Engine Electrification for Leaner, Greener Vehicles · world’s first self-regulating generator...

Edition 2:

Page 2UK Business Secretary Visits New Research Facility

Page 9-10The New Standard for Robust AC Generators

3Case Study: German Farmers set up CHP plant

insightgenerating

Edition 2

Engine Electrificationfor Leaner, GreenerVehicles Page 3

When the UK Secretary of State for Business, Innovation and Skills, Dr Vince Cable MP, visited the Cummins Innovation Centre at the University of Nottingham in early June he was clearly encouraged by what he saw and heard. The senior cabinet member’s policy brief straddles industrial policy and Universities so he understands the importance of effective partnerships between business and academia.

The University of Nottingham’s Cummins Innovation Centre in Electrical Machines is a multi-disciplinary group that pulls together academic staff and researchers from within the Faculty of Engineering, forming a centre of excellence in Electrical Machine Technology. The University has a long history of working with Cummins Generator Technologies on a wide range of electrical machines related projects, including projects on electromagnetic and

thermal modeling of synchronous generators, high speed machines for turbochargers and novel machine and control topologies for traction applications. As a result of this successful collaborative research, Cummins has decided to establish an Innovation Centre in electrical machine technology.

Dr Cable was given a tour of the centre by Dr Neil Brown of Cummins Generator Technologies and Professor Chris Gerada of the University of Nottingham. The central role that electrical machine technology will play in the development of the UK wind industry and automotive electrification were a specific focus for the visit. The Business Secretary left reassured that the two partners have a solid foundation for helping to meet the challenges of increasing efficiencies and cutting emissions in a range of domestic and industrial applications.

generating insight | edition 2generating insight | edition 2

Foreword UK Business Secretary Visits New Research Facility

Welcome to the second edition of Generating Insight, Cummins Generator Technologies’ magazine focusing on our products, customers and industry.

Our company’s history in electrical machinery innovation dates back to 1905 when a factory was first established on the Barnack Road site in Stamford, UK. The year was 1919, when Arthur van Kaick began developing electrical machines in Frankfurt, Germany. Through the ensuing decades, Newage and AvK revolutionised the generator industry and launched many cutting-edge technologies. AvK launched the world’s first self-regulating generator while Newage introduced the world’s first brushless generator and later, the first generator using PMG for AVR excitation. The manufacturing techniques we pioneered in the industry to build high-quality durable products include Vacuum Pressure Impregnation (VPI), an industry norm today. It is with no small pride that I can say that others in the industry have imitated us and we are looked upon as the standard bearers by competition and customers alike.

A glorious past is no guarantee of a glorious future, and we must not take our industry leading position for granted. We are investing in creating new advances in generator

technologies. Since 2007, we have nearly doubled the annual investment in Research and Technology and we have an engineering team with depth and breadth that would be the envy of any competitor.

Some of these investments are now coming to fruition and you can read about them in this edition. Our Grid Code compliant products are to be released in early 2013 while new low voltage 4-pole robust, bar-wound generators for marine and harsh environment applications are anticipated by the end of 2013. We have developed a new MotorGenerator for the hybrid commercial vehicle market. There is a new technology created in Active Torque Cancellation that can reduce the noise and vibration in some generating-sets. It is also no secret that you, our customers, are helping us learn more about how our products are used in applications. There is a feature on one of our customers, SCHNELL Motoren AG, who is using STAMFORD generators in a Combined Heat and Power (CHP) plant. In collaboration with customers like SCHNELL, we are learning how to make our solutions better.

There are other changes afoot. We have a new business leader, Vikrant Aggarwal, who took over this summer and one of his first decisions was regarding the way we approached the market. Though Newage and AvK merged in 2001 and was renamed Cummins Generator Technologies in 2006, the two companies have approached the market almost as two independent companies with separate sales force until now. We will now have a single selling organisation with our sales team equipped to sell the entire range of our products including STAMFORD, AvK and MARKON.

