(Q6). The other input controlling transistor Q5 is
either the 52a contact input (if used) connected to
relay terminal 1 8 or operation of the overcurrent
unit circuit. This is obtained when the reed relay
operates to remove the 1 00 ohm resistor (Rl 9)
from capacitor C 1 and to apply the input current
signal to terminal 5 of the IC 1 on the overcurrent
detector module. If this signal voltage is higher
than the reference voltage at terminal S ofiC l the
output voltage at terminal 1 0 (of IC l ) will drop
from its high state to less than 2.5 volts. This out
put change is then applied to the transistor logic
circuit consisting of transistor Q3, Q4 and Q5 (on
the timer module).
CHARACT E R I ST I C S
Overcurrent Detector
The overcurrent detector has a range of 0. 5 to
1 3.5 amperes. This is obtained by means of three
tap settings in conj unction with the tap m ultiplier
to give a continuous adj ustment over· the range.
The pickup point is determined by multiplying the
tap value by the tap multiplier setting. The operate
speed varies from 3 ms to 8 ms. The reset time is 3
ms maximum and would be measured as the time
for the secondary voltage to decay to 10 volts peak
(with the reed relay RR contacts open). This reset
time applies whether the input current is reduced
to zero or up to 95% of pickup current.
Continuous rating is 1 0 amperes. One second
rating is
250
amperes.
The accuracy of the pickup setting is 5% over
the full range and 1 0% from -20 to + 5 5 °C . Since
the setting is continously adjustable, closer setting
accuracy can be obtained by using a current source
and a precision ammeter.
CAUTION:
Since the tap block connector screw
carries operating current, be sure that the screw
is turned tight.
In o rder to avoid opening the cu r rent
transformer circuits when changing taps under
load, connect the spare tap screw in the desired tap
position before removing the other tap screw from
the original tap position.
I.L. 41-776.5
Control Timer
The range of the control timer is 1 50 to 250 ms.
The timer as received should be set for ap
proximately 200 ms.
The timer setting can be changed by means of a
screwdriver through the hole on the front plate of
the timer module.
The accuracy is 5% over the temperature and
voltage range.
BF Timer
The range of the RFI timer is 1 8 to 1 7 5 ms. It
is set by means of a knob and calibrated scale at
the front of the timer module.
The accuracy of the pickup setting is 5%. Since
the setting is continuously adj ustable, the tiner
may be set closer by instrumentation.
The accuracy is 5% over the temperature and
voltage range.
Power Supply
Consists of a 1 0 watt zener diode (Zs), a
resistor (Rs) and provides a regulated voltage of
24Vdc ± 1 0% over the voltage and temperature
range. A capacitor C3 is connected across the
zener diode to decrease the rate of rise and fall of
the output voltage to reduce transient effects.
Both modules and the telephone relay (X) are
energized by the power supply.
Temperature and Voltage
The relay is operative over a range of 80 to
1 1 0% of rated voltage and from -20 to + 55 ° C .
I t can be energized continuously at 1 1 0% of
rated input voltage.
Capacitive Effect
The capacitive surge immunity is as follows
(considering the 52a contact input present):
3
www
. ElectricalPartManuals
. com
