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<<!DOCTYPE html>
<html>
<head>
<title>EE568-Selected Topics in Electrical Machines</title>
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class: center, middle
# EE-568 Selected Topics in Electrical Machines
## Losses & Thermal Design
## Ozan Keysan
[keysan.me](http://keysan.me)
Office: C-113 <span class="meta">•</span> Tel: 210 7586
---
# Losses in an Electrical Machine
--
<img src="./images/ee564/motor_losses.png" alt="Drawing" style="width: 800px;"/>
---
# Losses in an Electrical Machine
--
- ## Stator Ohmic Losses
--
- ## Rotor Ohmic Losses (or field excitation)
--
- ## Core losses (hysteresis & eddy)
--
- ## Additional eddy losses (rotor surface, magnets, sleeves etc.)
--
- ## Mechanical losses (bearing, windage etc.)
--
- ## Stray Losses (leakage flux induced losses)
---
## Factors effecting core losses
--
## Material Quality and Thickness
<img src="https://www.researchgate.net/profile/Andreas-Krings/publication/266558530/figure/fig2/AS:669259046871043@1536575199292/Crystallographic-structure-on-the-short-035-mm-side-of-the-lamination-sheets-before-the.png" alt="Drawing" style="width: 600px;"/>
---
## Factors effecting core losses
## Lamination cutting techniques
- ### Stamping, Laser Cutting etc.
<img src="http://www.polarislaserlaminations.com/images/laser-slide.gif" alt="Drawing" style="width: 300px;"/>
- [High Speed Laser Cutting](https://www.youtube.com/watch?v=7-M6pgUO5XE)
- [Lamination Stamping](https://www.youtube.com/watch?v=s-9PhX6vKpI)
---
## Factors effecting core losses
## Fixing Stacking Together
- ### Riveting
- ### Welding
<img src="https://deesan.in/wp-content/uploads/2021/09/rivetting-img.webp" alt="Drawing" style="width: 350px;"/>
<img src="https://www.lasertechnologiesinc.com/upload/MotorCoreAssembly_4.jpg" alt="Drawing" style="width: 350px;"/>
---
## Losses: End Plate Losses
<img src="./images/ee564/endplate1.png" alt="Drawing" style="width: 700px;"/>
---
## Losses: Press Plate Losses
## Stepped laminations at the press plate , but why?
<img src="./images/ee564/endplate2.png" alt="Drawing" style="width: 600px;"/>
---
## Losses: Press Plate Losses
### Axial component of the fringing flux creates eddy current on large surfaces
<img src="./images/ee564/endplate_flux.png" alt="Drawing" style="width: 600px;"/>
---
## Losses: Press Plate Losses
### Methods to reduce press plate losses:
- ### Partitioning of end plates
- ### Slitting of press fingers
- ### Non-magnetic press plates (Aluminium, stainless steel)
- ### Stepping of end packet
- ### Laminated glued press plates
- ### Copper shielding
---
## Rotor Pole Shoe Losses
- ### Especially dominant in open-slots
<img src="./images/ee564/openslot_flux.png" alt="Drawing" style="width:300px;"/>
- ### Magnitude may be small, but the frequency is in the kHz range!
- ### \\(f= f_s \times Q \\)
---
## Rotor Pole Shoe Losses
### Methods for reduction:
- ### Use [magnetic slot wedges](https://www.spindustries.at/product/magnetic-slot-wedges/)
- ### Laminated pole shoes, sectioned poles (or magnets in a PM machine)
<img src="./images/ee564/laminated_rotor.png" alt="Drawing" style="width:350px;"/>
---
## Stray Field Losses
<img src="./images/ee564/stray_field.png" alt="Drawing" style="width:550px;"/>
---
# Resistances
--
## DC Resistance
### \\(R\_{dc}= \dfrac{l}{\sigma A}\\)
---
# AC Resistance
### Resistance factor: \\(k\_{Ru}=\dfrac{R\_{ac}}{R\_{dc}}\\)
<img src="https://raw.githubusercontent.com/ozank/ozank.github.io/master/presentations/images/coil.png" alt="Drawing" style="width: 300px;"/>
