13-08-2012, 05:10 PM
Motors
MotorPrimerGaTech.pdf (Size: 308.24 KB / Downloads: 27)
Introduction
This section contains information about implementing dc motors in a mechanical system. Pimary emphasis is placed on DC permanent magnet motors, since these motors are the most common, least expensive, and lightest type of motors.
Elementary Theory of DC Permanent Magnet Motors
Since this type of motor uses a permanent magnet to generate the magnetic field in which the armature rotates, the motor can be modeled by the electrical circuit in the armature alone. If we further simplify the circuit by ignoring the inductance of the armature coil, we arrive with the following circuit diagram for a simple motor:
Limitations of this motor model
There are several assumptions that we have made in the development of this model, which are very important to keep in mind when using the above relations to implement a dc permanent magnet motor:
Motor Specifications
Normally, when you obtain a motor from a commercial source, you will not immediately know all the information necessary to characterize the motor in terms of the theoretical development above. Some motors include the Stall Torque, the no-load speed, and the Resistance, while others include only the rated voltage and the power output at maximum power. In these cases, there are several things you can do to experimentally determine the motor constant, internal resistance of the motor, etc. Here are some basic steps to take to characterize your motor: