RATINGS AND GUARANTEES. I? I 



OVERLOAD CAPACITIES. 



89. All guarantees on heating, regulation, sparking, etc., should apply to the rated 

 load, except where expressly specified otherwise, and in alternating-current apparatus 

 to the current in phase with the terminal e.m.f., except where a phase displacement 

 is inherent in the apparatus. 



90. All apparatus should be able to carry the overload specified in Section 92, 

 without self-destruction by heating, sparking, mechanical weakness, etc., and with an 

 increase in temperature elevation not exceeding 15 C. above those specified for full 

 loads, the overload being applied after the apparatus has acquired the temperature 

 corresponding to full-load continuous operation. (See sections 30 to 34.) 



91. Overload guarantees should refer to normal conditions of operation regarding 

 speed, frequency, voltage, etc , and to non-inductive conditions in alternating appa- 

 ratus, except where a phase displacement is inherent in the apparatus. 



92. The following overload capacities are recommended : 



1st. In direct-current generators and alternating-current generators, 25 per cent, for 

 two hours. 



2d. In direct- current motors, induction motors and synchronous motors, not includ- 

 ing railway motors and other apparatus intended for intermittent service, 25 per cent, 

 for two hours, and 50 per cent, for one minute, for momentary overload capacity. 



3d. Synchronous converters. 50 per cent, for one half hour. 



4th. Transformers. 25 per cent, for two hours. Except in transformers connected 

 to apparatus for which a different overload is guaranteed, in which case the same 

 guarantees shall apply for the transformers as for the apparatus connected thereto. 



5th. Exciters of alternators and other synchronous machines, 10 per cent, more 

 overload than is required for the excitation of the synchronous machine at its guaran- 

 teed overload, and for the same period of time. 



7th. All exciters of alternating-current, single-phase or polyphase, generators should 

 be able to give at constant speed, sufficient voltage to excite the alternator, at the 

 rated speed, to the full-load terminal voltage, at the rated output in kilovolt-amperes 

 and with 50 per cent, power factor. 



