高频磁性元件与磁性材料

H
H DC
μ s = μ s′ − jμ s′′
1 = 1 −j 1
Ls Lp
Rs
Bm: Max. Flux Density
μp
μ'p
μ '' p
Rp
损耗参数 机械物理参数 磁滞伸缩系数
PCV = K ⋅ f α ⋅ B β ⋅ (C0 + C1 ⋅ T + C2 ⋅ T 2 )
弹性模量，热伸缩系数，导热系数等 音频噪声的主要来源
1
0
t
π
磁芯损耗测量 v.s.气隙/磁粉芯
铁氧体高磁导率材料 有气隙铁氧体或低磁导率磁粉芯
P cos θ = U ⋅I
Β
i u
Β
i u
U保持不变，B不变, P不变，但 由于电感大，I 很小，所以cosθ 较高，误差较小。
U保持不变，B不变, P不变，但 由于电感降低，I 增大，所以 cosθ降低，误差增大。
涡流损耗大小取决于铁磁材料本身的电导率 涡流损耗大小与激磁工作频率的平方成正比 涡流损耗大小与磁通密度大小的平方成正比
磁芯损耗模型-Steinmetz Model
PCV = Cm ⋅ f α ⋅ B β ⋅ (C0 + C1 ⋅ T + C2 ⋅ T 2 )
Core loss is related to: Material grade Frequency Temperature Flux density DC bias Excitation waveform
− 32
− 32
− 32
Hdc=20.77A/m, Pc=584 ( kw/m3 )
Hdc=27.69A/m, Pc=605 (kw/m3)
Hdc=34.62A/m,Pc=647 ( kw/m3)
铁粉芯的老化问题
铁芯损耗随时间的变化曲线
%Q 随时间变化曲线
电感失效
铁粉芯的老化机理
Micro eddy currents in each particle Macro eddy currents among particles
B
﹛
1) 起始磁导率: μi
Slope=μmax: Max. Permeability
μi =
1 ΔB μ 0 ΔH
ΔH →0
2) 幅值磁导率: μa 3) 增量磁导率: μ△ 4) 复数磁导率: μs
μa =
μΔ =
ˆ 1 B ˆ μ0 H
1 ΔB μ 0 ΔH
Slope=μi: Initial Permeability Slope=μΔ: Incremental Permeability Minor Loop
32
1.5
29 Hk
59.5
90 90
32
1.5
29 Hk
59.5
90 90
32
1.5
29 Hk
59.5
90 90
− 32
− 32
− 32
Hdc=0, Pc=504 (kw/m3)
0.37 0.37 0.27 0.17 Bk 0.075 0.023 0.12 − 0.22 0.22 32 1.5 29 Hk 59.5 90 90
Material Magnetics HF60 Powder Magnetics XFlux60 Magnetics KM60 Magnetics MPP60 Ferrite Ferroxcube 3C96 Ferroxcube 3C96
B (T) 0.1 0.1 0.1 0.1 0.2 0.1
f(kH z) 50 50 50 50 100 100
Pc = f s ⋅ Cm ⋅ fsin
Power loss factor, k, with same Bm and fs k= Pc_pulse Pc_sin
α=1.7
v(t) t
D
α=1.4
D
k=1 @ D=0.283
直流偏磁对磁芯损耗的影响
Core loss model
P 1+ K1dc ⋅ Bdc ⋅ e c =(
c)
μa(B)
高频磁芯损耗的测量-交流I*V法
H (t ) = i (t ) ⋅ N = K H ⋅ i (t ) le
B (t ) =
1 N ⋅ Ae
Ts
∫
t 0 +T
t0
u (t ) dt = K B ⋅ ∫
Ts
t 0 +T
t0
u (t )dt
1 1 dB H ⋅ le ( )⋅( ) ⋅ dt P = u ⋅ i ⋅ dt = A ⋅ N ⋅ core e ∫ Ts ∫ Ts dt N 0 0
b
b
a c
∫
b
c
b
i u
u(t)
i(t)
c e
a
0
T/2
d
T
