Study on Influence of Potting on Near-Field Coupling of Magnetic Elements in EMI Filters

doi:10.16628/j.cnki.2095-8188.2025.06.002

Abstract

Abstract:

To address the issue of degraded filtering performance in electromagnetic interference (EMI) filters after potting, a near-field coupling equivalent model of the filter considering both electric field coupling and magnetic field coupling is established. The near-field coupling equivalent parameters of magnetic elements are extracted before and after potting. The parameter extraction results show that potting can affect the self-parasitism effect of the filter and the near-field coupling effect between magnetic elements. Then, the sensitivity analysis of the near-field coupling equivalent parameters of the magnetic elements before and after potting is carried out. The results show that the change of the insertion voltage gain of the filter before and after potting is mainly caused by the change of equivalent capacity parameters of the magnetic elements which are greatly affected by the near-field coupling. The influence mechanism of the near-field coupling of the magnetic elements after potting is further clarified. Finally, a partial potting method is proposed to improve the conduction EMI noise, and the effectiveness of partial potting is verified by experiments.

Key words: EMI filter, potting, magnetic element, near-field coupling, electromagnetic interference

CLC Number:

TM133

HUANG Ju, LI Huanhuan, MAO Xingkui, DONG Jiqing. Study on Influence of Potting on Near-Field Coupling of Magnetic Elements in EMI Filters[J]. LOW VOLTAGE APPARATUS, 2025, 0(6): 7-16.

Figures/Tables 30

References 30

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参数	数值
硬度/HA	45±5
相对介电常数	2.8~4.0
体积电阻率/(Ω·cm)	≥1.0×10¹²
介电强度/(kV·mm^-1)	≥14
导热系数/[W·(m·K)^-1]	0.6~0.8

参数	Z_y1	参数	Z_y1
R/MΩ	R₁₃=1.89	C/pF	C₁₃=1.30
L/mH	L_a=35.00

参数		自参数	近场耦合等效参数
L_F3	R/kΩ	R₁₂=7.38	R_eq1=6.95
	L/μH	L₁=470.15	L_b=476.12
	C/pF	C₁₂=43.42	C_eq1=43.95
L_{F2_dm}	R/kΩ	R₃₄=96.56	R_eq2=95.96
	L/μH	L₂=181.30	L_c=182.21
	C/pF	C₃₄=2.06	C_eq2=2.55

参数		Z_y1	Z_y2	Z_y3
灌胶前	R/kΩ	R₁₃=1 890.00	R_eq1=6.95	R_eq2=95.96
	L/μH	L_a=35 000.00	L_b=476.12	L_c=182.21
	C/pF	C₁₃=1.30	C_eq1=43.95	C_eq2=2.55
灌胶后	R/kΩ	R₁₃=1 900.00	R_eq1=6.89	R_eq2=96.21
	L/μH	L_a=35 000.00	L_b=474.69	L_c=181.98
	C/pF	C₁₃=1.67	C_eq1=49.21	C_eq2=4.46

参数	Z_y1	参数	Z_y1
R/kΩ	R₁₃=134.60	C/pF	C₁₃=0.80
L/mH	L_a=49.00