Eaton PKZM4/XTPR DC1 Series Manual page 32

PKZM4/XTPR...DC1 motor-
protective circuit-breakers
28
switches over a quick-break switch when the limit value is
reached. At the same time, all three bimetallic releases shift
the differential bridge. If the path of action of one of the
bimetallic releases is reduced due to a phase loss, the
differential bridge is retarded and the distance is converted
into an additional tripping distance, which leads to an early
tripping.
c
ON
ab
Normal error-
e
free operation
Figure 3: Function of the phase sensitivity by means of
tripping and differential bridge
a Trip bridge
b Differential bridge
c Distance
d Differential travel
When a PKZM4/XTPR...DC1 is to be used for monitoring
h
an AC or DC motor, the current must flow across all three
current paths in order to avoid early tripping.
Figure 4: Wiring of the motor-protective circuit-breaker for
the protection of AC or DC motors (bimetallic
release switched in series)
(a section "Typenschild/Rating plate PKZM4/XTPR...01"
on page 41)
01/11 MN03402002Z-DE/EN
ON
Failure of one phase
three-phase
f
(two-phase load)
overload
d
OFF
g