TM11-6125-256-34
2-10. Frequency Regulation (4B93-1-A)
2-9. Voltage Regulation (4B93-1-A)
(fig FO-2 1)
(fig FO-2 1)
is rectified by diode CR11 and divided by resistors R24,
is converted to a square wave and shaped into a saw-
R25, R23 and R17 A portion of this voltage is filtered
tooth voltage having a period of one half the ac cycle
The comparator circuit, transistors Q2 and Q10, has
and shaped into a sawtooth waveform by capacitor C5
and applied to the pulse-forming amplifier consisting
two inputs One input is the sawtooth timing voltage,
of transistors Q9, Q7, Q8, and Q11 The pulse width
the other input is an adjustable dc reference voltage
of the amplifier output varies directly with the genera-
used to select frequency (potentiometer R5) Control
tor output and is compared with the reference voltage
of frequency (speed) is obtained by controlling shunt
established by the frequency regulator section
field strength
b When generator output voltage falls below the
rated value, positive bias applied to transistor Q9
by transistor Q3 and integrated by capacitor C2 and
through resistors R17 and R23 increases Transistors
resistor R11 Transistors Q4, Q5, and Q6 form an
Q9, Q7, and Q8 conduct for a larger portion of the
inverting amplifier which alternately conducts with the
sawtooth voltage, producing a series of output pulses
comparator Transistor Q4 is clamped at the reference
with increasing pulse width from transistor Q11 As a
voltage of Zener diode CR5 When transistor Q3 con-
result, generator control field excitation increases If
ducts, the increase in voltage across capacitor C2 cuts
generator output voltage rises above the rated value,
off transistor Q4 The resulting series of pulses drive
positive bias applied to transistor Q9 decreases, de-
the shunt field which controls motor-generator fre-
creasing the pulse width of the output from transistor
quency (speed)
Q11 This decreases generator control field excitation
c An increase in frequency produces a wide pulse
Full or maximum excitation is applied to the generator
which increases shunt field current, decreasing operat-
control field when output pulse width is maximum
ing frequency A decrease in frequency generates a
Minimum generator excitation is obtained when out-
narrow pulse causing shunt field current to decrease
put pulse width is minimum
and the operating frequency to increase
c Flywheel diode CR8 discharges inductive tran-
d Flywheel diode CR6 discharges inductive tran-
sients produced in the alternator field and prevents
sients produced in the shunt field and prevents reflec-
these voltages from being reflected back into the reg-
tion of these voltages back into the regulator
ulator
