prototype testing of the electric variable transmission · prototype testing of the electric...

Prototype testing of the ElectricVariable Transmission

Backx, P.W. (Peter)

DCT 2007-135

Traineeship report

Coach(es): Ir. M.A.C. Snoeren, Delft, TNO Automotive

Supervisor: Prof. dr. Ir. M. Steinbuch, Eindhoven, University ofTechnology

Technische Universiteit EindhovenDepartment Mechanical EngineeringDynamics and Control Technology Group

Eindhoven, April, 2008

Summary

The subject of this traineeship is writing a Test Plan for a new transmission concept. The ElectronicVariable Transmission (EVT) is designed to replace the ordinary transmission in a vehicle. Other func-tionalities in a conventional vehicle can be taken over by the EVT as well.

In this report the EVT design and workings will be explained by means of schematic drawings andbasic equations. The EVT is able to replace necessary components in an ordinary vehicle and has theability to drive the vehicle. Therefore a vehicle equipped with the EVT can be characterized as a hybriddriven vehicle. Different types and degrees of hybridization can be distinguished. One chapter wil beused to name the differences between the types and degrees in Hybrid Electrical Vehicles.

A prototype of the EVT is build by TNO in cooperation with Siemens. The prototype will be testedon various functionalities. This report contains a summary of a detailed test plan, which describes thetests performed on the EVT. The complete test plan is not published because it contains confidentialinformation. The main setup of the test plan is a generic document, which can be used for futureother tests as well.

The EVT prototype is modeled in the Matlab tool Advance. The measurements performed on theprototype will be used to estimate the model parameters of the EVT. The model will be validated usingvalidation measurements on the EVT prototype. Using this fine tuned model, simulations can be runwhich give the opportunity to accurately predict how the EVT behaves under different circumstances.

Some efficiency tests have already been simulated with the existing model. The results of the sim-ulations will be described in the last part of this report.

i

List of Symbols and Abbreviations

ωdes desired rotational speed on final drive [rad/s]

ωfi rotational speed of the inner air-gap field [rad/s]

ωm1 rotational speed of the input shaft [rad/s]

ωm2 rotational speed of the output shaft [rad/s]

ωslip slip angular frequency [rad/s]

I Current [A]

p number of pole pairs of the primary machine [-]

Pd electromagnetic part of the input power [kW]

Pe electrical part of the input power [kW]

PFe,i Iron loss in the inner induction machine [kW]

PFe,o Iron loss in the outer induction machine [kW]

Pmech,i mechanical loss in the inner induction machine [kW]

Pmech,o mechanical loss in the outer induction machine [kW]

Pci winding losses [kW]

Pde power loss in the inverters [kW]

Pdr power loss in the rotor [kW]

Pds power loss in the stator [kW]

Per net electrical power from the rotor [kW]

Pes net electrical power to the stator [kW]

Pfo air-gap power from stator to interrotor [kW]

Pm1 mechanical input power [kW]

Pm2 total mechanical output power [kW]

Pmci direct power corrected for winding loss [kW]

Pmco mechanical power on the interrotor [kW]

RDC Windings DC resistance [Ω]

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Tdes desired torque on final drive [Nm]

Tf1 electromagnetic field torque from the rotor [Nm]

Tf2 electromagnetic air-gap torque from the stator [Nm]

Tfo air-gap torque of the stator working on the interrotor [Nm]

Tm1 mechanical input torque [Nm]

Tm2 total mechanical output torque [Nm]

Tmci mechanical rotor torque applied on the interrotor [Nm]

Trs stator torque directly applied to the rotor [Nm]

V Voltage [V]

EVT Electric Variable Transmission

HEV Hybrid Electric Vehicle

ICE Internal Combustion Engine

iv

Table of Contents

Summary i

List of Symbols and Abbreviations iii

Introduction 1

1 The Electrical Variable Transmission 3

1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.2 Basic idea . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.3 Basic idea with losses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2 Hybrid Electric Vehicles 11

2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2.2 Parallel hybrid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

2.3 Serie hybrid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

2.4 Combined hybrid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

2.5 Hybrid configuration using the EVT . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

3 Applications of the EVT 15

3.1 Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

3.2 Hybrid functionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

3.3 Additional functionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

4 Testing 18

4.1 Test document contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

4.2 Test approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

4.3 Measurement setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

4.4 Functionality tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

4.4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

4.4.2 Electromechanical part . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

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Table of Contents

4.4.3 Hybrid functionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

4.4.4 Transmission and efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

4.4.5 Transient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

4.4.6 Vehicle test-rig with ICE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

5 Simulation 26

5.1 Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

5.2 Simulation results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

6 Recommendations 28

Bibliography 29

A Contents of the Test Plan 31

B Advance model 32

vi

Introduction

Hybrid electrical vehicles are subject of research for lots of car manufacturers. They are expectedto produce cars which have lower fuel consumption, fulfill the strict emission requirements or evenbuild zero emission vehicles. The combustion engine of a conventional car rarely works at maximumefficiency. The maximum efficiency for a petrol car is about 30% and for a diesel engine 40% [1]. Inpractice, the effective efficiency for a real drive cycle is much lower. The objective of a hybrid vehicleis to improve the total drive cycle efficiency, in order to bring the fuel consumption down. Less fuelconsumption implies lower emissions. Hybrid Electric Vehicles (HEVs) are an interesting alternativefor conventional vehicles, because they are able to maintain high performance while reducing fuelconsumption and harmful emissions compared to conventional combustion engine vehicles. Evenwith a simple hybrid application as start/stop system a significant reduction in fuel consumption canbe gained.

