EE362-Electromechanical Energy Conversion-II

class: center, middle

# EE-362 ELECTROMECHANICAL ENERGY CONVERSION-II

# Introduction to Synchronous Machines

## Ozan Keysan

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

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

## Rotating MMF generated by 3-phase winding

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# Review

## Rotating MMF generated by 3-phase winding

<img src="./images/ee362/vecmovieplus.gif" alt="Drawing" style="width: 850px;"/>
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# Fundamental Idea of all AC Machines

## Rotor tries to catch up with  the rotating MMF
## (to reach to the minimum magnetic energy point).

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# Synchronous Machines

### Generates 90% of the world's electricity

### PMSMs (Permanent Magnet Synchronous Machines) are used by many electric car brands

#### Suggested Video: [Matrix Reloaded](https://youtu.be/Ny_mr3QX9Q8?t=91)

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# Synchronous Machines

## Armature: 
- ### 3-phase cylindrical stator.

- ### Generates rotating MMF (ie moves the carrot)
--

## Rotor (Field Windings): 
- ### Either Salient Pole or Cylindrical Rotor
- ### Excited with DC!
- ### or can also have permanent magnets for excitation

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# Synchronous Machines: Rotor

## Rotor is excited with DC, becomes an electromagnet
## Needs two slip rings to carry to current to rotor

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## Theory of Operation:

### Stator winding create rotating MMF

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## Theory of Operation
### Rotor MMF (DC) locks with stator MMF, and rotates at the synchronous speed
 
<img src="http://www.simulation-research.com/help/userguide/em/bldcm/bldcm.gif" alt="Drawing" style="width: 300px;"/>

### A BLDC motor with concentrated stator windings

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## Theory of Operation
 
<img src="./images/ee362/pmsm.gif" alt="Drawing" style="width: 300px;"/>

### A smoother MMF distribution with distributed winding and AC excitation

### [Operation animation](https://youtu.be/Vk2jDXxZIhs?t=45s)

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# Stator of AC Machines

<img src="./images/ee564/slot_q6.png" alt="Drawing" style="width: 500px;">
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## MMF from three phase

### Number of coils can be increased to achieve a smoother MMF waveform. 
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# Distributed Winding Manufacturing

- ### [Production of electric machines](https://www.youtube.com/watch?v=5Mu42TzHy8M) (T=6:00)

- ### [Rewinding a Large Motor](https://www.youtube.com/watch?v=_65mXQ-GNVM) (T=0:20)

- ### [BMW Electric Motor - Drive](https://www.youtube.com/watch?v=Qktx5yx1Bjw)

- ### [Induction Motors: Overhauling a Motor](https://www.youtube.com/watch?v=yPvYd03cKJU)

### For curious students: [EE568](http://keysan.me/ee568)

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# Synchronous Machines: Rotor

# Cylindrical Rotor vs Salient Pole Rotor

<img src="http://1.bp.blogspot.com/-abfAw-qVR6g/T9il-2u0-wI/AAAAAAAABo0/gg53eqWmfyg/s1600/stator.png" alt="Drawing" style="width: 700px;"/>
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# Cylindrical Rotor vs Salient Pole Rotor

<img src="http://1.bp.blogspot.com/-y12ci3GcaX8/UQA1b3GLtFI/AAAAAAAAJXE/OlfQyz55J2M/s1600/Fig+2.2+AC+GENERATOR+ROTORS.jpg" alt="Drawing" style="width: 600px;"/>
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## Cylindrical Rotor Synchronous Machines

### Airgap (and hence inductance) is more or less constant

### No reluctance torque (\\(\frac{d L(\theta)}{d\theta}=0 \\)) but there is still synchronous torque (\\(\frac{d M(\theta)}{d\theta}\\))
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## Cylindrical Rotor Synchronous Machines

### Used in high speed turbo-generators (2 or 4 poles)

### [How a Gas Turbine Works](https://www.youtube.com/watch?v=zcWkEKNvqCA)

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# Salient Pole Rotor Synchronous Machines

### Airgap is not uniform.

### There are both reluctance and synchronous torque components
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# Salient Pole Rotor Synchronous Machines

## Used in large-pole low-speed generators (such as hydro-electric plants)

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## Synchronous Machines are usually big machines
--

### Direct-Drive Permanent-Magnet Synchronous Generator for Wind Turbines (Siemens)
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## Synchronous Machines are usually big machines

