Normal Inverse Overcurrent
Description
The TeSys Tera system provides the normal inverse (IEC class A – Standard inverse) overcurrent protection function.
The trip time of the
normal inverse overcurrent protection is given by the formula:
Where:
-
T = Trip time
-
TMS = Time multiplier
-
k and α are the curve type constant. For standard inverse curve, k = 0.140 and α = 0.020
-
I = Actual current
-
Ip= Pick up current setting
The normal inverse overcurrent protection function generates the following signals:
-
Alarm: Any of the three-phase currents of the motor goes above the alarm level.
-
Trip: Any of the three-phase currents of the motor goes above the pickup level for the time derived from IEC class A curve and time delay (TMS) setting.
Parameter Setting
The normal inverse overcurrent protection function has the following configurable settings:
|
Parameter |
Setting range |
Default value |
|---|---|---|
|
Function |
|
Disable |
|
Pickup |
20–1000% of IFLC in step of 1% |
50% of IFLC |
|
Time Delay (TMS) |
0.1–20.0 s in step of 0.1 s |
0.1 s |
|
Alarm Level |
20–1000% of IFLC in step of 1% |
50% of IFLC |
|
Reset Mode |
|
DI + Reset Key |
|
Auto-Reset Delay (applicable only if Reset mode is Auto) |
0.0–6000.0 s in step of 0.1 s |
0 s |