Faraday Coil Research Articles

Transfer-Power Measurement Using a Non-Contact Method for Fair and Accurate Metering of Wireless Power Transfer in Electric Vehicles

Wireless power transfer (WPT) is emerging as the preeminent way to charge electric vehicles, but there appears to be no fair way to measure the power transfer. In this article, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Faraday coil transfer-power measurement</i> (FC-TPM) is presented. FC-TPM employs non-contact, open-circuited sense coils to measure the electromagnetic field from WPT and calculates the real power propagating through the air gap between the transmitter and receiver coils. What is measured is the real electromagnetic power, representing the pure dispensation of energy that unambiguously demarcates the losses on either side. FC-TPM was demonstrated to be 0.1% accurate in hardware over an Rx coil misalignment of up to 10 cm using a 1-kW WPT system. Fair metering incentivizes businesses and individuals to make choices that conserve energy and advance technology by providing more information and by properly assigning the financial loss. This article is accompanied by a video highlighting the essential contributions of this article.

Closed-Loop Method Based on Faraday Effect in Resonant Fiber Optic Gyro Employing a low Coherence-Noise Resonator

The closed-loop method based on the Faraday effect is realized with a low coherence-noise resonator in resonance fiber optic gyro (RFOG). The resonator based on spun-fiber (SF) is designed and fabricated, which not only has the advantage of low coherent optical noises, but also has an outstanding circularly state of polarization (CSOP) maintaining ability that lays the foundation for the realization of a closed-loop method based on the Faraday effect. As the core component of the Faraday-based method, the Faraday coil is reasonably designed to meet the requirements of the sufficient frequency shift and power stability. In addition, the interval control method that is conducive to the improvement of system stability is applied to control Faraday coil for the first time. The experimental results show that the method we proposed can effectively achieve high-reciprocity and linear equivalent frequency shift by Faraday coil. Also, the short-term and long-term stability of Faraday-based RFOG system have been improved compared with other closed-loop methods, which provides a simple and efficient method for RFOG closed-loop signal processing.

Development of a Sandwich Coil and LCC Converter-Based Wireless Charging System for Intelligent Electric Vehicles

Wireless power transfer (WPT) is becoming the dominant method for charging electric cars, yet there is currently no equitable method for quantifying the power transfer. This article presents the Faraday coil transfer-power measurement (FC-TPM). FC-TPM utilizes sensor coils that do not make physical contact and are not connected to a circuit in order to measure the electromagnetic field generated by WPT. It then calculates the actual power that is sent across the space between the transmitter and reception coils. The measured quantity is the actual electromagnetic power, which represents the direct distribution of energy that clearly distinguishes the losses on both sides. The FC-TPM exhibited a hardware accuracy of 0.1% when tested with a 1-kW WPT system across a Rx coil sandwich with a maximum distance of 10 cm. Equitable metering encourages enterprises and people to adopt energy-conserving decisions and promote technological advancements by offering comprehensive information and accurately allocating cost burdens. This article is complemented by a film that emphasizes the crucial contributions made by this article.

Adaptive suppression of power line interference in ultra-low field magnetic resonance imaging in an unshielded environment

Power-line harmonic interference and fixed-frequency noise peaks may cause stripe-artifacts in ultra-low field (ULF) magnetic resonance imaging (MRI) in an unshielded environment and in a conductively shielded room. In this paper we describe an adaptive suppression method to eliminate these artifacts in MRI images. This technique utilizes spatial correlation of the interference from different positions, and is realized by subtracting the outputs of the reference channel(s) from those of the signal channel(s) using wavelet analysis and the least squares method. The adaptive suppression method is first implemented to remove the image artifacts in simulation. We then experimentally demonstrate the feasibility of this technique by adding three orthogonal superconducting quantum interference device (SQUID) magnetometers as reference channels to compensate the output of one 2nd-order gradiometer. The experimental results show great improvement in the imaging quality in both 1D and 2D MRI images at two common imaging frequencies, 1.3 kHz and 4.8 kHz. At both frequencies, the effective compensation bandwidth is as high as 2 kHz. Furthermore, we examine the longitudinal relaxation times of the same sample before and after compensation, and show that the MRI properties of the sample did not change after applying adaptive suppression. This technique can effectively increase the imaging bandwidth and be applied to ULF MRI detected by either SQUIDs or Faraday coil in both an unshielded environment and a conductively shielded room.

A fiber link equipment for the optical rotation measuring based on AC-DC modulation magneto-optical effect

Based on the magnetic-optical effect, an alternating current-direct current (AC-DC) two-stage modulation is applied in the newly developed equipment, which measures the concentration of solution through the optical rotation of optical active substance. A Faraday coil is combined with the AC-DC signal generator controlled by a pulse width modulation controller. To deduct the measuring error caused by the AC modulation or the DC modulation, a two-stage method based on the Superposition of DC component and AC component is demonstrated, which is characterized by removing the interference of the bigger magnetic rotation angle in the AC modulation alone. The tartaric acid, glucose, and sucrose sugar solutions are taken as the standard examples in testifying the equipment. A linear correlation is found between the measured optical rotation angle and the concentration of the solution, with the optical rotation angle being within a 1% margin of error and the maximum relative error smaller than 0.005g/ml. The results show that the equipment has the advantage of high precision, high integration, and strong anti-interference capacity. The fiber link makes the equipment portable and compact. The AC-DC two-stage modulation equipment can potentially be used in the optical rotation measurement.

Induction of Electromotive Force by an Autonomously Moving Magnetic Bot

AbstractWe report the observation of the induction of electromotive force (emf) into a Faraday coil by an autonomously moving composite magnetic particle in aqueous medium. The particle consisted of a micron‐sized polymer sphere, which was decorated with catalytic Pd nanoparticles (NPs) and attached to a micron‐scale (N‐42 grade) rare‐earth magnet. The Pd NPs catalytically decomposed H2O2 to generate O2, resulting in buoyancy‐driven vertical motion of the particle, while the micromagnet induced emf during the flight. Because a small volume of ethanol was layered on top of the liquid, the bubble burst when the particle ascended to the top and thus nearly continuous vertical motion was achieved. Spikes of alternating electrical signal could be observed up to 20 times per minute. The signal was sufficiently strong to illuminate light‐emitting diodes following appropriate amplification. This distinctive approach is expected to pave the way to developing synthetic bots which are autonomously propelled, generating their own signal for running complex circuitry.

SQUID‐detected MRI at 132 μT with T1‐weighted contrast established at 10 μT–300 mT

T(1)-weighted contrast MRI with prepolarization was detected with a superconducting quantum interference device (SQUID). A spin evolution period in a variable field between prepolarization and detection enabled the measurement of T(1) in fields between 1.7 microT and 300 mT; T(1) dispersion curves of agarose gel samples over five decades in frequency were obtained. SQUID detection at 5.6 kHz drastically reduces the field homogeneity requirements compared to conventional field-cycling methods using Faraday coil detection. This allows T(1) dispersion measurements to be easily combined with MRI, so that T(1) in a wide range of fields can be used for tissue contrast. Images of gel phantoms with T(1)-weighted contrast at four different fields between 10 microT and 300 mT demonstrated dramatic contrast enhancement in low fields. A modified inversion recovery technique further enhanced the contrast by selectively suppressing the signal contribution for a specific value of the low-field T(1).