With respect to the fact that wattage losses of the synchronous motor winding, not considering the iron losses, are in accordance with the relation

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1 Activity: draw and note the electric drive system of hybrid vehicles, with the voltage boost converter, the draft of the series, parallel and mixed hybrid systems, and the draft of the power transmission of the VOLVO hybrid buses. Note the applied voltage levels, the necessity of the voltage boost converters, the losses of high-speed synchronous machines, possibilities for the extension of the range pertaining to high efficiency, the structure and features of series, parallel and mixed hybrid power transmission systems. a general evolution of hybrid vehicles that have been discussed so far. Activity: study and note the causes of voltage levels to be increased by performances. the enlargement of the range, having good efficiency with gears, having 2, or more stage. Note the increase of the iron-loss in vehicle drive synchronous motors at increasing the rpm. Learn to draw The electric drive system of the hybrid vehicle, the integration of voltage increasing converters Introduction The most frequent synchronous drives with their number above 10 6 are used in hybrid passenger cars. Most of them have tow synchronous machines and the number of hybrid buses of similar type is estimated to be some 5 thousand. It is the French railways that use synchronous motors in railway vehicle drives; they have nearly one thousand of them. 1 Synchronous motor drives in road vehicles Voltage levels to be applied With respect to the fact that wattage losses of the synchronous motor winding, not considering the iron losses, are in accordance with the relation P loss =I 2 R and since reduction of machine size and mass is an important consideration, it is not expedient to apply large copper cross sections required for high currents with low voltage; the value of the voltage must be increased. At a kw power level of electric driven bicycles and scooters 36 and 48 V voltages can be used, however in the range above 30 kw, the battery voltage was increased by the manufacturers to 250 to 280 V.

2 The speed of synchronous machines of high-power hybrid vehicles has been doubled when it was installed into an automatic transmission, in order that the same level of power can be achieved with half the torque, thus, the top operating speed of these electric machines reaches a value of 12 to rpm. However, due to this construction the internal voltage of the machines rose too, so their voltage supply needs doubling as well. The voltage of the battery cannot be used for this due to disadvantages arising from the increasing the number of cells, consequently, buck-boost DC-DC converters had to be installed. All of these details can be followed in figure. In a definite vehicle the power of a synchronous machine functioning basically as a generator is 30 kw. This value is 50 kw in the case of motor synchronous machines. In continuous operation it is possible to take out a further 20 kw from the battery, not exceeding the limits of the storage capacity. Further power to drive a vehicle can be taken out from the internal combustion engine via the power divider and its value is 35 kw higher than the amount of the above mentioned power. Figure 1. The electric drive system of hybrid vehicles and installation of voltage boost converters Inductance is needed for the operation of the converter changing the voltage level The efficiency of the motors with enhanced speed remained still advantageous Figure 2. Changes in the field of the synchronous motor efficiency after speed doubling

3 The high speed and the normal number of poles of 10 to 12 can raise the value of the supplying frequency to 1000 Hz, where reducing iron loss, which is also proportional to the square of the frequency, can only be slightly corrected through decreasing the thickness of the rotor plates. Therefore, as it is shown in figure 3., the iron loss exceeds the value of the copper loss. Figure 3. An increase in the iron loss in synchronous motors driving the vehicle, in line with increasing the speed If the inverter is well dimensioned, its efficiency can be kept on a good value over a wide range. Figure 4. The field of inverter efficiency Using a two-stage transmission broadens the field of the best efficiency, since working ranges of the two stages can be close to each other in that of the motor if the gear ratio in the individual stages are sufficiently close to each other, figure 5.

4 Figure 5. Extension of the range of high efficiency using a two- or multi-stage transmission in the torque-speed figure of the electric motor. Figure 6. Role of the two-stage transmission in extending the range of the high efficiency. The following picture (figure 7.) shows the internal main drive train of an automatic transmission including multi-stage transmission. Figure 7. A high-power hybrid vehicle s rotors for the synchronous generator with double nominal speed and for its motor as well as the ravigneaux planetary gear set functioning as a power divider and the controllable clutches can be seen as parts of the power transmission related to the internal shaft section of the automatic transmission, placed and exhibited externally.

5 While travelling in towns, the vehicles operate the driving electrical machine at lower speeds and, in general, with lower torque (figure 8.); this is in accordance to the fields drawn on the basis of measuring results. Figure 8. Typical rpm-moment ranges for running in town 2. Hybrid systems of power-transmissions Activity: study and note the analytical nd comparative description of serial-, parallel, series-parallel hybrid drive systems. Learn to draw Figure 11., the figure of series-parallel hybrid drive systems the drive system of VOLVO parallel-hybrid autobus, Figure 12. Study and note the evaluation of hybrid drive systems. Hybrid systems for power trains Possible types of power transmission that have been developed so far and influencing both the construction and the operation, are as follows: - series, - parallel, - series-parallel hybrid. Systems, according to the simplified diagrams, are shown in the figures below.

