1
10
1
10
100
1000
2
40
3
4
5
20
30
kForIEEE
=
2
kForIEEE
=
3
kForIEEE
=
4
kForIEEE
=
5
kForIEEE
=
6
kForIEEE
= 7
kForIEEE
=
8
kForIEEE
= 9
kForIEEE
=
10
kForIEEE
=
20
kForIEEE
=
60
kForIEEE
= 1
OVEREXCITATION IN %
Time (s)
IEEE OVEREXCITATION CURVES
IEC09000115-1-en.vsd
(M-Emaxcont)*100)
IEC09000115 V1 EN
Figure 100:
Delays inversely proportional to the square of the overexcitation
The critical value of excitation M is determined via OEXPVPH setting
V/Hz>>
.
V/
Hz>>
can be thought of as a no-load voltage at rated frequency, where the inverse law
should be replaced by a short definite delay,
tMin
. If, for example,
V/Hz>>
= 140 %,
then M is according to equation
.
(
)
V Hz>> / f
M
1.40
Ur/fr
=
=
IECEQUATION2286 V1 EN
(Equation 83)
9.4.7.3
Cooling
The overexcitation protection function (OEXPVPH) is basically a thermal protection,
therefore a cooling process has been introduced. An exponential cooling process is
Section 9
1MRK 504 135-UEN A
Voltage protection
228
Technical manual
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