an investigation of dual stator winding induction machines

are applied in this kind of dual stator winding induction machine and the input voltage
frequency of each stator winding depends on the control objectives and is not required to
be fixed. Generally, the two simultaneous MMFs have different rotating speeds and the
peak value of the combination of two simultaneous MMFs changes with time. The
machine design is to make sure that even in the worst case, the machine can still avoid
operating in deep magnetic saturation.
Assuming the dual stator machine is wound for 2/6 pole and neglecting the saturation,
the flux density in the air gap at a given instant time can be expressed as:
2 / 6
2
[ cos(
θ ) − cos(
3θ
) ]
Bg ( θ ) = B K + δ
(2.6)
1
1
where the magnitude of the flux density induced by the 2-pole winding set is B 2 , the ratio
of the magnitude of the flux density induced by the 6-pole winding set and the 2-pole
winding set is K 1 and the phase angle between two flux densities, which may be a time
varying number , is 1
δ . In the worst case, the peak value of g 2 / 6
θ = θ p ; 1 K is a positive value and the delay angle δ 1 is zero.
50
B will be obtained when
On the other hand, the 4-pole single stator winding set induction machine has a flux
distribution expressed as:
( θ )
Bg θ ) = B cos 2
(2.7)
4 ( 4
To maintain the same magnetic saturation level produced by peak flux density, the
peak flux density value of the dual-winding design will be equal to the peak flux density
of the single 4-pole machine, which can be expressed as:
[ ( θ ) − K cos(
3 ) ]
cos
2 p 1
B = B
θ
(2.8)
4
p