Martin Hoeijmakers developed a new transmission concept called the Electric Variable Transmis-sion (EVT). A prototype of the EVT is build by Siemens in cooperation with TNO Automotive. Thisprototype will be tested, the tests will be carried out by TNO Automotive, in order to investigate thecapabilities of the EVT. Based on the test results the efficiency and performance of the concept canbe derived. This gains insight into future possibilities for use of the EVT in a hybrid configurationin automotive applications. The test results will also be used to verify the EVT model. A step by stepdescription of the complete test trajectory is presented in a test plan. To be able to describe futureother test in the same way, a generic document is needed. The two main goal of this project can bestated as:

• Writing a generic document in which the EVT tests, as well as future other tests can be described

• Design the experiments to test the functionalities of the EVT

Well knowledge of the workings of the EVT is necessary to define a proper test plan. During thistraineeship this knowledge is gained by reading papers describing the working of induction machines.Talking with people within TNO, as well as reading papers describing the EVT helped a lot in under-standing the working of the prototype. Besides the detailed test plan for testing the EVT, a genericdocument is created. This generic document can be used to describe test plans for future tests for avariety of systems. The contents of the generic test plan, will be presented in this report. A start ismade to describe the EVT prototype tests is this traineeship report. Within the test document, the testsetup is specified and the goal and purpose of the tests will become clear.

Because the EVT transmits high power with high currents as consequence, safety precautions needto be taken during the tests. The precautions are of high importance and need also to be described in

1

Introduction

the test plan.

The first part of this report contains the basic idea in which the working of the EVT will be ex-plained. After the explanation of the basic working different types of hybrid configurations in vehicleswill be given. A well known example of a hybrid driven car is the Toyota Prius. In the second part theapplications of the EVT will be described followed by the test plan for testing the prototype of the EVT.Finally conclusions will be drawn on the obtained results during this traineeship.

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Chapter 1

The Electrical Variable Transmission

1.1 Introduction

In a motor vehicle mechanical energy of a rotating shaft is used to drive the wheels. The torque gener-ated on the outgoing shaft of the vehicle engine is most of the time not equal to the torque demandedon the wheels. A gearbox helps to change the torque by means of creating a speed difference betweenboth shafts. A conventional gearbox has limited number of transmission ratios. The actual ratio de-pends on the size of the gearwheels inside the gearbox.

It is impossible with the limited number of gears of a conventional gearbox to have the combustionengine always operating in an optimal working point. The EVT is mainly designed to operate as anautomatic transmission. Because the power is not transferred mechanically in the EVT, but electro-magnetically like in an induction machine, the wear of the EVT is very low. This makes it maintenancefriendly with a higher reliability. No gearwheels are used in the EVT. This makes it works like a CVTwith continuous variable transmission ratios. Therefore the benefit of the EVT is the ability to keep theoperation of the combustion engine at the optimal operation line during different driving conditions.An example of an combustion engines optimal operation line is shown in Figure 1.1. The EVT is ableto adjust the working point of the combustion engine according to the desired speed and torque of thefinal gear. Theoretically this will result in higher efficiency and lower fuel consumption. Results oftests performed on the EVT will show the practical gain in emission reduction.

1.2 Basic idea

Basically the EVT is formed by an electro mechanic and a power electronic part. In different steps thedesign of the EVT will be explained. A cascade system of two induction machines, connected using apower electronic part, forms the basis of the EVT. On the rotor of the first induction machine electricalpower is generated by a brush slip-ring set. The inverters use the electrical power to drive the secondinduction machine. The basis of the EVT with two separate induction machine is shown in Figure 1.2.

The full input power of the EVT going through the inverters, will result in a relatively low efficiency.The mechanical input power is transformed four times before driving the second induction machine.An efficiency increase can be gained by directly lead a part of the input power from the primaryinduction machine to the secondary induction machine as shown in Figure 1.3. A part of the inputpower is converted to electric power by the brush slip-ring set, which besides the direct power transfer

3

1.2 Basic idea

Figure 1.1: Example of an ICE optimal operation line

Figure 1.2: Cascade setup of the EVT

is used to drive the secondary machine.

Figure 1.3: Basic representation of the EVT

In order to make the EVT more compact, the secondary induction machine is placed concentricallyaround the first induction machine as shown in Figure 1.4. In the course of this report the primaryinduction machine is called the inner machine and the secondary induction machine will be called

4

Chapter 1: The Electrical Variable Transmission

the outer machine. The concentrically build up of the two induction machines makes the EVT smallenough to be practically implementable in a vehicle.

Figure 1.4: Final design of the two concentrically placed induction machines of the EVT

The inner machine consist of two rotating parts, one called the rotor and one called the interrotor(Figure 1.5). The two rotating part makes the inner induction machine an extraordinary inductionmachine. A set of brush slip-rings with a three phase winding is mounted on the rotor. This windingis electrically accessible. On the interrotor a set of shorted windings are mounted. The outer machineconsist of a stator, with electrically accessible windings. The rotor of the outer machine is the outer partof the interrotor. Because this machine has one rotating and one fixed part this works like an ordinaryinduction machine. The interrotor is connected to the outgoing shaft. It is possible to exchange energybetween the slip-ring armature and the stator of the secondary machine by two back-to-back connectedpower electronic inverters. Back-to-back connection means that the DC sides of the inverters are facingeach other [2],[3].

Figure 1.5: EVT components

To make the explanation of the EVT working principle a bit more straightforward, the system will

5

1.2 Basic idea

be assumed to be lossless. In Figure 1.5 the component names as used in the rest of this report aredepicted. As described in [3] the primary shaft is powered following:

Pm1 = Tm1ωm1 (1.1)

Where: Pm1 = input power on the primary shaft [kW]Tm1 = mechanical torque [Nm]ωm1 = rotational speed of the primary shaft [rad/s]

The input power is split into an electromagnetic part and an electrical part. The amount of electricalpower generated by the slip-rings depends on the speed difference between the primary and secondaryshaft equals:

Pe = (ωm1 − ωm2)Tf1 = (ωm1 − ωm2)Tm1 (1.2)

Where: Pe = electrical part of the input power [kW]Tf1 = rotor electromagnetic field torque [Nm]ωm2 = rotational speed of the secondary shaft [rad/s]

The electromagnetic part of the split input power is directly transferred by an electromagneticcoupling between the primary and secondary shaft and can be calculated as:

Pd = ωm2Tf1 = ωm2Tm1 (1.3)

Where: Pd = electromagnetic part of the input [kW]power

Because the system is assumed to be lossless, the power balance looks like:

Pm1 = Pe + Pd (1.4)

The output power consist of the direct electromagnetic torque Pd and electromagnetic air-gaptorque from the stator, which can be calculated using the power balance of the outer induction machineand Equation (1.2):

