EE564-Design of Electrical Machines

class: center, middle

# EE-564 Design of Electrical Machines

## Ozan Keysan

[ozan.keysan.me](http://ozan.keysan.me)

Office: C-113 <span class="meta">•</span> Tel: 210 7586

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# Materials Used in Electric Machines
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- ## Conductors (Copper, Aluminium)
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- ## Ferromagnets (Iron, Electrical Steel, Ferrites)
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- ## Permanent Magnets (NdFeB, Samarium-Cobalt)

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# Conductors

## Copper is usually the best choice, but aluminium can be preferred to reduce cost.

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- ## **Copper:** \$1.68 \; 10^{-8} \; \Omega.m \$

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- ## **Aluminium:** \$2.82\; 10^{-8} \; \Omega.m \$
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- ## **Silver:** \$1.59 \; 10^{-8} \; \Omega.m \$

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- ## **Gold:** \$2.44 \; 10^{-8} \; \Omega.m \$

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# Copper vs. Aluminium
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![](https://raw.githubusercontent.com/ozank/ozank.github.io/master/presentations/aluminium_price.png)
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# Copper vs. Aluminium

![](https://raw.githubusercontent.com/ozank/ozank.github.io/master/presentations/copper_price.png)

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# AC Resistance vs DC Resistance
## Which one is higher?

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- ## AC Resistance > DC Resistance

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# Skin Depth
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# Distribution of Current in a Wire
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![](http://upload.wikimedia.org/wikipedia/commons/thumb/6/61/Skin_depth.svg/520px-Skin_depth.svg.png)
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# Skin Depth

### Due to circulating eddy currents
![](http://upload.wikimedia.org/wikipedia/commons/thumb/c/c7/Skineffect_reason.svg/293px-Skineffect_reason.svg.png)

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# Skin Depth

# Current Distribution: \$ J = J_0 e ^{-d/\delta_s}\$
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# Skin depth: \$\delta_s = \sqrt{\frac{1}{\pi f \mu \sigma}}\$

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# Skin Depth for Copper:
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- ## 50 Hz --> 9.3 mm

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- ## 1 kHz --> 2.1 mm

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- ## 10 kHz --> 0.66 mm

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- ## 100 kHz --> 0.21 mm

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- ## 1 MHz --> 66 um

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# How to increase conductor area without increasing thickness?

## Bundled Conductors
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![](http://i.stack.imgur.com/ZiMjy.png)
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# How to increase conductor area without increasing thickness?

## Foil Conductors
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![](http://i00.i.aliimg.com/wsphoto/v0/899573808_1/10m-Adhesive-Copper-Foil-EMI-Shield-font-b-Tape-b-font-font-b-Conductive-b-font.jpg)

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## Hollow Conductors
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<img src="http://sub.allaboutcircuits.com/images/52013.jpg" alt="Drawing" style="width: 400px;"/>
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# AC Resistance

## AC Resistance [Calculator](http://www.clemson.edu/ces/cvel/emc/calculators/Resistance_Calculator/round.html)

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## Rule of Thumb: For 50 Hz power systems
## $$Rac \simeq 1.1 Rdc$$
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# Temperature Effect

<img src="http://www.wilko.com/content/ebiz/wilkinsonplus/invt/0316169/0316169_l.jpg" alt="Drawing" style="width: 500px;"/>
### How does the resistance change with time?

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# Temperature Effect

## Temperature Coefficient
## $$R(T) = R(T_0)(1 + \alpha\Delta T)$$
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### For copper (at 20 C)

### $$\alpha = 0.003862\;K^{-1}$$

[Ref1](http://hyperphysics.phy-astr.gsu.edu/hbase/tables/rstiv.html), [Ref2](http://en.wikipedia.org/wiki/Electrical_resistivity_and_conductivity)

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## Resistivity of copper increases 30% from 20C to 100C.
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# Conductor Standard Sizes
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## - American Wire Gauge (AWG)
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## - National Electrical Manufacturers Association (NEMA)
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## - International Electrotechnical Commission (IEC)
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# Conductor Standard Sizes

