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Regenerative Electric Flight

Synergy and Integration of Dual-role Machines

J. Philip Barnes 25 Oct 2014

Animated slides: F5 key

Also: View ~ "Notes Page"

Regenerative Electric-powered Flight J. Philip Barnes


Great theoreticians and experimentalists (all Ph.D.)

Ludwig Prandtl - Germany

Albert Betz - Germany

Photo

Permission

requested

Photo

Permission

requested

Academy of

Achievement

Royal Aeronautical Society

Hermann Glauert - U.K.

Paul MacCready - USA

Regenerative Electric-powered Flight J. Philip Barnes


Presentation Contents

  • Regen. elec. flight: Origin & Introduction

  • Dual-role machines:

    • Propeller and wind turbine

    • DC motor-generator

    • Brushless motor-generator

  • Integration:

    • Inverter-rectifier

    • DC boost converter

    • "Chop" Vs. "Boost" architecture

  • “Regenosoar” aircraft concept

  • Summary & Look Ahead


Regen Aircraft Elements and Operation

  • Windprop

    • Fixed rotation direction

    • Sign change with mode

      • Thrust, Torque

      • Power, Current

Motor-Gen

(M-G)

Power

Electronics

  • Energy Storage Unit:

    • Battery and/or:

    • Ultra capacitor

    • Flywheel w/M-G

Exploit opportunities to

store Vs. expend energy

Regenerative Electric-powered Flight J. Philip Barnes www.HowFliesTheAlbatross.com


Presentation Contents

  • Regen. elec. flight: Origin & Introduction

  • Dual-role machines:

    • Propeller and wind turbine

    • DC motor-generator

    • Brushless motor-generator

  • Integration:

    • Inverter-rectifier

    • DC boost converter

    • "Chop" Vs. "Boost" architecture

  • “Regenosoar” aircraft concept

  • Summary & Look Ahead


Propeller Wake, Pitch, and Blade Angles

  • Wake induces downwash

  • (normal to local section)

  • Pitch:

    • helix length per rotation

    • htip = 2 p R tan btip

  • Uniform pitch:

    • r tanb = R tanbtip

  • Blade tip angle (btip):

    • 14o ~ low pitch

    • 30o ~ high pitch

Horseshoe

Vortices

R

r

  • Effect of more blades (fixed T, R):

  • Steep blade angle, much lower RPM

  • Lower tip Mach, much-reduced noise

  • High torque → dual & counter rotation

  • Numerically integrate wake for loading

Blade angle (b) at radius (r)

is measured from rotation

plane to the chord line at (r)

Regenerative Electric-powered Flight J. Philip Barnes www.HowFliesTheAlbatross.com


Test data validating Glauert's rationale on induced velocity

F.E. Weick, Aircraft Propeller Design, McGraw-Hill, p. 102-103

Gradual buildup

Immediate swirl, as predicted by Glauert

Regenerative Electric-powered Flight J. Philip Barnes


Rotor blade velocity diagram - "Pinwheeling" condition

  • Propeller or wind turbine

  • Angle of attack = 0

  • No change to flow direction

  • No change to relative wind

  • Helical drag wake (unloaded)

  • wr tanb= Vo (all sections)

  • or, r tanb= const.=R tanbtip

W2

Helical wake

w r

Blade section

Looking outboard,

Blade at 3 o’clock

Vo

Chord line

Axial

wind

b

Pinwheeling sets up "Betz Condition"

  • Propeller or turbine at no load

    Perturb w or Vo to load rotor

  • Helical wake (drag and/or vortex)

  • Sets blade angle distribution b(r):

    b = tan-1 [ Vo / (wr) ]

  • Says nothing about blade planform

Vo

Relative

wind W1

b

Rotational

wind,w r

Vo

J. Philip Barnes www.HowFliesTheAlbatross.com


Propeller blade - comprehensive velocity diagram

  • Non-rotational (axial) inflow

  • Axial velocity locally conserved

  • Finalswirl imparted suddenly

  • Helical wake anchored at c/4

  • Wake ~ aligned with chordline

  • Wake-induced velocity (Vi)

  • Glauert: 2Viq at "rotor out"