I hope you enjoy this edition. We would love to hear from you with your thoughts and ideas on how we can continue to innovate and create world class solutions for our customers and partners.

Ranjit MohanGeneral Manager -Europe, Middle East and Africa

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Generating Insight is the Cummins Generator Technologies magazine focusing on topics relevant to our products, our customers and our industry.

Copyright 2012. Cummins Generator Technologies Ltd. All Rights Reserved.STAMFORD, AvK and MARKON are registered trade marks of Cummins Generator Technologies Ltd.

Publication design by Media Mill Ltd.+44 (0) 1457 877 164

Editor: Anita FountainEmail: [email protected]

Editorial

Neil Brown (left) with Dr Vince Cable MP


Engine Electrification forLeaner, Greener VehiclesCummins Generator Technologies’ all-new patent-pending electric Motor Generator with CorePlus™ technology offers a high-torque solution to commercial vehicle manufacturers seeking the electrification of their drive-trains, all in an impressively compact package.

The ‘double-whammy’ of spiralling fuel costs and ever tightening laws on exhaust emissions is forcing commercial vehicle operators to look for leaner, greener alternatives to conventional diesel engine topologies, particularly in urban areas where air quality is a growing concern. Given their proven ability to save fuel and reduce emissions and CO² diesel, electric commercial vehicles offer many advantages over their diesel-only equivalients, the most obvious being that an additional electric motor provides zero emission ‘green’ motive power during the all important starting-off phase, where most fuel is burned by a standard vehicle. Incorporating an electrical motor generator into the drive-train of existing commercial vehicles is not without its problems. Naturally the motor has to provide sufficient power to accelerate a laden hybrid commercial vehicle away from rest, giving it a performance that’s traffic

compatible with other road users. But it must also be small enough to avoid any chassis packaging problems for the vehicle manufacturer, and light enough so the truck’s payload isn’t compromised either. No easy task! The good news is that the latest Cummins radial-flux motor generator, with its peak power of 90kW and 660Nm torque, measuring 200mm in length and with a weight of just 108kg, comfortably meets all those hybrid commercial vehicle challenges.

Cummins Generator Technologies’ hybrid drive investigations stretch back to 2000 when it originally set up an R&D team to examine new market opportunities for permanent magnet generators and power electronics convertors. Although the group’s focus was initially towards power-generation applications, in particular to help reduce the fuel consumption of diesel generating-sets, especially on mobile generators where similar challenges (notably size and weight) exist, it also found a market for its products in the military sector. Having developed specially packaged permanent magnet motor and power conditioning systems for special military projects, the natural next step was to develop a permanent magnet machine and power electronics converter specifically for the hybrid commercial vehicle market.

Battery Pack

Cummins Power Electronics

Cummins CorePlus™ Motor Generator

A typical Cummins CorePlus™ Motor GeneratorA typical hybrid system in a medium duty truck chassis

with a Cummins CorePlus™ Motor Generator

Cummins Motor Generator Quick Spec-Check

■ Peak torque - 660Nm

■ Peak power - 90kW @ 1,300rpm

■ Continuous power - 35kW @ 1,300rpm

■ Motor efficiency - > 95%

■ Overall length - 200mm

■ Weight - 108kg

■ Cooling - water-glycol

Cummins new CorePlus™ Motor Generator can be used in either series or parallel hybrid drive-train configurations, or a combination of both, with its ‘universal’ hollow rotor design allowing it to fit application dependent drive-shafts. Weight has also been saved in the machine rotor casting which only has to handle the torque produced by the electric motor rather than the torque from the diesel engine.

The motor is liquid (water-glycol) cooled by a water channel integrated within its aluminium housing; the water-cooling manifold, containing two threaded o-ports, allow the customer to fit a range of inlet and outlet connector pipes to the manifold. Hoses from the cooling system can then be connected to these pipes. By designing the cooling manifold as a separate component, customers have greater flexibility in the positioning of the motor within the truck’s drive-train.

