Shark -new motor design concept for energy saving- applied to - VBN

8
Chapter 1 Introduction
O
Fig.1.8 Typical energy conversion loop for a small displacement from θ 1
to θ 2
The process of conversion of the energy may be described by the following equation:
' ' ' '
OAA + A ABB 0 BB =−
OAB
(1.3)
'
OAA is the stored energy in position θ 1,
' '
where:
A ABB is the energy supplied from the source,
'
0BB is the stored energy in position θ 2 and OAB , the difference between the two, is the energy
converted to mechanical energy.
The instantaneous torque developed during the rotation from 1 to 2 may be mathematically
described by the following equations:
T
∂W
f
= −
∂θ
Ψ=
const
and in terms of co-energy, which is complementary to the field energy:
T
=
∂W
∂θ
i=
const
Ψ [Wb]
B '
A '
B ( 2)
A ( 1)
(1. 4)
(1. 5)
Ideally, the current should flow through the windings at the point when the inductance of the
magnetic circuit begins to increase. This point is close to the corner position. An example of a
conversion loop in an SRM is presented in Fig.1.9. Here it may be seen that the turn on angle
should be selected to be after the unaligned position and the turn off angle should be selected to be
before the aligned position. Selecting the turn off angle to be before the aligned position avoids a
period of production of generating torque, because the inductance of the magnetic circuit begins to
decrease with the increasing rotor angular position.