Operating Instructions ACTIVE06/07 187
06/07 Operating Instructions ACTIVE 187
17.5 Motor Circuit Breaker
Motor circuit breakers are used for protecting a motor and its supply cable against
overheating by overload. Depending on the overload level, they disconnect the motor
from mains supply immediately in the case of a short-circuit or they disconnect the
motor if an overload has occurred for some time.
Conventional motor circuit breakers are
commercially available for various applica-
tions with different trigger characteristics (L,
G/U, R and K), as shown in the diagram on
the right. As frequency inverters in most
cases are used for supplying motors which
are classified as operating equipment with
very high starting currents, exclusively the K
characteristic was realized in this function.
Unlike the operation of a conventional motor
Protection switch which disconnects the
equipment to be protected immediately if
the trigger threshold is reached, this func-
tion provides the possibility of issuing a
warning instead of disconnecting the equip-
ment immediately.
The rated current of the motor protection
switch refers to the rated motor current
stated via parameter
Rated Current 371 of
the corresponding data set.
The rated values of the frequency inverter
are to be considered accordingly when it
comes to dimensioning the application.
1/1000 seconds seconds minutes
x nominal current
The function of the motor circuit breaker can be linked to different data sets. In this
way, it is possible to operate different motors via one frequency inverter. Thus, each
motor can be equipped with its own motor protection switch.
In case a motor is operated via the frequency inverter for which some setting values,
e.g. minimum and maximum frequency, are changed via the data set switch-over,
only one motor circuit breaker may be installed. This functionality can be differenti-
ated by selecting the parameter
Operation Mode 571 for single motor operation or
multiple motor operation.
Operation Mode 571 Function
0 - Off The function is deactivated
1 -
K-Char.,Mul.Motor
Op.,Err.Sw.Off
In each of the four data sets, the rated values are
monitored. Overloading the drive is prevented by the
fault switch-off "F0401".
2 -
K-
Char.,Sing.Motor,Err.S
w.-Off
The rated values in the first data set are used inde-
pendently of the active data set. Overloading the drive
is prevented by the fault switch-off "F0401".
11 -
K-Char.,Multi-Motor
Op.,Warning
In each of the four data sets, the rated values are
monitored. Overloading the drive mechanism is sig-
naled by a warning message "A0200".
22 -
K-Char.,Single-
Motor,Warning
The rated values in the first data set are used inde-
pendently of the active data set. Overloading the drive
mechanism is signaled by a warning message "A0200".
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