### 2-pole 3000rpm Synchronous Generator (For Steam Turbines)
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## Very Big
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### Wind Turbine Synchronous Generator (12 rpm)
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# Very Very Big

### [Itaipu Hydro](http://en.wikipedia.org/wiki/Itaipu_Dam) Plant, Brazil

### 20 Turbines, 700 MW each, [Shaft of The Generator](https://www.youtube.com/watch?v=rHSSURaeDLY)
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## Very Very Big: [700 MW Synchronous Generator](https://www.itaipu.gov.br/en/energy/generating-units)

### 16 m diameter, 91 rpm, Rotor Mass: 2650 t
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# Even Bigger: [Three Gorges Dam](http://en.wikipedia.org/wiki/Three_Gorges_Dam), China
--

#### Total Power Capacity: 22.5 GW (1/3 of Turkey's  Consumption)
#### Slowed down the rotation of earth by [0.06 microseconds](https://futurism.com/how-infamous-hydroelectric-dam-changed-earths-rotation/)

[Video1](https://www.youtube.com/watch?v=sB6SwPHPEtQ), [Video2](https://www.youtube.com/watch?v=FUo8hrA0CEU),  [Richard Feynman on Generators and Our Civilization](https://youtu.be/P1ww1IXRfTA?t=1351)

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## Assume the stator is not excited, only the rotor is excited with DC.

### What is the shape of the induced voltage in the stator windings?
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<img src="http://www.alternative-energy-tutorials.com/images/stories/wind/alt64.gif" alt="Drawing" style="width: 800px;"/>

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## i.e. the machine is working as a generator (no-load)

--
<img src="./images/ee362/alternator.gif" alt="Drawing" style="width: 900px;"/>

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# Induced Voltage Magnitude Proportional to?
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## Induced voltage \\(\propto\\) Field Current \\(\times\\) Frequency
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### We would like to operate in the linear region, but beware of saturation & residual magnetism)
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##  Mechanical Rotation Frequency vs. Electrical Frequency
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### The machine on the right induces a voltage twice the frequency of mechanical rotation frequency.

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# Number of Poles: 2-pole machine

<img src="https://raw.githubusercontent.com/ozank/ozank.github.io/master/presentations/images/2pole_mmf.jpg" alt="Drawing" style="width: 450px;"/>
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# Number of Poles: 4-pole machine

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# How many poles does this machine has?

<img src="https://voith.com/corp-en/m_VH_Budarhals_rotor.png" alt="Drawing" style="width: 500px;"/>
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## What should be the rotational speed in RPM to induce 50 Hz voltage?

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## Electrical Speed is not equal to Mechanical Speed!

## \\(\omega\_{elec} = (\dfrac{p}{2}) \omega\_{mech} \\)

## \\(p\\) : Number of poles (always an even number)

## \\(\dfrac{p}{2}\\) : Number of pole pairs

# \\(\theta\_{elec} = (\dfrac{p}{2}) \theta\_{mech} \\)

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# Synchronous Machines

## Rotate only at synchronous speed!
--

## Synchronous Speed in RPM (revolutions per minute):

# \\(n\_s = \dfrac{60 f\_{elec}}{(p/2)} = \dfrac{120 f\_{elec}}{p}\\)

## They are constant speed machines (under constant stator voltage frequency)

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## A few videos to watch

### [Renault Zoe Synchronous Motor Manufacturing](https://www.youtube.com/watch?v=WSH983zUNIo)

### [Audi e-tron motor](https://youtu.be/uWBEPEspbWI?t=80)

### [Enercon Wind Turbine Generator](https://youtu.be/MgGk2WvK80M?t=409)

### [ABB Azipod Ship Propulsion Motor](https://youtu.be/lvHb4XTkC0A?t=71)

### [Siemens Turbo Generator](https://www.youtube.com/watch?v=g2AFCuJlH20)

### [Hydro Generator Manufacturing](https://www.youtube.com/watch?v=ccWl6F3mrZ8)

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# Equivalent Circuit of Synchronous Machines

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# Induced Voltage

# Cause \\(\rightarrow\\)Effect
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## \\(I\_{field(DC)}\\)
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\\(\rightarrow MMF\_{field}\\)
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\\(\rightarrow \Phi\_f \rightarrow\\)
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## \\( e\_a,e\_b, e\_c\\)
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\\(\rightarrow I\_a,I\_b,I\_c\\)
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\\(\rightarrow MMF\_{armature} \\)
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##\\(\rightarrow \Phi\_{ar} \\)
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### Resultant MMF:
##\\(\Phi\_{R}= \Phi\_f + \Phi\_{ar}\\)