Tf2 =Pe

ωm2=

ωm1 − ωm2

ωm2Tm1 (1.5)

Where: Tf2 = stator electromagnetic air-gap torque [Nm]

Using Equation (1.5) the total torque on the secondary shaft, which is equal to the sum of theelectromagnetic torque from the rotor and the stator, can be calculated as:

Tm2 = Tf1 + Tf2 =ωm1

ωm2Tm1 (1.6)

Where: Tm2 = total output torque [Nm]

It is desired to keep the engine operation point at the best possible efficiency during all operatingconditions. Theoretically the EVT is capable to achieve this purpose. The inner induction machine ad-justs the desired speed (ωdes) on the secondary shaft to a speed on the engines optimal operation line.The outer induction machine controls the requested torque (Tdes) on the secondary shaft. Thereforethe ICE is allowed to operate in one of the optimal operation conditions as shown in Figure 1.6[1].

6


Figure 1.6: Operation point transfer from a desired torque and speed on the final drive of a vehicle to apoint on the optimal operation line of the combustion engine.

1.3 Basic idea with losses

The EVT will again be considered as a continuously variable transmission in this explanation, but togo into more detail about the working of the EVT the most important losses will be taken into account.In Figure 1.7(a) the schematic of the EVT is shown. In Figure 1.7(b) the torque and power directionsare shown for the transmission mode of the EVT, during forward driving and depict the abbreviationsused in the equations to calculate the losses.

(a) (b)

Figure 1.7: Schematic representation of the EVT (a) and the power flows and torque flows inside theEVT in detail (b)

In the course of this report the quantities which refer to the inner induction machine will beindicated with a subscript i and the quantities referring to the outer machine will be indicated withsubscript o. As described in the previous section the input power Pm1 = ωm1Tm1 is split into anelectromagnetic part:

Pfi = ωfiTm1 (1.7)

7


Where: Pfi = electromagnetic part of the input [kW]power

ωfi = rotational speed of the inner air-gap [rad/s]field

The rotational speed of the inner air-gap field is directly passed to the secondary shaft via theinner squirrel-cage winding (Tm1 = Tfi = Tmci). Due to the resistance in the windings, causing thewindings to heat up, winding losses will occur. The direct transferred power, corrected for the windingloss in the primary machine, to the secondary shaft will be equal to:

Pmci = Pfi − Pci = (ωfi − ωslip,i

p)Tm1

ωslip,i = p(ωfi − ωm2)(1.8)

Where: Pmci = direct power corrected for winding [kW]losses in the inner machine

Pci = winding loss [kW]ωslip,i = slip angular frequency [rad/s]p = number of pole pairs [-]

In Equation (1.8), ωslip,i is defined as the difference between the speed of the rotor and the mag-netic field speed of the inner machine.

In the electrical part of the input power rotor losses will occur, consisting of copper and iron losses.Taking the rotor losses into account, the electrical power generated by the brushes on the primary shaftbecomes:

Per = (ωm1 − ωfiTm1 − Pdr) (1.9)

Where: Per = net electrical power from rotor [kW]Pdr = power loss in the rotor [kW]

The inverters also dissipate some energy. The energy dissipation in the inverters is called theinverter loss. The electric power the inverters supply to the stator will be equal to:

Pes = Per − Pde (1.10)

Where: Pes = net electrical power to stator [kW]Pde = power loss in the inverters [kW]

A small amount of power will get lost in the stator as copper and iron losses. Subtracting thisloss in the stator the remaining power is the air-gap power from the stator to the interrotor, which isdirectly related to the air-gap torque of the stator working on the interrotor:

Pfo = Pes − Pds = ωfoTfo (1.11)

Where: Pfo = air-gap power from stator to interrotor [kW]Pds = power loss in the stator [kW]

8


Tfo = air-gap torque of the stator working [Nm]on the interrotor

This electrical power is converted to mechanical power on the interrotor, where again some poweris lost in the outer squirrel cage winding. The total power on the secondary shaft is simply the sum ofthe mechanical power and the electrical power with subtraction of all mentioned losses:

Pm2 = Pmci + Pmco (1.12)

Where: Pfo = air-gap power from stator to interrotor [kW]Pmco = mechanical power on the interrotor [kW]Pm2 = total mechanical output power [kW]

on the interrotor

Figure 1.8: Resulting direct torque from interrotor yoke saturation

When the height of the interrotor yoke is equivalent to the rotor yoke and stator yoke height, theEVT can be seen as two separate induction machines. However, the interrotor yoke height is reducedto decrease the weight of the EVT and therefore is much smaller than the yoke heights of the rotorand the stator. As a result, the interrotor yoke saturates, causing a magnetic interaction between thetwo induction machines. The EVT starts behaving like one coupled electromagnetic machine witha direct interaction between the rotor and the stator. This magnetic interaction becomes clear whenthe stator current is kept zero, so also no current flows through the squirrel cage windings of thestator. When the rotor current is increased from zero to a certain value large enough to saturate theinterrotor yoke, the resulting rotor flux first will pass the interrotor yoke. When the interrotor yokesaturates, the remaining part of the rotor flux will pass the outer air gap and then the stator yoke.If now a current with opposite direction is applied to the stator, a direct torque from the stator to therotor appears as depicted in Figure 1.8. The direct torque leads to a more or less synchronous machinebehavior between the rotor and stator through the interrotor. Because of the interaction between bothinduction machines the air-gap torque Tfi of the inner machine now consists of two components:

Tfi = Tmci − Trs (1.13)

Where: Tmci = mechanical rotor torque applied on [Nm]the interrotor

Trs = stator torque directly applied to the [Nm]rotor

9


The interaction, shown in Figure 1.8, makes the modeling of the EVT quite complex. The completederivation of the EVT model is described in [3].