## A few References

- ### [AWG](http://en.wikipedia.org/wiki/American_wire_gauge)
- ### [AWG Sizes](http://www.engineersedge.com/copper_wire.htm)
- ### [Magnet Wire Types](http://mwswire.com/magnet-wire/)
- ### [MWS Wire Technical Data Book](http://mwswire.com/document-resource-center/)
- ### [Bemka (tr) Wire Sizes](http://www.bemkawire.com.tr/en/home/content/251)
- ### [NEMA Wire Catalogue](http://www.mwswire.com/pdf_files/mws_tech_book/TechBook040114.pdf)
- ### [Current Ratings](http://www.batt.co.uk/upload/files/table4d1abs6004bs6231bs6346_1220253954.pdf)

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# Ferromagnets

## Electrical Steel Laminations

- ## Used for Low Frequency (50-500 Hz)
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- ## Easy to [manufacture](https://www.youtube.com/watch?v=qmg_W_pcYhY) & [Cheap](https://www.alibaba.com/product-detail/electrical-silicon-steel-laminates_1891355946.html)
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## Electrical Steel Lamination Types
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## - Silicon Steel (Electrical Steel)
![](http://newimg.globalmarket.com/PicLib/81/2514081/prod/48_1353116886810_l.jpg)
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- ### Added silicon increases the resistance  (reduces eddy losses)

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## Electrical Steel Lamination Types

### - Cold Rolled Lamination Steel

<img src="http://retrorenovation.com/wp-content/uploads/2012/02/stainless-steel-countertop.jpg" alt="Drawing" style="width: 400px;"/>
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- ### Lowest Cost
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- ### Higher Core Losses

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## Electrical Steel Lamination Types

### - Nickel Alloys

<img src="http://i01.i.aliimg.com/photo/v2/1084596293/Nickel_Iron_alloy_1J79.jpg" alt="Drawing" style="width: 400px;"/>
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- ### Higher cost than silicon steel
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- ### High permeability, low core losses
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## Electrical Steel Lamination Types

## - Cobalt Alloys

<img src="http://www.aperam.com/alloysandspecialities/typo3temp/pics/5f302d128f.jpg" alt="Drawing" style="width: 300px;"/>
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- ### Highest cost
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- ### High saturation (up to 2.2 T)
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- ### Suitable for mass critic applications (aerospace, military)

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# Ferromagnets

## Motor Core Lamination Manufacturing

- [Lamination Stamping-1](https://www.youtube.com/watch?v=RgWh2G-2XuU)
- [Lamination Stamping-2](https://www.youtube.com/watch?v=dZ9FySos1t0)
- [Lamination Stamping-3](https://www.youtube.com/watch?v=7kKjxHOdC1A)
- [Lamination Stamping-4](https://www.youtube.com/watch?v=y0feSEkR3K4)
- [Continuous Stamping](https://www.youtube.com/watch?v=dcjlH8eq0hM)

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# Ferromagnets

## Reading List-Catalogue
- [Proto Laminations](http://www.protolam.com/page3.html)
- [JFE Steel](http://www.jfe-steel.co.jp/en/products/electrical/catalog/f1e-001.pdf)
- [Cogent Catalogue](http://perso.uclouvain.be/ernest.matagne/ELEC2311/T2006/NOFP.pdf) (page 5-6)
- [Grain Oriented Steel Catalogue](https://www.atimetals.com/Documents/goes_technical_data2_v1.pdf)
- [Enpay Transformer Core](http://www.travek.elektrozavod.ru/sites/default/files/images/production/enpay/Amorphous%20Core%20Catalogue.pdf)
- [Sura Catalogue](http://www.sura.se/Sura/hp_main.nsf/startupFrameset?ReadForm)
- [Cogent Elecrical Steel](https://cogent-power.com/products/non-oriented-electrical-steel/technical-specifications)
- [VacuumSchemlze](http://www.vacuumschmelze.com/en/products/materials-parts/soft-magnetic.html)
- [Motor Laminations](http://laminationspecialties.com/products.htm)

