DC high current ratio standard based on series-parallel calibration method

Shao, Haiming; Lin, Feipeng; Hua, Xiaoxin; Liang, Bo; Qu, Kaifen; Pan, Yang

doi:10.1109/cpem.2010.5544838

Cited by 3 publications

(2 citation statements)

References 2 publications

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“…To extend the operating currents from 1 A to 5 kA, four automatic balancing DCCs, 10 A:1 A (T 0 ), 50 A:5 A (T 1 ), 500 A:5 A (T 2 ), and 5 kA:5 A (T 3 ), have been developed [9]. Fig.…”

Section: Self-calibration Process Of Dccsmentioning

confidence: 99%

DC 5 kA Current Ratio Standards Based on Series–Parallel Self-Calibration DCCs

Shao¹,

Lin²,

Liang³

et al. 2013

IEEE Trans. Instrum. Meas.

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With proper design, accurate current ratios of direct current comparators (DCCs) can be achieved between series and parallel connections of n sections of primary windings with the same nominal number of turns. Based on this principle, a DCC could be calibrated with the windings connected in series, then operated in parallel, at rated current and therefore have its current ratio accurately extended by n times. By keeping the geometric position of the primary windings symmetrically and rigidly fixed to the cores, the leakage fluxes and their effects on the DCC current ratios would be minimized and relatively unchanged between the series and parallel connections. Four DCCs with current ratios of 10 A:1 A to 5 kA:5 A have been developed with relative ratio errors less than 2 × 10 −8 to 5 × 10 −7 , and calibrated by the series parallel method through only four step measurements. These measurement techniques for the selfcalibration of DCCs with current ratios of 10 A:1 A to 5 kA:5 A and corresponding uncertainties from 1.2 × 10 −8 to 1.6 × 10 −7 (k = 2) are described.

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“…To extend the operating currents from 1 A to 5 kA, four automatic balancing DCCs, 10 A:1 A (T 0 ), 50 A:5 A (T 1 ), 500 A:5 A (T 2 ), and 5 kA:5 A (T 3 ), have been developed [9]. Fig.…”

Section: Self-calibration Process Of Dccsmentioning

confidence: 99%

DC 5 kA Current Ratio Standards Based on Series–Parallel Self-Calibration DCCs

Shao¹,

Lin²,

Liang³

et al. 2013

IEEE Trans. Instrum. Meas.

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“…Even though CCCs capable of handling currents up to 100 A have been realized [7], these devices are research instruments not available in calibration laboratories. Ferromagnetic-core, room-temperature current comparators (CC) are current ratio devices which can achieve ratio errors lower than 10 −7 [8], and can be self-calibrated through step-up procedures [9,10] with similar levels of uncertainty. Thus, a CC can be employed as current ratio standard in a DCCT calibration setup.…”

Section: Introductionmentioning

confidence: 99%

On the Calibration of Direct-Current Current Transformers (DCCT)

Callegaro

Cassiago

Gasparotto

2015

IEEE Trans. Instrum. Meas.

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Modern commercial direct-current current transformers (DCCT) can measure currents up to the kA range with accuracies better than 1 × 10 −5 . We discuss here a DCCT calibration method and its implementation with commercial instruments typically employed in low resistance calibration laboratories. The primary current ranges up to 2 kA; in the current range below 100 A the calibration uncertainty is better than 3 × 10 −7 . An example of calibration of a high-performance DCCT specified for primary currents measurement up to 900 A is discussed in detail. INTRODUCTIONDirect-current current transformers (DCCT) are the most accurate dc high-current sensors commercially available [1], reaching specified relative accuracies in the 10 −5 range and integral nonlinearities below 10 −6 . The verification of such high performances and the calibration of the DCCT ratio require metrological facilities capable of handling high currents, with high accuracy and automated operability [2][3][4][5]. Ultimate current ratio accuracy is achieved in cryogenic current comparators (CCC) [6]. In a CCC, ratio accuracy is obtained by constraining the magnetic flux (generated by the current being compared) within superconducting shields. An extremely high sensitivity is achieved with a superconducting quantum interference device (SQUID) flux sensor. Even though CCCs capable of handling currents up to 100 A have been realized [7], these devices are research instruments not available in calibration laboratories. Ferromagnetic-core, room-temperature current comparators (CC) are current ratio devices which can achieve ratio errors lower than 10 −7 [8], and can be self-calibrated through step-up procedures [9, 10] with similar levels of uncertainty. Thus, a CC can be employed as current ratio standard in a DCCT calibration setup. Although complex and expensive instruments, high-current CC are common in electrical calibration laboratories, since they are part of commercial resistance ratio bridges employed for the measurement of low-value resistors. These instruments include also current sources, detectors, and firmware for automated operation. The calibration of the DCCT ratio with a reference current ratio standard (possibly having a different nominal ratio) can be performed by different methods. Recent papers [11,12] describe a method based on the comparison of the voltages developed by the secondary currents of the devices being compared on calibrated resistance standards. Here we present a simple method that allows the calibration of the ratio of a DCCT by using commercial components, originally designed for the calibration of low-value resistors. This method does not require calibrated resistance standards; the accuracy, dependent on the primary current, is better than 3 × 10

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Effects of stray magnetic fields on the iron core of DCC

Shao

Lin

et al. 2012

2012 Conference on Precision Electromagnetic Measurements

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DC high current ratio standard based on series-parallel calibration method

Cited by 3 publications

References 2 publications

DC 5 kA Current Ratio Standards Based on Series–Parallel Self-Calibration DCCs

DC 5 kA Current Ratio Standards Based on Series–Parallel Self-Calibration DCCs

On the Calibration of Direct-Current Current Transformers (DCCT)

Effects of stray magnetic fields on the iron core of DCC

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