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Automating Manufacturing Systems - Process Control and ...

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continuous actuators - 24.17<br />

torque<br />

speed<br />

Figure 24.15<br />

Torque Speed Curve for a Brushless DC Motor<br />

24.2.4 Stepper Motors<br />

Stepper motors are designed for positioning. They move one step at a time with a<br />

typical step size of 1.8 degrees giving 200 steps per revolution. Other motors are designed<br />

for step sizes of 1.8, 2.0, 2.5, 5, 15 <strong>and</strong> 30 degrees.<br />

There are two basic types of stepper motors, unipolar <strong>and</strong> bipolar, as shown in Figure<br />

24.16. The unipolar uses center tapped windings <strong>and</strong> can use a single power supply.<br />

The bipolar motor is simpler but requires a positive <strong>and</strong> negative supply <strong>and</strong> more complex<br />

switching circuitry.<br />

1<br />

a<br />

b<br />

1a<br />

1b<br />

a<br />

b<br />

2a<br />

2b<br />

unipolar<br />

2<br />

bipolar

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