Magnetic Field

Low-frequency passive magnetic shielding transformation

Shielding solution

● Materials/composition

High magnetic permeability materials - low carbon steel, silicon steel, Permalloy, etc.

● Principle

Guided demagnetization: The basic principle of low-frequency (such as industrial frequency 50Hz) electromagnetic interference shielding is magnetic circuit parallel bypass shunt. By using high magnetic permeability materials (such as low carbon steel, silicon steel, etc.) to provide magnetic bypass to reduce the magnetic flux density inside the shield. At the same time, try to increase the eddy current loss so that part of the energy is converted into heat energy and consumed.

Eddy current demagnetization: The conductor in the alternating magnetic field will induce a closed circular current on the cross section perpendicular to the direction of the magnetic field line, which will generate a new magnetic field in the opposite direction to offset the original magnetic field; there will also be eddy current loss.

● Installation process

Thermal and electrical conductive aluminate coating; anti-rust coating shot blasting and rust removal; stress relief; magnetic treatment frame + full welding

Low-frequency passive magnetic shielding construction process:

(1) Material selection: Hexahedral passive low-frequency electromagnetic shielding system, using 8mm thick high magnetic permeability material after demagnetization treatment, magnetic shielding door production and installation, and line waveguide port.

(2) Demagnetization treatment and process: continuous full welding to form a hexahedral structure, full welding, full sealing, Permalloy coating caulking process treatment, waveguide treatment, stress relief treatment (eliminating resonance), top waterproof treatment, outer insulation layer treatment, full-process special detection equipment magnetic field, vibration, noise staged process testing, full-load welding, angle steel channel steel support welding, anti-magnetic leakage measures, local repair welding, top plate double-layer overhead welding.

A passive magnetic shielding room is used to solve the AC magnetic field, and an active shielding system is used to solve the magnetic field problem. The AC magnetic field and DC magnetic field intensity changes after static geomagnetic field shielding in the central area of the magnetic shielding space (the equipment installation barrel sample area) are less than 50 nT, and the AC magnetic field change range in the central area of the magnetic shielding space (length 1.5m, width 1.5m, height 1.5m) is <50nT (10Hz-1kHz).

Hexahedron frame construction

Active degaussing system

Active degaussing device generally consists of three parts: three-dimensional detector, three-channel controller and degaussing coil. When the detector detects the three-dimensional field strength and its changes of the magnetic field, the controller generates a continuously tracked reverse current according to the obtained signal, and the reverse degaussing coil generates an electromagnetic field with the same waveform and amplitude and opposite phase to offset the original electromagnetic interference.