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# Armature Reaction

### The magnetic field created by the field winding is modified by the stator (armature) winding current.

### [Animation](https://andymikeknight.github.io/machines/synchronous/s_armature.html)

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# No Stator Current (No-load)

![](./images/sync_flux1.svg)
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# Armature Reaction: Lagging Current

![](./images/sync_flux2.svg)
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## \\(B\_{ar}\\): Armature reaction flux density

![](./images/sync_flux3.svg)
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## \\(B\_{R}\\): Resultant flux density

![](./images/sync_flux4.svg)
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# Torque in Synchronous Machines
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# \\(T = K \Phi\_f \Phi\_R sin (\delta)\\)
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### \\(K\\): Constant (we'll see what it is in the following lectures)
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### \\(\Phi_f\\): Field generated flux (rotor-side)
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### \\(\Phi\_R\\): Resultant (or Air-gap) flux (\\(\Phi\_R = \Phi\_f + \Phi\_{ar}\\))
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## \\(\delta\\): Load-angle (very important!)

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# Torque vs Load Angle

## \\(\delta > 0 \\): Generating Action
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## \\(\delta < 0 \\): Motoring Action
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## \\(\delta = \pm \dfrac{\pi}{2} \\): Maximum torque point
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## \\(\delta = 0 \\): Zero Torque (Donkey eats the carrot)
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# Torque vs Load Angle

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#Phasor Diagram

## \\(\vec{E\_{ar}}\;\\) lags \\(\;\vec{\Phi\_{ar}}\\) 90 degrees
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### Armature reaction can be represented as a voltage drop in an inductance
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## \\(\vec{E\_{ar}} = -j X\_{Q} \vec{I\_a}\\) 
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## \\(\vec{E\_{R}} = \vec{E\_{f}} -j X\_{Q} \vec{I\_a}\\)

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# Simple Equivalent Circuit

### Assumption: Cylindrical rotor (constant air-gap)
--

### \\(\vec{E\_{R}} = \vec{E\_{f}} -j X\_{Q} \vec{I\_a}\\)
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# Simple Equivalent Circuit

## However, there is also the leakage flux: \\(\;jX\_{l}\\)
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## Define stator total reactance as:
# \\(jX\_S = jX_Q + jX_l\\)

### Thus, the equivalent circuit becomes:

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# Simple Equivalent Circuit

## \\(\vec{E} = \vec{E\_{f}} -j X\_{s} \vec{I\_a}\\)
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## What about the resistance of the phase windings?
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## \\(\vec{V\_{ph}} = \vec{E\_{f}} -(j X\_{s}+R\_{a}) \vec{I\_a}\\)

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## Motoring and Generating Convention
### Remember synchronous machines are mostly used as generators.

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## Remember the Equivalent Circuit is per Phase

### Synchronous machines can be Wye or Delta connected

<img src="./images/synch_wye.png" alt="Drawing" style="width: 500px;"/>
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## Remember the Equivalent Circuit is per Phase

### Synchronous machines can be Wye or Delta connected

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# Most important definitions

- ## Load Angle (\\(\delta\\)): Angle between phase voltage and field voltage

- ## Power Factor Angle (\\(\theta\\)): Angle between phase voltage and current.

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# Load Angle and Power Factor
## Neglect \\(R\_a\\) just for now.
--

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## A few exercises with the simple equivalent circuit

## Neglect \\(R\_a\\) for now.

<img src="./images/sync_simple_equivalent2.png" alt="Drawing" style="width: 500px;"/>
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## A few exercises with the simple equivalent circuit

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# Full Equivalent Circuit with Field Circuit

### \\(L\_f\\) can be neglected at steady state (DC) conditions

## Remember \\(I\_f\\) can be controlled to adjust \\(E\_f\\) 
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## That big generator is equivalent to:

#### Enercon Wind Turbine Synchronous Generator (12 rpm)

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# Full Equivalent Circuit with Field Circuit

<!---

# What are these bars in the rotor for?

# What are the bars in the rotor?

## Synchronous motors cannot self-start.
## Needs induction coils (Damper windings)
-->

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## You can download this presentation from: [keysan.me/ee362](http://keysan.me/ee362)