Effective 8/2006
Page 7
I.L. 66A7534H04
Figure 1.7 Ground Alarm/Power Supply Module for the
520MCV Trip Unit
1.6.1 Auxiliary Power
When the module is wired as shown in Figure 1.8, it will
provide an auxiliary power supply so that the 520MCV
liquid crystal display (LCD) will be functional even when the
circuit breaker has no load. A Digitrip 520MCV tripunit
without
auxiliary power will not display data until load
current reaches approximately 30% 1 phase or 10%
3 phase of the
(I
n) rating.
1.6.2 Ground Alarm
A second function of the module is to provide either a
ground trip or ground alarm only output contact via the
relay supplied in the module. An LED on the front of the
unit also provides an indication of ground fault trip.
1.6.3 Ground Fault Trip
When the Ground Alarm/Power Supply module is used,
this unit will provide ground fault trip contacts when the
circuit breaker trips on a ground fault. You must then push
the Reset button on the Digitrip in order to reset the
contacts
(See Figure 1.8, Note 3)
.
1.6.4 Ground Fault Alarm
A ground fault alarm alerts a user to a ground fault condi-
tion without tripping the circuit breaker. A red Alarm Only
LED on the front of the trip unit will indicate the presence
of a ground fault condition that exceeds the programmed
setting.
The ground fault alarm relay is energized when the ground
current continuously exceeds the ground fault pickup
setting for a time in excess of a 0.1 second delay. The
alarm relay will reset automatically if the ground current is
less than the ground fault pickup
(See Figure 1.8, Note 4).
1.7 Display Feature (520MCV only)
The Digitrip 520MCV model has a user interface in addition
to the green and red LED trip indicators. This seven
element display performs a metering function and can be
used to monitor load currents.
When the Step button on the face of the trip unit is
pressed and released, the display will show PH 1, for
Phase 1 or A, and the current value. If the Step button is
not pressed again, the display will continue to show the
current value for Phase 1. Each time that the Step button
is pressed, the next monitored function will be displayed.
The other real time readings can be displayed in the
following sequence:
PH 2
Phase 2 (B)
PH 3
Phase 3 (C)
PH 4
Neutral
PH 5
Ground
HI
Highest phase current
OL
Overload (Digitrip in overload mode)
Pushing the Step button while the unit is in the OL
mode will have the unit again display the overload
current value.
HELP
This message can indicate more than one problem
with the trip unit. If the rating plug is missing, a
HELP message and an Instantaneous trip LED
light will be observed. The rating plug needs to be
installed and the Instantaneous trip LED must be
cleared by pressing the Reset/Battery Test button.
