Moeller PKZM0, Аппаратное обеспечение и инженерия

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PKZM0 motor-protective
circuit-breakers
26
04/06 AWB1210-1458D/GB
the ambient temperature. The influence of the ambient
temperature is automatically compensated within a
temperature range from –5 to +40 °C by means of an
additional current-free bimetallic release that continuously
corrects the tripping range.
Phase failure
The PKZM0 motor-protective circuit-breakers are phase
sensitive. The deflecting action of all three bimetallic
releases is directed towards a tripping bridge that 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.
Figure 3: Function of the phase sensitivity by means of tripping
and differential bridge
a Tripping bridge
b Differential bridge
c Gap
d Differential distance
ab
c d
e f
g
ON ON OFF
3-phase
overload Normal error-
free operation
Failure of one phase
(two-phase load)
h
When a PKZM0 is to be used for monitoring an AC or DC
motor, the current must flow across all three current paths
in order to avoid early tripping.