Patent ID: 11965942
Assignee: SOUTHEAST UNIVERSITY
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 0:
1. A measurement method for a magnetic flux density (B) magnetic field intensity (H) curve of magnetic material, wherein electromagnetic coupling modeling is performed on an Epstein frame based on a vector model of a magnetic circuit, an iron core of the Epstein frame is formed by laminating a silicon steel sheet to be measured, and an excitation coil and a detection coil with the same turns number are wound around the iron core, the measurement method comprising:
(1) a measurement process of a reference B-H curve:
S1, a voltage {dot over (U)}E with a reference frequency f1 is applied to the excitation coil, generating an exciting current İE, then an induced voltage {dot over (U)}D is generated on the detection coil, and a magnetic flux {dot over (Φ)} in the iron core of the Epstein frame can be derived as {dot over (Φ)}={dot over (U)}D/(2πf1N2), wherein N2 is the turns number of the detection coil;
S2, active power P fed to the excitation coil is measured by a power analyzer with copper loss of the excitation coil being removed, then a magnetic-inductance Lmc can be obtained according to a relationship of P=ω2Lmc∥{dot over (Φ)}∥2 between the active power and the magnetic-inductance, wherein ω is an angular frequency of a magnetic flux varied in the magnetic circuit;
S3, a maximum value of the exciting current İE is measured corresponding to each induced voltage {dot over (U)}D by using an oscilloscope to obtain a magnetomotive force (MMF) {dot over (F)} and the magnetic flux {dot over (Φ)} of the magnetic circuit of the iron core of the Epstein frame, then a magnetic impedance Żmc of the whole iron core can be derived, and next, a reluctance Rmc of the iron core under the action of the exciting current İE can be derived based on a formula ∥Żmc∥=√{square root over (Rmc2+(ωLmc)2)} and the magnetic-inductance Lmc;
S4, a magnetic flux density {dot over (b)} of the iron core can be derived from the magnetic flux {dot over (Φ)} and a cross-sectional area S of the iron core, then a magnetic permeability μ of the iron core can be obtained by a formula Rmc=l/(μS), and next a magnetic field strength {dot over (H)} corresponding to the magnetic flux density {dot over (B)} can be obtained, wherein l is an average length of the magnetic circuit of the iron core; and the exciting voltage {dot over (U)}E is adjusted and the measurement process is repeated to obtain the reference B-H curve which only considers the nonlinear reluctance of the iron core,
(2) the B-H curve considering an eddy current effect at any frequency of magnetic field can be derived from the reference B-H curve, wherein the specific process is as follows:
a reluctance Rmc can be obtained from the reference B-H curve when any magnetic flux density ∥{dot over (B)}∥ is known, the magnetic impedance Żmc of the magnetic circuit can be obtained under the condition that the magnetic-inductance Lmc is known corresponding to an eddy current reaction at any frequency, then the MMF {dot over (F)} can be derived in this case by {dot over (F)}=Żmc·{dot over (Φ)}, next the magnetic field strength {dot over (H)} can be obtained by {dot over (H)}={dot over (F)}/l, and the B-H curve considering the eddy current effect can be drawn.