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# Core Loss in  Laminations

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## Hysteresis Loss + Eddy Current Loss

[Real Data-sheet of electrical steel](http://cogent-power.com/products/non-oriented-electrical-steel/magnetic-qualities)

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# Other Magnetic Materials:
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(Soft) Ferrite

<img src="http://www.tomita-electric.com/mt/mt-static/themes/tomita/css/images/en/catimg-ferrite.jpg" alt="Drawing" style="width: 700px;"/>
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- ### Sintered Iron Oxide + Manganese/Zinc
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- ### Low Saturation Point (0.4-0.5 T)
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- ### Brittle
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- ### High Permeability (\$\mu_r\$: 1500-3000)

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# (Soft) Ferrite Cores

## Used as [Chokes](https://www.youtube.com/watch?v=LuMlM8zWQFk) and Filters
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#Quick Question
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## Is it easier to store energy with high or low permeable material?
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## \$W = \dfrac{1}{2}\dfrac{Volume}{\mu} B^2 \$

## Sometimes, air-gaps are added deliberately to increase energy storing capacity of a core.

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## E-core without gap
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## E-core with gap
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##Gapped Toroids

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# A Better Solution?
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## Distributed Gap Cores

### Powder Core

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# Distributed Gap Cores
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- ## Low Permeability (\$\mu_r\$: 20-200)
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- ## Has different types:
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- ## KOOL Mu Powder
- ## MPP
- ## Iron Powder

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## KOOL Mu Powder Core

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## KOOL Mu Powder Core

### Lower Core Loss wrt Steel

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# Distributed Gap Cores

<img src="https://www.mag-inc.com/getattachment/Products/Powder-Cores/Learn-More-about-Powder-Cores/PowderCoreOverviewMatrix.png" alt="Drawing" style="width: 400px;"/>
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# Distributed Gap vs. Gapped Ferrite
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### [Comparison](https://www.mag-inc.com/Products/Powder-Cores/Learn-More-about-Powder-Cores/Gapped-Ferrite-Comparison)
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## Distributed Gap vs. Gapped Ferrite
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- ## Fringing flux increases copper losses in gapped cores
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- ## Ferrite has sharp saturation, whereas powder cores has [soft saturation](https://www.mag-inc.com/getattachment/Products/Powder-Cores/Kool-Mu-Cores/Large-Kool-Mu-Core-Shapes/Kool-Mu-and-Gapped-Ferrite-Comparison/KoolMuvsFerriteDCBIAS.png)
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- ## Powder cores are usually smaller
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- ## Powder cores magnetic properties does not change much with temperature
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- ## But powder cores have higher inductance tolerances.

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# Design Exercise
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- ## Let's choose a [powder core toroid](https://www.mag-inc.com/Products/Powder-Cores/Kool-Mu-Cores)

- ## [Toroid Core Example](https://www.mag-inc.com/Media/Magnetics/Datasheets/0077354A7.pdf)

### Useful Links

- ### [Design Guides](https://www.mag-inc.com/Design/Design-Guides)

- ### [Powder Core Loss Calculation](https://www.mag-inc.com/Design/Design-Guides/Powder-Core-Loss-Calculation)

- ### [Powder Core Calculations](https://www.mag-inc.com/Design/Design-Guides/Powder-Core-Calculations)

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## Amorphous and Nanocrystalline Laminations

- ## Very High Perbeability (\$\mu_r\$: up to 10.000)
- ## High Efficiency transformers (for medium frequency)
- ## Expensive

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# Comparison of Materials

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# Comparison of Materials

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# More Reading Materials

- ### [Soft Magnetic Core Application Notes](http://www.allegromicro.com/~/media/Files/Technical-Documents/Arnold/Soft-Magnetics-Applications-Guide.ashx?la=en)

- ### [TI Magnetic Core Characteristics](http://www.ti.com/lit/ml/slup124/slup124.pdf)

- ### [Practical and Potential Applications of Soft Magnetic Powder Cores](http://global-sei.com/technology/tr/bn82/pdf/82-02.pdf)

