Product Overview

3RT1 contactors/3RH1 control relays
SIRIUS System Manual
3-112 GWA 4NEB 430 0999-02 DS 01
3.4.7.6 Paralleling links (3RT19 .6-4B.31)
If the current paths of a multiple pole switching device are connected in par-
allel, then the total current is spread over the individual poles in accordance
to their ohmic resistance and their mutual inductive interference. The ohmic
resistance is mainly made up of the contact resistance of the contacts,
whose value can change with erosion and oxidation. Therefore there is nei-
ther a symmetrical nor stabile distribution of current: individual current paths
can become overloaded and the overload trip may operate prematurely caus-
ing nuisance tripping.
Continuous loading
when connected in
Parallel
As long as there aren’t any other details in the catalog data, then the follow-
ing applies for continuous loading when connected in parallel:
• When three current paths are connected in parallel then the continuous
current can be 2.5 times of a single current path and 1.8- times the contin-
uous current with two current paths connected in parallel. It should be
noted that the making and breaking are not increased, because the con-
tacts don’t open and close at the same time and therefore the contacts of
an individual current path must be able to make or break the entire current
• The wiring arrangement should be such that every current path has the
same cable length.
• An eventual short-circuit current would be divided with relationship to the
resistance of the current paths.
Attention: Thereby, the tripping current of an instantaneous electromag-
netic short-circuit trip may not be reached.
Making/ breaking
capacity
The magnitude of making and breaking capacities of contactors, related to
load currents when connecting two/three poles in parallel are shown in the
table below:
3-pole switching
2 poles in
parallel
3 poles in parallel 4 poles in
parallel
Making
capacity
12 x I
e
(utilization
category AC -4)
Breaking
capacity
10 x I
e
(utilization
category AC -4)
Table 3-43: Parallel connection: making/breaking capacities
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⋅
18,
----------------- 667 I′e⋅,=
12 I′′e⋅
25,
------------------ - 48 I′′e⋅,=
12 I′′e⋅
31,
------------------ - 39 I′′e⋅,=
10 I′e⋅
18,
----------------- 555, I′e⋅=
10 I′′e⋅
25,
------------------ - 40, I′′e⋅=
10 I′′e⋅
31,
------------------ - 32, I′′e⋅=