3. PRINCIPLE OF MOTOR OPERATION
Construction of motor control for the PL-51A
is depicted in Fig. 2.
1. Applying power sets the oscillator into
operation. Output of this circuit passes to
the pole position detecting circuit (L1-LG).
2. Here, assume that coupling between L1 and
L4 is the tightest. Voltage induced in L4 is
rectified and applied to Q106/Q109 in the
driver.
3. Q109 in turn conducts and causes current to
flow in the associated drive coil (A-1). The
rotor moves in the direction shown by arrow
in Fig. 1. The magnetic pole affixed to the
rotor induces a voltage proportional to rotor
movement, in the sensing coil (A-4).
4. Voltage induced in A-4 is rectified by a
diode in the speed sensor and applied to
Q103 in the control stage. This point is also
fed from the reference voltage generator
(voltage Es)through a fine speed control pot.
5. Voltage applied to the base of Q103 in the
control stage controls current that flows in
Q104.
6. Q104 serves as a constant current source for
Q106 through Ql1 1 in the driver and
therefore controls current flow in the drive
coils.
7. When ambient temperature change causes
driver current to rise, the speed of rotation
increases above the rated value. Q104 current
increases and Q106-Q111 currents decrease. pOLE pOStTtON
As a result, the speed of rotation falls off. DETECTOR
OSCI LLATOR REFERENCE VOLTAGE
GENERATOR
POLE POSITION
DETECTOR
Pole Position Detector
Fig. 1 shows a simplified view of the drive and
sense coils. With power applied and coupling
between L1 and L4 high, Q109 causes current
to flow through A-1. As a result, the rotor end
of coil A-i becomes a south pole (S1) and
attracts N1. The rotor moves in the direction
shown by arrow. Coupling factor between L2
and L5 increases and operatior, of Q110 causes
current to flow in coil A-2. Pole S2 attracts pole
N2 and rotor rotation continues. In the same
manner, 53 attracts Pole N3. Continuation of
this process causes the rotor to turn on a steady
basis.
DIRECTION OF
ROTATION
CONTROL STAGE
Fig. 1
DRIVE SENSING
cotLS cotLs sPEED SENSO
ROTOR
Lr
Lz
L3
DRIVER Fig.2
