Marconi LORAIN RHM800E50, Manual

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Power PSA-A8
6.4 This power supply assembly provides the
and -12 VDC required to power the Regulator and
Alarm Circuit Card A7. An
DC output of this
assembly provides an input to the current walk-in circuit.
6.5 The VDC output of this assembly is derived
from AC voltage at the secondary winding of power
transformer
The AC voltage is applied to the power
supply through resistors and The
AC input is by diodes and and
a portion of DC is applied to the current
walk-in circuit of the Regulator and Alarm Circuit A7.
The remainder of the DC is passed through diode
CR3 to
regulator. diode CR13. in con-
junction filter capacitor a
VDC output which is applied to the Regulator and
A7.
6.6 The -12 VDC output of this assembly is derived
battery applied to the power
piy through resistor CR14, in
with filter capacitor produces the
-12 VDC output is applied to the
and Alarm Circuit A7.
Power
6.7 The phase star-connected secondary of
power transformer feeds a phase rectifier. Basi-
cally, the circuits consist of power diodes and
six thyristors. Each of the are identi-
cal; therefore, one is described as The conduc-
tion of the thyrfstor is controlled by a pulse circuit on A7
will explained later. the is not
conducting, the output of power transformer sup-
plied through the power only. When output
voltage is required, a pulse the causing it
to conduct. When the thyrfstor conducts. an additional
winding of the power is inserted the
increasing output voltage. amount of out-
put voltage is dependent upon the the
was fired. in to the phase of the AC
voltage. The outputs of the circuits
applied to an transformer. which
the outputs of the rectifier circuits before applying the
resultant output to the filter circuit. A resistor and
capacitor network the and the power
reduces conducted RF interference. The DC
output of the rectifier which contains appreciable
amount of ripple is passed
an LC type filter
which reduces the ripple to a minimum. The
DC output power is connected through the out-
Section 4387
put fuse and battery disconnect device to the output ter-
minals.
and Current
6.8 normal operation, the and
regulation the are controlled
by on Regulator and Alarm Circuit A7. During a
high output ripple caused by the loss of an AC
input phase, the regulation of rectifier output voltage
and current is
controlled by the Ripple
tor Circuit Card Al 1.
Circuit card A7 integrated circuitry to perform the
phase control regulation function. The regulation and
phase control
monitors the output of the
and a pulse which gates the
in the power circuit. Depending upon the output
voltage, the gate pulse is advanced or delayed in
relation to the phase of the AC input voltage to control
the rectifier output. If the thyristor is in the
AC cycle, the output voltage increases. If the thyristor is
gated later in
AC cycle, the output
decreases.
6.9
A current limiting circuit senses output
current and a signal to the regulator circuit
which limits output current to a preset, safe value. The
regulation function is performed by three separate but
interacting circuits. are refer-
ence and detection circuit. the current sensing and
current circuit. and the pulse generation and
phase circuit.
Reference and Error Detection
6.10 This circuit compares the output of the rectifier
a ffxsd voltage and an error signal which
represents the magnitude and direction of any differ-
ence. The negative sense is applied to a resis-
tance network consisting of resistors and
and ADJUST potentiometers
and R12 resistors R13 and and range
potentiometer Potentiometer R16 is connected to
the cathode of reference diode CR3. The
of CR3 is connected to common (0). Therefore, the
age at the junction of diode CR3 and potentiometer R16
is more than the positive sensing lead. The
resistors in resistor network mentioned above are
such that the R12
is at ground potential when the voltage on the sensing
leads at the correct regulated value.
the
output is too high, the at the slider of
potentiometer R12 becomes negative with respect to
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