6 2.1 Series hybrid power trai: The mechanical energy from the internal combustion engine is fully converted to electric energy in the generator and then it flows to the electric motor both directly and from the battery such motors are synchronous or asynchronous motors in hybrid buses, and synchronous motors in passenger cars. This is the simplest version; however, since the electric driving motor of the vehicle must develop the output torque towards the vehicle alone, the engine has higher nominal torque, size and mass than the other versions Figure 9.. Figure 9. Series hybrid type power train 2.2 Parallel hybrid power train It has one electrical machine, which functions either as an electric motor or a generator Figure 10. The mechanical energy of the internal combustion engine is only partly converted to electric energy in the generator. In this case energy can flow into the electric motor only from the battery. At the same time, a part of the torque of the internal combustion engine can get to the driven wheels as mechanical energy, getting through the elements of the power transmission chain. Thus, the wheels receive the driving torque from two ways. The electrical machines charges the battery as a generator then driving can be performed only by the internal combustion engine. This is a simple version but it is not able to develop an electrical torque when it charges as a generator since there is only one electric machine.

7 Figure 10. Parallel hybrid drive system. In generator operation the energy flows from the generator to the battery via the DC/DC converter, in this case arrows on the right point upward 2.3 Series-parallel or mixed hybrid power train: Figure 11. Series-parallel mixed hybrid vehicle drive. The power divider permits energy to flow simultaneously from the internal combustion engine to the wheels and via the generator towards the battery. The electric motor on the right side can drive the vehicle wheels without limitation. It is a further modification for the parallel version, in order to benefit from the advantages of both previous versions. It has two electrical machines and depending on the operating state of the drive, either solely the electric motor is used to develop driving torque, usually at start-up, or the drive train is used with the electric motor and the internal combustions engine.

8 A part of the torque of the internal combustion engine goes to the driven wheels as mechanical energy via the elements of the power train. Also in this case the other part goes to the generator via the planetary gear power divider and, from here, either to the battery or directly to the electric motor. From the aspect of power management of the vehicles this is the most complicated version, since a part of all torque, driving the vehicle tyres come from the internal combustion engine and another part of it comes from the electric motor. At the same time a part of the torque of the previous one is used to drive the generator. It is a complex task to establish the desired accordance of the above items. The solution is simplified by the fact that the generator and motor operations of the electrical machines can be adjusted with zero and an admissible maximum torque via their inverters, and these inverters are controlled through a computer and are directed by the vehicle control system. In the case of certain special operating conditions of the vehicle driving, for example, for the limit of wheel slip or for the detection of it, for the regulation of the generator braking torque and for torque controlling in cornering in modern stability control systems, it is necessary to be able to handle both sources of torque. For this it is essential to provide efficient and rapid interventions into the actual operation of the individual electrical machines, which also cover rapid detection, judgement and response, in accordance with modern principles. The power and its torque of the electrical motor may be lower here than in the case of the inline version. The latter hybrid type, also called a mixed version, is obviously more complicated from the aspect of systems engineering but it is the most efficient type too. The following Figure 12. shows a parallel hybrid drive installed into a Volvo hybrid bus, which has another construction according to the drawing but its features are identical with those of the above described drive. When decoupled, the hydraulic clutch can operate from the battery of the vehicle and, when coupled, the torque both of the diesel engine and the electrical machine go through the transmission. This time it is not able to charge since there is only one electrical machine here too. Figure 12. The drive system of VOLVO parallel hybrid buses

9 The bus manufacturer BAE supplies a great number of hybrid buses to overseas and to certain British towns, which are characterised by the following main data, Figure 13.: Figure 13. Double decker hybrid buses with series parallel power transmission, synchronous generator and synchronous motor drive - energy storage system that has 200kW power here too, lithium-ion nanophosphate lithium-ion battery, with a weight of 340 kg; - converter (propulsion control system): continuous power: 320 kw, weight: 75 kg; - traction motor: continuous power: 120 kw, peak power: 175 kw, continuous torque: 650 Nm, max. torque: 900 Nm (the latter value can be delivered for 4 minutes), motor weight: 280 kg, oil-cooled synchronous motor; - generator: continuous power: 145 kw, synchronous machine, weight: 135 kg; - with a power of DM 185 hp, with a displacement of 4.5 litres. Animation of the hybrid drive can be found on: Note the directions of energy-flow in case of the certain hybrid types 3 Brief extracts from studies released on the evaluation of vehicles using hybrid drives: The number of the hybrid passenger cars sold out shows an increasing trend. Their boom depends on the achievable decrease in the fuel consumption, which can reach a value above 30 % in travelling in towns. According to studies on the evaluation of buses with hybrid drives: their economic and energy efficiency is good, the rate of the decrease achieved for the diesel oil consumption is 25 to 30 %,

10 compared to normal diesel buses, the GHG emission decreased by 35 to 40 %, but the rate of NOx emissions increases by some 5 %, the noise level shows a few decibels of decrease at start-ups, when the electric motor takes over a high proportion of torque, which is a positive change for the inhabitants of towns, -systems engineering related properties: these buses demand high standard for the engineering, manufacturing and maintenance, -series hybrid system: it can be constructed using classic electrical machines, even DC types, and it can run with an analogue control system, but this version demands more space and mass, and regarding the installed masses, it has lower energy efficiency than the parallel or mixed hybrid types. parallel or mixed hybrid types: they are more complicated, from mechanical, electrotechnical as well as from IT aspects. There are several units that require computer aided or microprocessor control themselves, with an own diagnostic system. The drive control of the vehicle must be based on computer, which can perform energy management too.