Sony PS-X7 - Page 37

4. Hall Motor
The PS-X6/X7 is equipped with the newly
developed BSL (brush and slotless) dc servo motor,
which has the following major advantages.—
1. Extremely uniform torque.
2. All-electronic switching (no mechanical con-
tacts used at all), resulting in very little noise.
3. Extremely stable performance, and long opera-
tional life.
Magnetic Pole Arrangement (See Fig. 4-1)
@ The motor coils LI] and L2 (plus L3 and L4)
form a pair, connected in series.
® The reason for positioning two Hall elements H1
and H2 at an angle of 22°30’ from each other is
to displace the electrical phase angle by 90°,
thereby rotating the rotor in a 2-phase action.
@ For the same reason, the positions of the coil
pairs are set at an angle of 67°30’.
@ The coil windings are wound in a partial cone
shape to match the similarly shaped magnets,
8 of which are arranged in a circle underneath the
rotor.
Motor Internal View (top view)
magnet
{sectional view)
rotor magnet
shaft
/
bearing coil stator
sine wave nature of the magnetic
field in the 8-pole rotor
Ss
Point “Aa”
Fig. 4-7.
| PS-X6/X7
@ Hall elements and motor coils have been set apart
at an angle of 22°30’ so that the peak of an N or
’ § pole magnetic field will cut across the center of
a motor coil at the same time that the magnetic
field peak of the preceeding or following S or N
pole cuts across a Hall element.
Generation of Rotational Force (See Fig. 4-2)
According to Fleming’s left hand rule, the force
generated in the motor coils will be in the counter-
clockwise direction, but since the coils are fixed, the
magnets (attached to the rotor) will rotate in the
clockwise direction. (Refer to Figs. 3-3 and 3-4.)
direction of
magnetic field
(direction of
x] magnetic lines
a of force)
direction of force
direction of
current
Fleming’s left hand rule
direction of
magnetic field
direction of direction of
magnetic field pole current
rotor :
direction of
———>
current
[
e7
—P
direction
of
force
magnet IN pote] ae | (generated in motor coil)
coil direction of force
(generated in motor coil} direction of current
Stator =
Fi g. 4-2, conductor
When an N pole corresponds to the Hall element
H1 (shown in the Fig. 4-3), a positive voltage is
generated in H1. This voltage is then amplified by
IC1-4, and applied to Q211.
When Q211 is turned on, B+ voltage is applied to
L1 and L2. The current flowing through L1 and L2,
and the magnetic field produce an electro-magnetic
force which spins the rotor in the direction of the
arrow as shown in Fig. 4-3.
When an N pole corresponds to the Hall element
H2 as shown in Fig. 4-3, current flows through L3
and L4, thereby generating the same electro-magnetic
force to continue spinning the rotor.
When an S pole corresponds to the Hall element
H1 (shown in Fig. 4-4), a negative voltage is generated
in Hl. This voltage is then amplified by IC1-4, and
applied to Q212.
When Q212 is turned on, B- voltage is applied to
Ll and L2. The current flowing through L1 and L2,
and the magnetic field produce an electro-magnetic
force which spins the rotor in the direction. of ‘the
arrow as shown in Fig. 4-4.