Cooper Power Systems Kyle Type ME Series, Maintenance Instructions Manual, Page: 9 / 50

S280-75-2
9
Figure 9.
Diagram of Form 3A tie board showing plug-in circuit board location. Form 3 tie boards are similar (see Figure 18), except some of
the terminals are missing or in a slightly different location.
From this point, phase- and ground-trip signals are very
similar, and only phase signals will be described.
The phase-trip No. 1 board circuitry, consisting of a three-
phase full-wave rectifier, which converts the ac input signal
from three phase to a single do signal. The do signal is
applied to the phase-trip No. 2 board which measures the do
level, and determines whether a fault current exists at the
recloser.
If the load current conditions are in the fault region, the mini-
mum-trip portion of the phase-trip No. 2 board switches on, allow-
ing the time-current curve circuits to start their programmed time
delay. The time-current curves are driven by the same do voltage
output of the phase-trip No. 1 board, and as a result higher fault-
current levels will result in a shorter time delay before tripping.