| (2) | Equipment with a rated current exceeding 20 A/phase
Defined in Japanese Guideline for Reduction of Harmonic Emission, for the measurement power supply source and measurement equipment are to be applied for it. The values indicated below shall be applied for the impedance of the measurement circuit.
The measurement system impedance Z S +Z M specified in the Japanese Guideline for Reduction of Harmonic Emission is 90% of the cumulative value for the low- Voltage distribution circuit impedance, and the voltage drop VS due to the Measurement system impedance (Z S +Z M =Z) at the rated current I is approximately 8% (for a 100 V circuit).
VS = I x Z = 20 x 0.42 = 8.4 V
(for a 100 V circuit, Z =  =0.42Ω)
8.4 / 100 x 100 = 8.4%  8%
(from the Interim Report on a Survey Study on Prevention of Harmonics in Low- Voltage Circuits, Specialist Subcommittee on Prevention of Harmonics in Low-Voltage Circuits, Technical Committee, Japan Electrical Construction Association, September 1983)
Hence the impedance at 90% of the cumulative value of the rated input for equipment with rated input exceeding 20 A/phase, for which the voltage drop VS due to the measurement system impedance is 8%, was specified to be the measurement system impedance Z for equipment exceeding 20 A/phase. (The cumulative percentages of rated currents for equipment were obtained from survey results by member companies of the Specialist Committee on Suppression of Harmonics of this association.)
Moreover, the phase angle between resistive and inductive components (θ= cos-1R S / ) was matched to the phase angle of the impedance at 60 Hz as given in the Japanese Guideline for Reduction of Harmonic Emission.
| (1) | Single-phase 100 V equipment
90% of the cumulative rated current I of the equipment is approx. 40 A, and the voltage drop VS due to the measurement system impedance is 100 V x 0.08 = 8 V
Hence, the impedance Z is
Z = VS / I = 8 / 40 = 0.2 Ω
The phase angle is 19.3° (θ= cos -1 R s / Z =19.3°),
R S = 0.2 x cos19.3 = 0.19 Ω
X S = 0.2 x sin19.3 = 0.07 Ω
L S = X S / 2πf = 0.18 mH (where f = 60 Hz). |
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| (2) | Single-phase 200 V equipment
90% of the cumulative rated current of the equipment is approximately 70 A, and the voltage drop VS due to the measurement system impedance is 200 V x 0.08 = 16 V.
Hence the impedance Z is
Z = V S / I = 16 / 70 = 0.229 Ω.
The phase angle is 24.1°,
R S = 0.229 x cos24.1 = 0.21 Ω
X S = 0.229 x sin24.1 = 0.09 Ω
L S = X S / 2πf = 0.25 mH (where f = 60 Hz). |
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| (3) | Three-phase 200 V equipment
90% of the cumulative rated current for the equipment is approximately 140 A, and the voltage drop per phase due to the measurement system impedance is V S / √ 3 = 200 V x 0.08 / √ 3 = 9.24 V
Hence the impedance Z is
Z = VS / √3 / I = 9.24 / 140 = 0.066 Ω.
The phase angle is 24.53°,
R S = 0.066 x cos24.53 = 0.06 Ω
X S = 0.066 x sin24.53 = 0.03 Ω
L S = X S / 2πf = 0.07 mH (where f = 60 Hz).
Moreover, the accuracy of the measurement system impedance value is ±8% in household and general-use equipment, but at smaller impedance values it is difficult to maintain a high accuracy. Hence the accuracy in the impedance of the measurement system for equipment with rated input exceeding 20 A / phase is ±10%. |
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