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PB103366
Micrologic TM-D trip unit.
Functions and
characteristics
Special applications
Protection of 400 Hz systems
Compact NSX circuit breakers may be used
on 400 Hz systems.
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The main 400 Hz applications are in aeronautics and certain military ships. Modern
aircraft have three-phase 115/200 V 400 Hz networks.
Impact on protective devices
Due to the higher frequency, circuit breakers are sub
j
ected to additional temperature
rise for identical current levels, resulting from higher losses caused by Foucault
currents and an increase in the skin effect (reduction in the useful CSA of
conductors). To remain within the rated temperature-rise limits of devices, current
derating is required.
The power levels of 400 Hz applications rarely exceed a few hundred kW with
relatively low short-circuit currents, generally not exceeding four times the rated
current.
The standard Compact NSX and Masterpact NT/NW ranges are suitable for 400 Hz
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derating table below.
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NSX100
10 kA
NSX160
10 kA
NSX250
10 kA
NSX400
10 kA
NSX630
10 kA
Trip units equipped with thermal-magnetic
protection
The 400 Hz current settings are obtained by multiplying the 50 Hz values by the
IROORZLQJ DGDSWDWLRQ FRHI¿FLHQW
K1 for thermal trip units
b
K2 for magnetic trip units.
b
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Thermal trip units
The current settings are lower at 400 Hz than at 50 Hz (K1 < 1).
Magnetic trip units
The current settings are conversely higher at 400 Hz than at 50 Hz (K2 > 1).
Consequently, when the trip units are ad
j
ustable, they must be set to the minimum
value.
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Circuit
EUHDNHU
Trip unit
In (A)
50Hz
Thermal at 40°C Im (A)
50Hz
Magnetic
K1
400 Hz
K2
400 Hz
NSX100
TM16G
16
0.95
15
63
1.6
100
TM25G
25
0.95
24
80
1.6
130
TM40G
40
0.95
38
80
1.6
130
TM63G
63
0.95
60
125
1.6
200
NSX100 TM16D
16
0.95
15
240
1.6
300
TM25D
25
0.95
24
300
1.6
480
TM40D
40
0.95
38
500
1.6
800
TM63D
63
0.95
60
500
1.6
800
TM80D
80
0.9
72
650
1.6
900
TM100D
100
0.9
90
800
1.6
900
NSX250 TM100D 100 0.9
90
800
1.6
900
TM160D 160 0.9
144
1250
1.6
2000
TM200D 200 0.9
180
1000 to 2000 1.6
1600 to
3200
TM250D 250 0.9
225
1250 to 2500 1.6
2000 to
4000
Example
NSX100 equipped with a TM16G with 50 Hz settings Ir = 16 A and Im = 63 A.
400 Hz settings Ir = 16 x 0.95 = 15 A and Im = 63 A x 1.6 = 100 A.
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559E1600.indd
version: 1.0