THE INDUCTION MOTOR. 



The test is carried out by observing the primary and 

 secondary amperes of the induction motor, the watts sup- 

 plied, and the slip, first at no-load, and then for a series of 

 increasing values of the load up to about 25 per cent, over- 

 load for an ordinary commercial test, or up to the point 

 of stoppage of the motor in the case of a more complete 

 experiment. 



The results should be entered under headings similar 

 to those shown below, and curves plotted with either 

 watts or horse-power output horizontal, and primary and 

 secondary current, slip, efficiency, apparent efficiency 

 / = _ watts output, y ^ factor yertical 



V volt-amperes input,/ 



In the tests of motors usually carried out, it is not the 

 general practice to measure the current in the secondary, 

 as its exact value is not of first importance in the behaviour 

 of the motor, and its approximate value can be deduced 

 from the other quantities observed, as already explained 

 on page 378. 



Several other useful curves may be plotted from the 

 results of this experiment, such as : watts absorbed 

 and primary current on a load base. 



LOAD TEST OF THREE-PHASE INDUCTION MOTOR. 



Motor No Type '. 



Output h.p., at revolutions per minute. 



Voltage. ^ 



The three columns for watts are to be employed when 

 readings are taken in two phases, so that their sum gives 

 the total power. Where a 3-phase wattmeter is em- 

 ployed only one column will be required. 



