7
1
1
1
1
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1
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1
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1
MaGnuM PRoDuct GuiDe
CA013002EN—April 2017 www.eaton.com
42
Magnum trip units and communication devices
The trip units themselves are self-powered; no external power
is required to operate the protective systems . Current signal
levels and the control power are derived from integrally mounted
toroidal wound current sensors . The use of toroidal wound
sensors reduces magnetizing currents, resulting in improved
metered value accuracy over a broad range of sensor ratings .
otee:
N
Auxiliary power is required for all Digitrip 520MC and Digitrip 1150+
models for powering the display, communications, metering,
alarming, and auxiliary relay functions .
All three parts of the tripping system are discussed in this
section . For additional information pertaining to the different trip
unit models available for all Magnum circuit breakers, refer to
the specific trip unit instructional leaflet (
IL70C1036
for 1150+
models and
IL70C1037
for 520 models) .
Common Digitrip trip unit features
All Digitrip RMS models offer a wide array of common features .
These common features ensure unsurpassed versatility, no
matter which trip unit model is selected .
•
Current Sensors: Three toroidal wound current sensors
are installed at the rear of the circuit breaker on the lower
terminals . The sensors produce an output current proportional
to the load current . Under preselected conditions of current
magnitude and time, the sensors furnish the trip unit with a
signal and the energy required to trip the circuit breaker .
•
Rating Plug: All Magnum circuit breakers use a fixed type
rating plug . The current rating (also known as In) of the rating
plug must match the current rating of the integrally mounted
current sensors . As a safety feature, if the rating plug is
removed from the trip unit, the circuit breaker will trip if it sees
load current . There is a viewing window on the back of the
breaker that displays the current rating of the installed rating
plug . The rating plug performs several functions:
1 . It tells the trip unit the rating of the current sensors .
2 . It determines the maximum instantaneous setting,
which is a function of the current sensor rating .
3 . Identifies the trip unit as a UL rated device or
IEC rated device .
•
Intuitive operator interface
•
Interchangeable models
•
Self powered device
•
Hand held functional test kit (Digitrip RMS 1150 Model also
has integral testing capabilities)
•
Status LED: A green light emitting diode (LED), labeled Status,
blinks approximately once each second to indicate that the trip
unit is operating normally . This Status LED will also blink at a
faster rate if the Digitrip is in a pickup, or overload, mode .
•
Cause of trip LED: A red LED on the face of the trip unit
flashes red next to the protection feature to indicate the
cause for an automatic trip operation, for example earth fault,
overload or short circuit . A battery in the trip unit maintains the
trip indication until the Reset/Battery Test button is pushed . The
battery is satisfactory if its LED lights green when the Battery
Check button is pushed .
•
Security cover: A tamper-proof Plexiglas
®
cover sits on the
front of the circuit breaker over the trip unit . The cover is
held in place by two cover screws . Security is insured by the
insertion of a standard meter seal through the holes in both of
the cover retention screws .
otee:
N
Refer to the Table 12 for specific programming details associated
with a particular UL or IEC rated Digitrip model .
Cutler-Hammer
Trip unit
Toroidal
current
sensor
Rating
plug
Trip actuator
A
B
C
N
G
A
B
C
N
01
02
03
Note:
Alternate ground locations
may be required to meet installation
requirements.
Typical Magnum DS
circuit breaker
Sensors
Diagram of typical Magnum current sensing, processing, and
tripping system
Current sensors (rear view)
1
The National Electrical Code (NEC) requires that the maximum ground
fault pickup value not exceed 1200A for UL rated breakers . IEC rated
breakers do not have this current limitation .
1
