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Survey of Sensor Mechanisms
Published in Robert B. Northrop, Introduction to Instrumentation and Measurements, 2018
Magnetic reluctance, ℜ, is defined as the ratio of magnetomotive force to the magnetic flux, Φ, existing in a closed, magnetic circuit. It may be thought to be analogous to electrical resistance in an electrical circuit where the MMF is analogous to voltage and the flux Φ is analogous to current. A schematic of a simple, variable-reluctance phonograph pickup transducer is shown in Figure 6.26. The source of MMF is a permanent magnet (PM). Flux from the PM is split and passed through a right and left branch magnetic path so that the total flux in the magnet is the sum of left and right path fluxes. Thus, () Φ=ΦR+ΦL W.
Fundamental Electrical Engineering Concepts and Principles
Published in S. Bobby Rauf, Electrical Engineering Fundamentals, 2020
Magnetic reluctance can also be perceived as magnetic resistance; a resistance that opposes the flow of magnetic flux. Like resistance, reluctance is a scalar entity, but unlike electric resistance, it stores magnetic energy instead of dissipating it. Reluctance is measured in ampere-turns per weber or turns per henry. Ferromagnetic substances such as iron have low reluctance while dielectric substances like air and vacuum offer high reluctance to magnetic flux. That is the reason why transformers, contactors, relays, and other similar electromagnetic devices utilize iron – or iron alloy – cores.
Electrical Engineering Basics
Published in S. Bobby Rauf, Electrical Engineering for Non-Electrical Engineers, 2021
Magnetic reluctance can also be perceived as magnetic resistance; a resistance that opposes the flow of magnetic flux. Like resistance, reluctance is a scalar entity, but unlike electric resistance, it stores magnetic energy instead of dissipating it. Reluctance is measured in ampere-turns per weber, or turns per henry. Ferromagnetic substances such as iron have low reluctance while dielectric substances like air and vacuum offer high reluctance to magnetic flux. That is the reason why transformers, contactors, relays and other similar electromagnetic devices utilize iron—or iron alloy—cores.
The Research on Correlated Sensitivity Factors of Flux-Regulation Capability for Axial–Radial Flux-Type Synchronous Motor with Hybrid Poles
Published in IETE Journal of Research, 2018
Hongbo Qiu, Wenfei Yu, Wei Wang, Yuanqing Mu, Weili Li, Cunxiang Yang
As shown in Figure 13, the thickness of PPMs (Wppm) has a small effect on air-gap flux density when the axial exciting current is 0 A. In addition, the flux-regulation capability of negative If was limited by the bypass effect. Therefore, the air-gap flux densities of motor with different Wppm are close. With the increase of positive exciting current, the bypass effect was completely counteracted. After the bypass effect was completely counteracted, the positive excitation flux started to provide the air-gap flux. In this stage, the saturation of rotor magnetic circuit is the key factor that affects the flux-regulation capability. The magnetic reluctance of rotor magnetic circuit is reduced by reducing the Wppm. Therefore, the reduction of Wppm could improve the adjusting ability. As shown in Figure 13, the motor-adjusting range with Wppm of 5 mm increased by 0.1 T from the situation of 8 mm. The adjusting multiple K is 1.41, 1.35, 1.3, and 1.27, when the Wppm is 5, 6, 7, and 8 mm, respectively.
Effect of flaw orientation on magnetic flux leakage and remote field eddy current inspection of small diameter steel tubes
Published in Nondestructive Testing and Evaluation, 2023
W. Sharatchandra Singh, S. Thirunavukkarasu, Anish Kumar
Experimental studies were carried out using a multi-NDE instrument MS5800 supplied by M/s. Olympus as shown in Figure 1(a). The experimental setup consists of a tube, probe, probe movement controller and pusher/puller system, multi-NDE instrument and data acquisition/analysis laptop. Measurements were made by pulling the probe from inside the tube at a speed of 60 mm/s using a pulley based probe pusher/puller system. The probe pusher/puller system consists of a DC servo motor (CROUZET 80,149,605) connected to a pulley through a gearbox having a gear ratio of 5:1 for controlling the linear speed. In the present study, the linear speed ranges from 20 mm/s to 100 mm/s in steps of 20 mm/s were used. A probe movement controller was used to control the linear speed of pulling or pushing and direction (forward or reverse) of movement of the system. Data acquisition and analysis were performed using Multiview 6.1R0 softw are [19]. For MFL testing, MFL module of the instrument was used. The MFL probe (Figure 1b) consists of two cylindrical permanent magnets (each of length 10 mm, diameter 10 mm separated by 35 mm) to axially magnetise the tube close to magnetic saturation (1.3 T) and a differentially connected pick-up coil (2 coils each of length 2 mm, height 2 mm, 34 SWG and 50 no. of turns separated by 3 mm) placed in between the magnets to measure the leakage magnetic flux. Magnetic reluctance increases at the flaw region of the tube leading to some of the magnetic flux to leak out of the tube surface. The variation of the flux leakage induces a voltage in the coil, thereby causing a signal output. As the flaws are localised in nature, a coil connected in differential configuration was used in this study.
Experimental Study of Converging Ferrofluid Seal With Small Clearance and Double Magnetic Sources
Published in Tribology Transactions, 2021
Xiaolong Yang, Ying Guan, You Li, Decai Li
Figure 8 shows that when the axial clearance increases from 0.1 mm to 0.4 mm, the magnetic flux density in the axial clearance decreases. The reason is that the magnetic reluctance of the axial clearance increases, which causes a reduction of the magnetic flux density in the axial clearance, according to the magnetic circuit law.