---
# Skin Effect
--
### AC current tends to flow close to surface (valid for a conductor surrounded by air).
--
<img src="https://upload.wikimedia.org/wikipedia/commons/6/61/Skin_depth.svg" alt="Drawing" style="width: 360px;"/>
### [Skin Effect](https://en.wikipedia.org/wiki/Skin_effect), [AC Resistance](https://www.youtube.com/watch?v=Cf80ZybFgoE)
---
# Skin Effect
### Current Density distribution in [solid copper in a slot](http://www.anttilehikoinen.fi/technology/electrical-engineering/what-are-circulating-eddy-currents/)
--
<img src="http://www.anttilehikoinen.fi/wp-content/uploads/2017/03/2017-3-2_skin_effect_slot-139x300.png" alt="Drawing" style="width: 200px;"/>
---
# Leakage Flux in Slot
<img src="./images/ee564/eddy_slot1.png" alt="Drawing" style="width:600px;"/>
### Leakage flux density increases in the direction of slot opening
### That leakage flux is pulsating with fundamental frequency, and creates eddy currents (into the page)
---
# Eddy Current in a Slot
<img src="./images/ee564/eddy_slot2.png" alt="Drawing" style="width:500px;"/>
### Direction of the eddy current creates a field opposite to the original field (Lenz Law)
### Eddy current increases the current density at the top of the conductor, causes non homogeneous current distribution
---
# Eddy Current in a Slot
<img src="./images/ee564/eddy_slot3.png" alt="Drawing" style="width:600px;"/>
### Current also reduces the leakage flux on the top of the winding, and hence reduces the leakage flux component
### Therefore, \\(R\_{ac} \gt R\_{dc}\\) but
### \\(L\_{leakage-ac} \lt L\_{leakage-dc}\\)
---
# Proximity Effect
--
### Close conductors effect each other's current distribution
--
### Conductors with the same current direction
<img src="./images/ee564/proximity1.jpg" alt="Drawing" style="width: 600px;"/>
### [Proximity Effect](https://circuitglobe.com/proximity-effect.html), [Skin and Proximity Effect](http://www.anttilehikoinen.fi/technology/electrical-engineering/what-are-circulating-eddy-currents/)
---
# Proximity Effect
### Close conductors effect each other's current distribution
### Conductors with the opposite current direction
<img src="./images/ee564/proximity2.jpg" alt="Drawing" style="width: 600px;"/>
### [Proximity Effect](https://circuitglobe.com/proximity-effect.html), [Skin and Proximity Effect](http://www.anttilehikoinen.fi/technology/electrical-engineering/what-are-circulating-eddy-currents/)
---
# Proximity Effect
### Distribution in a slot (same winding)
<img src="./images/ee564/proximity_slot.png" alt="Drawing" style="width: 600px;"/>
---
# Proximity Effect
### Distribution in a slot (same winding)
### Current Density distribution in [a copper winding in a slot](http://www.anttilehikoinen.fi/technology/electrical-engineering/what-are-circulating-eddy-currents/)
--
<img src="http://www.anttilehikoinen.fi/wp-content/uploads/2017/03/2017-3-2_proximity_effect-1-138x300.png" alt="Drawing" style="width: 200px;"/>
---
# Proximity Effect
### Distribution in a transformer winding
<img src="./images/ee564/proximity_transformer.png" alt="Drawing" style="width: 600px;"/>
---
# Ways to Reduce AC Resistances
--
- ### Divide conductors into subconductors
--
- ### Instead of dividing large conductors and transposing them, use parallel paths
--
- ### Use multi-thread twisted conductors (litz wire, roebel cable)
---
# Circulating Currents
### Different leakage inductance, length, phase difference in induced voltage causes circulating current
<img src="http://www.anttilehikoinen.fi/wp-content/uploads/2017/03/2017-3-2_circulating_current.png" alt="Drawing" style="width: 800px;"/>