  • Absolute velocity (V) increased

  • Relative wind (W) decreased

  • Immediate static pressure rise

W2

Blade section

Looking outboard

Blade at 3 o’clock

Helical wake

vortex sheet

w r - 2Viq

V1

Chord line

V2

b

Axial

wind

Vix

V1  Vo+Vix

Vi

Viq

Glauert: consistent physics & geometry

Vortex wake ~ aligned with chord line

Betz cond. (wake helix), prop or turbine,

with or without rotor loading, provided:

r tan b= const. and z=0 (sym. sections)

f

Zero-lift line

Rotational wind

Wq w r - Viq

z

Relative

wind W1

a

V1

J. Philip Barnes www.HowFliesTheAlbatross.com


Windprop Blade Angle and Operational Mode

b

L

b

b

v

v

v

w r

-L

w r

w

w r

w

w

  • Symmetrical sections and r tanb = R tanbtip

Turbine

Propeller

Pinwheel

  • Pinwheeling: Zero angle of attack, root-to-tip

    • - No thrust, no torque, small drag

  • Efficient prop: Rotate ~115% of “pinwheel RPM,” or fly at 87% of “pinwheel airspeed”

  • Efficient turbine: Rotate ~ 87% of “pinwheel RPM,” or fly at 115% of “pinwheel airspeed”

Define: “Speed ratio,” s v / vpinwheel = v / [ wR tanbtip ]

Regenerative Electric-powered Flight J. Philip Barnes www.HowFliesTheAlbatross.com


o

o

b

b

= 14

= 30

Low-RPM8 Blades,

tip

tip

1.0

Efficiency

0.8

c

c

l_min

l_max

Blades_btip

2_14o

8_30o

0.6

h

Propeller

f v / (t w)

Turbine

t w / (f v)

0.4

0.2

Speed Ratio, s ≡ v / (w R tan btip)

0.0

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

1.6

1.7

1.8

1.0

0.9

Propeller ~ climb

Force Coefficient, F ≡ f/(qpR2)

0.8

High-RPM2 Blades,

B=8

0.7

B=2

0.6

0.5

0.4

Propeller

~ cruise

0.3

F

Sym. Sections

0.2

b

b

tan

R

r

=

tan

tip

Max efficiency

0.30

0.1

Blade Geometry

Regeneration

Max capacity

0.25

0.0

Regeneration

Pinwheel

0.20

R

Chord, c/

-0.1

0.15

F= -0.011 @ B=2

Thickness

2

-0.2

0.10

F= -0.008 @ B=8

8

hub

-0.3

0.05

Speed Ratio, s≡ v / (w R tan btip)

R

r /

-0.4

0.00

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

1.6

1.7

1.8

0.00

0.25

0.50

0.75

1.00

Windprop Efficiency and Thrust

  • Comparable efficiency by mode

  • Eight blades quieter than two

  • Climb power ~ 7x cruise power

Regenerative Electric-powered Flight J. Philip Barnes www.HowFliesTheAlbatross.com


Presentation Contents

  • Regen. elec. flight: Origin & Introduction

  • Dual-role machines:

    • Propeller and wind turbine

    • DC motor-generator

    • Brushless motor-generator

  • Integration:

    • Inverter-rectifier

    • DC boost converter

    • "Chop" Vs. "Boost" architecture

  • “Regenosoar” aircraft concept

  • Summary & Look Ahead


Motor-generator Principles

t

Electromotive force, e

= potential energy / charge

= work / charge, (Fp / q) L

= 2 N w (D/2) B L

e = NDBL w ≡ k w

(+) Charge (q) with velocity, V

in magnetic field of strength, B:

Force vector, F = q V x B

L

N turns

k = "EMF constant"

B

w

Fq

e

i

i

Fp

Torque, t

= 2N (D/2) B (dx/dt) dq

= 2N (D/2) B (dq/dt) dx

t = NDBiL = NDBL i = k i

vi

B

vq

E

t w = e i

Both

modes

t

Motoring

N turns

w

Fq

e

i

i

Fp

vi

B

Change to generator mode:

Same direction, rotation, w

Same sign for EMF, e

Sign change of torque, t

Sign change of current, i

vq

E

Generating

Regenerative Electric-powered Flight J. Philip Barnes www.HowFliesTheAlbatross.com


System Motoring and Regeneration Efficiencies

Typical controller pulse-width

modulation (PWM) of duty cycle

(d) and efficiency h ≈ d 0.25 (*)

Rt

System total

resistance

em=kw

t

eb

w

Torque

Motor

Regen

i

  • "Ideal system efficiency" ignoring controller and all losses

  • system motor ≈ t w/(eb i) ≈ emi / (eb i) = em/ eb = k w / eb

  • system regen ≈ ebi / (tw) ≈ eb i / (emi) = eb / em=eb / (k w)

