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3-46
Protection Functions
Thermal Overload
Protection T> (49)
857-UM001A-EN-P – July 2009
Table 3.26 – Recorded values of the residual overvoltage stages
U
>, U
>> (59N)
0
0
Parameter
Value
yyyy-mm-dd
hh:mm:ss.ms
Flt
EDly
The thermal overload function protects the motor in the motor mode
or cables in the feeder mode against excessive heating.
Thermal model
The temperature is calculated using rms values of phase currents and
a thermal model according IEC 60255-8. The rms value is calculated
using harmonic components up to the 15
τ
=
t
Trip time:
=
a
k
Alarm:
=
a
Trip:
τ
=
t
Release time:
=
a
Trip release:
=
a
Start release:
T
=
Operation time
τ
=
Thermal time constant tau (Setting value)
ln
=
Natural logarithm function
I
=
Measured rms phase current (the max. value
of three phase currents)
Unit
Time stamp of the recording, date
Time stamp, time of day
%
Fault voltage relative to Un/√3
%
Elapsed time of the operating time setting.
100% = trip
th
.
−
2
2
I
I
⋅
P
ln
−
2
2
I
a
⋅
Θ
⋅
⋅
k
I
alarm
mod
e
⋅
Θ
⋅
k
k
I
mod
e
2
I
⋅
⋅
P
C
ln
τ
−
2
2
a
I
×
×
. 0
95
k
I
n
×
×
×
. 0
95
k
I
alarm
n
Description
(Alarm 60% = 0.6)
(Alarm 60% = 0.6)
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