---
# Ways to Reduce AC Resistances
### Just using parallel wires DO NOT cancel the circulating currents
<img src="./images/ee564/paralel_wire.png" alt="Drawing" style="width: 800px;"/>
### Twisting is also required!
---
## Twisting (or Transponding)
<img src="./images/ee564/transponding.png" alt="Drawing" style="width: 800px;"/>
### In a single layer winding all the flux can be cancelled,
### but in double layer winding, the flux on the top and bottom portion are different, so that reduces but does not eliminate all current
---
## Twisting (or Transponding)
### Overhang connections can be used for twisting
<img src="./images/ee564/transponding2.png" alt="Drawing" style="width: 800px;"/>
---
# Roebel Winding
<img src="./images/ee564/roebel.png" alt="Drawing" style="width: 800px;"/>
### [Roebel Winding Manufacturing](https://www.youtube.com/watch?v=TaM3EuTMxBs)
---
# Roebel Winding
<img src="./images/ee564/roebel_180.png" alt="Drawing" style="width: 800px;"/>
### With 180 degrees transposition
---
# Roebel Winding
<img src="./images/ee564/roebel_360.png" alt="Drawing" style="width: 800px;"/>
### With 360 degrees transposition
---
# Roebel Winding
<img src="./images/ee564/roebel_end_winding.png" alt="Drawing" style="width: 800px;"/>
### End winding connection options
---
# Roebel Cable
### For very high frequencies, superconductors
<img src="http://cds.cern.ch/record/1744900/files/_B1A8948.jpg?subformat=icon-1440&version=1" alt="Drawing" style="width: 800px;"/>
[More info](http://www.itep.kit.edu/hts4fusion2011/downloads/1C3.pdf), [Transpositiion of conductors](http://www.electrotechnik.net/2011/10/transposition-of-conductors.html), [Transposition](http://en.wikipedia.org/wiki/Transposition_%28telecommunications%29), [Continuously Transposed Conductors](http://www.samdongamerica.com/products/ctc-continuously-transposed-conductor)
---
# Ways to Reduce AC Resistances
# Litz Wire
<img src="http://www.coonerwire.com/wp-content/gallery/litz-wire/litz-wire_003.jpg" alt="Drawing" style="width: 500px;"/>
[Types](http://www.newenglandwire.com/products/litz-wire-and-formed-cables/types-and-constructions), [Litz Wire Applications](http://www.litz-wire.com/applications.php), [Litz Wire theory](http://www.newenglandwire.com/products/litz-wire-and-formed-cables/theory)
---
# Ways to Reduce AC Resistances
# Litz Wire
<img src="http://www.eis-asia.com/litz%20wire/Image3.jpg" alt="Drawing" style="width: 750px;"/>
[Types](http://www.newenglandwire.com/products/litz-wire-and-formed-cables/types-and-constructions), [Litz Wire Applications](http://www.litz-wire.com/applications.php), [Litz Wire theory](http://www.newenglandwire.com/products/litz-wire-and-formed-cables/theory)
---
# Insulation
--
## Average dielectric strength: 1 kV/mil (~ 40 kV/mm)
#### (*)1000 mil = 1 inch
--
## Stator should be insulated for:
- ### In-turn shorts
- ### Phase-Ground shorts
- ### Phase-Phase shorts
---
# Insulation
<img src="https://raw.githubusercontent.com/ozank/ozank.github.io/master/presentations/images/insulation.png" alt="Drawing" style="width: 700px;"/>
---
# Insulation
<img src="https://raw.githubusercontent.com/ozank/ozank.github.io/master/presentations/images/slot_insulation.png" alt="Drawing" style="width:600px;"/>
---
# Slot Insulation Types
<img src="https://raw.githubusercontent.com/ozank/ozank.github.io/master/presentations/images/slot_insulation_types.png" alt="Drawing" style="width:750px;"/>
---
# Insulation Temperature Class
- ## Class A: 105 C
--
- ## Class B: 130 C
--
- ## Class F: 155 C
--
- ## Class H: 180 C
### Insulation life time halves for each 10 C rise in operating
---
# Insulation
- ## PWM inverters cause voltage spikes or standing voltage waves
- ## PWM inverters can cause corona insulation faults
- ## Under 250 VAC, phase-to-phase insulation is not required
- ## For higher voltages end turns should be insulated
---
# Slot Design
<img src="https://raw.githubusercontent.com/ozank/ozank.github.io/master/presentations/images/slot_design.png" alt="Drawing" style="width:800px;"/>
Ref: Tim Miller - Lecture 14
---
# Slot Design
<img src="https://raw.githubusercontent.com/ozank/ozank.github.io/master/presentations/images/slot_fill.png" alt="Drawing" style="width:800px;"/>