(*) AiAA 2010-483, Lundstrom, p.8

Regenerative Electric-powered Flight J. Philip Barnes www.HowFliesTheAlbatross.com


Motor-generator & Battery ~ Performance Envelope and Data

100% Duty Cycle

eb /(kw)

THEO. EFFICIENCY, kw/eb

CURRENT GROUP, i Rt / eb

TORQUE GROUP, t Rt / (k eb)

REGENERATION

LMC "generator curve"

48V / 3,600 RPM

k = 0.16 N-m/A

Rt = 0.041 Ohm

LMCLTD.net

MOTORING

EEMCO 427D100

24V / 15,000 RPM

k = 0.015 N-m/A

Rt = 0.075 Ohm

Windprop synergy

i

t

Phil Barnes Apr-08-2011

Trends match theory

Regenerative Electric-powered Flight J. Philip Barnes www.HowFliesTheAlbatross.com


Presentation Contents

  • Regen. elec. flight: Origin & Introduction

  • Dual-role machines:

    • Propeller and wind turbine

    • DC motor-generator

    • Brushless motor-generator

  • Integration:

    • Inverter-rectifier

    • DC boost converter

    • "Chop" Vs. "Boost" architecture

  • “Regenosoar” aircraft concept

  • Summary & Look Ahead


Brushless "DC" Motor-generator ~ "Y" configuration

Brushed Vs. Brushless

Virtues, features, & limits

Brushed:

Theory foundation

tw=ei ; e=kw ; t=ki

2-wire interface

Simplified control

Brush maintenance

~120V limit (arcing)

Low-speed cogging

N

S

Brushless:

Inverter required

3-wire interface

>1000V capable

Minimal cogging

Same as brushed:

tw=ei ; e=kw ; t=ki

Regenerative Electric-powered Flight J. Philip Barnes


Brushless motor-gen. & inverter: Equivalent DC machine

t w = emi

motor or gen

Equivalent DC machine

Inverter-

Rectifier

t

M-G

eb

w

i

Brushless machine with inverter/rectifier as a system follows brushed DC machine principles: tw = emi ; em = kw ; t = k i

Both systems have 2-wire interface with the power circuit

Regenerative Electric-powered Flight J. Philip Barnes www.HowFliesTheAlbatross.com


Presentation Contents

  • Regen. elec. flight: Origin & Introduction

  • Dual-role machines:

    • Propeller and wind turbine

    • DC motor-generator

    • Brushless motor-generator

  • Integration:

    • Inverter-rectifier

    • DC boost converter

    • "Chop" Vs. "Boost" architecture

  • “Regenosoar” aircraft concept

  • Summary & Look Ahead


Transistor and flyback diode

  • "High-tech, high-power light switch"

  • Inverter commutation & DCBC boost adjust

  • Lo-freq. (20-100 Hz) for commutation

  • Hi-freq. (>10 kHz) pulse-width-mod (PWM)

  • VGE (say 12 V) sets the collector current IC

  • Collector voltage VCE(say 600 V) sets power

  • Flyback diode for switch energy dissipation

  • iGBT & diode unidirectional (via arrows)

  • Transistor ~ 2V loss ; Diode ~ 0.7V loss

IC

iGBT

MOSFET

VCE

Collector

Flyback

Diode

Gate

VGE

Emitter

Gate voltage (VGE) "opens the valve"

Gate voltage, VGE

Gate voltage, VGE

Regenerative Electric-powered Flight J. Philip Barnes


Inverter-rectifier ("inverter" for motoring mode)

VB

1

1

2

2

3

3

VB

  • Switch pairs: one "upper" & one "lower"

  • Avoid short circuit: Always "diagonalize"

  • Each phase, per cycle:

  • - Connect to battery voltage 120o

  • - Connect to ground 120o

  • - "Float" twice for 60o each float

  • Inverter converts 2-wire DC to 3-wire "AC"

  • Commutation toggles each phase 0-to-VB

Regenerative Electric-powered Flight J. Philip Barnes


DC-to-AC conversion ~ "inverter" commutation waveforms

AC basis

"Dead time" avoids short circuit

Inverter

Regenerative Electric-powered Flight J. Philip Barnes


Inverter-rectifier ("inverter" for motoring mode) ~ Snapshots

VB

VB

VB

VB

1

1

1

1

1

1

1

VB

VB

VB

1

2

2

2

2

2

2

VB

2

2

3

3

3

3

3

3

3

3

"Upper" switch pairs diagonally with a lower switch

Two phases are operating; one phase is "floating"

Regenerative Electric-powered Flight J. Philip Barnes


Inverter-rectifier ("rectifier" for generating mode) - iGBT Snapshots

Snapshot

E1 - E3 > EB

1

1

2

2

EB

Diodes provide

"free" regen!

