Ferrite Specifications and ACME Ferrites (4)

ACME Electronics Corporation 1

Ferrite Specification&

ACME Ferrites

Technical Aspects

By Ray Lai, FAEJune 2015

With Supports of RD & Marketing Teams

ACME Electronics Corporation

Table of Content

1. Specifications of Ferrites – Materials & Products2. ACME ferrite road map and development trend

3. Technical Application Example: CMC

4. Technical Application Example: DC-DC choke

5. Technical Application Example: SMPS transformer

6. Appendix A: Further on ferrite specifications

7. Appendix B: (a) Fringing effect of gapped core (b) Manipulating magnetizing curve

8. Appendix C: An analogy and differentiation on R, C, and L and why magnetic components are so UNIQUE

Q & A2



Appendix A explains the meaning and catch of

1. Remanence (Brms) and Coercivity (Hc),

2. Loss Factor

3. Hysteresis Material Constant (ηB),

4. Disaccommodation Factor (DF) and Temperature Factor of Permeability (αF)

5. Total Harmonic Distortion (%THD)

6. Quality Factor (Q)

which are important in understanding the operation and quality of ferrite products.


6. Appendix A: Further on ferrite specifications1. Magnetic Remanence (Brms) and Coercivity (Hc),

Brms is a magnetic flux density remaining in material before being magnetized to its saturation point, when magnetic field strength decreases to zero.

Hc is the magnetic field strength which the magnetic flux density of material has previously magnetized to the saturation point decreased to zero.

The unit of H is The unit of B is why?


6. Appendix A: Further on ferrite specificationsSo the vector dot integral across the B-H loop is the core loss.

(unit )

(unit ) lower core less depends on the lower Brms and/or Hc

☆ NiZn materials generally has lower Bsat/Brms ratio. This will mislead the test result and judge a good part to a failed one if no correct perception.

Low Loss Material EMI-Suppression Material Low Loss Material

Freq. Flux den. Temp. P41 K15 K081

Initial Permeability μi ≤ 10KHz 0.25mT 25°C 2400 ± 25% 1500 ± 25% 800 ± 25%

25°C 495 330 41025°C 170 200 27225°C 11 10 27

Symbol Unit Measuring Conditions

H=1200A/m

mT 10KHz

Saturation Flux Density Bms mT 10KHz

H=1200A/m

Coercivity Hc A/m 10KHz H=1200A/m

Remanence Brms



Ferromagnetic Material

Magnetic Field H

Flux density BPermanent magnetics

Soft magnetic material

Bsat

Brms1

Brms2

Brms3



LS(uH)DCR

AppliedVoltage

LS(uH) LS(uH)DCR

AppliedVoltage

LS(uH)

BeforeDCR （mV）

AfterDCR Before DCR （mV） After DCR

1 128 36.6 0.326 8.91E-03 129 3.80 127 41.6 4.25 1.02E-01 104 43.622 132 38.2 0.339 8.87E-03 134 3.79 131 42.1 4.45 1.06E-01 112 45.153 130 47 0.298 6.34E-03 132 2.70 129 38.3 3.85 1.01E-01 111 42.884 132 36.8 0.32 8.70E-03 133 3.71 129 40.5 4.22 1.04E-01 104 44.455 128 37.2 0.331 8.90E-03 129 3.80 129 41.8 4.3 1.03E-01 102 43.886 131 35.4 0.326 9.21E-03 133 3.93 133 40.8 4.19 1.03E-01 105 43.867 129 35.2 0.313 8.89E-03 130 3.79 128 40.5 4.15 1.03E-01 101 43.738 129 48.8 0.318 6.52E-03 130 2.78 129 39.5 4.13 1.05E-01 102 44.639 129 39.8 0.31 7.79E-03 130 3.32 129 39.5 4.1 1.04E-01 99 44.2510 129 33.4 0.298 8.92E-03 130 3.81 127 38.4 3.99 1.04E-01 102 44.38

ACME Inductance Check before/after DCR test 2014.9.24

Sample #

K081T14*8*9CTest Condition: 100kHz/0.1mAWinding: 0.5mm*14TsACME: WK3620 Precision Bridge

MDM016552000

DCR(mΩ) DCR Idc (A) H (A/m) DCR(mΩ) DCR Idc H (A/m)

Measured by local instrument

DCR GainKaiTa 502B

Using non-balanced bridge type instrument to measure DCR of NiZn parts could result in “magnetization of the core and thus reducing the inductance after DCR measurement.


