2-8. Frequency Regulation (CSV2215-2,
dent of any change in ac voltage level; frequency con-
trol is independent of voltage control.
c. The signal obtained by comparison of the two
a. One side of the motor shunt field is connected to
above mentioned potentials is fed to the base of a driver
negative dc and the other side is connected to the col-
transistor which is part of the amplifier circuit. The
lector of power transistor Q3. When power transistor
amount of the differential voltage fed to the base of the
Q3 is on, practically total dc voltage appears across the
driver transistor establishes the length of on-time or
field. When transistor Q3 is off, total dc voltage ap-
off -time of power transistor Q3. Any increase in fre-
pears across the transistor.
quency will cause a decrease in the differential voltage
b. Frequency regulation is accomplished by sensing
that will increase the on-time of power transistor Q3,
an ac potential developed in the frequency sensing cir-
resulting in a higher field current and a corresponding
cuit. The value of this ac potential is proportional to the
reduction in frequency.
frequency and is constant for any one frequency. This
d. The regulator reacts instantaneously to any
potential is compared with another potential obtained
change in output frequency and maintains it con-
stantly at a preset level. Free-wheeling diode CR3 is
approximately 180 out-of-phase one positive, and one
used to provide a path for the field current during the
negative. Thus, the difference between these potentials
off-time of transistor Q4.
becomes a representation of the frequency, indepen-