27.02.2013 Views

an investigation of dual stator winding induction machines

an investigation of dual stator winding induction machines

an investigation of dual stator winding induction machines

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

voltage tr<strong>an</strong>sient when this test current is switched to dc. A self-tuning system based on<br />

this measurement method has also been demonstrated. An adaptive control has been<br />

presented in [10.5] to correct the rotor time const<strong>an</strong>t estimation. The one step prediction<br />

<strong>of</strong> the correction that is necessary for the slip calculation c<strong>an</strong> be obtained by using the<br />

proposed controller. The control scheme depends on the value magnetizing induct<strong>an</strong>ce<br />

which is a varying component under practical circumst<strong>an</strong>ces. Hence a magnetizing<br />

induct<strong>an</strong>ce correction strategy has been adopted by the authors. In [10.6], three rotor time<br />

const<strong>an</strong>t estimation methods based on Model Reference Adaptive System (MRAS) have<br />

been proposed <strong>an</strong>d the perform<strong>an</strong>ces <strong>of</strong> those methods have been compared. It has been<br />

found that depending on the application, <strong>an</strong>y one <strong>of</strong> those estimation methods may be the<br />

most suitable one. The method based on regulating the energy stored in the magnetizing<br />

induct<strong>an</strong>ce has been proposed to estimate the rotor time const<strong>an</strong>t in [10.7]. The input<br />

voltages <strong>an</strong>d currents are all needed to calculate the magnetizing induct<strong>an</strong>ce energy. The<br />

authors found that the proposed method c<strong>an</strong> solve the thermal variation problems <strong>of</strong> both<br />

rotor time const<strong>an</strong>t <strong>an</strong>d <strong>stator</strong> resist<strong>an</strong>ce.<br />

The direct field orientation control is based on the position signal <strong>of</strong> the rotor flux.<br />

The adv<strong>an</strong>tages <strong>of</strong> this method are elimination <strong>of</strong> rotor position sensor <strong>an</strong>d less machine<br />

parameter sensitivity. However, a sensor that c<strong>an</strong> measure the rotor flux position is<br />

required, which increases the cost <strong>an</strong>d the complexity <strong>of</strong> machine <strong>an</strong>d seems impractical.<br />

Although the alternative methods for flux measurement, such as searching coil <strong>an</strong>d<br />

tapped <strong>stator</strong> <strong>winding</strong>s [10.8-10.9], have been introduced, the perform<strong>an</strong>ce most likely<br />

degrades at the low speed region. In [10.8], a low cost direct field orientation control that<br />

requires little knowledge <strong>of</strong> machine parameters has been presented, in which the tapped<br />

28

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!