10

Chapter 2

Hybrid Electric Vehicles

2.1 Introduction

Hybrid Electric Vehicle (HEV) are defined as:

”Vehicles which combine a conventional propulsion system with an on-board rechargeable energy storagesystem” [4]

The goal of a HEV is to obtain lower fuel consumption and emission levels than a vehicle drivenby a conventional combustion engine. At the same time people do not want to be hampered by therange of battery charging units. Therefore the batteries are charged by an internal source in mostHEVs developed nowadays. In almost all cases a conventional combustion engine is used to chargebatteries, drive a generator or directly drive the wheels. The actual vehicle setup depends on the hybridarchitecture. Different existing architectures are:

• Parallel hybrid

• Series hybrid

• Combined hybrid

In each architecture different degrees of hybridization can be distinguished depending on the size ofthe electrical system:

• Mild hybrid

• Power assist hybrid

• Full hybrid

The most simple hybrid application is called mild hybrid. In this hybrid architecture implementsa start/stop system where the starter of the conventional drive system is replaced by a system able toregenerate brake energy. When the vehicle brakes, the brake energy will be regained and stored in abattery pack. If the vehicle stands still, the engine will be turned off. The stored energy is used to spinup the combustion engine to it’s idle speed. Turning off the engine at vehicles stand-still will result ina significant decrease of fuel consumption and emission.

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2.2 Parallel hybrid

In power assist hybrid vehicles an electrical engine is connected to the conventional vehicle pow-ertrain. This hybrid type has not only the mild hybrid functionality, but also assists the ICE whenhigh power is demanded. When a vehicle accelerates heavily a power boost is required. The electricalengine delivers this extra power to the wheels. Using this hybrid application, a smaller dimensionedcombustion engine is needed to achieve he same performance level. The advantages of using a smallerdimensioned ICE are a lower fuel consumption and more favorable engine operating points. Thepower assist hybrid application therefore results in lower emissions and higher efficiency. The elec-tric engine is powered using a battery system. The battery pack is charged online by the combustionengine.

The last hybrid configuration discussed in this report is called full hybrid and is the most stronghybrid configuration. A full hybrid vehicle can be driven by conventional propulsion, pure electricor in a combination of both ways. The best known example of a fully hybrid car is the Toyota Prius.It can drive pure electric by a electric engine using energy stored in a high capacity battery pack. Inthe Toyota Prius a power split device is present in the form of a planetary gearset, which operatesas the CVT. The controlled planetary gearset adjusts the amount of power from the combustion en-gine and electric motor/generator as demanded on the driven wheels and rechargeable batteries. Thegasoline engine can be used to drive the vehicle or charge the battery pack and shuts off at standstill.All accessoires are powered using electrical power from the batteries in case the engine is not running.

2.2 Parallel hybrid

Parallel hybrid vehicles are the most common type. Both an ICE and an electric engine are connectedto the same mechanical transmission. The electric engine replaces the starter and is used to drive theaccessoires such as power steering and airconditioning which are normally driven by the alternator.The alternator is directly coupled to the engine crankshaft by a rubber belt. Therefore the propulsionspeed of the power steering pump and air conditioning pump depends on the speed of the combustionengine. Using the electric engine to drive these components will result in an efficiency gain becausenow the accessoires can run at constant speed, independent of the ICE rotational speed. The electricpower needed to drive the electric engine is stored in high capacity battery packs, which are chargedby the electric motor in generator mode. Figure 2.1(a) shows the schematic setup of a parallel hybridvehicle. This structure is called parallel, because both the electric motor and the ICE deliver power tothe transmission in parallel.

2.3 Serie hybrid

In a series hybrid vehicle the ICE drives an electrical generator instead of directly driving the wheels.It is the generator which transfers the power to the battery pack. An electric engine is used to drivethe wheels, as can be seen in Figure 2.1(b).The advantage of a series hybrid is the lack of a direct mechanical link between the combustion engineand the wheels. The combustion engine therefore is able to run at a constant and efficient rate, even asthe car changes speed. This advantage makes the serie hybrid the most efficient in a city environmentwhich can make this type of hybrid very useful in for example city busses.A disadvantage is that the power from the ICE runs through both the generator and electrical engine.During long-distance highway driving, where a constant velocity keeps the combustion engine alreadyat constant speed, power losses in the electrical transmission will make this type of hybrid less efficientthan a conventional power train.

12

Chapter 2: Hybrid Electric Vehicles

(a)

(b) (c)

Figure 2.1: Schematic representation of different hybrid architectures: (a) represents a parallel hybridarchitecture, (b) represents a serie hybrid and (c) a combination of parallel and serie hybrid

2.4 Combined hybrid

Combined hybrid systems have features of both series and parallel hybrid drive trains. A power-splitdevice splits the power generated by the engine into two power paths. A mechanical and an electricalpath can be used to drive the wheels. The main principle behind the power-split device is the decou-pling of the power supplied by the engine from the power demanded by the driver.In a conventional vehicle, a larger engine is used to provide acceleration from standstill than oneneeded for steady speed cruising. Reason for this is the minimal torque of the ICE at low rotationalspeed, where high torque is required during acceleration.An electric motor exhibits maximum torque at stall and is well suited to complement the enginestorque deficiency at low rotational speed. In a combined hybrid therefore a smaller, less flexible andmore efficient engine can be used. The application of the combined hybride structure contributessignificantly to the higher overall efficiency of the vehicle. [4]

2.5 Hybrid configuration using the EVT

A combined hybrid configuration is created by implementation of the EVT. The input power is splitinto a electromagnetic and an electric part. Implementation of the EVT allows the combustion engineto work independently from the required load and the electric system does not have to transfer thefull power. In Figure 2.2 the difference between a conventional system and a system with the EVTimplemented is shown. The power electronic part connected to the EVT determines the transmissionratio and the additional power supplied from the energy storage (battery package) to the secondarymachine. This makes hybrid and electrical driving possible. In short can be concluded that the EVTreplaces the transmission, the starter and the alternator of an ordinary vehicle.

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2.5 Hybrid configuration using the EVT

(a) (b)

Figure 2.2: Block scheme of the conventional vehicle setup (a) compared to the configuration with avehicle equipped with the EVT (b)

14

Chapter 3

Applications of the EVT

The EVT is mainly designed as a transmission. Because the continuous variable transmission ra-tios the EVT can generate it is best to describe the EVT as the electrical variant of the ContinuousVariable Transmission (CVT). In fact, the EVT has the advantage it has more than the transmissionfunctionality only. It can be used to replace some vital other components in an ordinary vehicle. Thetransmission application and the other additional functionalities of the EVT will be elucidated in thischapter.

