18.07.2013 Views

SENSORLESS FIELD ORIENTED CONTROL OF BRUSHLESS ...

SENSORLESS FIELD ORIENTED CONTROL OF BRUSHLESS ...

SENSORLESS FIELD ORIENTED CONTROL OF BRUSHLESS ...

SHOW MORE
SHOW LESS

Create successful ePaper yourself

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

Ne<br />

d( ) Ipsin( ) cos( t) sin( ) cos( t) sin( ) cos( t) 2<br />

N 1 sin( t) sin( t) sin( t ) sin( t)<br />

e <br />

I p<br />

2 2<br />

<br />

sin( t) sin( t)<br />

<br />

<br />

<br />

3 Ne<br />

d( ) Ip sin( t)<br />

(3.65)<br />

2 2<br />

It is clear that the effective number of amp-turns is a function around the stator and rotates<br />

according to the electrical position of the currents. Setting 0 the amp-turn distribution<br />

becomes Equation (3.66).<br />

3 Ne<br />

d( ) Ipsin( t)<br />

(3.66)<br />

2 2<br />

This can be rewritten in terms of the current space vector as in Equation (3.67).<br />

3 Ne<br />

d( ) Ipsin(<br />

t)<br />

2 2<br />

3 Ne<br />

Ipcos( t / 2)<br />

2 2<br />

Ne<br />

3j( t/2) <br />

Re<br />

Ie p <br />

2 2 <br />

Ne<br />

j/2 3 jt Ree<br />

Ipe <br />

2 2 <br />

Ne<br />

Reji<br />

2<br />

<br />

N <br />

e d ( ji) 2<br />

(3.67)<br />

It is seen that if the rotating amp-turn distribution were described by a space vector it would be<br />

90° ahead of the current SV ([42, p.181], [166]), and since we know that a sine-distributed<br />

winding produces a cosine-distributed MMF this should not come as a surprise. Likewise<br />

Equation (3.67) is very similar to the MMF expression (Equation 3.42), which is reproduced here<br />

as Equation (3.68).<br />

(3.42):<br />

Ne<br />

<br />

f i<br />

2<br />

<br />

<br />

(3.68)<br />

The MMF and current SVs are related by only a scalar constant of proportionality thus their<br />

“distributions” must be the same. But Equation (3.67) showed that the actual amp-turn (or current<br />

density) distribution is not equal to the “distribution” of the current SV (and we really should not<br />

expect this to be true anyway). This leads us to conclude that the current space vector does not<br />

112

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

Saved successfully!

Ooh no, something went wrong!