Marconi LORAIN RHM800E50 Manual Download Page 29

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Circuit Card All.

6.25

This circuit card continuously monitors the ripple

current

the rectiiier DC output filter capacitors.

normal rectifier operation,

current is

within the adjustable limits set by the ripple regulator cir-
cuit card and no output signal is provided. However, if
one AC input phase is lost or another failure occurs
which results in a high output ripple condiiin exceeding
the

current setting of circuit card Al the ripple

regulator provides a

output signal. This signal

is applied to the regulation circuitry of Regulator and
Alarm circuit card A7 causing a subsequent reduction in

output

The ripple regulator reduces

rectifier output voltage until the ripple current through
the filter capacitor is reduced to normal

626

Current transformer

senses

ripple current

through the DC filter capacitor and applies a voltage to

Regulator circuit card Al 1 at pins 1 and 2. This

input is

by diodes CR1 through CR4 and

by resistor

and capacitor Cl. The

voltage is applied through resistor R5 to the non-invert-

ing input of comparator Al. The variable input at the
non-inverting

of Al is compared to a reference

voltage applied at the inverting input of Al The

voltage is derived from potentiometer R3 and

resistor

and is adjustable depending upon the set-

ting of potentiometer R3. This reference input deter-
mines the value of ripple current at

the ripple

provides a signal to

regulation cir-

cuitry on circuit card A7. When the ripple current

the

me ripple

of potentiometer R3, comparator Al provides a positive
output signal through diode CR5 to Me regulator and

627 This

signal is applied to the inverting

input of voltage follower A18 on circuit card A7
generates a negative error signal of equal amplitude but
opposite polarity. The resulting

and negative

error signals are men applied to me pulse generation
circuitry previously described.

Fuse Alarm Circuit

626

The fuse alarm circuit initiates

shutdown

and provides visual indication of an open fuse ii any
fuse in the

the exception of fan fuses F5

and

opens. The DC output and filter fuses are con-

nected to associated alarm fuses

and

An alarm type fuse, F2,

the negative battery

input circuits

for control purposes. If any of these

fuses open, me alarm contact of me fuse connects

Section 4397

battery to the coil of K4 and the cathode of the

FUSE ALARM light emitting diode. The LED illuminates

and contacts of K4 open which

Kl and K2.

When

releases,

contacts open

interrupt AC

input power to the rectifier. This automatic shutdown

external rectifier failure alarms, connected.

Sensina

6.29 This rectifier is equipped with cooling fans and
fan

and temperature sensors. The fan fail

are located on

cards A12 and Al3 which are

mounted beneath each

fan while the tempera-

ture sensors S3 and S4 are mounted at the approximate

center of the heat sinks. The fan fail circuits

ously monitor the presence of air flow across

heat

sinks while temperature sensors S3 and S4 continu-
ously monitor the temperature of the heat sinks. If the
air flow ceases, relay KS releases and, in addition, illu-
minates indicator FAN FAILURE. If the air flow ceases
or the temperature of the heat sink reaches

relay K3 opens a set of contacts which reduce

output current to 66% of full rated load and acti-

vate an external rectifier fail alarm. if connected.

6.30

Fan fail circuit cards A12 and Al3 and tempera-

ture sensors

and S4 are connected in series with the

coil of relay K3. In addition. fan fail circuit cards A12

and Al3 are connected in series with the coil of relay
K5.

normal operation. the temperature sensors

and fan fail monitors are closed which energizes the coil
of K3. Contacts of relay

energized, provide closed