Building a motor that’s light-yet-powerful, with a high torque, and which takes up as little space as possible brings with it thermal and mechanical design-issues. To ensure the smallest external dimensions, the new Cummins Motor Generator features a permanent magnet topology with a high number of poles and concentrated non-overlapping stator winding. These maximise the available space in ‘short’ machines by reducing the length of the end turns, in proportion to the stator core pack length. The stator slots are ‘open’, enabling the use of externally-wound coils, featuring plastic bobbins that are then inserted into the stator. This technique allows a high degree of manufacturing automation and a very good slot-fill factor.

During the concept stage our engineers considered a number of different permanent magnet rotor configurations including: Surface magnet; inset magnet; and embedded

magnet (with either a flat or ‘V’-shape). Ultimately, the embedded magnet layout offered the best solution thanks to its mechanical retention and environmental protection of the magnets, good field-weakening capability and low short-circuit current.

Likewise, having looked at flat and flux-focusing V-shape magnets, a flat magnet installation was chosen as the best solution thanks to a lower magnet mass per unit (lower flux leakage than a V-shape), lower rotor inertia-end constraints for the rotor’s internal diameter and a simpler manufacturing process with a lower number of magnets.

To optimise the complex electromagnetic, thermal and mechanical factors Cummins’ engineers applied a number of different computer-based design and modelling tools during the motor’s development, examining a number of technical and design options within a relatively-short period of time. In particular, computer-based systems allowed a detailed 3-D analysis of the segmented rotor in order to provide a full insight into optimal magnet temperatures, as well as the motor’s overall thermal performance. Cummins Generator Technologies also devoted much time to fully-integrating the power electronics controller into the overall hybrid-system, ensuring a highly efficient and full torque-speed operating range for the motor. The result of our endeavours is a lightweight and dimensionally-compact motor generator that can be fitted to any manufacturer’s drive-shaft, with a very high peak-torque rating and good efficiency over the entire torque-speed range, ensuring a highly-flexible hybrid drive-train capable of delivering impressive fuel savings. That's a definite ‘win-win’ for both commercial vehicle makers and operators alike.

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‘Active’ ApproachTo Good VibrationsCummins Generator Technologies has been looking at new ways to reduce noise and vibration from generating-sets powered by small-displacement, ‘low-count’ cylinder engines.

Stand close to any generator big or small that’s powered by a reciprocating engine and you know when it’s working. The noise and vibrations from the engine are the obvious giveaway, and generating-set makers are constantly looking at ways to minimise them. In its quest for smoother, quieter-running products, Cummins Generator Technologies has come up with a new way of tackling generating-set engine vibration using an innovative solution known as ‘Active Torque Cancellation’ (ATC).

One simple way to make a generating-set quieter is to run its engine at low speeds. Unfortunately, at lower speeds vibration ‘modes’ can shift to lower frequencies too, to the point where the engine’s mounting system may not be able to cancel them out. Even worse, the lower frequency can trigger a resonance in the mounting system itself, resulting in unacceptable vibration levels. This can be a significant issue when the engine is a small displacement diesel with a ‘low cylinder-count’ (i.e. one or twin-cylinders) running at speeds of less than 2,000rpm.

Normally, there are a number of ways manufacturers can reduce transmitted vibration from the use of multiple-layers of isolation, improving the engine’s balance through counterweights and by fitting ‘active’ mounts. But those solutions aren’t always practical due to cost, weight and size-limitations. Ironically, when building small generating-sets, for example to provide electrical loads in recreational vehicles (RVs), an engine with the lowest

number of cylinders is extremely attractive thanks to its cost, size and weight. Nevertheless, dealing with its inherent noise and vibration remains a major issue - especially as the user is often in close proximity to the generating-set.

Cummins Generator Technologies’ ATC system has been specifically developed to reduce the transmitted vibrations from generating-sets equipped with those lower cylinder-count engines and the first phase of the prototype-testing project was completed in 2009, with ATC successfully applied to a small, 0.48-litre displacement, two-cylinder engine and a 7.5kW permanent magnet synchronous machine.

