THE INDUCTION MOTOR. 



381 



The nature of the curves to be obtained from this 

 experiment may be judged from Fig. 185, taken from 

 tests of a 3| h.p. 3-phase Oerlikon motor running at a 

 frequency of 50, and having a synchronous speed of 1,500 

 revs, per minute. 



As a further illustration, some additional curves 

 obtained in another experiment in a rather different 

 manner are shown in Fig. 186. The motor employed 

 this case was a 2 % h.p. Brown-Boveri motor with slip rings 

 having a synchronous speed of 1,500 revs, per minute on a 

 200-volt 50-cvcle circuit. These curves are given as an 



100 



2 4 6 8 10 12 14 16 18 20 



Amperes load on d.c. generator. 



FIG. 186. LOAD TEST OF INDUCTION MOTOR COUPLED TO DIRECT-CURRENT 

 GENERATOR. 



illustration of a simple method of obtaining load curves 

 of a motor by coupling it to a direct-current generator. 



The test was carried out with a voltage supply of 120 

 volts instead of 200, as it was found that the currents 

 flowing in the motor windings when heavily loaded at the 

 full voltage produced dangerous overheating. The load 

 on the motor shaft was a direct-current generator driven 

 by a belt, and excited with a constant current. The 

 currents plotted horizontally in Fig. 186 are the currents, 

 generated by the direct-current machine + $.e no-load 