6. Appendix A: Further on ferrite specifications2. Loss Factor Ferrite uses complex permeability to model the inductive and lossy part nature )

This representation is the keystone of CMC in EMC/EMI application. The phase shift caused by magnetic losses is and is termed “Loss Factor” is the “quality factor” [test condition is critical, and winding resistance is incorporated in real life]


6. Appendix A: Further on ferrite specifications2. Loss Factor

is the core’s total loss factor composing of hysteresis, eddy current and residual losses; it’s a function of frequency.


6. Appendix A: Further on ferrite specifications3. Hysteresis Material Constant (ηB) The parameter characterizes the hysteresis losses in ferrite. It does not depend on the air gap. It represents the nonlinearity of BH curves and is an index of the hysteresis.

(unit

Using this term, core’s hysteresis loss can be singled out from the lumped loss by

This factor is more core nature oriented.




Disaccommodation is understood as a time variation of the initial permeability occurring after each demagnetization under constant operating conditions. It has been proven by experiments that initial permeability decreases in a linear way by plotting time on a logarithmic scale.

(unit: dimensonless

This is a specification in power ferrite material.




The permeability of ferrite is a function of temperature.

(unit:

is independent of the air-gap. Temperature coefficient of a coil inductance, having ferrite core with an air-gap, may be calculated by multiplying of the ferrite material, with effective permeability of the core:

inductance thus impedance variation over time, but ui vs. Temp is a “two-peak” curve. chosen is critical, i.e., application specified.



5. Total Harmonic Distortion (THD) Harmonic distortion is generated when a sine wave magnetic field H, which is proportional to the current (), induces a non-sinusoidal flux density B ().

This is due to a non linear relation between B and H in the ferrite core of a transformer. is not a constant but a function of H, also.

in absolute value, normally expressed as %THD in power application




in dB for telecom application.

V3/V1dB -67 -66 -65 -64 -63 -62 -61 -60

Absolute 4.467E-04 5.012E-04 5.623E-04 6.310E-04 7.079E-04 7.943E-04 8.913E-04 1.000E-03

66 vs. 67 112.20%

65 vs. 67 125.89%

64 vs. 67 141.25%

63 vs. 67 158.49%

62 vs. 67 177.83%

61 vs. 67 199.53%

60 vs. 67 223.87%

THD




in dB for telecom application.

As in telecom application, the THD requirement is tough, the process and measurement must be taken great care of to avoid ineffective measurement.



5. Total Harmonic Distortion (THD)Example by PSPICE Simulation, by 10 turns (Example in Power) * TX22_14_13_3E27 CORE model (Ae=50.7mm^2, le=54.2mm).MODEL TX22_14_13_3E27 CORE+ MS=377.56E3 A=12.672 C=.20161 K=5.5151 AREA=.507+ PATH=5.4200

Excitation(100kHz)

Magnetic FieldStrength

FluxDensity(1st)

V1 THD (B) THD (B) THD (V) THD (V)

mA H (A/M) mT Volt % (Vn/V1) dB (Vn/V1) % (Vn/V1) dB (Vn/V1)

1 0.185 1.19 0.378 0.81% -41.81 2.52% -31.9610 1.845 15.01 4.764 6.00% -24.43 18.79% -14.5250 9.225 132.49 41.590 12.62% -17.98 38.79% -8.23

100 18.450 269.07 84.761 15.23% -16.35 47.15% -6.53200 36.900 398.77 125.052 19.48% -14.21 64.61% -3.79



5. Total Harmonic Distortion (THD)Example by PSPICE Simulation, by 10 turns * TX22_14_13_3E27 CORE model (Ae=50.7mm^2, le=54.2mm)

B-H curve can be simulated with ferrite core model incorporated




I=1mA

I=50mA

𝐵𝑐𝑜𝑟𝑒

𝑉 𝐿

𝐻𝑐𝑜𝑟𝑒



5. Total Harmonic Distortion (%THD)I=100mAB=270mT



6. Quality Factor (Q) Quality factor is related to loss factor but more a finished product specification.

This Q factor is a good index for CMC or signal filtering type applications, i.e., for “signal” level application. But for power choke, using the Q as the index of quality is really misleading and this mistake is seen commonly.



