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an investigation of dual stator winding induction machines

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1<br />

= 12<br />

2<br />

0.<br />

0024414<br />

The tr<strong>an</strong>sformation from the actual number to the number in Q12 format is given as:<br />

X Q<br />

= ⋅ X<br />

12<br />

12 2 (11.11)<br />

where, X is the actual number <strong>an</strong>d X Q12<br />

is the number in Q12 format.<br />

11.6 Current/Voltage Measurement<br />

The proposed control scheme requires two line-to-line voltages <strong>an</strong>d two phase<br />

currents as inputs. Therefore, two LEM type voltage <strong>an</strong>d current tr<strong>an</strong>sducers are used to<br />

sense these voltages <strong>an</strong>d currents. The current sensors <strong>an</strong>d voltage sensors are LA 55-P<br />

<strong>an</strong>d LV 100-1000 respectively.<br />

Since the A/D conversion ports <strong>of</strong> the DSP have the voltage r<strong>an</strong>ge [0 V; 3.3 V], the<br />

current sensors have been designed for operation in the desired output voltage region by<br />

varying the number <strong>of</strong> turns <strong>an</strong>d measuring resist<strong>an</strong>ce values. Similarly, the voltage<br />

sensors have been properly designed for operation in the desired voltage region by<br />

varying the primary side resistor value <strong>an</strong>d the value <strong>of</strong> measuring resist<strong>an</strong>ce. It should be<br />

noted that because <strong>of</strong> the bipolarity <strong>of</strong> the current <strong>an</strong>d voltage signals, the actual output<br />

voltage r<strong>an</strong>ge <strong>of</strong> current <strong>an</strong>d voltage sensor should be [-1.65 V; 1.65 V]. Then the voltage<br />

<strong>an</strong>d current sensor outputs therefore need to be rearr<strong>an</strong>ged <strong>an</strong>d scaled so that it c<strong>an</strong> be<br />

used by the control s<strong>of</strong>tware as Q12 format values. The complete processes <strong>of</strong> acquiring<br />

the voltages <strong>an</strong>d currents are depicted in the Figure 11.8 <strong>an</strong>d Figure 11.9 respectively.<br />

The process <strong>of</strong> dc voltage measurement is a little different from the ac voltage <strong>an</strong>d ac<br />

current measurement <strong>an</strong>d its block diagram is shown in Figure 11.10.<br />

433

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