1 PKZM0-…/XTPR…BC1NL, PKZM0-…-T/XTPT…BC1NL motor-protective circuit-breakers
1.3 Description of device
PKZM0-…/XTPR…BC1NL, PKZM0-…-T/XTPT…BC1NL
01/22 MN03402003Z-DE/EN
www.eaton.com
27
1.3.3 Temperature compensation
Two parameters influence the deflection of the bimetallic releases. There is
for one the heat which is generated in proportion to the current flow, and
secondly, the influence of the ambient air temperature. The influence of the
ambient air 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.
1.3.4 Phase failure
The PKZM0-…/XTPR…BC1NL and PKZM0-…-T/XTPT…BC1NL 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
Trip bridge
b
Differential bridge
c
Distance
d
Differential travel
Figure 4: Wiring of the motor-protective circuit-breaker for the protection of AC or DC motors
(bimetallic release switched in series)
(
section 5.2, “Auslösekennlinien/Tripping characteristics PKZM0-…/
XTPR…BC1NL, PKZM0-…-T/XTPT…BC1NL”, page 37)
Normal error-free
operation
three-phase overload
Failure of one phase
(two-phase load)
￫
When a PKZM0-…/XTPR…BC1NL, PKZM0-…-T/XTPT…BC1NL
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.
ab
c
d
e
f
g
ON
ON
OFF