However, since then the R&D team has taken the concept significantly further. In 2011, with ATC it was able to successfully cancel out low speed (idling) vibrations from a four-cylinder 4.5-litre engine installed in a DAF truck. This was clearly a far bigger challenge than the original small test engine and demonstrates the potential of ATC not only for generating-set applications, but also for commercial

vehicles where it could also help reduce fuel consumption. So how does it work? In simple terms, ATC applies a controlled torque on the engine’s crankshaft to reduce the roll motion (around the crankshaft axis) which cuts down the amount of vibrations transmitted by the engine. Naturally there’s a bit more to it than that.

The two main causes of engine vibration are the varying cylinder pressures and the moving-masses inside it. In a four-stroke engine, during the power-stroke the cylinder pressure applies a huge amount of torque on the crankshaft, with that peak torque being significantly higher than the average torque. Conversely, the reciprocating masses of the engine result in a cyclic torque on the crankshaft, which is a function of the square of the speed. The resulting combined torque from these two inputs can be derived from the engine slider-crank mechanism and cylinder pressure data. For multi-cylinder engines, the torque contribution from each cylinder is added together with the appropriate phase shift. At low-speeds and for small engines, the reciprocating mass and the crank radius are small, resulting in a very low inertial torque component.

With the ATC, the flywheel mounted on the crankshaft smoothes out the speed variation due to the alternating nature of those twin-torque sources with the flywheel’s filtering action notably effective for high-order ripples.

Torque inputs generated by the engine’s power stroke and reciprocating action aren’t the only sources that have to be dealt with. ‘Reaction’ torque also tries to rotate the engine frame, causing further vibrations. Normally, the engine mounting system curbs the amount of vibration transmitted from the engine frame to the foundation, and simple rubber mounts are frequently used for mounting engines. Together they function as a low-pass filter with a good level of attenuation at a high-frequency range.

However, the vibrations caused by lower-order components of the roll torque also present a challenge in the mounting-system design. ‘Soft’ generating-set mounting designs attenuate the lower frequencies so that any transmitted vibration is reduced. When the mounting system design is not sufficient, a secondary isolator may be included to achieve the desired result. In some instances, even with the help of secondary isolators, acceptable vibration levels are still not attained. This forces the designer to raise the minimum running speed although this inevitably means compromising on noise. Thus, Cummins Generator Technologies’ strategy is to reduce roll torque at the lower orders using ATC, so that lower speed operation is still possible but without the risk of excessive vibration.

Moreover, although previous studies have concentrated on reducing speed variation in order to address crankshaft torque. When looking at the problem of transmitted vibration Cummins’ view is that performance should be evaluated using other means than simply adjusting the engine’s operating speed. In tests using the experimental generating-set, when running at 1400rpm at no load, ATC showed a number of major improvements in the engine’s roll, translational and transmitted vibrations.

Given the inherent characteristics of lower cylinder count engines, ATC has proved to be an eminently practical way to reduce transmitted vibrations with significant improvements achieved during tests. With ATC, Cummins Generator Technologies’ practical approach not only targets the critical roll-torque component of vibration, thereby avoiding the need to over-size the machine or power electronics components but also, by attenuating low frequency and critical vibration modes, its benefits could also extend to the design of more effective-mounting systems too. That sounds like an all-round win-win to us - for the next generation of generating-sets, big or small.For further information please contact Krzysztof Paciura - [email protected]

Cummins Generator Technologies has been looking at new ways to reduce

noise and vibration from generating-sets powered by small-displacement,

‘low-count’ cylinder engines.

Speed Position Sensor

ATCController

ElectricalMachine

CS1

Sa

AC/DCActive Rectifier

DC CurrentRegulator

Torque

Engine Output Power ATC Torque TVR

+ +

VDCPI

DC

Lin

k

Volta

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enso

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CS2

Sb Sc

Testing on a four cylinder 4.5-litre engine

Control diagram

65

Figure 3

10kW, 80000rpm, 20MW/m3 Induction Machine Rotor

Figure 4

Induction Machine on test bed


Electrical Boost forHesitant VehiclesCummins Generator Technologies’ engineers have been looking at ways to improve the performance of automotive diesel engines using high-speed electrical machines.

