OM 2012
(3) Overload module
’ -
The over load module (7)
is a solid-state device designed to interpret a signal
from transfamers (3)and to send a signal to the protective monitor module
(4, Fig. 10) when an overload condition exists in any generator output phase.
A pull-apart electrical connector is mounted on the overload module to provide
_ -.
quick-dbconnect facilities for all wiring to the module. The overload module
- is equipped with a hermetically-sealed, reed-type relay. Relay contacts are
ncmal ly open.
The solid-state circuitry is designed to close relay contacts
--when output curre;lt in ANY phase reaches 125% of normal rated output capacity.
The closed relaysen& a signal to the protective monitor. This signal “gates”
the overload SCR (silicone-controlled rectifier) in the protective monitcr
and interrupts the load contactor holding circuit, allowing the load contactcr
to open.
The following k a list of overload module characteristics:
NOTE:
The overload protective system will function when any phase
carries 123% to 127% of rated load.
At 125% load the moduk will function in 4 minutes -
At 150% load the module will function. in 16 seconds. ’
At 200% load the module will function in 4 seconds.
NOTE:
All times are plus cc minus 25%and are nonadjustable.
(4) Rectifier
A diode-bridge ret tif ier (5) rece ives 400-H~ AC from phase C of the generatcr
output and converts it to a pulsating, direct current for energiration of the
load contacta holding coil only.
Thb DC coil-holding circuit is controlled
indirectly by controlling the 400-H~ AC to the rectifier. The ground circuit
for the rectifier’s AC supply must pass through the relay contacts in the pro-
tective monitcr module to ground cable N. Therefore, any time a protective
device functions to open the protective monitcr relay, the rectifier’s AC cir-
cuit k opened.
No DC is then available for the load contactcr holding coil,
hence, the load contactor opens.
(5) Terminal boards
Three terminal boards (2) provide connection facilities fcr small leads.
1-l
Page 32
Aug 25’85
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