Phase Failure - Eaton PKE12 Handbuch

1.4.1 Phase failure

1 Motor-protective circuit-breaker PKE12, PKE32 and PKE65
￫
Use the rated motor current and the tripping class to get the
relevant tripping characteristic (￫ section 5.3, "Auslösekennli-
nien/Tripping characteristics", page 50).
The switchgear is designed for CLASS 10 in normal and overload operation.
In order to prevent the switchgear and cables from being overloaded during
heavy starting, the switchgear's and cables' rated operational current I
must be oversized depending on the tripping class setting on the PKE motor-
protective circuit-breaker.
Table 2: Overload protection for heavy starting
CLASS Rated operational
current I
e CLASS
A
5 I
e
10 I
e
15 1.22 x I
e
20 1.41 x I
e
The PKE motor-protective circuit-breakers are phase failure sensitive.
In the event of a phase failure, i.e., in the event of an imbalance f 50 %,
the tripping time will be reduced to Q 40 % of the three-phase trip value.
￫
If you intend to monitor an AC motor with a PKE motor-
protective circuit-breaker, the current must be conducted via all
three conductors in order to prevent early tripping.
Figure 6: Wiring the PKE motor-protective circuit-breaker for protecting AC motors
(series connection of the overload releases)
CAUTION

DC motors cannot be monitored!
PKE12, PKE32, PKE65 11/17 MN03402004Z-DE/EN www.eaton.com
1.4 Setting the tripping CLASS
eCLASS
33