- ### [Choice of the Magnetic Core](http://www.sirio-ic.com/index.php/en/i-magneticore-en.html)

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# Permanent Magnets
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##Applications
<img src="http://www.cndailymag.com/images/about/application.jpg" alt="Drawing" style="width: 500px;"/>

### [Why magnets attract each other?](http://www.youtube.com/watch?v=uTcuDprmues) by Richard Feynman
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# History
<img src="http://www.magnetnrg.com/uploads/2/0/0/5/20054943/2633149.jpg" alt="Drawing" style="width: 800px;"/>
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# Neodymium Magnets (NdFeB)

### Strongest
### Expensive (250 TL/kg, £70/kg)

[Levitating a man](http://www.youtube.com/watch?v=q9m-hHg0gFk), [Magnet smashing](http://www.youtube.com/watch?v=Vt8NOdINJ1s), [Crushing hand](http://www.youtube.com/watch?v=0t8yDnyOaQ8)

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# Magnetization Directions
![](http://www.macmillmagnet.com/imges/Glossary_clip_image001.gif)
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#B-H Curve of a Magnet

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## Desired Properties:
### Large retentivity (Remanence flux density)

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### Large coercivity (point that crosses H axis)
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![](http://www.electronics-tutorials.ws/electromagnetism/mag20.gif)

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# Magnet Strength Comparison
<img src="http://www.kjmagnetics.com/images/blog/demag.curves2d.gif" alt="Drawing" style="width: 600px;"/>
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# Magnet Grades
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- ## Specifies the magnet's max. energy (in MGOe)
--

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# Magnet Grades

- ## Specifies the max. operating temperature
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- #### N: 80 C
- #### M: 100 C
- #### H: 120 C
- #### SH: 150 C
- #### UH: 180 C
- #### EH: 200 C

- ## [Example Catalogue](https://www.first4magnets.com/tech-centre-i61/information-and-articles-i70/neodymium-magnet-information-i82/grades-of-neodymium-magnets-i92)

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## Intrinsic vs Normal B-H Charateristics

### We can only measure normal curve

[More info about magnets](http://what-when-how.com/electric-motors/hard-magnetic-materials-permanent-magnets-electric-motors/), [Magnet Guide](http://www.allianceorg.com/pdfs/Magnet_Tutorial_v85_1.pdf), [Demagnetization](http://www.shinetsu-rare-earth-magnet.jp/e/design/)
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# Demagnetization of PMs

### If external magnetic fields get below the knee point, PM will lose strength
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# Demagnetization of PMs

## Recoil Line

### Magnets will loose strength if the reverse magnetic field goes beyon knee point.

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# Magnetic Circuits with Magnets, Load Line
## Example

[More info on load lines](https://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-061-introduction-to-electric-power-systems-spring-2011/readings/MIT6_061S11_ch11.pdf), 
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# Magnets with Temperature
### Real Datasheet of Sm-Co (Samarium-Cobalt Magnet)
<img src="http://www.x-magnet.net/hard-magnet/images/Sm2Co17-YX-30A-Demagnetization-Hysteresgraph.gif" alt="Drawing" style="width: 600px;"/>

### Magnets become less stable with increasing temperature.
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# Magnets with Temperature

### NdFeB magnets lose around 0.1% Br for every degree C above 20 C, which is called reversible temperature coefficient.

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# What is Magnetic Force?

### [Why magnets attract each other?](http://www.youtube.com/watch?v=uTcuDprmues) by Richard Feynman

### [Magnets and Special Relativity](https://www.youtube.com/watch?v=1TKSfAkWWN0)

Reading Suggestion: [Eminim Şaka Yapıyorsunuz Bay Feynman](http://www.idefix.com/Kitap/Eminim-Saka-Yapiyorsunuz-Bay-Feynman-Merakli-Bir-Sahsiyetin-Maceralari/Richard-P-Feynman/Bilim/Populer-Bilim/urunno=0000000427673)

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## You can download this presentation from: [keysan.me/ee564](http://keysan.me/ee564)