2-6-08

Ref. Sht. GA31-01 DC Motors and Generators
Revised 2-6-08
OEET 120

Back to Main Page

 DC Motors With Armature and Field Windings Connected to Separate DC Supplies

  • Increasing the armature current causes the motor to speed up.
  • Increasing the field current causes the motor to slow down.
  • An increase in the mechanical load causes the speed to decrease and the armature current to increase.
  • If the mechanical load is increased, and you want the speed to remain constant, you must increase the armature current.
 
DC Generators With Field Winding Powered by a Separate DC Supply
  • The output power comes from the armature windings.
  • Increasing the speed increases the armature voltage.
  • Increasing the field current increases the armature voltage.
  • Increasing the current coming out of the armature (by having a smaller load resistance) decreases the speed and the voltage produced.
    • For most AC motors, an increase in load (mechanical torque being driven) changes the speed only slightly. Once the load becomes too large the motor stalls. These motors either run at close to their normal speed, or they don't run at all.
  • Increasing the current coming out of the armature increases the torque required to maintain the same speed and voltage.
 
Back to Main Page
1