3

3

Current to battery!

  • Rectifier converts 3-wire AC to 2-wire DC

  • Battery is recharged via flyback diodes

  • Diodes enable only two phases at once

  • Commutation "ignored" (unidirect. iGBT)

Regenerative Electric-powered Flight J. Philip Barnes


Inverter-rectifier ("rectifier" for generating mode) - MOSFET

E1 - E3 > EB

1

1

2

2

3

3

EB

Current to battery

  • Rectifier converts 3-wire AC to 2-wire DC

  • Charge battery via MOSFETs & flyback diodes

  • Bi-directional: Comm. MOSFET assists diode

Regenerative Electric-powered Flight J. Philip Barnes


Pulse-width modulation: Energy loss due to "chopping" MOSFET

  • Commutation voltage cycle

ion

iav

  • Comm. + PWM superimposed

|| dt

| t |

  • At a given voltage, cruise current ≈ 15% of climb or accel current

  • Superimposed on commutation: PWM "chopping" at part load

  • Typical switching frequency (f) for chopping ≈ 20 kHz (inaudible)

  • Reduce the duty cycle (d) to reduce average current (iav = d ion)

  • Energy is lost (iGBT & diode) with each on/off switching cycle

  • Per-iGBT switching energy loss (Sp) ≈ 20 mJ per switch cycle

  • To minimize chopping losses, apply PWM only to "upper" phase

  • Switch power loss = f Sp = 0.4-1.0 kW = 13-05% @ 3-20 kW/phase

Remove PWM from commutation; Incorporate DC boost converter

Regenerative Electric-powered Flight J. Philip Barnes


Presentation Contents MOSFET

  • Regen. elec. flight: Origin & Introduction

  • Dual-role machines:

    • Propeller and wind turbine

    • DC motor-generator

    • Brushless motor-generator

  • Integration:

    • Inverter-rectifier

    • DC boost converter

    • "Chop" Vs. "Boost" architecture

  • “Regenosoar” aircraft concept

  • Summary & Look Ahead


DC boost converter enables efficient motoring & regen MOSFET

VM

L

M-G

brushed

or

brushless

with inv.

VB

C

iGBT

PWM

Boost battery voltage to efficiently drive the M-G as a motor

Boost motor-generator EMF to efficiently recharge the battery

  • DCBC: Key enabler, efficient bi-directional power management

    • Only the motoring mode is shown in the introductory graphic above

  • “Boosts” DC voltage ~ 0-500 % with minor input/output ripple

  • Power conservation: doubling the voltage halves the current

  • Enables reduced battery totem pole length, i.e. Toyota Prius*

  • DC voltage gain or “boost” is controlled by PWM “duty cycle”

  • PWM used for DCBC gate current, not motor-gen main current

Regenerative Electric-powered Flight J. Philip Barnes


DC boost converter – Equivalent circuits MOSFET

VM

L

M-G

brushed

or

brushless

with inv.

VB

C

iGBT

PWM

iGBT on

iGBT off

iB

iB

VM

VM

iM

iM

L diB /dt

L diB /dt

C dVM/dt

VB

VB

C dVM/dt

dt |--t--|

iGBT gate PWM

d≡ duty cycle ; t≡ period

Regenerative Electric-powered Flight J. Philip Barnes


DC boost converter – Voltage gain & conversion efficiency MOSFET

Time segment 1: iGBT on for Dt = dt

Segment 2: iGBT off for Dt = (1-d)t

[a] Voltage loop: VB - L DiB1 /(dt) = 0

[b] VB - L DiB2 /[(1-d)t] = VM

iB

iB

VM

VM

[c] Output current: iM - C DVM1 /(dt) = 0

[d] iB - C DVM2 /[(1-d)t] = iM

iM

iM

L DiB2 /[(1-d)t]

L DiB1 /(dt)

[e] PWM cycle: DiB1 + DiB2 = 0

[f] DVM1 + DVM2 = 0

C DVM1/(dt)

C DVM2 /[(1-d)t]

[g] Combine [a,b,e]: VM/VB = 1/(1-d)

