Development of an AC Standard Shunt with Small Phase Angle and High Precision Copyright, 2002 © Japan Electric Meters Inspection Corporation JEMIC Takuhiro Tsuchiyama Takuya Tadokoro

Introduction A shunt is commonly used in order to measure current with high accuracy. A shunt is commonly used in order to measure current with high accuracy. Phase angle causes phase shift between the input current and the output voltage. Phase angle causes phase shift between the input current and the output voltage. Ratio error and phase angle cause error for AC power measurement. Ratio error and phase angle cause error for AC power measurement.

Introduction As a practical AC standard shunt; As a practical AC standard shunt; estimatable small phase angle estimatable small phase angle large rated current large rated current high stability high stability easy handling - small and light easy handling - small and light New AC standard shunt has been developed.

Design features 1. Use superior resistors

Structure of the resistors Package Ceramic substrate Insulation film Resistor substrate 4 mm 13 mm Metal foil thickness= 5μm Silicon grease Resistance (10±0.001)Ω Rated power 0.3W TCR <10μΩ/Ω/ ℃ Stability <10μΩ/Ω/ year Alpha Electronics TypeDEP-97044

Design features 2. Connect 100 resistors in parallel 1. Use superior resistors

Design features 3. Separate the current circuit and the voltage circuit 1.Use superior resistors 2. Connect 100 resistors in parallel

Configuration

Design features 1. Use superior resistors 2. Connect 100 resistors in parallel 3. Separate the current circuit and the voltage circuit 4. Remove hand-made parts to improve long-term stability

Developed AC shunt

Specifications

Characteristics 1 Self-heating characteristics <1μΩ/Ω <0.1μΩ/Ω

Characteristics 2-2 Temperature characteristics

Characteristics 2 Temperature characteristics <0.3μΩ/Ω 1℃1℃

Characteristics 3 Current characteristic <±0.5μΩ/Ω ±2%

Characteristics 4 Long-term stability

Quadrature components 1. inductance of the resistors 2. distributed capacitance of the circuit boards 3. influence of mutual inductance among the resistors 4. influence of mutual inductance between the current circuit and the voltage circuit 5. other influences

Quadrature components 1. Inductance of the resistors It is estimated by comparing the resistor and a resistance wire. It is estimated by comparing the resistor and a resistance wire. Inductance of the resistance wire can be calculated from its length and cross sectional radius. Inductance of the resistance wire can be calculated from its length and cross sectional radius. Estimated inductance of each resistor: Estimated inductance of each resistor: 10nH 10nH

Quadrature components 2. The distributed capacitance of the circuit board It was measured using an LCR meter. It was measured using an LCR meter. Estimated distributed capacitance of each circuit board: 560pF Estimated distributed capacitance of each circuit board: 560pF

Quadrature components 4. Mutual inductance between the current circuit and voltage circuit Interaction among the current lead, the voltage lead, and the circuit boards is sufficiently small. Interaction among the current lead, the voltage lead, and the circuit boards is sufficiently small. negligible negligible

Quadrature components 5. Other influences Temperture, current characteristics, long-term stability, etc. of the resistance value Temperture, current characteristics, long-term stability, etc. of the resistance value Influence of skin effect and eddy current Influence of skin effect and eddy current Influence of resonance Influence of resonance

AC resistance value and phase angle

Conclusion A resistor and a circuit board for the shunt have developed. Developed shunt satisfies expected characteristics; -stability -phase angle. Practicality has been enhanced.