162 



ELECTRICAL MACHINERY 



were taken off a series motor the speed would rise to such 

 a value that the centrifugal forces brought into play would 

 be so large that the winding would be thrown off the arma- 

 ture core and the commutator would probably be thrown 

 to pieces. 



Limited Application of Series Motor. This peculiarity 

 of the series motor limits its use to those classes of service 



Armature current 



FIG. 101. Speed-load Curves for A-shunt motor, 5-series Motor, 

 C-compound Motor. 



in which the motor may be directly (or by gears) connected 

 to its load so that under no condition would it be running 

 without enough load to hold its speed down to a safe value. 

 A series motor should never be belted to its load, because 

 if the belt should run off the motor pulley, the motor would 

 immediately start to " race " and in a few seconds would 



