Hardware Reference
In-Depth Information
Figure 4.9: Magnetic
fi
eld generated by the distributed winding with 1 pole-
pair
Consider a magnetic circuit around the line AB going through the airgap,
where the cross section of the circuit is ∆hl
c
,andthelengthisg as shown in
Figure 4.9. ∆h is selected to be so small that the magnetic
fi
eld in this section
of area ∆hl
c
can be considered to be evenly distributed. From the symmetry
of the electromagnetic structure, it can be said that no
fl
ux goes through the
pass AB, which also means that the MMF acting on this part of airgap is zero,
that is F
AB
=0.
In Figure 4.10, there are 4 closed loops indicated by broken lines in the left
side of the motor. We can apply Ampere's law to each of these loops. As the
permeabilities of the stator core and rotor core are in
fi
nite, the MMFs acting
on the circuits in these cores are zero, and the loop circuit can be considered
as formed only by two airgap reluctances,
AB
and
g
(θ)showninFigure
4.11. For such circuit, the MMF consumed in the airgap reluctances can be
described as
X
F
AB
+ F
g
(θ)=
i
j
,
(4.29)
j
P
j
i
j
is the net current surrounded by the loop. As F
AB
is zero, the
above equation can be rewritten as
where,
X
F
g
(θ)=
i
j
,
(4.30)
j
where θ is the rotor position.
