Lecture 1: IntroductionELEC-E8405 Electric Drives (5 ECTS)

Marko Hinkkanen

Aalto UniversitySchool of Electrical Engineering

Autumn 2015

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Learning Outcomes

After this lecture you will be able to:I Explain the basic function of electric drivesI Describe typical applications of electric drives

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Outline

Energy Conversion

Electric Drive

Application Examples

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Electric Energy Is an Energy Carrier

I Examples of energy sourcesNon-renewable: Crude oil, coal, natural gas, natural uranium. . .Renewable: Solar, wind, biomassSecondary: Hydrogen, electric energy

I Secondary energy sources are also referred to as energy carriersI Energy has to be converted to a useful form

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Conversion Efficiency

I Power is the rate at which energy isconverted

P =dEdt

I Power balance

Pin = Pout + Pd

I Conversion efficiency

η =Pout

Pin

is between 0 and 1I In steady state, η = Eout/Ein

Losses Pd

System

UsefuloutputpowerPout

InputpowerPin

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Examples of Energy Conversion

Energy conversion Input Useful output Typicaldevice energy energy efficiency (%)Power plant boiler Chemical Thermal 85Steam turbine Thermal Mechanical 45Electric generator Mechanical Electric 95Incandescent lamp Electric Light 5Electric heater Electric Thermal 100Silicon solar cell Solar Electric 15Battery Chemical Electric 90

I Electric energy can be flexibly and efficiently converted to other formsI Storing electric energy is a problem

Efficiency values: http://www.ems.psu.edu/∼radovic/Chapter4.pdf6 / 20

Outline

Energy Conversion

Electric Drive

Application Examples

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Electric Drive

I Electric drive is a system, whichconverts electric energy intomechanical work

I Direction of the energy flow canalso be opposite

I Energy flow can be controlled bymeans of an electric energyconverter Grid

Frequency converter(electric energy converter)

Electric motor(electromechanical energy converter)

Mechanicalload

ABC

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Energy Consumption of Electric Motors in the EU

78%

22%40%

60%

electric

other

energy use electric energy use

other

electricmotors

I Share of electricity in final energy use is estimated to rise up to 28% by 2050I Electric drives and electric energy converters are important for sustainable

use of energyI Similar technologies are used in grid integration of renewable energy sources

(wind, solar)9 / 20

Outline

Energy Conversion

Electric Drive

Application Examples

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Water Pumps at Google Data Center, Hamina, Finland

Figure: Google11 / 20

Heavy-Duty Industrial Centrifugal Fan

I 1.35-MW 690-V induction motors (most commonly used machine type)

Figure: www.pollrichdlk.com12 / 20

Pump and Fan Drives

I Fluid flow is controlled by adjusting the speed ωM with the frequency converterI If the fluid flow reduces to 50%, load power PL may drop down to ∼30%I Significant energy savings are possible (in comparison with fixed-speed

drives, where the flow is controlled with a valve)

Frequency converter Induction motorGrid

PL

ωM

PL ∝ ω3M

Power PL

ωM

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Wind Turbine

Frequencyconverter

GearboxGenerator

Figure: ABB (modified)14 / 20

Wind Turbine: Permanent-Magnet Synchronous Generator

I Power levels up to 8 MWI Typical gear ratios around 100:1 (but direct drives also exist)I Optimal blade speed (which yields the maximum power) is controlled by the

frequency converter

Frequency converterPMSGGearbox Grid690 V / 20 kV

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Battery Electric Vehicle Powertrain

I Nissan Leaf (2014)I Maximum power 80 kWI Maximum torque 280 NmI Gear ratio 8:1I Li-ion battery pack 24 kWh

PMSM

Inverter

Gearbox

ChargerDC-DC converterJunction box

Figures: Nissan (modified)16 / 20

Battery Electric Vehicle PowertrainI Most common motor types in electric vehicles

I Permanent-magnet synchronous motor (PMSM)I Induction motor (IM)I Permanent-magnet-assisted synchronous reluctance motor (PM-SyRM)

I When braking, the power flows from wheels to the battery packI Electric machines are capable to operate both as a motor and a generator

Inverter PMSMGearboxBattery pack Wheels

Motoring

Generating (braking)

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Goliath Shipyard Crane

I Modern cranes can besemi- or fully-automated

I Constant load torque dueto the gravity

I When lowering the load,the hoist motor operatesas a generator

I How much power isneeded to hoist mass mat speed v?

Figure: Konecranes18 / 20

Why Controlled Electric Drives Are Needed?

1. Enabling fast and accurate motion controlI Robotics, elevators, cranes, process automation. . .

2. Improving energy efficiencyI Process flow is controlled by means of the motor speedI Pumps, fans, compressors. . .

3. Conserving braking energyI Transportation, cranes. . .

Similar technologies are applied in grid integration of renewable energy sources(wind, solar, etc.)

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Multidisciplinary Topic

I MechanicsI ElectromechanicsI Power electronicsI Power systemsI Control engineeringI Signal processingI Industrial internet

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