Contactless Loop Method for Measurement of AC Losses in HTS Coils

Amaro, Nuno; Šouc, J; Pina, João Murta; Martins, João; Ceballos, J M; Gömöry, Fedor

doi:10.1109/tasc.2014.2374155

Cited by 8 publications

(3 citation statements)

References 13 publications

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“…However, it has lower measurement speed and accuracy, and only works at the boiling temperature of liquid coolant. Magnetic measurement method measures hysteresis loss in AC magnetic field by a pick-up coil enclosing the measurement sample and requires calibration of the ratio between the hysteresis loop area and losses in the coil [20,21]. The output voltage of the pick-up coil is used to calculate AC loss by the calibration equation.…”

Section: Introductionmentioning

confidence: 99%

A novel AC loss measurement method for HTS coils based on parameter identification

Li¹,

Li²,

Guo³

et al. 2022

Supercond. Sci. Technol.

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In the presence of AC current or AC magnetic field, superconductors will suffer AC loss. The measurement of AC loss is of great significance for applied superconductivity field. There are main three different methods for AC loss measurement. Among them, electrical measurement method is widely researched by different laboratories. The existed electrical measurement method mainly has two shortcomings: difficult to be used in HTS coils with high inductance and only available for periodic current conditions (only obtains average value of AC loss for one or several current periods and cannot obtain AC loss at any instant). In this paper, a novel AC loss measurement method based on parameter identification is proposed to solve the second shortcoming (only available for periodic current conditions). This novel method measures AC loss through identifying HTS coils’ resistance and inductance at any moment, which is completely different from previous measurement methods. The theoretical basis of this novel method mainly contains three parts: equivalent circuit of HTS coils, instantaneous power identification from Poynting theorem and parameter identification based on recursive least squares with fixed forgetting factor (FFRLS). Compared with AC loss measurement results of previous electrical method (integral method), the validity of this novel measurement method is demonstrated. In theory, this novel method can measure AC loss for any current waveform (periodic and aperiodic current), which greatly widens measurement range of previous electrical method. The principle of this novel method and detailed experimental results are discussed and analyzed in this paper.

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Section: Introductionmentioning

confidence: 99%

A novel AC loss measurement method for HTS coils based on parameter identification

Li¹,

Li²,

Guo³

et al. 2022

Supercond. Sci. Technol.

View full text Add to dashboard Cite

show abstract

“…These methods allow for any waveform of the current [11], [12], but only work at the boiling temperature of the liquid coolant. Magnetic measurement methods measure hysteresis in the magnetic field, and require a pickup coil enclosing the coil under test [13], [14]. These methods require calibration of the ratio between the hysteresis loop area and losses in the coil.…”

Section: Introductionmentioning

confidence: 99%

AC losses in HTS coils for high-frequency and non-sinusoidal currents

Bruyn

Jansen

Lomonova

2017

Supercond. Sci. Technol.

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2017). AC losses in HTS coils for high-frequency and nonsinusoidal currents. Superconductor Science and Technology, 30(9), [095006]. https://doi.Abstract-AC losses in racetrack coils that are wound of YBCO tapes are measured for sinusoidal and non-sinusoidal transport currents with fundamental frequencies up to 1 kHz. An electrical method to measure losses for non-sinusoidal currents is developed for this purpose. The measured losses are compared to the losses calculated by 2D finite element models with power-law material models. The frequency and waveform-dependency of the measured losses are shown, and compared to the results of the models over a wide range of frequencies and waveforms. Finally, it is shown that the finite element models can accurately predict AC losses resulting from non-sinusoidal transport currents as are present in highly dynamic motors with AC armature coils.

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“…The principle of magnetization loss measurement is to detect the magnetization (M) of a sample which is exposed to an AC magnetic field (B). Therefore, a magnet generating uniform magnetic fields, and a measuring coil for detecting the change rate of magnetization (𝑑𝐌/𝑑𝑡) are essential components in the measurements [30,99,102,[125][126][127] . Following this, two commercially available instruments are developed for precise magnetization measurements, i.e., superconducting quantum interference devices (SQUIDs) and vibrating-sample magnetometers (VSMs) [30] .…”

Section: Ac Loss Measurementsmentioning

confidence: 99%

AC Loss Research of REBCO High-Tc Superconductors Carrying a DC Current in an AC Magnetic Field

