LOAD. In apparatus generating, transforming or t: 

 mitting alternating currents, regulation should be understood to refer to 

 non-inductive load, that is, to a load in which the current is in phase with 

 the e.m.f. at the output side of the apparatus, except where expressly 

 specified otherwise. 



206 WAVK FORM. In alternating apparatus receiving electric power, regu- 

 lation should refer to a sine wave of e.m.f., except where expressly speci- 

 fied otherwise. 



207 EXCITATION. In commutating machines, rectifying machines, and syn- 

 chronous machines, such as direct-current generators and motors, alter- 

 nating-current and polyphase generators, the regulation is to be. deter- 

 mined under the following conditions: 



(1) At constant excitation in separately excited fields. 



(2) With constant resistance in shunt-field circuits, and 



(3) With constant resistance shunting series-field circuits; i.e., the 

 field adjustment should remain constant, and should be so chosen 



give the required rated-load voltage at rated-load current. 



208 IMPEDANCE RATIO. In alternating-current apparatus, in addition to the 

 non-inductive regulation, the impedance ratio of the apparatus should be 

 specified; i.e., the ratio of the voltage consumed by the total internal im- 

 pedance of the apparatus at rated-load current, to its rated-load voltage. 

 As far as possible, a sinusoidal current should be used. 



209 COMPUTATION OF REGULATION. In synchronous machines the open- 

 circuit exciting ampere-turns corresponding to terminal voltage plus arma- 

 ture-resistance-drop, and the exciting ampere-turns at short-circuit for 

 rated-load current should be combined vectorially to obtain the r 



ant ampere-turns, and the corresponding internal e.m.f. should be taken 

 from the saturation curve. 



1C. INSULATION. 



(I) INSULATION RESISTANCE. 



210 INSULATION RESISTANCE is the ohmic resistance offered by an insulating 

 coating, cover, material or support to an impressed voltage, tending to 

 produce a leakage of current through the same. 



211 OHMIC RESISTANT K AND DIKLECTRIC STRENGTH. The ohmic resistance 

 of the insulation is of secondary importance only, as compared with the 

 dielectric strength, or resistance to rupture by high voltage. Since the 

 ohmic resistance of the insulation can be very greatly increased by baking, 

 but the dielectric strength is liable to be weakened thereby, it is preferable 

 to specify a high dielectric strength rather than a high insulation resist- 

 ance. The high-voltage test for dielectric strength should always be ap- 

 plied. 



212 RECOMMENDED VALUE OF RESISTANCE. The insulation resistance of 

 completed apparatus should be such that the rated terminal voltage of the 



apparatus will not send more than j QOO 000 * the ratcd * loa<i current 



