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Power Electronics And Electric Drives For Tract...

Motor controllers from MAHLE are intended for the operation of brushed and brushless DC motors in various automotive applications. From control units for air conditioning blowers, controllers for electric pumps to control units for power train cooling fan motors, MAHLE can offer the right solution. The controllers are characterized by their compact and lightweight dimensions, cost efficiency and their customer-specific design. Regardless of whether as a PWM or linear controller, whether communication protocols need to be integrated or additional functions such as over-temperature, over-voltage, or reverse polarity protection are required, MAHLE offers the best suitable possible solution for the specific customer requirements.

Power electronics and electric drives for tract...


Today, exhaust aftertreatment systems are an important component of the overall engine system for further reducing pollutant emissions. In order to achieve the operating temperatures required for cleaning diesel particulate filters even in short-distance operation, MAHLE develops control units that take over the temperature management of the system. This is done, for example, by briefly increasing the engine power in idle mode, so that more hot exhaust gases reach the filter, inject chemical substances to promote particle combustion, or increase the temperature in the exhaust tract through fuel injection or electric heaters in the exhaust tract. In addition to the electrical controls, MAHLE also supplies the sensor elements required for particle filter management.

In this paper, a novel dv/dt filter is presented targeted for 100-kW to 1-MW voltage source converters using silicon carbide (SiC) power devices. This concept uses the stray inductance between the power device and the converter output as a filter component in combination with an additional small RC-link. Hence, a lossy, bulky, and costly filter inductor is avoided and the resulting output dv/dt is limited to 5-10 kV/mu s independent of the output current and switching speed of the SiC devices. As a consequence, loads with dv/dt constraints, e.g., motor drives can be fed from SiC devices enabling full utilization of their high switching speed. Moreover, a filter-model is proposed for the selection of filter component values for a certain dv/dt requirement. Finally, results are shown using a 300-A 1700-V SiC metal-oxide-semiconductor field-effect transistor (MOSFET). These results show that the converter output dv/dt can be limited to 7.5 kV/mu s even though values up to 47 kV/mu s weremeasured across the SiC MOSFET module. Hence, the total switching losses, including the filter losses, are verified to be three times lower compared to when the MOSFET dv/dt was slowed down by adjusting the gate driver.

These devices are usually powered by small batteries, but conventional batteries self-discharge over time and pose a possible safety risk. To overcome those disadvantages, Langer and Traverso worked with Nadeau and Chandrakasan, who specialize in developing low-power electronics.

Electric motors are a common means of powering a train, whether the energy required is carried on-board the train in the form of a diesel engine and its fuel or obtained from outside the train by connection with an external power supply carried by an overhead line or third rail. Electric traction is widely used around the world, particularly for routes with dense traffic, like urban and suburban railways or long distance, high speed lines that need electric traction to obtain the speeds required for inter-city travel. There are a number of different systems of electric traction and these are described here.

Historically, the DC motor was the mainstay of electric traction drives on both electric and diesel-electric rolling stock. Many examples are still in use around the world. The motor consists of two parts, a rotating armature and a fixed field (Figure 1). The fixed field consists of tightly wound coils of wire fitted inside the motor case. The armature is another set of coils wound round a central shaft. It is connected to the field through "brushes" which are spring loaded contacts pressing against an extension of the armature called the commutator. The commutator collects all the terminations of the armature coils and distributes them in a circular pattern to allow the correct sequence of current flow.

Thyristor control can create a lot of electrical interference - with all that chopping, it's bound to. The "line filter" comprises a capacitor and an inductor and, as its name suggests, it is used to prevent interference from the train's power circuit getting into the supply system.

Modern electronics has given us the AC drive. It has only become available with modern electronics because the speed of a 3-phase AC motor is determined by the frequency of its supply but, at the same time, the power has to be varied. The frequency used to be difficult to control and that is why, until the advent of modern electronics, AC motors were almost exclusively used in constant speed applications and were therefore unsuitable for railway operation. A modern railway 3-phase traction motor is controlled by feeding in three AC currents which interact to cause the machine to turn. The three phases are most easily provided by an inverter which supplies the three variable voltage, variable frequency (VVVF) motor inputs. The variations of the voltage and frequency are controlled electronically.

