6.20.4)
Reasons'for
failure of the
regulator-rectifier
a)
Power circuit
(Silicon
Controlled
Rectifier; SCR)
The silicon conrolled
rectifier can
be ruined by
excessive
voltage
peaks
(>+400
or
-350
V) and high temperatures
(above
80o
C
ll75"F).
Inadmissible voltage
peaks
can be
caused
by:
inductive voltage due
to electro-welding
on the
aircraft,
loose
connections,
loose
connection
on terminals
of battery,
insuffi
cient
mass
connection,
disconnecting battery
while engine
runs,
rapid
charging of battery
or using
inferior
charging unit.
Harmful temperature to
SCR
is
caused
not only by too
high ambient temperatures
but
also due
to
contact
resistance,on
R
or
B+ connector,
heating up the connection and
ruining
the SCR.
The
damage of the SCR
might
lead
to
shorting the
battery via stator coil or the
regulator, resulting in
burned-out
coils
and empty
battery.
b) Control circuit
(transistorized
voltage control)
This circuit
is less
sensitive
to high temperature
than the
power-circuit
and can be
ruined
therefore only by excessive
voltage.
This excessive voltage on
point
"C"
(>+80
V or
-6
V) can
be
caused
by:
Disconnecting the battery
while engine runs
with
main
switch ON
(positive
voltage
peak).
No
danger
with
ignition
switch
OFF,
wrongly connected battery,
inductive voltage in the board circuit,
conductive
connection between
terminal
G and C
(e.g.
wet
connector).
A failure of the control
circuit will
result
in
uncontrolled
battery charge
(either
continuous
full
charge or
no charging at
all).
rl'912:
ffi,grAx]
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