Idmt Alarm - Deep Sea Electronics Plc DSE6120 MKII Operator's Manual

6.6.2 IDMT ALARM

If the IDMT Alarm is enabled, the controller begins following the IDMT 'curve' when the trip level is
passed.
If the Trip is surpassed for an excess amount of time the IDMT Alarm triggers (Shutdown or Electric
trip as selected in Action).
High current shutdown is a latching alarm and stops the Generator.
Remove the fault then press the Stop/Reset Mode
High current electrical trip is a latching alarm and removes the generator from the load, before
stopping the Generator after the off load cooling timer.
Remove the fault then press the Stop/Reset Mode
The higher the overload, the faster the trip. The speed of the trip is dependent upon the fixed
formula:
Where: T is the tripping time in seconds
I is the actual current of the most highly loaded line (L1 or L2 or L3)
A
I is the delayed over-current trip point
T
t is the time multiplier setting and also represents the tripping time in seconds at twice full load (when I
Factory settings for the IDMT Alarm when used on a brushless alternator are as follows (screen
capture from the DSE Configuration Suite PC software :
These settings provide for normal running of the generator up to 100% full load. If full load is
surpassed, the Immediate Warning alarm is triggered, the set continues to run.
The effect of an overload on the generator is that the alternator windings begin to overheat; the aim
of the IDMT alarm is to prevent the windings being overload (heated) too much. The amount of time
that the set can be safely overloaded is governed by how high the overload condition is.
With typical settings as above, the tripping curve is followed as shown below.
This allows for overload of the set to the limits of the Typical Brushless Alternator whereby 110%
overload is permitted for 1 hour.
If the set load reduces, the controller then follows a cooling curve. This means that a second
overload condition may trip much sooner than the first as the controller knows if the windings have
not cooled sufficiently.
For further details on the Thermal damage curve of your alternator, you are referred to your alternator
manufacturer and generator supplier.
Protections
button to reset the module.
button to reset the module.
T = t / ((I / I ) – 1)
A T
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2
/ I = 2).
A T
I
(Trip setting value)
T
t
(time multiplier)
057-236 ISSUE: 1