Most drivers have experienced a phenomenon known as 'Turbo Lag'. This is the time delay between the driver pressing the accelerator pedal and the engine accelerating to the required speed. A possible solution to reducing turbo lag is to assist the turbo charger electrically.

Electrically Assisted Turbocharging (EAT) consists of integrating a high-speed electrical machine to help overcome the turbo lag on a diesel engine, especially at low engine revs, by incorporating an electrical assist motor between the turbine and compressor wheel. This reduction in turbo lag not only improves the driver experience, the fuel is burnt more cleanly and more energy is extracted from the fuel, which reduces emissions and fuel consumption.

In particular, the system is well-suited to turbocharged diesel engines fitted with an exhaust wastegate (used to avoid ‘over-boosting’) where the by-pass gases would drive the electrical machine, which would then feed power back to the vehicle’s electrical system, further improving its efficiency and reducing the impact of the generator which drains power from the engine in normal operation.

Fitting a high speed machine to a turbocharged diesel engine presents some real engineering challenges. Not only are its components operating close to their mechanical limits, but as the machine is likely to sit in-between the turbocharger’s turbine and compressor wheels, as shown in Figure 1, it also has to operate in a very thermally-aggressive environment with exhaust temperature as high as 800˚C. Tackling those thermal and mechanical challenges has been a key aspect of Cummins Generator Technologies’ work on the type of high speed machine that would be suitable for use with a turbocharged engine.

Three different electrical machine designs shown in Figure 2 were examined by Cummins Generator Technologies’ engineers, including the Induction Machine (IM), selected for its robustness and two different Permanent Magnet Synchronous Machines (PMSM) options. These were the distributed wound inset PMSM and a concentrated wound surface mount PMSM.

All three options were subjected to intense scrutiny by Cummins Generator Technologies’ researchers, in order to determine the best high speed machine configuration. In particular the group focused on the heat-resisting performance of different solid and laminated metallic components used in the rotor and stator of the Induction Machine. Likewise, the distributed wound PMSM option was also considered in detail, utilising 2-D computer modelling and 3-D finite-element analysis (FEA), not least to estimate complex rotor losses. Similar in-depth analysis

was also applied to the concentrated wound PMSM \design, particularly concerning the abilities of the design to withstand and operate effectively within thehigh-temperature environment.

By comparing not only the electromagnetic, but also the thermal and mechanical issues within those three possible designs, Cummins Generator Technologies’ researchers were able to apply a truly ‘multi-domain’ approach to the design of future high speed electrical machines, taking into full account their very challenging operating environment. The group ultimately concluded that the distributed wound inset PMSM cannot achieve the required performance without significant Power Electronic converter over-sizing, while the concentrated wound six-slot, four-pole PMSM has excessive rotor losses at the frequencies considered, resulting in elevated rotor temperatures which are well above the magnet’s capability to withstand them.

Although the Induction Machine rotor losses are relatively high, by suitable choice of rotor materials, multi-domain optimization and the invention of a new rotor design by Cummins Generator Technologies’ engineers, high power-densities can be achieved (20MW/m3 compared 1MW/m3 for a conventional synchronous machine). Based on the aforesaid considerations the induction machine is chosen for electrically-assisted turbocharging. Figure 3 shows a cross section of the rotor and figure 4 the machine on test.

ExhaustCompressor Electrical Machine

A possible solution to reducing turbo lag is to assist the turbo charger electrically.