VB

[h] via [c,d,f]: iM/iB = 1-d

VB

Combine [g,h]: h ≡iMVM /(iBVB) = 1

iGBT gate PWM

dt |--t--|

  • Voltage gain is set by duty cycle (d)

  • Efficiency = 1 (resistance neglected)

d≡ duty cycle ; t≡ period

Regenerative Electric-powered Flight J. Philip Barnes


DC boost converter - efficiency and regen application MOSFET

233 Vdc in

Regen

Cruise

Climb

Regen

5 10 15 20 kW

Motor

"Evaluation of 2004 Toyota Prius,"

Oakridge National Lab, U.S. Dept. of Energy

L

VB

M-G

C

iGBT

PWM

  • DC boost converter integrates windprop and motor-generator

  • Adjust PWM duty cycle to hold voltage gain as RPM decreases

  • Efficient bi-directional power over a wide operating range

Regenerative Electric-powered Flight J. Philip Barnes


Voltage Map - Motoring and Regen with DC boost converter MOSFET

Batt, boost factor 3.0

Voltage

Climb

Batt: 600V

M-G: 400V

M-G, boost = 2.0

M-G, boost = 1.5

Batt, boost factor 2.0

Cruise

Max Regen

M-G: 260V

Batt: 200V

Motor-gen EMF, no boost

Opt. Regen

Battery, no boost

  • Boost the battery for motoring

  • Boost the M-G for regeneration

%RPM

Regenerative Electric-powered Flight J. Philip Barnes


Presentation Contents MOSFET

  • Regen. elec. flight: Origin & Introduction

  • Dual-role machines:

    • Propeller and wind turbine

    • DC motor-generator

    • Brushless motor-generator

  • Integration:

    • Inverter-rectifier

    • DC boost converter

    • "Chop" Vs. "Boost" architecture

  • “Regenosoar” aircraft concept

  • Summary & Look Ahead


Architectures compared MOSFET

i

Inverter-

Rectifier

eb

M-G

PWM superimposed on commutation

"Chopper" architecture

PWM main current chop

Cruise: high chopping loss

Regen: none or inefficient

PWM

w

w

t

t

Commutation

12V

i

Inverter-

Rectifier

DC Boost

Converter

2-way boost

eb

M-G

"Boost" architecture

PWM sets DCBC boost

Efficient motor & regen

Regenerative Electric-powered Flight J. Philip Barnes www.HowFliesTheAlbatross.com


Presentation Contents MOSFET

  • Regen. elec. flight: Origin & Introduction

  • Dual-role machines:

    • Propeller and wind turbine

    • DC motor-generator

    • Brushless motor-generator

  • Integration:

    • Inverter-rectifier

    • DC boost converter

    • "Chop" Vs. "Boost" architecture

  • “Regenosoar” aircraft concept

  • Summary & Look Ahead


Regenosoar - Features and Design Rationale MOSFET

Regen parked in the wind

With safety perimeter

Counter rotors

Symmetric flow

Zero net torque

8-blade rotors

Low RPM, quiet, Low vibration

Low tip Mach

Ground handling

No assistance req'd

Winglet tip wheels

Pod-air-cooled MG & PE

Compact power train

Battery, motor-gen

and powertrain

Pusher Config.

Symmetry upstream

Max. laminar flow

Regenerative Electric-powered Flight J. Philip Barnes


Min. Sink MOSFET

Section

Windprop

System

Removed

Max L/D

Section and Vehicle Drag Polars

"Clean configuration" ~ Windprop System Removed

1.50

Lift Coefficient, c

or c

L

l

1.25

1.00

"Clean" aircraft

0.75

0.50

0.25

Drag Coefficient, c

or c

D

d

0.00

0.00

0.01

0.02

0.03

0.04

0.05

Regenerative Electric-powered Flight J. Philip Barnes www.HowFliesTheAlbatross.com


Steady-state MOSFET load factor (nn) ~ “g-load” and turn radius

L= nn w

v

nn L/ w = cosg / cosf *

Glide: nn 1

Turn: nn 1 / cosf

f

g

* SAE 2004-01-3088 EQN 5.2, dg/dt = 0

w

Load Factor and Bank Angle

Load Factor and Turn Radius

400

1.05

50

350

n

Bank Angle

Turn Radius, m

n

300

fo

40

1.1

250

r = v2(cosg) / (g tanf)

30

200

1.2

f = cos-1[(cosg)/nn)]

