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Frequent Start
Protection N> (66)
Table 3.13 – Parameters of the stall protection stage: I
Parameter
Setting values
ImotSt
Ist>
Type
tDT>
tInv>
Recorded
SCntr
values
TCntr
Flt
EDly
The simplest way to start an asynchronous motor is just to switch the
stator windings to the supply voltages. However every such start will
heat up the motor considerably because the initial currents are
significantly above the rated current.
If the motor manufacturer has defined the maximum number of starts
within on hour or/and the minimum time between two consecutive
starts this stage is easy to apply to prevent too frequent starts.
When current has been less that I
situation is recognized as a start. A typical setting for I
x I
When the current is less than 10 % x I
MOT.
regarded as stopped.
The stage will give a start signal when the second last start has been
done. The trip signal is normally activated and released when there
are no starts left. Figure 3.14 shows an application.
Protection Functions
> (48)
st
Value/unit
Description
xImot
Nominal motor starting current
%Imot
Motor start detection current. Must be
less than initial motor starting current.
DT
Operation charact./ definite time
Inv
Operation charact./ inverse time
s
Operation time [s]
s
Time multiplier at inverse time
Start counter (Start) reading
Trip counter (Trip) reading
xImot
Max. value of fault.
%
Elapsed time as compared to the set
operate time, 100% = tripping
and then exceeds I
STOP
the motor is
MOT,
857-UM001A-EN-P – July 2009
3-21
the
StartMin
is 150 %
StartMin
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