Sun¹

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AbstractREBCO (REBa2Cu3O7-d, RE stands for rare earth) high temperature superconducting (HTS) coated conductors (CCs) have become the preferred wire choice for HTS applications due to their high current carrying capacity and advanced mechanical properties. In many HTS applications such as HTS synchronous motors, HTS flux pumps and HTS persistent current switches, REBCO CCs, stacks and coils carry DC currents in an AC magnetic field environment, generating AC loss comprising of dynamic loss component arising from dynamic resistance and the magnetization loss component due to the shielding currents. AC loss behaviours of commercial-available REBCO CCs in such operating conditions haven’t been fully explored with the most prominent research question of how the AC loss and each loss component evolve and behave in the single REBCO CC, REBCO stacks and REBCO coils at different temperatures with various operating conditions. Other interesting open questions are also put forward to underpin relevant engineering applications: how the shielding effect of REBCO CCs influences the eddy current loss in adjacent copper layers at various field orientation; what kind of inherent correlation exists between the asymmetric field-orientation-dependent critical current characteristics and the magnetization loss behaviors; and how the loss behaviours in REBCO stacks and coils differentiate from the REBCO CC; what’s the difference between the REBCO racetrack coil and the REBCO double pancake coil regarding characteristics of the critical current, magnetization loss, dynamic resistance and AC loss under the condition of the combined DC current with the AC magnetic field. This thesis aims to underpin the REBCO HTS applications and reveal the underlying AC loss mechanism through systematically experimental and numerical research on AC loss and dynamic resistance in REBCO CCs, REBCO stacks and REBCO coils that operate at various electromagnetic conditions and temperatures (65 K ~ 77 K). This research has revealed many new phenomena in the loss evolution process and reached illuminating conclusions. We uncover the shielding effect of REBCO CCs under various field orientations is dominated by the perpendicular magnetic field component, and so does the reduced eddy current loss in the adjacent copper layers of the copper-superconductor stacks. When exploring the role of asymmetric field-orientation-dependent critical current on the magnetization loss of REBCO CCs, we reveal that the asymmetry of critical current about the ab-peak within the 360 full-field-angle range causes differences in magnetization loss values at the field angles which are in mirror symmetry relative to the ab-plane. Furthermore, it is surprising and contradicting to find that magnetization loss at any given field orientation is unequal between the positive and the negative half-field cycle due to the asymmetry of critical current upon the field reversal. The asymmetric field-orientation dependence of both critical current and magnetization loss becomes more obvious with the increasing magnetic field amplitudes and the decreasing temperatures. The complicated AC loss evolution process in REBCO CCs under AC magnetic fields and DC currents is probed by demonstrating the striking behaviours: the dynamic loss region and magnetization loss region vary across the conductor width at high magnetic fields or high DC current levels; the (positive) DC current is superposed with the anti-parallel (negative) shielding current at high DC current levels that approaching to the self-critical current, which drives the local current density of one conductor edge to the subcritical stage and leads to one-sided loss generation in each half-cycle. At the liquid nitrogen temperature range, experimental and simulation results exemplify that the AC loss is mostly dominated by magnetization loss when DC current is less than 20% critical current, while dynamic loss makes a comparable, even greater contribution to AC loss when DC current is larger than 50% critical current. The dynamic resistance shows an obvious frequency dependence due to the heating accumulation at high field amplitudes, high DC current levels and high operating temperatures, which provides a useful reference for the application designs of HTS flux pumps and HTS persistent current switches. Compared with the single REBCO CC, the onset of dynamic resistance/loss in REBCO stacks and REBCO coils is much slower, and the contribution of the dynamic loss component to the AC loss is also much smaller. Dynamic loss in the stack becomes greater than the magnetization loss when the DC current is larger than 70% critical current, while always less than the magnetization loss in the coils when the AC magnetic field is less than 0.1 T. We also conclude that the critical current, magnetization loss and dynamic resistance/loss per unite length in the REBCO racetrack coil is slightly larger than those of the REBCO pancake coil. The main contribution of this work is to reveal the complex AC loss mechanism in REBOC CCs, stacks and coils carrying DC currents in the AC magnetic field and characterize the loss behaviours via solid experimental measurements and numerical simulations. Meanwhile, the magnetization loss as the dominant loss component is further explored concerning its shielding effect and the asymmetric critical current characteristics. This work exemplifies the underlying nature of AC loss behaviours, providing a valuable reference to understand the loss mechanism and to underpin relevant HTS applications.

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Contactless Loop Method for Measurement of AC Losses in HTS Coils

Cited by 8 publications

References 13 publications

A novel AC loss measurement method for HTS coils based on parameter identification

A novel AC loss measurement method for HTS coils based on parameter identification

AC losses in HTS coils for high-frequency and non-sinusoidal currents

AC Loss Research of REBCO High-Tc Superconductors Carrying a DC Current in an AC Magnetic Field

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