Fluke 434-II/435-II/437-II
Users Manual
A-2
The calculator shows an estimated cost using the measured values and the cost per kWh.
For more accurate results long term measurements (for example one week/month) can be
made showing results over time in the trend screen.
The Unified Method
The Unified Method allows to split power measurement into meaningful components
which can be used to identify the source of the various power components.
The various components are:
- Full Power
contains harmonic and unbalance components, also called
active power
- Fundamental Power
contains unbalance components, no harmonic components
- Symmetrical Power
contains no harmonic and no unbalance components
- Harmonic Power
harmonic components only
- Unbalance Power
unbalance components only
Furthermore distinction is made between:
- Phase Power
powers of the individual phases A, B, C (or L1, L2, L3)
- System (Total) Power powers of the total multi-phase system
Note that the System Power is not always the sum of the phase powers!
The basis for power measurements are the voltage and current sample values measured
on all inputs simultaneously. Power is measure over a 10/12 cycle (50/60Hz) time
window (T
w
) as required by IEC 61000-4-30.
Voltage:
∑
=
=
w
T
0
n
2
n
w
u
T
1
Urms
in which u
n
are the voltage signal samples
Current:
∑
=
=
w
T
0
n
2
n
w
i
T
1
Irms
in which i
n
are the current signal samples
FFT algorithms
FFT algorithms in accordance with IEC 61000-4-7 are used to calculate the fundamental
and harmonic components of each input signal over a 10/12 cycle (50/60 Hz) time
window. This time window is approximately 200 ms but depends on the fundamental
frequency. Phase locked loop algorithms are required to capture an exact number of
cycles.
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