Hardware Reference

In-Depth Information

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

)