284 



SYNCHRONOUS MOTORS. 



each of four values of the excitation, viz., '9, I'l, 1*36, and 

 1*8 amps. 



The most favourable excitation at the voltage em- 

 ployed in this experiment was about T36 amps., 

 hence the curves show the relation between the load and 

 the watts, current and power-factor for two values of the 

 excitation below the normal, and for one value above the 



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 Pull in Ibs. at rim of pulley. 



FIG. 133. VARIATION OF ARMATURE CURRENT WITH LOAD IN A 



SYNCHRONOUS MOTOR AT VARIOUS EXCITATIONS. 



Pulley, Sin. (Ham. 



normal, as well as the relation for the condition of normal 

 excitation. 



The current curves (Fig. 133) show that with normal 

 excitation the current increases almost in direct proportion 

 to the load, in much the same way as it does with a direct- 

 current shunt-wound motor. With a lower excitation of 

 I'l amps, the current is much greater at light loads, on 

 account of the low power-factor, but approximates to the 

 same value as for normal excitation at higher loads. With 

 the excitation still further- diminished to "9 amps, the 

 initial current is still higher, and although the current 



