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Automating Manufacturing Systems - Process Control and ...

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continuous actuators - 24.16<br />

V1<br />

V2<br />

N<br />

S<br />

V3<br />

Figure 24.14<br />

A Brushless DC Motor<br />

To continuously rotate these motors the current in the stator coils must alternate<br />

continuously. If the power supplied to the coils was a 3-phase AC sinusoidal waveform,<br />

the motor will rotate continuously. The applied voltage can also be trapezoidal, which will<br />

give a similar effect. The changing waveforms are controller using position feedback from<br />

the motor to select switching times. The speed of the motor is proportional to the frequency<br />

of the signal.<br />

A typical torque speed curve for a brushless motor is shown in Figure 24.15.<br />

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