1SFC132081M0201 | Installation and commissioning manual | Functions 83
7.7 Current limit
Current limit sets a maximum value of the starting current
output to the motor. The time to come at full voltage can
be longer than the set Start ramp Time when Current limit
is enabled.
There are 3 different Current limit functions:
• Normal current limit
• Dual current limit
• Ramp current limit
WARNING
If the load is very heavy, current limit can prevent
the current to decrease below the set current
level and cause overheating.
Normal current limit
When using Normal current limit and the set current
limit is reached, the output voltage stays stable until the
current level falls below the set current limit. Then the
start ramp continues.
Dual current limit
Dual current level has 2 current limit levels. When the
Current limit is reached, the output voltage stay constant
until the set time expires or the current decreases. If the
current decreases, the Softstarter continues the voltage
ramp. If the second current limit time expires and the
current has not decreased, the Softstarter increases the
current to the Dual current limit. See Figure 7.6 . When
the current comes at the Dual current limit the Softstarter
behaves as for normal Current limit.
Dual current limit can be used as a back-up function to
prevent overheating.
Ramp current limit
When the current comes at the first current limit level the
output voltage restricts the current from increasing at a
maximum linearly curve up to the second current limit.
The set time determines the time it takes for the current
limit to come at the second current level.
When the current comes at the second current limit, the
Softstarter behaves as for the normal current limit.
You can use Ramp current limit as a back-up function to
prevent overheating.
Current limit has these parameters:
Parameter Description Setting range Default value
03.01 Current limit type Set the Current limit type. Off, Normal,
Dual, Ramp
Normal
03.02 Current limit level Sets the first level to which the current is limited during start. 1.5 ... 7.5 x I
e
4.0 x I
e
03.03 2nd curr lim level Sets the level of the second current limit. 1.5 ... 7.5 x I
e
7.0 x I
e
03.04 2nd curr lim time Sets the time limit from the start signal when the second
current limitation comes in operation.
2 ... 120 s 8 s
Figure 7.6
Dual current limit
1SFC132081M0201
U
30%
100%
I
Time
Current limit
2nd current limit time
Dual current limit
Time
7
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