01/02 AWB8230-1415GB
Current limit
157
Current limit
With the current limit setting, the motor current can be limited. To
reduce the load current, the frequency inverter ends the frequency
increase in the acceleration phase or reduces the output frequency
during static operation as soon as the output current rises above
the current limit set with this function, (the time constant for
control at the current limit is defined under PNU b023 or b026). As
soon as the output current drops below the set current limit, the
frequency increases again to the configured setpoint value. The
current limit can be deactivated for the acceleration phase, so that
higher currents for acceleration are allowed for brief periods
(a PNU b021 or b024).
With PNU b024 to b026, you can program a second current limit,
which can be called up through digital input OLR (a Section
“Change over current limit (OLR)“, Page 90).
The current limit can not prevent a fault message being issued and
the frequency inverter being switched off due to a sudden overcur-
rent, for example caused by a short circuit.
Figure 161: Current limit
I
M
: Motor current
I
1
: Current limit
Caution!
Note that the current limit cannot prevent a fault message
and shutdown due to a sudden overcurrent (e.g. caused
by a short-circuit).
I
1
A004
f
I
t
PNU b023
PNU Name Adjustable in RUN mode Value Function WE
Normal Extended
b021 Current limit
characteristic 1
– j 00 Motor current limit not active 01
01 Motor current limit active in all operating states
02 Motor current limit not active during acceleration
03 Motor current limitation is active in every operating state. If
the motor current limit is reached in regenerative mode, the
frequency is increased until the current has fallen below the
set motor current limit.
04 Motor current limitation to achieve higher starting currents
is not active in the acceleration phase. If the motor current
limit is reached in regenerative mode, the frequency is
increased until the current has fallen below the set motor
current limit.
b022 Tripping
current 1
– j 0.5 to 2 x I
e
Setting range of the tripping current as a multiple of the
frequency inverter rated current, i.e. the range is given in
amperes (A).
1.5 x
I
e
1)
b023 Time constant 1 – j 0.1 to 30 s When the set current limit is reached, the frequency is
reduced in the time specified here.
Caution: If possible, do not enter a value below 0.3 here!
1.0
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