Roketsan Training

class: center, middle

# Roketsan Training - Session II

# Permanent Magnets and Types of PM Machines

## Ozan Keysan

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

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

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# Permanent Magnets

## Why do we use PMs?

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#Applications
<img src="https://www.researchgate.net/publication/383260096/figure/fig1/AS:11431281278417367@1726635109758/The-application-of-permanent-magnets-in-different-sectors-mentioned-in-consumption.jpg" alt="Drawing" style="width: 800px;"/>

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# History
<img src="http://www.magnetnrg.com/uploads/2/0/0/5/20054943/2633149.jpg" alt="Drawing" style="width: 750px;"/>
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# Magnetization Directions

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#B-H Curve of a Magnet

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### Desired Properties:
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### Large Remanence flux density (retentivity, point that crosses B axis)
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### Large [coercivity](http://hyperphysics.phy-astr.gsu.edu/hbase/solids/imgsol/coercivity.gif) (point that crosses H axis)
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![](https://www.electronics-tutorials.ws/wp-content/uploads/2013/08/mag20.gif)

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# Magnet Strength Comparison
<img src="./images/demag_curves2d.gif" alt="Drawing" style="width: 700px;"/>

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# Neodymium Magnets (NdFeB)

### Strongest and the most common (60% market share)
### Expensive ( $100/kg)
### Prone to corrosion (needs surface treating)

[Levitating a man](http://www.youtube.com/watch?v=q9m-hHg0gFk), [Magnet smashing](https://youtu.be/Vt8NOdINJ1s?t=41s), [Crushing hand](http://www.youtube.com/watch?v=0t8yDnyOaQ8)

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# Samarium Cobalt Magnets (SmCo)

### Around 2/3 strength of NdFeB magnets
### Can withstand higher temperatures
### More resistant to corrosion

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# Ferrite (Ceramic) Magnets

### Lowest cost
### Magnet strength is quite low (Br: 0.2 - 0.4 T)
### No corrosion problem but brittle

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# AlNiCo Magnets

### Can be manufactured by cast or sintering
### Best choice for high temperature applications (up to 500 C)
### Easier to demagnetize by external magnetic fields

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# Iron Chrome Cobalt (FeCrCo) Magnets

### Malleable and easy to machine
### Does not require corrosion coating
### Strong flux density (>0.8 T) but low coercivity (easy to demagnetize)
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## Intrinsic vs Normal B-H Characteristics

### 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 beyond the knee point.

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# Magnets with Temperature
### Real Datasheet of Sm-Co (Samarium-Cobalt Magnet)

### Magnets become less stable with increasing temperature.
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# What is Magnetic Force?

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

<img src="https://cdn-images-1.medium.com/max/2000/1*4MnjkvCDAAJt7d0KrvFBOw.png" alt="Drawing" style="width: 600px;"/>
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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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# Magnetic Circuits with Magnets, Load Line

[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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# Magnetic Circuits with Magnets, Load Line

## Be aware of the temperature variation

# The magnet can lose some of its strength

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# Magnet Grades

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# Magnet Grades

## Last letter defines the working temperature

- ## No Letter:  < 80 C
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- ## M: Medium, <100 C
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- ## H: High, <120 C
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- ## SH: Super High, <150 C

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# Magnet Coatings

### Beware NdFeB magnets are prone to corrosion and need to be coated
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# Modelling of Magnets

## Operation range of a magnet

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# Modelling of Magnets

## Equivalent Circuit (Flux Source)

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# Modelling of Magnets

## Thevenin Equivalent Circuit (MMF Source)

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# Modelling of Magnets

## If the magnet is operating in linear region

### \$B_m = B_r + \mu_R \mu_0 H_m \$

### \$H_m\$ is negative (third quadrant in BH graph)
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### \$\Phi = B_m A_m \$
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\$\ = B_r A_m + \mu_R \mu_0 A_m H_m  \$
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### \$\Phi = B_m A_m \$
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\$\ = \Phi_r + \dfrac{F_m}{R_m} \$

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# Modelling of Magnets

### \$\Phi =  \Phi_r + \dfrac{F_m}{R_m} \$
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### A constant flux source with a reluctance in parallel (i.e Norton circuit)

### \$R_m = \dfrac{l_m}{ \mu_0 \mu_r A_m} \$

### \$P_m = \dfrac{1}{R_m} \$: Permeance 
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## Thevenin Equivalent Circuit (MMF Source)

### Magnet can be considered as a coil (MMF source) with:

### \$NI =\$
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\$\Phi_r R_m =\$
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\$B_r A_m \dfrac{l_m}{\mu_o \mu_r A_m} \$
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\$=  \dfrac{B_r l_m}{\mu_o \mu_r} \$

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# Group Exercise-#1
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### Calculate the airgap flux density for:

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# Group Exercise-#2
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### Calculate the airgap flux density for:

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# General PM Machine Structure
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### Surface Mount Permanent Magnet Machine

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# Magnetic Circuit Model

### SMPM magnetic circuit

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# Magnetic Circuit Model

## Ideal Airgap Flux Distribution

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### Let's see the induced voltage waveform for a full-pitch coil
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### Flux and Induced Voltage in the Coil
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# PMSM vs BLDC 
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## PMSM: Permanent Magnet Synchronous Motor

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# PMSM vs BLDC 
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## BLDC: Brushless DC Motor

### Usually preferred in low cost, high speed, small motors

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# PMSM 
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## Sinusoidal Back-EMF

### Sinusoidal back-emf, vector control, precise motion control

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# BLDC 
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## Trapezoidal Back-EMF

### Driven by square wave pulses, small power/low cost applications

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# D-Q Axes Revisited
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## SM-PMSM
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 (Surface Mount Permanent Magnet Synchronous Machine)

<img src="./images/ee564/smpm_Ld_Lq.png" alt="Drawing" style="width: 600px;"/>
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## Ld = Lq for SMPM machines

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# D-Q Axes Revisited
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## IPM
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 (Interior Permanent Magnet Synchronous Machine)

## Lq > Ld for IPM machines (as \$\mu_r \approx 1 \$ for PMs)

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## IPM: (Interior Permanent Magnet)

<img src="https://mpcomagnetics.com/wp-content/uploads/2023/09/IPM-vs-SPM-Electric-Motors-768x538.jpg" alt="Drawing" style="width: 800px;"/>
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## Several Other Topologies

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