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2 Engineering
2.3 Tripping characteristics
2.3.2 Tripping CLASS
32
The ZEB overload relay is suitable for both normal startups as well as for
heavy duty starting. The CLASS setting enables a particular tripping
characteristic to be selected. These are the following:
•
CLASS 10A and CLASS 10 = normal startups,
•
CLASS 20 and CLASS 30 = heavy to very heavy starting.
￫
With ZEB variants with ground fault detection
(ZEB-...-GF...) only the selection between CLASS 10 and
CLASS 20 is available.
DANGER
The motor, the wiring diameter and the switching device must
be suitable for the selected tripping CLASS.
DANGER
The current-dependent protective device must be selected so
that not only the motor current is monitored but also the blocked
motor is switched off within the temperature rise time t
This means that the protective device must be rated so that the
tripping time t
specified by the characteristic curve, is not greater than the
temperature rise time t
within this time (see the following example).
Example
I
/I
= 6, t
= 10 s
A
N
E
10
8
6
4
2
1
40
20
10
8
6
4
2
1
0.8
0.6
0.4
0.2
0.1
1
2
Figure 3: Tripping characteristic of the overload relay
ZEB (XTOE, C440) 11/16 MN03402007Z-DE/EN www.eaton.com
for the I
/I
ratio of the Ex e motor, that is
A
A
N
in order to switch off the motor safely
E
3
4
5
6
7 8 9 10
1
.
E
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