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SENSORLESS FIELD ORIENTED CONTROL OF BRUSHLESS ...

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Figure 5.12 – Torque control of sinusoidal motor; rotor reference frame.<br />

Now, according to Figure 5.8-a, the current loop compensators deal with DC quantities when the<br />

motor is in steady state (during transients the signals will have transients components). There are<br />

several things to note about Figure 5.12. First, since the current command exists (at some point in<br />

the control flow) in terms of αβ components, the SVM inverter would integrate well with this<br />

control system (SVM is an “open loop” inverter just as the sine-triangle PWM inverter in Figure<br />

5.12). Second, a wye-connected motor can not have no ZS current, thus we can obtain the αβ<br />

components by measuring just two phase currents and by using one of the modified 0 Clarke<br />

transforms. (Practical implementations in SVM may require the third measurement, thus all three<br />

will continue to be shown.) Replacing the sine-triangle PWM the SVM inverter results in the<br />

system shown in Figure 5.13.<br />

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