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559E1200.indd
version: 1.0
Functions and
characteristics
Protection of distribution systems
TM thermal-magnetic and MAmagnetic trip
units
TM thermal-magnetic and MAmagnetic trip
units can be used on Compact
NSX100/160/250 circuit breakers with
performance levels B/F/H/N/S/L.
TM trip units are available in 2 versions:
b
TM-D, for the protection of distribution
cables
b
TM-G, with a low threshold, for the
protection of generators or long cable
lengths.
Vigi modules or Vigirex relays can be added
to all the circuit breakers to provide external
earth-leakage protection.
TM-D and TM-G thermal-magnetic trip units
Circuit breakers equipped with thermal-magnetic trip units are used mainly in
industrial and commercial electrical distribution applications:
TM-D, for protection of cables on distribution systems supplied by transformers
b
TM-G, with a low pick-up for generators (lower short-circuit currents than with
b
transformers) and distribution systems with long cable lengths (fault currents limited
by the impedance of the cable).
Protection
..............................................................................
Thermal protection (Ir)
Thermal overload protection based on a bimetal strip providing an inverse time curve
I
2
t, corresponding to a temperature rise limit. Above this limit, the deformation of the
strip trips the circuit breaker operating mechanism.
This protection operates according to:
Ir
b
that can be ad
j
usted in amps from 0.7 to 1 times the rating of the trip unit (16 A to
250 A), corresponding to settings from 11 to 250 A for the range of trip units
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b
Magnetic protection (Im)
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b
200 and 250 A ratings
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b
Protection against insulation faults
Two solutions are possible by adding:
a Vigi module acting directly on the trip unit of the circuit breaker
b
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b
Protection versions
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b
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v
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v
4-pole:
b
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and neutral).
MAmagnetic trip units
In distribution applications, circuit breakers equipped with MAmagnetic-only trip
units are used for:
short-circuit protection of secondary windings of LV/LV transformers with overload
b
protection on the primary side.
as an alternative to a switch-disconnector at the head of a switchboard in order to
b
provide short-circuit protection.
Their main use is however for motor protection applications, in con
j
unction with a
thermal relay and a contactor or motor starter (see "Motor protection",
SDJH $
).
Protection
..............................................................................
Magnetic protection (Im)
Short-circuit protection with an ad
j
ustable pick-up Im that initiates instantaneous
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Im = In x ...
b
set in amps on an ad
j
ustment dial
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for 2.5 to 100 A ratings or 9 to 14 In for 150 to 220 A ratings.
Protection versions
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b
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b
Note:
all the trip units have a transparent lead-sealable cover
that protects access to the adjustment dials.
DB112046
DB112047
A-14