22
Instructional Leaflet
IL70C1037H05
Effective October 2009
Digitrip models 520, 520i; and 520M, 520Mi,
520MC, 520MCi trip units for use only in
Magnum and Magnum DS circuit breakers
eaton corporation
www.eaton.com
Figurt 28. Digiorip 520MC ARMLSIA
Figurt 29. Digiorip 520MC ARMWLSIG
Section 4: protection settings
Gtntral
Before placing any circuit breaker in operation, set each trip
unit protection setting to the values specified by the engineer
responsible for the installation. The number of settings that must be
made is determined by the type of protection supplied by each unit,
as illustrated in
Figurt 16
through
Figurt 27
. Each setting is made
by turning a rotary switch, using a small screwdriver. The selected
setting for each adjustment appears on the trip unit label.
The installed rating plug must match the current sensors that
establish the maximum continuous current rating of the circuit
breaker (I
n
). Instantaneous and ground current settings are defined
in multiples of (I
n
).
To illustrate the effect of each protection curve setting, simulated
time-current curves are pictured on the face of the trip unit. Each
rotary switch is located nearest the portion of the simulated time-
current curve that it controls. Should an automatic trip occur (as a
result of the current exceeding the pre-selected value), the LED in
the appropriate segment of the simulated time-current curve will
light red, indicating the reason for the trip.
The available settings, along with the effects of changing the
settings, are given in
Figurt 30
through
Figurt 37
. Sample settings
are represented in boxes 2 .
LNng dtlay currtno stooing
There are eight available long delay settings, as illustrated in
Figurt
30
. Each setting, called (I
r
), is expressed as a multiple (ranging from
0.4–1) of the current (I
n
). The nominal current pickup value is 110%
of the setting.
Note:
N
(I
r
) is also the basis for the short delay current setting (see page 23).
Figurt 30. LNng Dtlay Currtno Stooings
Long Delay Setting
l
r
1 x
l
n
=
l
r
l
r
Available Settings
0.4, 0.5, 0.6, 0.7,
0.8, 0.9, 0.95, 1.0
In Multiples of
Amperes (
l
n
)
l
r
