Eaton Power Xpert PXM 4000, Руководство пользователя и инструкция по установке

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Page 181
12 Glossary
9’s of Availability
A measurement used to show the availability of service. The
9’s translate into how much downtime is allowed per year.
90.0000% = 37 days
99.0000% = 3.7 days
99.9000% = 8.8 hours
99.9900% = 53 minutes
99.9990% = 5.3 minutes
99.9999% = 32 seconds
Apparent Power
For sinusoidal quantities in either single-phase or polyphase
circuits, apparent power is the square root of the sum of the
squares of the active and reactive powers.
AWG
American Wire Gauge. Standard wire-cross section area.
CBEMA Factor
A transformer harmonic derating factor (THDF) defined as a
pure sine wave’s crest factor (1.4141) divided by the mea-
sured crest factor.
Crest Factor
Ratio of peak current to rms current. A pure sine wave has a
crest factor of 1.414.
CT (Current Transformer)
An instrument transformer that is intended to have its primary
winding connected in series with the conductor carrying the
current to be measured or controlled.
Demand
The average value of power or a related quantity over a
specified interval of time.
dv/dt
Delta voltage divided by delta time.
Flicker
A variation of input voltage, either magnitude or frequency,
sufficient in duration to allow visual observation of a change
in electric light source intensity. See EN 61000-4-15 for
details.
Fourier Coefficients
Fourier Series
A single-
valued periodic function (that fulfills certain mathematical con -
ditions) may be represented by a Fourier series as follows:
Note: 0.5A0 is the average of a periodic function f(x) over one
primitive period.
12 GLOSSARY