n RATING OF ELECTRICAL MACHINERY 



VARIATION OF PRESSURE AND SPEED 



BELGIUM. 



Generators. The pressure variation of a generator is 1 by 



the greatest difference observed, at constant speed, between any two 

 values of the pressure corresponding with loads, the current of which 

 does not exceed that defined by the rated load, the ; la-ing regu- 



at this current, to the rated load value. The brushes to remain 

 adjusted in the working position. 



i . The excitation of a generator, intended to work at constant pr 

 mu*t be capable of maintaining the rated value of the pressure under normal en: 

 of angular speed, at all loads from no load up to and including l.l.'i times the rated load 



Motors. The speed variation is defined as the difference in angular 

 speed at rated load and at no load at normal working pressure, and with- 

 out a "f field rheostats adjusted for the rated load. 



FK\XCE. 



ne rotors. The pressure variation shall be measured in passing 

 from the rated load to no 1 nt speed, in the case of self- 



S machines, whilst maintaining constant the resistance in the field 

 circuit; in the case of separately excited machines, whilst maintaining 

 constant the exciting current. During this test, and unless oil. 

 specified, the brushes shall remain fixed in the rated load sparkless position. 

 Motors. The speed variation shall be measured in passing trom the 

 rated load to no load, with constant pressure at the terminals. 



GERMANY. At constant rated load speed and excitation, the pressure 

 to be observed at, at least, four points practically equidistant on the 

 load curve. The greatest difference between the observed press^: 

 a measure of the variation. In regard to the adjustment of brushes, the 

 conditions are to be governed acco-ding to the rating. 

 GREAT BRITAIN. 



DEN. At constant rated load speed an<! itio of 



the increase in pressure at raUd load and the pressure at no load, shall 

 be taken: 



(1) By observing the values of the pressure at no load and at rated load: 



(2) By observing the values of the pressure with increasing val 

 the field current, both with no load on the armature and with tht 

 load current in the ermature. Tolerance allowed 2 per cent. 



I" MI i I. STATES. 



Generators. Ratio of maximum variation of terminal pressure from 

 the normal (occurring between rated load and no load) to the rated 

 load pressure. 



Motors. Ratio of maximum variations in speed from the normal 

 (occurring between rated load and no load) to the rated load spe< 



HEA TING 

 General Notes 



BELGIUM. The test is to be carried out as nearly as possible under 

 ordinary working conditions. An overload may be applied at th< 

 mencement of the test in order to attain more rapidly the final conditions 

 of temperature. 



The maximum temperature is to be compatible with the 

 employed. Special precautions are to be taken when employing ther- 

 mometers. Unless otherwise specified, apparatus for variable speed and 

 pressure shall be tested under the most severe conditions. 



FRANCE. The maximum temperature is to be compatible with the 

 insulation employed. 



GERMANY. The tests are to be carried out under the conditions of 

 service specified. Any ventilation which would naturally be produced 

 under ordinary working conditions and which was provided for in the 

 design may be imitated during the test. If a thermometer is employed, 



