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Motors that are driven by direct current come in a
vast assortment of physical sizes, with or without integral reduction
gears, and with and without shaft position encoders. Electrically,
these motors come in three basic forms:
- The series motor, Figure 1a. These motors have the
field windings in series with the armature. They have a high starting
torque. When lightly loaded they have a tendency to increase in
speed with time to the point that they can actually be damaged, so
they should not be run without a load or a speed control mechanism.
- The shunt motor, Figure 1b. These motors have the
field windings in parallel with the armature. Shunt motors have
less starting torque than a comparable series motor, but they are
usually very good. These motors have the property that once spun
up they approach a set speed and maintain a nearly constant speed
over a wide range of loads.
- The compound motor, Figure 1c. A compound motor has
both series and parallel field windings. They have the high starting
torque characteristics of series motors and the constant speed
characteristics of shunt motors.
From the perspective of controlling the motor all three of these
motors are identical.
Next: Controlling the motor speed
Up: number4
Previous: Introduction
Skip Carter
2008-08-20