1  component clarke3 "Clarke (3 phase to cartesian) transform";
 2  description """The Clarke transform can be used to translate a vector
 3  quantity from a three phase system (three components 120 degrees
 4  apart) to a two phase Cartesian system (plus a homopolar component
 5  if the three phases don't sum to zero).\n.P\n\\fBclarke3\\fR implements
 6  the general case of the transform, using all three phases.  If the
 7  three phases are known to sum to zero, see \\fBclarke2\\fR for a
 8  simpler version.""";
 9  see_also """\\fBclarke2\\fR for the 'a+b+c=0' case, \\fBclarkeinv\\fR for
10  the inverse transform.""";
11  pin in float a;
12  pin in float b;
13  pin in float c "three phase input vector";
14  pin out float x;
15  pin out float y "cartesian components of output";
16  pin out float h "homopolar component of output";
17  function _;
18  license "GPL";
19  ;;
20  
21  /* for the details, google "clarke transform", or see section 3 of
22     http://focus.ti.com/lit/an/bpra048/bpra048.pdf and/or appendix B of
23     http://www.esat.kuleuven.be/electa/publications/fulltexts/pub_1610.pdf
24  */
25  
26  #define K1 (0.666666666666667)  /* 2/3       */
27  #define K2 (0.333333333333333)  /* 1/3       */
28  #define K3 (0.577350269189626)  /* 1/sqrt(3) */
29  #define K4 (0.471404520791032)  /* sqrt(2)/3 */
30  
31  FUNCTION(_) {
32      x = K1*a - K2*(b+c);
33      y = K3*(b-c);
34      h = K4*(a+b+c);
35  }
36  
37  
38  #if 0
39  #define K1 (2.0/3.0)
40  #define K2 (1.0/3.0)
41  #define K3 1.154700538  /* 2/sqrt(3) */
42  
43  FUNCTION(_) {
44      x = K1 * a - K2 * (b - c);
45      y = K3 * (b - c);
46      h = K1 * (a + b + c);
47  }
48  #endif