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is determined by the winding pole-pairs,
F a1 (θ)=F p1 sin(pθ)=Ki a sin(pθ)
(4.32)
where, p is the pole-pair of the motor. The constant K is determined by the
turns and structure of the winding, and it can be obtained through Fourier
series analysis. If the winding current i varies with time as
i a (t)=I m sin(ωt)
(4.33)
where, ω is the angular frequency of the current. Then the MMF waveform of
equation 4.32 changes to
F a1 (θ)=KI m sin(ωt)sin(pθ)= KI m
2
[cos(ωt −pθ) −cos(ωt + pθ)
(4.34)
Figure 4.15: Three-phase distributed winding
Two other windings, B-phase winding and C-phase winding, can also be
installed on the stator to form a set of 3-phase symmetric windings in the
motor space. Figure 4.15 shows such 3-phase windings which is developed
from the 1-phase winding shown in Figure 4.14. It is clear, the fundamental
MMF harmonic of B-phase and C-phase windings can be expressed as
F b1 (θ)=Ki b sin(pθ−120 ),
F c1 (θ)=Ki c sin(pθ−240 )
(4.35)
Moreover, if the currents i b and i c vary with time,
i b (t)=I m sin(ωt −120
),
(4.36)
i c (t)=I m sin(ωt −240
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