Thermaling

150

20

1.4

1.6

100

10

50

Load Factor, nn

Airspeed, v_km/h

0

0

0

20

40

60

80

100

120

140

1.0

1.1

1.2

1.3

1.4

1.5

1.6

Regenerative Electric-powered Flight J. Philip Barnes www.HowFliesTheAlbatross.com


Load Factor and “Clean” Sink Rate MOSFET

0.0

dz/dt ~m/s

Sea level

Max L/D

2

25 kg / m

Min Sink

A = 16

-0.5

1.0

-1.0

1.2

1.4

-1.5

1.6

g-Load, nn

-2.0

Airspeed, v ~ km/h

-2.5

50

60

70

80

90

100

110

120

130

140

150

cL= nn w / (qs)

“Clean” REGEN

Windprop removed

Regenerative Electric-powered Flight J. Philip Barnes www.HowFliesTheAlbatross.com


Steady-state MOSFETclimb or descent ~ New Formulation, New Insight

Derive steady-climb Equation

f

v

L= nn w

T-D

g

g

w

Note:nn= cosg /cosf *

cL= nn w / (qs)

  • Glider, soaring bird, or "clean" regen

    • T/D=0 (no thrust)

    • Sink rate (-dz/dt) = nn(D/L)v

  • With or without propulsion system

    • Sink increases with g-load (nn)

    • D/L also increases with (nn)

    • Sink increases with airspeed (v)

  • Regen operating mode T/D

  • climb 6.3

  • cruise = 1.0

  • pinwheel glide -0.1

  • efficient regen (thermal) -0.4

  • capacity regen (descent) -1.0

* SAE 2004-01-3088 EQN 5.2, dg/dt = 0

Regenerative Electric-powered Flight J. Philip Barnes www.HowFliesTheAlbatross.com


Regenerative Electric Flight Equation and Implications MOSFET

  • Regen must have

  • Updraft

  • High L/D, Low sink

  • High efficiency

    • Prop & turbine

    • Energy storage

“Clean”

sink rate

Windprop

Effect

Updraft

  • e ≡ “Exchange Ratio,” as applicable:

  • turbine system efficiency ~71%

  • 1 / propeller system efficiency

  • 0 for pinwheeling (no exchange)

“Total

Climb”

“Total Sink”


Thermal updraft contours
Thermal Updraft Contours MOSFET

Elevation, zo ~ m

  • 1oC warmer-air column

  • 20-minute lifetime

  • ~ solar power x 10

U ~ m/s

1

2

3

Total Energy

= Kinetic

+ Potential

4

Total Energy

= Kinetic

+ Potential

+ Stored

Regenerative Electric-powered Flight J. Philip Barnes www.HowFliesTheAlbatross.com


Climb and Regeneration in the Thermal MOSFET(minimum-sink airspeed)

Elevation, m

Elevation, m

Climb rate Contours

Energy rate Contours

Optimum

Elevation, m

Equilibrium Regeneration

Regenerative Electric-powered Flight J. Philip Barnes www.HowFliesTheAlbatross.com


Regenerative Electric Flight Equation Applied for RegenoSoar MOSFET

0.82

0.88

Regenerative Electric-powered Flight J. Philip Barnes www.HowFliesTheAlbatross.com


Presentation Contents MOSFET

  • Regen. elec. flight: Origin & Introduction

  • Dual-role machines:

    • Propeller and wind turbine

    • DC motor-generator

    • Brushless motor-generator

  • Integration:

    • Inverter-rectifier

    • DC boost converter

    • "Chop" Vs. "Boost" architecture

  • “Regenosoar” aircraft concept

  • Summary & Look Ahead


Regenerative Electric-powered Flight MOSFET

  • Windprop: 8 blades spin slow, quiet, & efficient

  • DC & BLDC machines: EMF proportional to RPM

  • M-G & battery verify theoretical efficiency trends

  • Synergy of windprop & MG: Efficiency Vs. RPM

    - Optimum “speed ratios” ~ 85% & 115% by mode

  • Popular "chopper" control: inefficient at cruise

  • DC boost converter: efficient climb, cruise, regen

  • Regen applications:

    • Thermal, ridge, wave, final descent, ....

    • UAV fleet, storm rider, earth observer, ....

  • Give up 2% prop efficiency w/symmetric sections to gain perhaps 5-15% range and/or flying time

VM

M-G

iGBT

A "regen" is coming soon to an airport near you!

Regenerative Electric-powered Flight J. Philip Barnes www.HowFliesTheAlbatross.com


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