6. Quality Factor (Q) The concept “Q” (quality factor) actually comes from resonant circuits relating to the frequency of “half-power point”, it corresponds to the bandwidth (i.e., filtering quality) of a filter circuit.

Note that “resonant” circuit means L-C in series or parallel configuration and the “Q” is meaningful only when

So really as Tony said, this is a finished product specification (and under some proper definition), not a core definition.

With no C to match, Q is nothing and the application & interpretation must be careful.



LC fixed

smaller

larger

Illustration of serial resonant circuit




6. Quality Factor (Q) If this Q is to be employed as the core loss quality indicator, we already know the flux and flux density can be obtained by:

where is the highest possible flux density in the design

The inductance of a specific core

where is the zero gap single turn inductance (permeance)




For to be able to reflect the core’s (or the choke’s) quality in terms of losses. The “flux” level must meet the real application scenario to obtain the meaningful figure.

For example: A core with Ae=146.67mm^2, le=61.36mm with 22 turns of winding for power choke. The operational condition will require flux density well above 200mT. To have this , the applied voltage will be

Assuming the switching frequency is 100kHz



6. Quality Factor (Q) If the Q measuring requirement in the approval sheet is specified as 1Vrms/100kHz, the flux density will be

The Q number obtained with this flux level will never reflect the real quality scenario in the loss aspect of real application.

If this is DC-DC choke, the perturbation of V and I is small, theoretically, small Vrms is nothing wrong. But …….




Idc must be applied in doing the Q measurement, why? Q=

𝜔𝐿𝑅


7. Appendix B: (a) Fringing Effect of Gapped Core

Most of the time, the inductance calculation of gapped cores ignores the fact of “fringing effect” and the distribution of MMF and magnetic field strength H across the flux loop is

But for “big” gap, the effect can not be ignored, it means1. The effective area for the core, Ac, and air, Ag, will be different. 2. Bigger results in a smaller air flux density , thus a smaller ,

The result, the actual inductance is higher than the calculation result by assuming no fringing effect for the same gap.






The simplest way to model is to assuming the fringing area extended one gap length around the gap, thus

for rectangular cores

for circular path



McLyman treated the issue by adding an F factor for UU or EE core. where

Many studies and publications on modelling the effects of gap, but all proprietary thus cannot be applied in a universal way. Magnetic component design is still an interesting case-by-case task.



Even for a simple EE core, there are at least two distinctive , and the coherence between the inductance calculation (modeling) and real measurement becomes very interesting and challenging.

Ampere’s law and Faraday’s law of magnetic induction still work

=

But the bondage between and thus and is broken, that’s why so many modeling effort before FEM tool came into place.



For ur=3000 material of core EEL25E (Ae=32.62mm2 & le=81.48mm), assuming the B-H curve from standard ring core can be directly applied, then a 50um gap will have the magnetizing curve inflated as show below.

7. Appendix B: (b) Manipulating magnetizing curve


The “gap” not only decreases the inductance but also increases the power dissipations on the core.

𝑃𝑐=𝑉 𝑐𝑜𝑟𝑒 ∙ 𝑓𝑟𝑒𝑞 ∙ ∮𝑑 𝑦𝑛𝑎𝑚𝑖𝑐 𝑙𝑜𝑎𝑑

❑

�⃗� 𝑑 �⃗� 𝑃𝑐=𝑑 ( Λ⃗ ∙ �⃗�)𝑑𝑡

7. Appendix B: (b) Manipulating magnetizing curve


8. Appendix C: An analogy and differentiation on R, C, and L


8. Appendix C: An analogy and differentiation on R, C, and L Resistor (R) & Capacitor (C)1. Highly standardized in size, power rating, and tolerance per different

applications need.

2. Electrical/electronic engineers know how to use it “out-of-box” per vendor’s part number and specification sheet, due to its high degree of standardization.

3. R might be a function temperature or its many intrinsic material properties. But it is uniquely determined by the and at the instant. No time varying nature of the and involved.

4. C is defined to describe the electrical energy transfer in between the potential energy (voltage) and kinetic energy (current) forms. It is the coefficient for the time variant behavior but purely electrical in nature, beside the intrinsic material properties.


