STANDARDIZATION RULES OF Till .\.I.E.E. 



173 () COLLECTOR BRUSH-CONTACT RESISTANCE. See Measurement of 

 Losses (), Sec. 1 



174 ffl FIELD-EXCITATION. See Measurement of Lossr 



176 (t) LOAD LOSSES. See Measurement of Losses (/), Sec. Ill 



(//) RECTIFYING APPARATUS, PULSATING-CURRENT GENERATORS. 



176 This division includes: open-coil arc machines and mechanical and 

 other rectifiers. 



177 In RECTIFIERS the most satisfactory method of determining the efficiency 

 is to measure both electric input ana electric output by wattmeter. The 

 input is usually inductive, owing to phase displacement and to wave dis- 

 tortion. For this reason the power factor and the apparent 



should also be considered, since the latter may be much lower than the 

 true efficiency. The power consumed by auxiliary devices, such a 

 synchronous motor or cooling devices, should be included in t 

 input. 



178 In Cos RRENT RECTIFIERS, transforming from constant poten- 

 tial alternating to constant direct current, by means of constant-current 

 transforming devices and rectifying devices, the losses in the transforming 

 devices are to be included in determining the efficiency and have to be 

 measured when operating the rectifier, since in this case the losses may be 

 greater than when feeding an alternating secondary circuit. In constant- 

 current transforming devices, the load losses may be considerable, and 

 therefore, should not be neglected. 



179 In OPEN-COIL ARC Y . the losses are essentially the same 

 direct-current (closed coil) commutating machines. In this case, how- 

 ever, the load losses are usually greater, and the efficiency should prefer- 

 ably be measured by input- and output-test, using wattmeters for m 

 ing'the output. 



179a In alternating-current rectifiers, the output should, in general, be 

 measured by wattmeter and not by voltmeter and ammeter, since 

 owing to pulsation of current and voltage, a considerable discre; 

 may exist between watts and volt-amperes. If, howev t-current 



and an alternating-current meter in the rectified circuit (either a volt- 

 meter or an ammeter) give the same reading, the output ma ; sured 

 by direct-current voltmeter and ammeter. The type of alternatin 

 rent instrument here referred to should indicate the effective or root-of- 

 mean-square value and the type of direct-current instrument the arith- 

 metical mean value, which would be zero on an alternating-current circuit. 



(/) TRANSMISSION LINES. 



180 The EFFICIENCY of transmission lines should be measured with non- 

 inductive load at the receiving end, with the rated receiving voltage and 

 frequency, also with sinusoidal impressed wave form, except where ex- 

 pressly specified otherwise, and with the exclusion of transformers or 

 other apparatus at the ends of the line. 



(/) PHASE-DISPLACING APPARATUS. 



183 In SYNCHRONOUS PHASE-MODIFIERS and exciters of induction generators, 

 the determination of losses is the same as in other synchronous machines. 



184 In REACTORS the losses are molecular magnetic friction, eddy losses 

 and 7* r loss. They should be measured by wattmeter. The losses of 

 reactors should be determined with a sine wave of impressed voltage 

 except where expressly specified otherwise. 



185 In CONDENSERS, the losses are due to dielectric hysteresis and leak- 

 age, and should be determined by wattmeter with a sine wave of voltage 

 or by an alternating-current bridge method. 



186 In POLARIZATION CELLS, the losses are those due to electric resistivity 

 and a loss in the electrolyte of the nature of chemical hysteresis. These 

 losses may be considerable. They depend upon the frequency, voltage 

 and temperature, and should he de .-rminv 1 with 



pt \vher- i ntheru 