3.1 Transmission

The EVT is build up of two concentric, in each other placed induction machines (Figure 1.4). Together,the two machines are able to convert an applied torque and speed on the primary shaft to a (demanded)torque and speed on the secondary shaft. As long as the power balance is fulfilled the EVT is able todo the conversion as depicted earlier in Figure 1.6. A power splitter splits the input power into twoparts, an electromagnetic and power electronic part. The electromagnetic power directly drives theouter machine, whereas the electric power also drives the outer machine indirectly on the stator side.

The EVT changes a rotational speed on the primary shaft to a lower (or higher in case of an over-drive gear) speed on the secondary shaft. The torque conversion between both shafts is equal to whata conventional gearbox does. By means of two different sized gearwheels the speed of the input shaftof the transmission is changed to an output speed in order to adjust the torque on the driven wheels.In the EVT the outer machine converts the primary shaft torque to a required torque on the secondaryshaft. Because any speed difference of both shafts is possible, the EVT operates as a continuously vari-able transmission. A higher speed difference between both shafts induces a faster rotating magneticfield. The current through the windings increase with the speed of the magnetic field, and causes thetemperature of the copper windings to rise as well. In practice the maximum speed difference is ex-pected to be limited by a maximum winding temperature, because otherwise the heat in the windingsbecomes to high. The design dimensions of the EVT, to which the temperature rise in the windings iscoupled, will determine the practical maximum transmission ratio.

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3.2 Hybrid functionality

3.2 Hybrid functionality

A battery pack can be coupled to the electrical DC port of the EVT. The size of the battery pack deter-mine the possible grade of hybridization. In case enough electrical power is available in the batteries,it is possible to create a full hybrid configuration using the EVT.Even with a small battery attached to the EVT, the EVT can work as a starter for the ICE when it isturned off. In case of heavy acceleration, a battery pack on the DC port of the EVT can add an extrapower boost to the wheels. [5]

As mentioned the EVT can be connected to a battery package on the DC side of the inverters. Thegenerated power by the slip-rings on the primary shaft can be used to charge the battery package in-stead of powering the secondary induction machine. The energy stored in the batteries can be usedto support the ICE during driving, by adding power to the stator windings. This electrical power willbe supplied to the stator of the secondary induction machine. Because the electrical power is suppliedparallel to the mechanical power generated by the ICE, this drive mode can be regarded as a parallelhybrid drive mode.

The mechanical brake energy can be regained via the stator of the outer machine, which transformsthe mechanical energy into electrical energy. The outer machine works as a generator is this case andthe electrical energy can be stored in the battery package. In the Figures 3.1(a)-(d) the different hybridand electrical operation modes of the EVT are depicted [6].

3.3 Additional functionality

Due to wear of the starter, the number of start actions is limited. The limited starter actions are thereason why city busses cannot turn their engines off each time they stop at bus stops. Switching ofthe engine would result in a considerably reduction of fuel consumption. Another disadvantage of theconventional mechanical and electrical system is the low efficiency of the belt driven generator. Usingthe starter functionality of the EVT makes it possible to equip busses with a start stop system to reducethe fuel consumption, without the concern of the wear of an ordinary starter.

The generator which feeds the battery in a conventional setup had very low efficiency. Replacingthe alternator by the EVT operating in generator mode, will result in an efficiency gain. Also ac-cessoires normally driven directly by the belt in the conventional setup, such as power steering andairconditioning, can be driven electrically with significantly higher efficiency. The higher efficiencyis achieved because the power steering pump runs on constant power in case it is driven using theEVT. In case the pump is driven by the belt driven generator, which is generally coupled to the enginecrankshaft, the power supply depends on the ICE speed.

16

Chapter 3: Applications of the EVT

(a) (b)

(c) (d)

Figure 3.1: Pure electric driving (a), the EVT used as a generator for regenerative braking (b), hybriddriving (c) and hybrid driving during heavy acceleration (power boost) (d)

17

Chapter 4

Testing

In order to carry out the tests on the EVT and future other tests as well, a document is created in whichthe complete test trajectory is described. This enables the tests to be done in structured efficient wayand gives a clear overview of the complete test trajectory. Within TNO no such document was present.All previous tests where described in different documents, which sometimes made it unclear for theoperators. A generic document based on the tests to be performed on the EVT is drawn up, but isdesigned in such way it can be used for other future tests as well. In this chapter the contents of thegeneric document will be evaluated and the desired experiments to test the functionalities of the EVTwill be explained. Due to confidential reasons no detailed equations and schemes of the EVT will begiven in this report.

4.1 Test document contents

The test document starts with a detailed description of the measurement setup, in which all compo-nents and measurement devices of the test bench are described. The measurement setup is drawnschematically in a block scheme in which the wiring scheme and connections between the compo-nents are included.

Safety is an important aspect of each test trajectory. Therefor a chapter containing all safety mea-sures is drawn. In this chapter describes which safety precautions need to be taken on beforehandand what actions need to be taken in case of any kind of failure during a test. A list of people allowedto enter the test cell in case anything fails during one of the tests is presented.

The next part of the generic document is a step by step checklist, which will help the operator toperform the desired tests in the right way. It describes the important steps to be taken before, andduring each test. The checklist contains a summary of the wiring scheme of the test setup, sensors tobe connected, input settings for each test and the signals to be measured. After running through thechecklist, the tests are ready to start.

The test program is the part where all tests to be done are described. A clear description andthe goal of each test are drawn. The test program makes clear why the tests are done and how themeasurement results will be processed to come to logical conclusions about the functionalities. Inthe section preconditions is described what the initial condition of the test setup are. In case of thefunctionality tests the input for both electrical engines to drive the EVT are described in Excel tables.In the section post conditions will be evaluated what the expected outcome of the test will be. This

18

Chapter 4: Testing

can be used by the operator to compare the outcome of the test with the expectations. This gives anindication of the reliability of the test.

The last part of the document is a chapter logging. This chapter contains Excel sheets in which themeasurement results can be saved. The sheets contain the equations which process the measurementdata and immediately shown the test results in graphical charts. This makes it easy for the operatorsto interpret the measurement data.