8. Appendix C: An analogy and differentiation on R, C, and L Inductor (L) & Transformer (X’mer)1. Inductor L is created to interpret the phenomenon of generated counter-

force (electro-magnetic force, EMF) from a time-varying current through a closed-loop circuit (by the Faraday Law of Electromagnetic Induction)

+i

Electron orbiting the nucleus of an atom produces a magnetic field..


8. Appendix C: An analogy and differentiation on R, C, and L Inductor (L) & Transformer (X’mer)

2. Ferrite is a magnetic material, but not magnetic component like L or X’mer.

ACME only produces ferrites that can be applied to make L or X’mer in applications.

3. The nature of L and X’mer involves magneto-electrical conversion (highly non-linear) based on the properties of the magnetic material; and can only be designed under case-by-case condition.

No “out –of-box” L or X’mer is available when designing them with ferrite cores.



Different from capacitors, the intrinsic natures of magnetic material are more “non-linear” or highly variant, thus more elaborated design-in effort to the customer side is needed. [Note: this “design-in effort” is not as intense as the case of L in R & C, as it is taken care of by the neat component properties and during the component making.]









In application, engineer picks up not only AL but the following factors together to make his inductor or transformer works

1. Permeability (μi , μa , μΔ in filtering, AC, and DC power transfer applications) even AL depends on this property

2. Bmax (or Bsat, saturation flux density) How big the core to use3. Pv vs. Temperature (core loss in mW/cm3) efficiency of the component4. Tc (Curie Temperature) applicable temperature Property 1 ~ 3 are strongly material and operational conditions dependent and careful selection & design per given specifications is absolutely needed.

5. Core Geometry: Shape/Size are another critical factor in magnetic component design and the degree of freedom is almost unlimited (unless by process and material limit) to meet the specific application needs



Unlike inductor which is a single winding device, any core wound with two (or above) windings can be called a transformer. Still the “magnetizing inductance” is the essence underlining the “transformer” operation.

Equivalent circuit model of a two-winding transformer, the red rectangle part is the magnetizing inductance



Ideal transformer

𝑖𝑠𝑢𝑚=𝑖𝑚+𝑖1

𝑣1=𝐿𝑚𝑑𝑖𝑚𝑑𝑡

Lm is the key that a transformer works



All the components on the figure can have “out of box” parts, except the ones in the red rectangular boxes * Digested from TI SLUS180E UC3524 Application Note


8. Appendix C: An analogy and differentiation on R, C, and L Illustrated with a qualitative design interpretation Cutting out all the supporting and controlling circuits, the main body of a buck converter is like (called power stage)

The controller IC vendor (like TI) has some cookbook recipes and tools for determination of all the “electrical” specifications.





The voltage and current waveforms across the inductor

Volt-second balance principle:The above two shades must be equal in area,

the area V*time actually is the magnetic flux linkage.This value determines whether the magnetic material should be silicon steel, amorphous, SiFe compound or ferrite.



System design engineer by his/her knowledge usually knows how to choose L correctly.

But the majority of them have no idea on how to make the L work for the design. This is assigned to another group of people with adequate knowledge in magnetic component making.

From the information of the blue rectangle, an inductor with inductance 500uH can be made.

How L is determined? By the tolerable current ripple:


8. Appendix C: An analogy and differentiation on R, C, and L How L is determined? By the tolerable current ripple:

From the information of the blue rectangle, an inductor with inductance 500uH can be made per the following steps.1) First select the valid material suitable (frequency range,

mr 、 Hc 、 Br 、 Bsat 、 temperature coefficient of mr)

2) Determine the CORE’s mechanical dimensions and gap sizeThe degree of freedom is high

3) Applying the windings N to have the desired inductance. This procedure can be summarized as:



1) Material selection stage Figure (a), the slope is permeability mr

2) Geometry determining state Figure (b), the slope is permeance or just AL

3) Inductance realization stage Figure (c), the slope is inductance L (a) (b) (c)

ACME produces (a) and makes it into (b), the customer (or his winding house) makes (c)


7. Open Discussions


ACME Electronics Corporation Aggressively Committed to Manufacturing Excellence

Thank You~

Ferrite Specifications and ACME Ferrites (4)

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