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3RT1/3RH1 contactors
SIRIUS System Manual
GWA 4NEB 430 0999-02b
3-83
3 3RT1/3RH1 contactors
3.4.7.5 Parallel connections
If the conducting paths of multipole switching devices are connected in par-
allel, the total current is distributed to the individual conducting paths
according to their ohmic resistance and the inductive effect they have on
each other. The ohmic resistance is mainly formed by the transfer resistance
at the contact pieces, the value of which can be changed by contact erosion
and oxidation. The distribution of current is therefore neither even or stable:
Individual conducting paths can be overloaded and the overload release or
overload relay may be prematurely triggered (triggering fault).
Permanent load in
parallel connection
The following applies to permanent loads in the case of parallel connection
unless specified otherwise in the catalogs:
• When three conducting paths are connected in parallel, 2.5 times the
amount of continuous current can be applied, and when two conducting
paths are connected in parallel, 1.8 times the continuous current can be
applied. Make sure, however, that the making and breaking capacity do
not increase because the contact pieces do not close and open at the
same time, and therefore the contact pieces in a conducting path have to
switch the entire making and breaking current.
• The wiring must be routed in such a way that each conducting path has
the same line length.
• Any short-circuit current is distributed in proportion to the conducting
path resistances.
Important:
The operating current of electromagnetic, instantaneous
short-circuit releases is not reached.
Making/breaking
capacity
You can find out the making and breaking capacity of contactors in relation
to the load currents in the parallel connection of two or three conducting
paths from the following table:
Table 3-31: Parallel links making and breaking capacity
1) Voltage at each clearance between open contacts:
3-pole switching
1)
2 conducting paths
in parallel
1)
3 conducting paths
in parallel
1)
4 conducting paths
in parallel
1)
Making
capacity:
12 x I
e
(utilization
category AC -4)
Breaking
capacity
10 x I
e
(utilization
category AC -4)
1
2
3
4
5
6
I
e
I
e
I
e
I
e
I
e
I
e
1
2
3
4
5
6
I
’
e
I
e
I
’’
e
1
2
3
4
5
6
I
e
1
2
3
4
5
6
7
8
I
’’
e
I
e
12
I
′
e
⋅
1 8
,
-----------------
6 67
I
′
e
⋅
,
=
12
I
′′
e
⋅
2 5
,
-------------------
4 8
I
′′
e
⋅
,
=
12
I
′′
e
⋅
3 1
,
-------------------
3 9
I
′′
e
⋅
,
=
10
I
′
e
⋅
1 8
,
-----------------
5 55
,
I
′
e
⋅
=
10
I
′′
e
⋅
2 5
,
-------------------
4 0
,
I
′′
e
⋅
=
10
I
′′
e
⋅
3 1
,
-------------------
3 2
,
I
′′
e
⋅
=
U
Ue
3
-------
=
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