磁滞损耗大小取决于铁磁材料本身的品质 磁滞损耗大小与激磁工作频率成正比 磁滞损耗大小与磁通密度大小的平方成正比
铁芯的损耗 (涡流损耗)
B, f
U0 = dφ = 2π f ∗ B ∗ π r 2 dt 2 U0 4π 4 f 2 B 2 r 4 4π 4 f 2 B 2 r 4 = = dP = 2π r l0 dR 0 ρ ρ S0 drdz = 2π 3 f 2 B 2 r 3
− Bac K2dc
) ⋅ K1ac ⋅ Bac
K2ac
fs
K3ac
⋅ (Kt1τ 2 + Kt 2τ + Kt3)
B-H Loop @ fs=100kHz, Bac=200mT, To=100℃
0.37 0.37 0.27 0.17 Bk 0.075 0.023 0.12 − 0.22 0.22 Bk 0.37 0.37 0.27 0.17 0.075 0.023 0.12 − 0.22 0.22 Bk 0.37 0.37 0.27 0.17 0.075 0.023 0.12 − 0.22 0.22
Pcv=500 kw/m3
f*B(HzT)
Pcv=300 kw/m3
Pcv=100 kw/m3
N49
N97
5000 0
f(kHz)
1000
磁性材料的储能特性与材料选择
PWM波形激励下的磁芯损耗
加权平均磁密变化率 B w
Bw = B max 1 − B min
V
∫
T
(
dB 2 ) dt dt
B
B w sin = ( B max − B min ) ⋅
Bsource Jeddy
Ae le
ρ
drdz drdz = 2π 3 f 2 B 2
Peddy =
∫∫
2π 3 f 2 B 2 r 3
ρ
ρ
∫
r _ face
0
r dr ∫ dz
3 0
le
πf 2 B 2 π 2 2 = Ae 2 le = f B leAe 2σ 2ρ 2
Pe ddy =
π
2
f 2 B 2 ⋅ le ⋅ Ae 2 ⋅ σ
B(Ts)
= Ae ⋅ le ⋅
B(0)
∫ H ⋅ dB = V ⋅ P
e
cv
计算机
通讯
示波器 （数据采集）
i(t)
信号发生器 高频功率放大器 电流采样
DUT
u(t)
Chamber
高频磁芯损耗测量的误差分析与困难
P = U ⋅ I ⋅ cos θ
ΔP ΔU ΔI = + + tg (θ ) Δ θ P U I
f sin = 2
π2
2
⋅ f sin
B warb =
( B max
α −1
( B k +1 − B k ) 2 1 ∑ t −t − B min ) k k +1 k
⋅ Bac ⋅ (Ct 0 + Ct1 ⋅ T + Ct 2 ⋅ T 2 ) ⋅Ve
β
π
2
∑ (B
k
B k +1 − B k 2 1 ) ⋅ t k +1 − t k max − B min
High-frequency Large signal Low Loss
200 160 120 80 40 0
i(t)
u(t)
Large Δθ =Δt*f Large Δt θ approaches to 90°
1
i(t) u(t)
0
tg (θ )
1
0
t
π
1
i(t)*u(t)
0
80 81 82 83 84 85 86 87 88 89 90 80 θ 90
铁氧体磁材料(块材)
Mn-Zn Ni-Zn
非晶磁材料(带材)
Silicon steel (硅钢片)
Permalloy (玻膜合金)
Amorphous (非晶)
粉芯磁材料的结构
Alloy particle Flux uneven Æ higher core loss Min. polymer needed for forming Æ Lower μ Powder conglutination Æ more eddy current Polymer Æ Lower max. temperature (140-170℃) Force stress Æ Poor μ consistency (>10%) Inorganic coating (oxide, SiO2, etc) Distributed air-gap Æ Lower winding losses Polymer binder Distributed air-gap Æ Larger Hdc