Having got AC drive using GTO thyristors universally accepted (well, almost) as the modern traction system to have, power electronics engineers then produced a new development. This is the IGBT or Insulated Gate Bipolar Transistor. The transistor was the forerunner of modern electronics, (remember transistor radios?) and it could be turned on or off like a thyristor but it doesn't need the high currents of the thyristor turn off. However it was, until very recently, only capable of handling very small currents measured in thousandths of amps. Now, the modern device, in the form of the IGBT, can handle thousands of amps and it has appeared in traction applications. A lower current version was first used instead of thyristors in auxiliary supply inverters in the early 1990s but a higher rated version has now entered service in the most recent AC traction drives. Its principle benefit is that it can switch a lot faster (three to four times faster) than GTOs. This reduces the current required and therefore the heat generated, giving smaller and lighter units. The faster switching also reduces the complex "gearing" of GTOs and makes for a much smoother and more even sounding acceleration buzz from under the train. With IGBTs, "gear changing" has gone.

The next development in electric motor design is the permanent magnet motor. This is a 3-phase AC synchronous motor with the usual squirrel cage construction replaced by magnets fixed in the rotor. The motor requires a complex control system but it can be up to 25% smaller than a conventional 3-phase motor for the same power rating. The design also gives lower operating temperatures so that rotor cooling isn't needed and the stator is a sealed unit with integral liquid cooling. By 2011, a number of different types of trains had been equipped with permanent magnet motors, including 25 AGV high speed train sets, trams in France and Prague and EMUs in Europe and Japan. The reduced size is particularly attractive for low floor vehicles where hub motors can be an effective way of providing traction in a compact bogie. Development of motor design and the associated control systems continues and it is certain that the permanent magnet motor will be seen on more railways in the future. A good description of the motor by Stuart Hillmansen, Felix Schmid and Thomas Schmid is in Railway Gazette International, February 2011.

Dr. Mehrdad Kazerani is a Full Professor at the Electrical and Computer Engineering Department of the University of Waterloo. Since joining the University of Waterloo in 1997, he has been involved in teaching, theoretical and experimental research in the general field of power electronics, and administrative activities. Specific research areas include modeling and control of DC/DC, voltage-sourced and current-sourced converters, grid integration of renewable energy sources, plugin electric and hybrid electric vehicles, energy storage systems, smart battery chargers with V2G capabilities, energy access and microgrids. Dr. Kazerani's research program has been financially supported by various governmental agencies (such as NSERC, ESTAC, Railpower, OCE, CFI, OCE, Automotive Partnership Canada, and Natural Resources Canada) and industry partners (such as Hydro One, GM, First Solar, Rail Power, Magna and Hatch). He has actively participated in numerous multidisciplinary projects and has supervised/co-supervised numerous post-doctoral fellows, graduate students, visiting scholars, and undergraduate students in research projects and Capstone design projects. Beyond his regular teaching load, he regularly teaches online graduate courses to the power industry employees within University of Waterloo MEng in Power Engineering program. He holds several patents and has authored/co-authored numerous journal and conference papers, and technical reports. As a senior member of IEEE he has served on several IEEE technical sub-committees, organized several special Sessions in IEEE Conferences, and acted as an editor of several special sections and issues in IEEE Transactions. He has acted as an editor for the IEEE Transactions on Vehicular Technology. Dr. Kazerani has acted as the faculty advisor for the University of Waterloo Alternative Fuels Team (UWAFT) and Formula Electric Vehicle team, and had the role of an investigator for Association of Professional Engineers Ontario (PEO). Dr. Mehrdad Kazerani is a registered professional engineer in the province of Ontario. He has served on the review panels of national research foundations of several countries.

Hydro-electric power, using the potential energy of rivers, now supplies 17.5% of the world's electricity (99% in Norway, 57% in Canada, 55% in Switzerland, 40% in Sweden, 7% in USA). Apart from a few countries with an abundance of it, hydro capacity is normally applied to peak-load demand, because it is so readily stopped and started. It is not a major option for the future in the developed countries because most major sites in these countries having potential for harnessing gravity in this way are either being exploited already or are unavailable for other reasons such as environmental considerations. Growth to 2030 is expected mostly in China and Latin America. 041b061a72


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