In this traineeship a start is made to fill the generic document for the prototype testing of the EVT.In Appendix A the contents of the complete test plan based on the EVT tests are shown.

4.2 Test approach

Inside the power electronics, controllers are implemented to control the power split on the primaryshaft of the EVT. This control is implemented by Siemens and will be checked for stability before fur-ther tests will be done. It is desired to guarantee this stability first, before testing the functionalities ofthe EVT. The response of the secondary shaft of the EVT on a low power step input will be measured.The step response will show the stability of the power electronic controllers.

After the power electronic controller stability is checked, the electromagnetic part of the EVT willbe tested. The power electronic part therefor will be decoupled from the EVT. This decoupled first testsare used to determine mechanical losses in the electromagnetic part. With rotor-block measurementsinformation of the mechanical power losses and efficiency in different components of the EVT will beobtained.

Three phase AC no-load test are performed, with uncoupled power electronics, to obtain parame-ter estimators of the electromagnetic part. A model of the EVT already is available. The data measuredfrom the no-load test can be used to fit this existing EVT model.

After the electromagnetic measurements, the power electronics are coupled to the EVT. The func-tionalities of the EVT will be examined with these tests. Most important is to check whether the EVTis able to operate as transmission. The power electronics operate as power split device, which deter-mine the power directly transferred to the secondary shaft and the power flow through the invertersto the stator of the secondary machine. The desired transmission ratio determines the power-splitratio of the input power. During these tests also the total efficiency becomes clear and the results willbe used for the evaluations of the EVT concept. Using the efficiency at a range of speed, torque andtransmission ratios, a three dimensional efficiency map will be created. The efficiency map visualizesthe optimal working points of the EVT, for a range of input working points and load conditions. Basedon the results conclusions can be drawn on the suitability of the EVT as an alternative for the conven-tional gearbox or continuous variable transmission in low duty and heavy duty vehicles.

4.3 Measurement setup

The EVT tests are performed in one of the test cells at TNO Automotive Delft and later on at TNOAutomotive Helmond. In the used test stand a dynamic generator/brake is available which will applythe desired load torque on the secondary shaft of the EVT. For the first tests in Delft, the primary shaftis driven using a Siemens four quadrant electrical machine, where in Helmond the primary shaft will

19

4.3 Measurement setup

be driven using an ICE (a Diesel Injection or gasoline engine) to simulate real vehicle implementationof the EVT.

(a) (b)

Figure 4.1: Possible test bench configurations: the EVT powered by the Digatron (a) and the EVTpowered by a battery box (b)

As can be seen in Figures 4.1 (a) and (b), the generators/brakes will be controlled using imple-mented software in MACS. The MACS is a device, developed at TNO in which Matlab/Simulink modelscan be downloaded. It sends signals to the generator/brakes and controls the desired input and outputof the EVT. Also vehicle models will be implemented in MACS, to test the EVT with simulated vehicledata. Interruption procedures in case maximum values are exceeded are programmed in the MACS aswell, to introduce build in safety measures.

The Digatron is a battery box in which current and voltage can be limited and controlled. TheDigatron is connected to the electrical port of the EVT and operates as a buffer for unexpected highcurrent overflows trough the EVT. If the current in the windings becomes too high due to large speeddifference of both shafts, the Digatron will interrupt the measurement.

The data used to calculated the efficiency and parameters to fit the model are obtained using atorque and speed sensor on both the primary and secondary shaft. Also the DC and AC powers aremeasured on both sides of the inverters. The measurement data will be logged using STARS, whichcommunicates between the sensors and PC using CAN communication. Excel sheet are used to pro-cess the measurement data and create plots of the obtained test results. Different test bench setupsare considered as shown in Figures 4.1(a) and 4.1(b), which differ on some minor details.

Both setups have advantages and disadvantages, which are evaluated in Table 4.1. Based on the(dis)advantages Configuration 4.1(a) is chosen as measurement setup for the EVT functionality tests.

20

Chapter 4: Testing

Table 4.1: (Dis)advantages of different test bench setups (the abbreviation SOC stands for the State ofCharge of a battery)

Advantage DisadvantageConfiguration 1 EVT current limit controlled by Digatron Battery discharges

EVT voltage controllable by DigatronConfiguration 2 Battery as physical buffer for EVT No adjustable current limit

No battery SOC control

4.4 Functionality tests

4.4.1 Introduction

The EVT operates on a DC voltage of UDC = 288 V. Both induction machines in the EVT have p = 4pole pairs. The specifications of the EVT prototype are given in Table 4.2. Eventually, the tests on theEVT must show whether the performance of the EVT meets the design specifications and whether theEVT handles the functionalities it is designed for.

Table 4.2: Design specifications of the EVT prototypeEVT input EVT output

rotational speed ω [rpm] 6000 6000continue power [kW] 57 57peak power [kW] 87torque [Nm] 115 350peak torque [Nm] 610

The sequence of testing is not necessarily the same as mentioned in this report. In Figure 4.2 aflowchart is shown in which the possible sequence of testing is shown.

Figure 4.2: Flowchart of different possible test sequences

21


4.4.2 Electromechanical part

The measurements described in this subsection are performed with uncoupled power electronics.Only torque and speed on both shafts and three-phase voltage on the electrical port of both machinesneed to be measured.

Mechanical losses

First the mechanical losses in the inner machine are determined. Therefore the interrotor is blockedby a zero speed setpoint on the secondary shaft implemented in MACS. On the primary shaft the power(P1) is measured using torque and speed sensors, where on the slip-rings the power (Protor) is mea-sured using an AC power meter. The difference between the measured power is the sum of themechanical and iron loss in the inner machine as indicated by Equation (4.1). With varying speedinputs on the primary shaft, the losses are determined as a function of speed.

