RATING OF ELECTRICAL MACHINERY 



In the case of a generator inseparable from its prime mover, bearing 

 friction is to be excluded. 



The losses in exciters or in auxiliary apparatus are to be considered 

 separately, and charged t<> the plant consisting of the machine toge' 

 ;>pnratus. 



The plant efficiency is to be distinguished from the efficiency of the 

 machine alone. The of a machine is to be me > 



reduced to, the temperature which the machine assumes under i 

 load conditions, referred to a surrounding air temperature of 25 deg. cent. 



Method 



ALL Cot SIKH.-. D i< tly by input output, where possible. 

 Indirectly by losses, if the direct method is not possil 



Enumeration of Losses 

 BELGIUM. 



FRANCE. 



^inical. (a) Bearing friction and ventilation. 



(6) Friction of brushes on commutators and collecting 



rings. 

 Electrical. (c) Hysteresis and Foucault currer 



(d) Joule effects in the circuits. 

 GERMANY. The losses are not enumerated in tabular form. 



GREAT BRITAIN. 



SWEDEN. 



(a) Bearing, brush and air friction. 

 (6) Hysteresis and Foucault currents. 



(c) Ohmic losses in armature. 



(d) Ohmic losses in brushes. 



(e) Ohmic losses in exciting coils. 

 UNITED STATES. 



(a) Bearing friction and windage losses. 



(b) Molecular magnetic friction and Foucault current losses. 



(c) Armature resistance losses. 



(d) Commutator-brush friction loss. 



(e) Brush and brush-contact resistance losses. 

 (/) Field excitation loss. 



(g) Load losses. 



NOTES. FRANCE. Association Alsatienne includes under electrical losses brush con- 

 tact resistance. 



UNITED STATES. (/) Losses may be considerable with carbon brushes in low voltage 

 machine*. <<> Difference between total lostes under load and sum of losses as here 

 specified. 



DIELECTRIC TESTS 

 General Conditions of Test 



iiUM. Dielectric tests take the place of insulation tests unless the 

 machine is intended for localities in which special conditions are imposed. 



The test is to be carried out before the machine is put into actual 

 service. The repetition of the test is to be avoided. 



The test is to be carried out hot. 



The windings of machines and transformers must be capable of with- 

 standing, for a period of half an hour, a working pressure of 30 per cent 

 in excess of the highest pressure of the service. 



FRANCE. The test of the insulation is to be carried out hot, when 

 possible, and shall only be made in the works of the manufacturer. 



The test pressure is to be applied gradually. The circuits of ma- 

 chines and transformers shall be capable of withstanding, without undue 

 strain, for a period of three minutes, a pressure 30 per cent in excess of 

 the ordinary working pressure, provided no mechanical or electrical 

 considerations are against it. 



