Download - ORCA

(4.6)
The average power is calculated by summing the values of instantaneous power and
dividing by the number of samples for the cycle, thus:
(4.7)
where N is the number of samples per cycle, which in the present work is 400.
The accumulated energy with time during the test is calculated by adding the
energy per cycle for each record to a running total. The energy is calculated from the
average power, from Equation (4.8):
(4.8)
An FFT computes the Discrete Fourier Transform (DFT) and produces exactly
the same result as evaluating the DFT definition directly; the only difference is that an
FFT is much faster. The DFT is defined by the formula:
(4.9)
where k=0,…, N-1 and N are the total number of samples, which in the present work is
400. The frequency content of the applied voltage and leakage current signal is
calculated by means of a LabVIEW library „Amplitude Spectrum VI‟. The calculated
frequency components are the amplitudes of the harmonics of the input signal. The
chosen sampling rate of N = 400 samples per cycle, allows the harmonic content of the
leakage current to be calculated up to the first 200 harmonics.
The harmonic content of the applied voltage and leakage current signal is
calculated using the THD equation:
(4.10)
91