1 10
1
10
100
1000
2 403 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 140: 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
91.
( )
V Hz>> / f
M 1.40
Ur/fr
= =
IECEQUATION2286 V1 EN (Equation 91)
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 502 048-UEN A
Voltage protection
282
Technical manual
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