Pmech,i + PFe,i = P1 − Protor (4.1)

Where: Pmech,i = mechanical loss in the inner machine [kW]PFe,i = Iron loss in the inner machine [kW]

The mechanical and iron losses in the outer machine are determined in a similar way, accordingto Equation (4.2). Now the outer machine is driven and the rotor (primary shaft) is blocked using azero speed setpoint. Both P1 and Pstator are measured. The difference between both measured signalsrepresent the mechanical and iron losses in the outer machine:

Pmech,o + PFe,o = P2 − Pstator (4.2)

Where: Pmech,i = mechanical loss in the inner machine [kW]PFe,o = Iron loss in the outer machine [kW]

DC resistance

The resistances of both the rotor and stator windings are determined using this experiment. On one ofthe three-phase windings of both the rotor and interrotor a DC voltage is supplied using the Digatron.This will result in an electric torque on respectively the stator and rotor. The applied voltage andcurrent over the windings is measured. Using Equation (4.3) the resistance of both the stator androtor can be calculated:

RDC =V

3I(4.3)

Where: RDC = Windings DC resistance [Ω]V = Applied DC voltage [V]I = Measured current [A]

22

Chapter 4: Testing

Parameter estimation

To improve the existing model of the EVT, some test will be performed to obtain a data set on whichthe model parameters can be estimated. More accurate model parameters lead automatically to a morereliable model. If an accurate model is obtained, it can be used to do simulations on the behavior ofthe EVT under different circumstances.

It is possible to use different identification techniques to obtain proper data sets for a satisfyingsystem identification. Step inputs and noise measurements result in data sets for both low and highfrequent system behavior. Free-run experiments will give insight in nominal system conditions. Theparameters of the dynamic equations can be determined using optimization routines. Due to confi-dential reasons, the describing equations of the EVT may not be mentioned in this report. Matlab hasa number of optimization routines, such as fmincon and lsqnonlin. No system identification hasbeen performed on the EVT, so it is recommended to do to fit and validate the model.

4.4.3 Hybrid functionality

Using this tests, the hybrid functionalities of the EVT will be investigated. These experiments willprove whether the EVT is capable to operate in all four quadrants and can be used in a HEV setupas a replacement of the electric machine in most common HEVs. Also the capability of the EVT tooperate as a starter for the ICE will be tested here. By applying alternating positive and negative loadson the output shaft, as shown in Table 4.3 and Figure 4.3, all steady-state operating conditions areinvestigated. In this table a ”+” sign indicates a positive input, a ”−” sign indicates a negative inputand a ”0” means no input.

Table 4.3: The steady-state electrical and hybrid drive modes of the EVT which will be investigated totest the functionalities.

Mode P1 P2 Protor Pstator

Electric drive 0 + 0 +Electric regenerative brake 0 − 0 −Hybrid drive + + + −Hybrid, battery charge + + − −Hybrid, high power demand + + + −

Also dynamical tests will be performed with an ICE coupled to the input shaft of the EVT. Thisneeds of the dynamical tests will be explained later on in this report.

4.4.4 Transmission and efficiency

As mentioned earlier, the EVT is mainly designed as a transmission with continuous transmissionratios like a CVT. By varying the power split ratio the transmission ratio can be changed. The changeof transmission ratio makes it possible to accelerate the vehicle. The ratio change speed, together withthe dimensions of the driving engine determine the maximum acceleration of the vehicle. The mini-mum ratio determines the top speed of the vehicle. Therefore the ratio change speed of the EVT mustbe determined as well as the minimum and maximum transmission ratio.

On the primary shaft of the EVT a torque will be applied by the Siemens EM. By a user definedinput power on the primary shaft, also the rotational speed of this shaft is fixed:

23


Figure 4.3: Visualization of the power directions according to the electric and hybrid modes given inTable 4.3

ω1 =P1

T1(4.4)

No battery is attached to the EVT, so only transmission functionality of the EVT is used during thistest. Because no battery is coupled to the electrical port of the EVT to deliver or store the input powerand for simplicity the EVT is assumed to be lossless, the power balance becomes:

P1 = P2 = P (4.5)

Where: P1 = Applied power on the primary shaft [kW]P2 = Power on the secondary shaft [kW]

On the output shaft the speed is prescribed. Because the power on the output shaft is known, theoutput torque of the EVT can be calculated:

T2 =P2

ω2(4.6)

Where: T2 = EVT output torque [Nm]ω2 = Prescribed speed on the output shaft [rad/s]

The gear change speed will be increased in order to investigate the maximum gear change speed ofthe EVT. In order to test the EVT as CVT, for each torque/speed input on the primary shaft a smoothlyvarying output speed must be prescribed. These tests are used to determine what the maximum andminimum transmission ratio is which the EVT can produces, which is expected to have a wide rangecompared to an ordinary gearbox.

For each operating condition, defined by the power supply on the input shaft and the torque onthe output shaft, the efficiency of the EVT is calculated. Combining the transmission test with thecorresponding overall efficiency will result in a three dimensional efficiency plot for all possible trans-mission ratios.

Also the efficiency of different components of the EVT will be investigated. This will show whichpart of the EVT is responsible for the biggest energy losses and thus are the first parts of the EVT tobe improved to reach better overall efficiency of the EVT.

24

Chapter 4: Testing

4.4.5 Transient

The transient tests are used to investigate the dynamic behavior of the EVT. The engine start/stopfunction of the EVT as well as the switching between steady-state operating points, accelerating anddecelerating, will be investigated. The dynamic test must prove the profitability of replacing an ordi-nary gearbox with the EVT. An improvement in efficiency compared to a conventional gearbox, willresult in lower fuel consumption and emissions. In this test accelerations are alternated with deceler-ations and constant speed intervals. A drive cycle is such a transient input to test the desired behavior.

The dynamic test will be used to identify how the EVT behaves as a transmission when a completetest cycle is simulated. A drive cycle in terms of torque an rotational speed is used as input to theprimary shaft of the EVT. On the secondary shaft, the load a vehicle experiences during the cycle isprescribed in terms of rotational speed. The input power and output power are logged during the testto be able to calculate the efficiency and performance over the EVT during the dynamic tests.