Ref: Tim Miller - Lecture 14
---
# Common Faults in Windings
--
: Good Winding
<img src="./images/ee564/goodwinding.jpg" alt="Drawing" style="width: 500px;">
### [Reference](https://www.easa.com/resources/booklet/typical-failures-three-phase-stator-windings)
---
# Common Faults in Windings
## One Phase Open Circuited (Y-connected)
--
<img src="./images/ee564/phase_open_wye.jpeg" alt="Drawing" style="width: 450px;">
### [Reference](https://www.easa.com/resources/booklet/typical-failures-three-phase-stator-windings)
---
# Common Faults in Windings
## One Phase Open Circuited (Delta-connected)
--
<img src="./images/ee564/phase_open_delta.jpeg" alt="Drawing" style="width: 450px;">
### [Reference](https://www.easa.com/resources/booklet/typical-failures-three-phase-stator-windings)
---
# Common Faults in Windings
## Phase to Phase Short Circuit
--
<img src="./images/ee564/phase_to_phase.jpeg" alt="Drawing" style="width: 450px;">
### [Reference](https://www.easa.com/resources/booklet/typical-failures-three-phase-stator-windings)
---
# Common Faults in Windings
## Phase to Phase Short Circuit
--
<img src="./images/ee564/turn_to_turn.jpeg" alt="Drawing" style="width: 450px;">
### [Reference](https://www.easa.com/resources/booklet/typical-failures-three-phase-stator-windings)
---
# Common Faults in Windings
## Phase to Ground Short Circuit
--
<img src="./images/ee564/phase_to_ground.jpeg" alt="Drawing" style="width: 450px;">
### [Reference](https://www.easa.com/resources/booklet/typical-failures-three-phase-stator-windings)
---
# Common Faults in Windings
## Damage due to Overload
--
<img src="./images/ee564/overload.jpeg" alt="Drawing" style="width: 450px;">
### [Reference](https://www.easa.com/resources/booklet/typical-failures-three-phase-stator-windings)
---
# Common Faults in Windings
## Damage due to Locked Rotor
--
<img src="./images/ee564/locked_rotor.jpeg" alt="Drawing" style="width: 450px;">
### [Reference](https://www.easa.com/resources/booklet/typical-failures-three-phase-stator-windings)
---
# Cooling Types:
--
- ## Forced air cooling (internal or external)
- ## Liquid Cooling (frame with sleeves or the core)
- ## Direct cooling of conductors
- ## Oil Splash Cooling or spray cooling
- ## Hydrogen Cooling
---
# Thermal Design of Electric Machines
--
## Why is it important?
---
# Temperature vs Operating Life
<img src="https://raw.githubusercontent.com/ozank/ozank.github.io/master/presentations/images/temp_vs_life.png" alt="Drawing" style="width: 500px;"/>
---
# Temperature vs Efficiency
### Losses dependent on temperature and temperature on losses
--
## Copper Losses \\(\propto\\) Resistance
## $$R(T) = R(T_0)(1 + \alpha\Delta T)$$
### For copper (at 20 C)
### $$\alpha = 0.003862\;K^{-1}$$
---
# Torque Output
# Torque \\(\propto\\) Electric Loading
## Electric loading limited by maximum temperature
---
# Methods for Thermal Analysis
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### From difficult to easy
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- ## Experiment
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- ## CFD (Computational Fluid Dynamics)
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- ## FEA (Finite Element Analysis)
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- ## Lumped Parameter Model
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# Thermal CFD
## Requires intense computation
<img src="https://laurencemarks.files.wordpress.com/2013/06/heatsink.jpg" alt="Drawing" style="width: 550px;"/>
---
# Thermal FEA
## Only models conduction
<img src="https://raw.githubusercontent.com/ozank/ozank.github.io/master/presentations/images/temp_distribution.png" alt="Drawing" style="width: 350px;"/>
#### Temperature distribution of a slot
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# Thermal Lumped Parameter Network
<img src="https://www.researchgate.net/profile/Yvan_Lefevre/publication/318348628/figure/fig1/AS:572815197257728@1513581193848/Sketch-of-lumped-parameter-thermal-model-of-LCTE-PMSM.jpg" alt="Drawing" style="width: 700px;"/>
#### Have a look at [Motor-CAD](http://www.motor-design.com) software
---
# Thermal Lumped Parameter Network
<img src="http://www.usinenouvelle.com/industry/img/motor-cad-thermal-optimisation-of-motors-000040140-4.jpg" alt="Drawing" style="width: 600px;"/>
