Dual 721 - Description of Function; Phase Windings and Transistor Control; Magnetic Field Interaction

Desuiption of
Fumion
The 4 phase windings are each in the
collec—
tor
circuit of the 4 switching transistors
T 4 to T 7 (Fig. 5) and are connected
to—
gether in star form at one
point. This point
is connected to the
minus pole of the supply
voltage.
The position of the rotor illustrated in
Fig. 6 has the
effect that the magnetic
field of the south pole of a
pair of poles
at connection 11 of the Hall generator H 1
gives rise to a Hall voltage maximum of ne—
gative polarity.
Transistor T 4 whose base is joined to con—
nection 11 of the Hall
generator therefore
receives a
negative base
emitter voltage and
is fully connected through whereby
the cur—
Fig. 5
Fig. 6
-14V 0
rent
flows through the
phase winding W 1
lo—
cated in the
collector
section or
it is
switched on.
Transistor T
5 whose base
is joined to
con—
nection 9 of
Hall
transistor H 1 is
blocked
by the
positive Hall
voltage potential.
As
Hall generator H 2 is
in the neutral zo—
ne
of the pair of
magnetic poles during
this period, no
Hall voltages occur at its
connections 7 and 5.
The transistors T 6
and T 7
joined to these
connections are,
therefore,
blocked as well.
The switched
on phase winding W 1 (Fig. 7
a)
produces clockwise rotation
of the rotor
through 22
1/2°. This cycle takes
place,
displaced electrically
in each case by 90
0
,
in
sequence in all four
phase windings.
7
T3
12
W1
2
D9
4
•
D102
T5
T5i
5
21311
W4 j
D122
H2
N z'
-
,
-
N
,
\
N ‘ 1- 1 1
iiii ii
it
H1