performance & efficiency aspects of electric vehicles

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Performance & efficiency aspects of Electric Vehicles

Webinar 3

Dr Andrew Halfpenny

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Agenda

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Battery Performance & Efficiency

DC Battery

Wh

ole V

ehicle Inverter

Motor

Transmission

DC AC Mechanical KineticEff Eff Eff

Energy conversion & efficiency losses

Inverter outputNon-sinusoidalMulti-phaseTransient

Active, Reactive and Apparent PowerHalf-cycle resolution

Inverter switching resolution

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HBM eDrive for electric power testing

Power Source

Inverter

Electric Machine

Measurement

PC All signals recorded 2 MS/s per channel

Accuracy 0.015% +0.02%

• And Auto Range

Data collection of all electro-mechanical signals

Transient power measurements

Feedback to control systems

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Power analysis in nCode GlyphWorks

• Battery DC

• Inverter DC-AC• Motor AC

• Transmission

• Vehicle

DC

Bat

tery

Whole VehicleIn

vert

er

Mo

tor

Tran

smis

sio

n



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Efficiency of an Electric Vehicle



DC power ☺𝑃 = 𝐼𝑉

Mech power ☺𝑃 = 𝑇𝑤

Kinetic power ☺GPS Glyph

Inertial resistance 𝐹𝐼 = 𝑚𝑎 Gradient resistance 𝐹𝛼 = 𝑚𝑔 sin(𝛼) Aerodynamic resistance 𝐹𝐿 =

1

2𝜌𝐶𝑑𝐴𝑠𝑣

2

Rolling resistance 𝐹𝑅 = 𝑚𝑔𝐶𝑟𝑟

Conventional AC Power Grid Waveform: 3-phase sinusoidal

Apparent – total power provided by source Active – useful power consumed by resistive load Reactive – useless power resulting from phase

differences between voltage and current;not consumed but negates power on the grid

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Active power

Reactive power

Apparent power

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Conventional AC Power Grid Waveform: 3-phase sinusoidal

Apparent – total power provided by source Active – useful power consumed by resistive load Reactive – useless power resulting from phase differences between voltage

and current; not consumed but negates power on the grid

EV Digital Power Inverter Waveform: Multi-phase, non-sinusoidal, varying amplitude & frequency

Apparent – total power provided to the motor Active – consumed to drive the vehicle Reactive – not consumed but causes efficiency losses




DC power ☺𝑃 = 𝐼𝑉

Mech power ☺𝑃 = 𝑇𝑤

Kinetic power ☺GPS Glyph

Inertial resistance 𝐹𝐼 = 𝑚𝑎 Gradient resistance 𝐹𝛼 = 𝑚𝑔 sin(𝛼) Aerodynamic resistance 𝐹𝐿 =

1

2𝜌𝐶𝑑𝐴𝑠𝑣

2

Rolling resistance 𝐹𝑅 = 𝑚𝑔𝐶𝑟𝑟

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EV Inverter output

Spectralgap

Fundamentalfrequency

Switchingharmonics

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Power analysis of the fundamental frequency Active, Reactive, Apparent power

Pure Sine Definition of Power Factors

Time (s)

Active power P = mean(𝑢 × 𝑖)

Apparent power S = rms 𝑢 × rms(𝑖)

Reactive power Q = 𝑆2 − 𝑃2

Power factor 𝜙 =𝑃

𝑆

These calculations become more complicated with

broadband AC current and voltage

nCode’s new Power Analysis glyph has this covered!

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Power analysis of the fundamental frequency

Pure Sine Definition of Power Factors Broadband Definition of Power Factors

Time (s) Time (s)

Active, Reactive, Apparent power

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Power analysis of the inverter switching

Time (s) Time (s)

Vo

ltag

e (V

)

Vo

ltag

e (V

)

Active, Reactive, Apparent power

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DC Battery

Wh

ole V

ehicle Inverter

Motor

Transmission






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Kinetic energy

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Deformation of the tire and road surface

Aerodynamic drag Gradient resistance Inertial resistance

Bosch Automotive Handbook Density of air ρ ~ 1.25kg.m-3

Cd for my car 0.32Frontal exposed area As

~1.9m2

v = velocity in m.s-1

Vehicle mass m = 1900kgg = 9.81α = incline angle in radians

Vehicle mass m = 1900kga = acceleration in m.s-2

𝛼 = 𝑡𝑎𝑛−1𝑑𝑎𝑙𝑡𝑑𝑡

𝑣

Total tractive force N = Rolling resistance + Air resistance + Gradient resistance + Inertial resistance

Total tractive power = Total tractive force * v𝛼

GPS logging at 1Hz

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GPS log

Real-world battery usage and target customer analysis

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Overall trip statistics• Trip date, start & end time• Trip duration & distance

• Average & maximum speed• Idle time• Number of stop-start cycles• Average stop duration• Average running duration

• Distance on city roads• Distance on urban roads• Distance on highway

• Average traction power• Average braking power• Energy consumed• Efficiency

• Cornering acceleration• Steering angle

Time at level histograms• time or distance vs. road speed• time vs. acceleration or braking• time vs. traction power• time vs. braking power• time vs. cornering acceleration• time vs. steering angle• distance vs. gradient angle• etc…

CAN log

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DC Battery

Wh

ole V

ehicle Inverter

Motor

Transmission






June 29th

In this webinar we consider:•Electric motor efficiency and loss mapping•Power measurement and analysis of digital inverters and

electric motors•Real-world battery usage and target customer analysis

Benefits include:•Better vehicle range•Better accuracy•Better understanding of real customer usage

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performance & efficiency aspects of electric vehicles

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