A New Measuring System for Determining the Magnetic Viscosity in Permanent Magnets

A new system for measuring magnetic viscosity in bulk hard magnetic materials base on a pulsed field method is presented. After the magnetizing field pulse, the stray field of the sample, which is proportional to the magnetic moment, is measured with a compensated set of two Hall probes. The set of Hall probes is driven with an AC voltage source and the Hall voltage is detected using a lock-in amplifier. By this method the system is able to measure the time dependence of the magnetization (viscosity). The magnetic viscosity coefficient (S) is obtained through a linear fitting of the magnetization decay versus ln t. Two typical Nd-Fe-B samples were measured and good agreement with the results from the traditional viscosity experiment was obtained.

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EXPERIMENTAL STUDY OF EDDY CURRENT BRAKING APPLICABLE TO GRAVITY ROLLER CONVEYOR

Fundamental and Applied Problems of Engineering and Technology ◽

10.33979/2073-7408-2020-342-4-1-106-116 ◽

2020 ◽

Vol 4 (1) ◽

pp. 106-116

Author(s):

I.A. SHARIFULLIN ◽

A.L. NOSKO ◽

E.V. SAFRONOV ◽

D.V. KIRILLOV

Keyword(s):

Eddy Current ◽

Main Parameter ◽

Permanent Magnets ◽

Experimental Studies ◽

Viscosity Coefficient ◽

Air Gap ◽

Safe Operation ◽

Roller Conveyor ◽

Magnetic Viscosity ◽

Conductive Body

One of the main elements of safe operation of gravity conveyors used in gravity racks for pallets is the brake roller. The most promising design is a brake roller of magnetic (eddy current) type. A mathematical model of the process of moving pallets on a magnetic brake roller is developed. The equation of the speed of movement of the pallets on the brake magnetic roller obtained. The main parameter that determines the braking functions of the brake magnetic roller, and therefore the speed of movement of the pallet on the gravity roller conveyor is the coefficient of roller, experimental studies have been carried out to determine the magnetic viscosity coefficient. It was found that the coefficient of magnetic viscosity decreases with increasing air gap between the conductive body and the permanent magnets, and this dependence has a power-law character; decreases by 10... 25% with increasing speed of the conductive body; independent of changes in the distance between the centers of the conductive body and the permanent magnet; decreases when an edge effect appears in accordance with the air gap.

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Developing a reference material set for the magnetic properties of NdFeB alloy-based hard magnetic materials

Reference materials ◽

10.20915/2077-1177-2019-15-1-21-27 ◽

2019 ◽

Vol 15 (1) ◽

pp. 21-27

Author(s):

E. A. Volegova ◽

T. I. Maslova ◽

V. O. Vas’kovskiy ◽

A. S. Volegov

Keyword(s):

Magnetic Properties ◽

Magnetic Materials ◽

Permanent Magnets ◽

Magnetic Loss ◽

Magnetic Hysteresis ◽

Hysteresis Loops ◽

Magnetic Hysteresis Loop ◽

Magnetic Characteristics ◽

Hard Magnetic Materials ◽

Certified Values

Introduction The introduction indicates the need for the use of permanent magnets in various technology fields. The necessity of measuring the limit magnetic hysteresis loop for the correct calculation of magnetic system parameters is considered. The main sources of error when measuring boundary hysteresis loops are given. The practical impossibility of verifying blocks of magnetic measuring systems element-by-element is noted. This paper is devoted to the development of reference materials (RMs) for the magnetic properties of hard magnetic materials based on Nd2Fe14B, a highly anisotropic intermetallic compound.Materials and measuring methods Nd-Fe-B permanent magnets were selected as the material for developing the RMs. RM certified values were established using a CYCLE‑3 apparatus included in the GET 198‑2017 State Primary Measurement Standard for units of magnetic loss power, magnetic induction of constant magnetic field in a range from 0.1 to 2.5 T and magnetic flux in a range from 1·10–5 to 3·10–2 Wb.Results and its discussion Based on the experimentally obtained boundary hysteresis loops, the magnetic characteristics were evaluated, the interval of permitted certified values was set, the measurement result uncertainty of certified values was estimated, the RM validity period was established and the first RM batch was released.Conclusion On the basis of conducted studies, the RM type for magnetic properties of NdFeB alloy-based hard magnetic materials was approved (MS NdFeB set). The developed RM set was registered under the numbers GSO 11059–2018 / GSO 11062–2018 in the State RM Register of the Russian Federation.

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