---
# Basics of Heat Transfer
--
<img src="./images/heat-transmittance-means.jpg" alt="Drawing" style="width: 800px;"/>
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# Lumped Thermal Network
## Thermal systems can be represented as electric circuits
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## Temperature = Voltage
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## Heat Input = Current Source
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## Thermal Conductivity = Electrical Conductivity
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## Heat Capacity = Capacitance
---
# Thermal Conductivity
--
<img src="https://ecx.images-amazon.com/images/I/61oA4gophKL._SL1001_.jpg" alt="Drawing" style="width: 500px;"/>
---
# Thermal Conductivity
<img src="http://www.kisinambalaj.com/image/cache/catalog/kap-grubu/bar1-800x600.JPG" alt="Drawing" style="width: 600px;"/>
---
# Thermal Resistance
<img src="https://raw.githubusercontent.com/ozank/ozank.github.io/master/presentations/images/thermal_resistance.png" alt="Drawing" style="width: 500px;"/>
---
# Thermal Resistance
### Similar to electrical resistance
#\\(R= \dfrac{l}{kA}\\)
--
- ## \\(k\\): thermal conductivity
- ## \\(l\\): Length
- ## \\(A\\): Cross Section Area
---
# Thermal Conductivity of Some Materials
--
- ## Water:
--
0.58 W/(mK)
--
- ## Ice:
--
2.2 W/(mK)
--
- ## Concrete: 1-1.5 W/(mK)
--
- ## Insulating Brick: 0.15 W/(mK)
---
# Thermal Conductivity of Metals
--
- ## Aluminum:
--
205 W/(mK)
--
- ## Iron:
--
80 W/(mK)
--
- ## Copper:
--
400 W/(mK)
--
- ## Gold:
--
310 W/(mK)
--
- ## Epoxy: 0.35 W/(mK)
--
### [Ref](http://en.wikipedia.org/wiki/List_of_thermal_conductivities)
---
# Conduction Heat Loss
# \\(P = \dfrac{\Delta T}{R}\\)
# \\(P = \dfrac{T\_2 - T\_1}{R}\\)
---
# Fluid Temperature Rise
### For a liquid cooled system
# \\(\Delta T = \dfrac{P}{Q . d. C\_p}\\)
### \\(Q\\): Volume flow rate (m3/s)
### \\(d\\): Density
### \\(C\_p\\): Specific heat capacity (J/kgC)
---
# Convection
# Heat transfer on the surface between solids and liquids (or gaseous) with mass transfer
---
# Convection
## Difficult to analyze accurately
--
## Two types of Convection:
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- ## Natural Convection
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- ## Forced Convection
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## Convection Thermal Resistance
--
# \\(R_c = \dfrac{1}{A h}\\)
--
## A: Area
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## h: Convection heat transfer coefficient (W/m2/C)
---
# h: Convection Heat Transfer Coefficient
--
## Depends on the surface properties
--
## Flow Rate, density
--
## Reynolds Number
--
## And others (Nusselt number, prandtl number)
#### Have a look at MotorCAD and Dave Staton's presentation if you're interested
#### [Dave Staton, Thermal Design](https://www.icloud.com/iclouddrive/06dc3pf2gQcBggncx325WMTnQ#Dave_Staton_Thermal_Design), [Dave Staton, Thermal Training](https://www.icloud.com/iclouddrive/006WCcqSAZ13rIVol82QnIodQ#David_Staton_Thermal_Training_Handouts_May_2007)
---
# Radiation
## Radiant Heaters
<img src="http://willowbrookhangars.com/wp-content/uploads/2014/01/AmbiRad-radiant-tube-heater.jpg" alt="Drawing" style="width: 750px;"/>
---
## Radiant Heaters
<img src="http://www.gardenista.com/wp-content/uploads/2015/04/img/sub/uimg/05-2012/700_endless-summer-and-dcs-patio-heaters-700x516.jpg" alt="Drawing" style="width: 700px;"/>
---
# Reflective Blankets
<img src="http://www.containerstore.com/catalogimages/175768/10061869EmergencyBlanketSlvr_x.jpg" alt="Drawing" style="width: 500px;"/>
---
# Radiation Heat Loss (Black body radiation)
### \\(q_R\\): radiation heat flow (W/m2)
## \\(q\_R = \rho \epsilon F (T\_1^4-T\_2^4)\\)
--
### \\(\rho\\): Stefan-Boltzmann constant (\\(5.67x10^{-8} W/m^2/K^4\\) )
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### \\(\epsilon\\): emissivity of radiating surface (ε ≤ 1)
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### \\(F\\): view factor (≤ 1) – calculated from geometry
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### \\(T\_1, T\_2\\) absolute temperature of radiant and ambient (K)