4.4.6 Vehicle test-rig with ICE

In this tests, the Siemens EM electric machine is replaced by an ICE. The load on the secondary shaftis still provided by the electrical brake of P2. One of the problems of replacing the electric engine witha combustion engine to drive the input shaft of the EVT are the vibrations of ICE. Another problemdriving the EVT with an ICE is the rippled torque output of the ICE. The torque output of an electricengine is nice and smooth, where the output torque of the ICE shows rough variations. Because ofthese rough input variations, the stability of the EVT power electronic controllers with ICE drive mustbe checked again. Therefore small input torque and speed must be used as input to see how the EVTbehaves on the input provided by the ICE. The EVT controllers must be quick enough to transducethe rapidly varying input torque to a smooth constant output to get the desired comfort.

This test simulates the EVT actually implemented in an ICE driven vehicle. The EVT will be testedas transmission and as parallel hybrid engine next to the ICE. Also will be tested whether the EVT isable to operate as a starter for the ICE. This results of this test are used to do efficiency calculations. Itwill prove whether use of the EVT either as replacement of an ordinary transmission or in hybrid orpure electric mode will result in lower fuel consumption and therefore in lower emissions.

25

Chapter 5

Simulation

5.1 Model

TNO automotive has developed an own modeling tool in Matlab called Advance. This tool is used tomake a model of the EVT. On the input shaft an electro motor is used to drive the EVT. This motor iscontrolled using a PID speed controller. The secondary shaft is connected to a second electro motor.The motor on the secondary shaft is PID torque controlled. The choice of torque or speed control isbased on the power demand in a conventional ICE driven vehicle. The position of the throttle pedaldetermines the rotational speed of the engine. Depending on the gear a certain speed and torque aretransferred to the secondary shaft. On the secondary shaft, mainly depending on the friction and dragforces, a load torque has to be overcome. With the torque controlled motor/brake on the secondaryshaft of the EVT, different driving circumstances can be simulated. In Appendix B the model used forthe simulations is depicted.

5.2 Simulation results

Figure 5.1: Efficiency map from simulation data

26

Chapter 5: Simulation

The efficiency of the EVT is calculated according to Equation (5.1):

η =(

1− Ploss

P1

)· 100%

P1 = T1 ·ω1

Ploss = P1 − P2

(5.1)

The standard electric engine in Advance is used. This engine is implemented such that maximumpower is delivered to the primary shaft of the EVT, which is not desired. An extra input variable canbe implemented in the EVT model, in which a desired input torque can be prescribed. Therefore theEVT model needs to be remodeled.

A few simulations have been performed in order to determine the efficiency of the EVT using themodel. For a range of input speed and input torque the overall efficiency of the EVT is calculatedaccording to Equation (5.1). The results of this simulation are shown in Figure 5.1.

In this simulation the desired input torque on the input shaft of the EVT cannot be prescribed.Therefore always maximum input power is applied to the input shaft. The simulation results thereforeshow lower efficiency than can actually can be expected.

27

Chapter 6

Recommendations

A few recommendations for further research can be stated. For simulation purposes the EVT modelhas to be extended with an extra variable for the desired input power. Therefore the Advance model ofthe EVT has to be redesigned.

To create a more accurate model the model parameters need to be estimated. This can be done us-ing identification techniques on the EVT prototype. By performing a free run experiment, step inputexperiment and an experiment with noise injection the EVT system can be identified. This identi-fication can be used to determine the parameters of the dynamic equations which describe the EVTbehavior.

The obtained model needs to be validated using the measurement results from the tests. Thismodel validation is something that has to be done in the future as well. A proper data set must bemeasured on the EVT prototype, with the correct input signals. A black-box model can be calculatedfrom the identification data, which can be used to fit and validate the Advance model.

28

Bibliography

[1] E. Nordlund and S. Eriksson, “Test and verification of a four-quadrant transducer for HEV applica-tions,” September 2005.

[2] Y. Cheng, S. Cui, L. Song, and C. Chan, “The study of the operation modes and control strategiesof an advanced electromechanical converter for automobiles,” Transactions on Magnetics, vol. 43,pp. 430 – 433, January 2007.

[3] M. J. Hoeijmakers and J. A. Ferreira, “The electrical variable transmission,” Industry ApplicationsConference, 2004. 39th IAS Annual Meeting. Conference Record of the 2004 IEEE, vol. 4, pp. 2770 –2777, October 2004.

[4] http://en.wikipedia.org/wiki/hybrid_vehicle_drivetrain. Hybrid Vehicle Drivetrain on Wikipedia.

[5] R. Kruse, S. Mourad, D. Foster, and M. Hoeijmakers, “Concept and functionalities of the electricvariable transmission,” vol. 15, (Aachen), pp. 1387 – 1398, October 2006.

[6] S. Châtelet, “Efficiency measuring system for hybrid electric vehicle energy transducers.” Divisionof Electrical Machines and Power Electronics, Royal Institute of Technology, 2004.

Bibliography

30

Appendix A

Contents of the Test Plan

1 INTRODUCTION2 TEST BENCH SET-UP

2.1 INTRODUCTION2.2 BLOCKSCHEME2.3 COMPONENTS2.4 MEASUREMENTS2.5 CALIBRATION MEASUREMENTS DEVICES2.6 DETAILED SET-UP2.7 SECURITY ISSUES

3 CHECKLIST3.1 INTRODUCTION3.2 CONNECTION3.3 MEASUREMENT DEVICES3.4 FIRST TEST

4 TEST PROGRAM4.1 INTRODUCTION4.2 PRE TESTING4.3 STABILITY OF POWER ELECTRONIC CONTROLLERS4.4 LOSSES

4.4.1 No-load: mechanical and iron losses4.4.2 Rotor-block: winding losses

4.5 STANDARD HYBRID FUNCTIONALITY TEST4.6 TRANSMISSION AND EFFICIENCY TEST

4.6.1 Overall efficiency4.6.2 Inverter loss4.6.3 Transmission ratio4.6.4 Ratio change speed

4.7 PERFORMANCE TEST4.7.1 Efficiency map4.7.2 Maximum (peak) power

4.8 TRANSIENT TEST4.10 VEHICLE TEST-RIG WITH ICE CONNECTED4.11 HYBRID FUNCTIONALITIES WITH ICE CONNECTED

31

Appendix B

Advance model

Figure B.1: Advance model of the EVT drive

32

Chapter B: Advance model

Figure B.2: Advance model of the EVT powertrain

33

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