16 STANDARDIZATION Kt'/.l // A.I.E.E. 



nections of cross-connected armatures, TV and other losses in armature- 

 coils and armature-leads which are short-circuited by the brushes 

 as these losses are due to rotation. 



131 i. Ai IIKNMIM; or TRANSFORMER Loss. These losses are measured 

 by wattmeter in the field circuit, under the conditions of test b. 

 include molecular magnetic friction and eddy-currents due to the alter- 

 nation of the magnetic field, TV losses in cross-connections of cross-con- 

 nected armatures, Pr and other losses in armature coil and commutator 

 leads which are short-circuited by the brushes, as far as these losses are 

 due to the alternation of the magnetic flux. 



132 The losses in armature-coils and commutator leads short-circuited by 

 the brushes, can be separated in ft, and c, from the other losses, by run- 

 ning the machine with and without brushes on the commutator. 



133 d. 7 1 /? Loss, other load losses in armature and compensating wind- 

 ing and TV loss of brushes, may be measured by a wattmeter connected 

 across the armature and compensating winding. 



134 f. FIELD Ex< n AIK.N Loss. See Measurement of Losses (//), Sec. 113. 

 136 /. COMMUTATOR BRUSH-FRICTION. See Measurement of Losses (B), 



Sec. 103. 



(C) SYNCHRONOUS COMMUTATING MACHINES. 



136 1. In DOUBLE-CURRENT GENERATORS, the efficiency of the machine 

 should be determined as a direct-current generator, and also as an alter- 

 nating-current generator. The two values of efficiency may be different, 

 and should be clearly distinguished. 



137 2. In CONVERTERS the losses should be determined when driving the 

 machine by a motor. These losses are: 



138 a. BEAR'ING FRICTION AND WINDAGE. See Measurement of Losses (A), 

 Sec. 102. 



139 b. MOLECULAR MAGNETIC FRICTION AND EDDY CURRENTS. See Meas- 

 urement of losses (D) Sec. 105. 



140 c. ARMATURE-RESISTANCE Loss. This loss in the armature is q 7 2 r, 

 where / = direct current in armature, r = armature resistance and q. a 

 factor which is equal to 1.47 in single-circuit single-phase, 1.15 in double- 

 circuit single-phase, 0.59 in three-phase, 0.39 in two-phase, and 0.27 in 

 six-phase converters. 



141 d. COMMUTATOR-BRUSH FRICTION. See Measurement of Losses (B), 



103. 



142 e. COLLECTOR-RING BRUSH FRICTION. See Measurement of Losses (C), 

 Sec. 104. 



143 /. COMMUTATOR, BRUSH AND BRUSH-CONTACT RESISTANCE Loss. See 



urement of Losses (F) Sec. 111. 



144 g. COLLECTOR-RING BRUSH-CONTACT RESISTANCE Loss. See Measure- 

 ment of Losses (C), Sec. 112. 



145 h. FIELD-EXCITATION Loss. See Measurement of Losses (//), Sec. 109. 

 148 i. LOAD LOSSES. These can generally be neglected, owing to the ab- 

 sence of field distortion. 



147 3. i ICIENCY OF Two SIMILAR CONVERTERS may be determined 

 by operating one machine as a converter from direct to alternating, and 

 the other as a converter from alternating to direct, connecting the alter- 

 nating sides together, and measuring the difference between the direct- 

 current input and the direct-current output. This process may be modi- 

 fied by returning the output of the second machine through two boosters 

 into the first machine and measuring the losses. Another modification 

 is to supply the losses by an alternator between the two machines, using 

 potential regulators. 



(D) SYNCHRONOUS MACHINES. 



148 In SYNCHRONOUS MACHINES the losses are: 



149 a. BEARING FRICTION AND WINDAGE. See Measurement of Losses (A). 

 Sec. inj 



160 b. MOLECULAR MAGNETIC FRICTION AND HDDY CURRENTS. See Mea- 

 surement of Losses (/>), Sec. 105. 



