Setting parameters
10/05 AWB8230-1541GB
112
Monitoring functions
The functions described here are used to monitor the power
section for overload and to protect the connected motor.
Limiting motor current
If the output current (= motor current, I
M
) exceeds the value set
with PNU b022 (b222), the output frequency (rotating field
frequency) is reduced. You can set the deceleration time constant
with PNU b023 (b223).
With PNU b028 (b228) you can match the current limitation to the
process. The reference frequency must be provided digitally
through:
• Digital inputs 1 to 5:
– Fixed frequency (f
1
to f
15
)
– Electronic motor potentiometer (UP, DWN)
• Keypad
– Fixed frequency PNU A020
– Electronic motor potentiometer: Arrow keys Í and Ú.
With an analog 0 to +10 V reference value signal (terminal O-L)
you can adjust current limitation (I
LVL
) in a range from 10 to 150 %
of the rated device current (I ). The change of the analog current
limitation is delayed by 100 to 200 ms by the “sampling time a
(internal process time of CPU and controller).
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).
Figure 114:Current limit enabled
a Deceleration time constant (PNU b023/b223)
b022 (b222): Tripping current limit
I
M
: Motor current
b022
f
I
M
t
a
a
Figure 115:Connection of potentiometer to the external overload
limitation
Figure 116:Variable overload limitation
a Sampling time (internal processing time of CPU and controller)
0 – 10 V
I
LVL
= 10 – 150 % I
e
O LH
t
0
10 V
t
0
150 %
10 %
100...200 ms
a
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