Power Circuit; Voltage Reference And Error Detection - Marconi LORAIN RHM800E50 Manual

Power Suoolv Assemblv PSA-A8
6.4 This power supply assembly provides the +12
and -12 VDC required to power the Regulator and
Alarm Circuit Card A7. An addlional DC output of this
assembly provides an input to the current walk-in circuit.
6.5 The +12 VDC output of this assembly is derived
from AC voltage at the secondary winding of power
transformer Tl The AC voltage is applied to the power
supply circuft through resistors R7. R9. and RlO. The
AC input is rectiiied by diodes AB-CRI and A&CR2 and
a portion of the resuttant 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 AE
CR3 to the zensr regulator. Zener diode CR13. in con-
junction with filter capacitor A&C2. provides a regufated
6.6 The -12 VDC output of this assembly is derived
piy through resistor Ri2. Zener diode CR14, in con-
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Power Cirouft
6.7 The six phase star-connected secondary of
power transformer Ti feeds a six phase rectifier. Basi-
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cally, the rectifier circuits consist of sb power diodes and
six thyristors. Each of the six rsctifier circufts are identi-
cal; therefore, one is described as typical. The conduc-
tion of the thyrfstor is controlled by a pulse circuit on A7
conducting, the output of the power transformer is sup-
plied through the power diode only. When higher output
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voltage is required, a pulse fires the tfwrtstor causing it
to conduct. When the thyrfstor conducts. an additional
winding of the power ttansfom'ter is inserted into the cir-
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put voltage added is dependent upon the time the
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applied to an interphsse transformer. which balances
the outputs of the rectifier circuits before applying the
resultant output to the filter circuit. A resistor and
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capacitor network acmss the thyrlston and the power
output of the rectifier which contains appreciable
amount of ripple is passed tf~rough an LC type filter
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which reduces the ripple to a minimum. The resuftmg
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put fuse and battery disconnect device to the output ter-
minals.
6.8
by circuftry on Regulator and Alarm Circuit A7. During a
high output ripple condkiin caused by the loss of an AC
input phase, the regulation of rectifier output voltage
and current is partially controlled by the Ripple Regufa-
tor Circuit Card Al 1.
Circuit card A7 utifiies integrated circuitry to perform the
phase control regulation function. The regulation and
phase control circuft monitors the output of the rectdier
and uftimateiy produces a pulse which gates the thyris-
voltage, the gate pulse is etiher advanced or delayed in
relation to the phase of the AC input voltage to control
the rectifier output. If the thyristor is gated earb in the
AC cycle, the output voltage increases. If the thyristor is
gated later in tfte AC cycle, the output voltage
decreases.
A current limiting circuit senses rectiitr output
6.9
current and pmvfdes 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.
ence and error detection circuit. the current sensing and
current regufation circuit. and the pulse generation and
phase contml circuit.
6.10 This circuit compares the output of the rectifier
represents the magnitude and direction of any differ-
ence. The negative sense voltage is applied to a resis-
tance network consisting of resistors R8 and RlO.
and R12 respsctffefy, resistors R13 and R74. and range
potentiometer R16. Potentiometer R16 is connected to
the cathode of zsnsr reference diode CR3. The anode
of CR3 is connected to common (0). Therefore, the voft-
age at the junction of diode CR3 and potentiometer R16
is more poskiis than the positive sensing lead. The
resistors in resistor network mentioned above are
is at ground potential when the voltage on the sensing
leads fs at the correct regulated value. lf the recttier
output v&age is too high, the voltage at the slider of
potentiometer R12 becomes negative with respect to
Section 4387
Page 17