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# Radiation Heat Transfer
### \\(h_R\\): heat transfer coefficient for radiation (for lumped parameter network)
## \\(h\_R = \dfrac{\rho \epsilon F (T\_1^4-T\_2^4)}{T\_1 - T\_2}\\)
--
### \\(\rho\\): Stefan-Boltzmann constant (\\(5.67x10^{-8} W/m^2/K^4\\) )
--
### \\(\epsilon\\): emissivity of radiating surface (ε ≤ 1)
--
### \\(F\\): view factor (≤ 1) – calculated from geometry
---
# Emissivity of Materials
--
### Have you ever wondered why most heat sinks are black?
--
<img src="http://www.coolingsource.com/wp-content/uploads/2014/03/Board-Level-Heatsink-447x270.jpg" alt="Drawing" style="width: 600px;"/>
---
# Emissivity of Materials
## Aluminum:
- ### Black anodized: 0.86
- ### Polished: 0.04-0.1
--
### Radiation is more dominant with naturally cooled heatsinks, than the ones with forced cooling
### More info:
- #### [Effects of Anodization on Radiational Heat Transfer](http://www.aavid.com/product-group/extrusions-na/anodize)
- #### [How Heat Sink Anodization Improves Thermal Performance](http://www.qats.com/cms/2010/11/09/how-heat-sink-anondization-improves-thermal-performance-part-1-of-2/)
---
# Emissivity of Materials
--
## Aluminum: (black anodized: 0.86), (polished: 0.03-0.1)
## Copper: (polished:0.02, heavily-oxidized:0.78)
## Iron: (polished:0.07, heavily-oxidized:0.38)
### Example problem (Dave Staton's Thermal Design presentation pg 52)
---
# Rule of Thumbs
### Not very accurate but useful for initial calculations
--
## Current Density
--
- ## Totally Enclosed: 1.5-5 A/mm2
--
- ## Fan-cooled: 5-10 A/mm2
--
- ## Liquid-cooled: 10-30 A/mm2
#### [Dave Staton, Thermal Design](https://www.icloud.com/iclouddrive/06dc3pf2gQcBggncx325WMTnQ#Dave_Staton_Thermal_Design), [Dave Staton, Thermal Training](https://www.icloud.com/iclouddrive/006WCcqSAZ13rIVol82QnIodQ#David_Staton_Thermal_Training_Handouts_May_2007)
---
# Rule of Thumbs
## Heat Transfer Coefficient
--
- ## Air-Natural Convection: 5-10 W/(m2.C)
--
- ## Air-Forced Convection: 10-300 W/(m2.C)
--
- ## Liquid-Forced Convection: 50-20.000 W/(m2.C)
---
# Common Cooling Methods
- ## Forced air cooling
- ## Forced air + liquid heat exchanger
- ## Liquid cooling
- ## Hydrogen cooling
---
## Shaft Mounted Fans
<img src="./images/ee564/shaft_fan.png" alt="Drawing" style="width: 800px;"/>
---
## Shaft Mounted Fans
<img src="https://upload.wikimedia.org/wikipedia/commons/thumb/a/a9/Rotterdam_Ahoy_Europort_2011_%2814%29.JPG/1920px-Rotterdam_Ahoy_Europort_2011_%2814%29.JPG" alt="Drawing" style="width: 700px;"/>
---
## Shaft Mounted Fans
<img src="./images/ee564/shaft_fan2.png" alt="Drawing" style="width: 800px;"/>
---
## Effect of Motor Fins
<img src="./images/ee564/motor_fins.png" alt="Drawing" style="width: 800px;"/>
---
## Cooling Type Standards
<img src="./images/ee564/cooling_methods.webp" alt="Drawing" style="width: 500px;"/>
---
# Rotor-Stator Cooling Ducts
<img src="./images/ee564/cooling_ducts.png" alt="Drawing" style="width: 800px;"/>
---
# Rotor-Stator Cooling Ducts
<img src="./images/ee564/cooling_ducts2.jpg" alt="Drawing" style="width: 350px;"/>
<img src="./images/ee564/cooling_ducts.jpg" alt="Drawing" style="width: 350px;"/>
---
## Stator Vent Plates
<img src="./images/ee564/vent_plates.png" alt="Drawing" style="width: 700px;"/>
---
# Cooling Jacket
<img src="./images/ee564/early_tesla.png" alt="Drawing" style="width: 600px;"/>
### Early Tesla Motor
---
# Cooling Jacket
<img src="https://leandesign.com/wp/wp-content/uploads/2020/03/Tearing-Down-Tesla-Cooling-Housing-1024x639.jpg" alt="Drawing" style="width: 800px;"/>
### Tesla vs BMW i3
---
# Cooling Jacket
<img src="./images/ee564/tesla_audi.png" alt="Drawing" style="width: 800px;"/>
### [Tesla vs. Audi Comparison](https://ieeexplore.ieee.org/document/9503055)