Micrologic™ 2.0A, 3.0A, 5.0A, and 6.0A Electronic Trip Units | |
Rev. 01, 07/2012 | Section |
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Short-Time Protection
Figure 8: Short-Time Protection Switches
Micrologic 5.0A Trip Unit
Micrologic 6.0A Trip Unit
against short circuits.
• |
5.0A and 6.0A trip units. It is not available on |
3.0A trip units. |
• |
time pickup (Ir). |
• The |
level (below instantaneous trip level) at |
which circuit breaker will trip after the preset |
time delay. |
• The |
of time that the circuit breaker will carry an |
A
B
06133204
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| long time |
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| Ir | .8 .9 |
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| tr |
|
| 8 |
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| .7 |
|
| (s) | 4 | 12 |
| |||||
| .6 |
|
| .95 | 2 |
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| 16 |
| ||
| .5 |
|
| .98 | 1 |
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| 20 |
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| .4 x In 1 |
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| .5 @ 6 Ir24 |
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| short time |
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| Isd | 4 |
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| tsd |
| .4 | .3 |
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3 | 5 |
|
| (s) | .4 |
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| .3 |
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| .2 |
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2.5 |
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| 6 |
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2 |
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| 8 |
| .2 |
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| .1 |
| |||
1.5 |
| 10 |
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| .1 | 2 | 0 |
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| x Ir |
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| on | I t | off |
| ||
delay
alarm
instantaneous
I i
8
6 
10
4
12
3
15
2off
x In
A
B
06133351
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| long time |
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| Ir | .8 |
|
| tr |
| 8 |
|
| |
| .7 | .9 |
| (s) 4 | 12 |
| ||||
| .6 |
|
| .95 | 2 |
|
| 16 |
| |
| .5 |
|
| .98 | 1 |
|
| 20 |
| |
| .4 x In 1 | .5 @ 6 Ir24 |
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| short time |
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| Isd | 4 |
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| tsd | .4 | .4 .3 |
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3 | 5 |
| (s) |
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|
| .3 |
|
| .2 |
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2.5 |
|
| 6 |
|
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|
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2 |
|
| 8 |
| .2 |
|
| .1 |
| |
| 1.5 x Ir | 10 |
| .1 |
| 0 |
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| on I2t off |
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| delay |
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| |
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| E |
|
| tg | .4 | .4 .3 |
| |
| D | F | (s) |
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| .3 |
|
| .2 |
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| C |
| G |
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|
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| B |
| H | .2 |
|
| .1 |
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| A |
| J | .1 | I2t | 0 |
| |||
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| on | off |
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ground fault
alarm
instantaneous
I i
8
5 
10
4
12
3
15
2off
x In
test
ENGLISH
overcurrent above the |
current level before tripping. It is adjustable |
on the 5.0A and 6.0A trip unit and factory set |
to zero on the 2.0A trip unit. |
• The I2t on/I2t off option provides improved |
selectivity with downstream protective |
devices: |
— With I2t off selected, fixed time delay is |
provided. |
— With I2t on selected, inverse time I2t |
protection is provided up to 10 x Ir. |
Above 10 x Ir, fixed time delay is |
provided. |
• Intermittent currents in the |
range which do not last sufficiently long to |
trigger a trip are accumulated and shorten |
the trip delay appropriately. |
• |
interlocked (ZSI) with upstream or |
downstream circuit breakers. |
• Setting tsd to the 0 setting turns off zone- |
selective interlocking. |
• |
measurement. |
• |
to provide selectivity with upstream or |
downstream circuit breakers. |
Table 2: | Micrologic Trip Unit | |||||
Setting |
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I2t off (Isd at 10 Ir) (seconds) | 0 | 0.1 | 0.2 | 0.3 | 0.4 | |
I2t on (Isd at 10 Ir) (seconds) |
| 0.1 | 0.2 | 0.3 | 0.4 | |
tsd (min. trip) (milliseconds) | 20 | 80 | 140 | 230 | 350 | |
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tsd (max. trip) (milliseconds) | 80 | 140 | 200 | 320 | 500 | |
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NOTE: Use I2t off with ZSI for proper coordination. Using I2t on with ZSI is not recommended as the delay in the upstream device receiving a restraint signal could result in the trip unit tripping in a time shorter than the published trip curve.
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