ABB PSTX Series Installation And Commissioning Manual page 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
03.01 Current limit type
03.02 Current limit level
03.03 2nd curr lim level
03.04 2nd curr lim time
Description
Set the Current limit type.
Sets the first level to which the current is limited during start.
Sets the level of the second current limit.
Sets the time limit from the start signal when the second
current limitation comes in operation.
1SFC132081M0201
U
Current limit
100%
30%
2nd current limit time
I
Figure 7.6
Dual current limit
Setting range
Off, Normal,
Dual, Ramp
1.5 ... 7.5 x I e
1.5 ... 7.5 x I e
2 ... 120 s
| Installation and commissioning manual | Functions
Dual current limit
Time
Time
Default value
Normal
4.0 x I e
7.0 x I e
8 s
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