Figure 2

Compared electrical machines topologies:

a) Induction Machine, b) Distributive-wound Inset PMSM

c) Concentrated-wound Surface PMSM

Figure 1

87


The New Standard forRobust AC GeneratorsCummins Generator Technologies are designing a new range of AC generators to meet the demands of marine, prime power and Grid Code Compliant applications. The highly robust generators in the power range of 1,500 to 4,100kVA have been developed to meet the prime and auxiliary power needs of the marine industry, including diesel electric propulsion as well as providing a robust solution for prime power and Grid Code compliance.

The new range is the culmination of many years’ experience supplying marine and prime power products as well as utilising the latest research and design tools to drive forward our AvK range with regard to Grid Code compliance. Advanced manufacturing techniques and a robust bar-wound make the new range of AC generators the perfect choice for continuous operation.

Providing an estimated power range of 1500-3400kVA at 50Hz and 1800-4100kVA at 60Hz and voltages between 400-690V with insulation Class H as standard, the new generator will also be compliant with marine industry classifications.

A unique modular design construction and a range of options will allow flexibility to suit typical marine and harsh environment applications, including an air to water cooler, rolling element or sleeve bearing options and Ingress Protection ratings SOLAS IP23 and IP54.

Market leading weight, size and efficiency ratings will further establish the product as a leader within its field.

This range was introduced at the SMM Hamburg Show in September 2012, availability is expected late 2013 with medium and high voltage variants to be announced at a later date.

109

Key Features: ■ Low Voltage 4-Pole ■ 1500-3400kVA @ 50Hz ■ 1800-4100kVA @ 60Hz ■ 400-690V ■ Insulation Class H ■ Vacuum Pressure Impregnation ■ IP23 and IP54 TEWAC (SOLAS) ■ Rolling Element or Sleeve Bearing Options ■ Latest Digital Control Systems ■ Marine Classification Compliant


While it is dangerous to make general characterizations about anything as complex as generator design, we describe the difference in design between bar-wound (also called form-wound) and wire-wound (also called random-wound) generators, and provide recommendations for the use of each type by system designers. Bar-wound generator designsBar-wound generators differ from wire-wound designs in that the copper windings of the stator are composed of individual copper bars, rather than wire bundles.

Figure 1 shows section views of typical stator slots inbar-wound and wire-wound machines. Note that the stator windings in the bar-wound machine are composed of bar assemblies that are laid in the slot in a precise mechanical configuration.

In order to lay the bars into the slot, the opening to the slot has to be quite large, and this leads to some of the most important differences in performance between bar-wound and wire-wound machines.

Wire-wound generator designsIn a wire-wound design, the generator windings are usually pre-formed wire bundles, which are inserted into the stator, often by machine processes. Note that with the wire-wound design the slot opening is significantly smaller, and the individual windings are composed of much smaller cross-section materials. Note also that the insulation space between the individual wires is less than with the bar-wound coils.

Performance differencesThe differences in the physical designs between the two systems lead to some obvious performance differences that you can expect, and some that are less apparent.

■ In general, you can expect that a copper bar is a more rigid object than a wire bundle. What you can’t see in these illustrations is that it is probably easier to brace a bar-wound machine for mechanical stresses than it is a wire-wound machine. This being said, it should not be assumed that a wire-wound machine is always less durable than a bar-wound machine - it is simply easier to provide a mechanically rugged structure.

■ The bar-wound machine will generally have more space for insulation than there is available between the wires in a wire-wound machine. Added insulation is most important in medium-voltage generators where the difference in voltage between the conductors is greater. On the other hand, the greater levels of insulation in the bar-wound design tend to make it more difficult to cool the machine, so more materials are needed to reach similar temperature rise goals.

■ In general, the larger air gap and slot opening size will result in greater levels of inherent voltage waveform distortion (particularly at higher frequencies). So, bar-wound machines will typically exhibit poorer waveform quality than wire-wound machines of similar mechanical characteristics.

■ Since the slot opening is greater in bar-wound machines, the magnetic circuit that exists between the rotor and stator is more efficient in the wire-wound design. Also, bar-wound designs tend to have longer end-turn arrangements. These two factors lead to better overall performance of the wire-wound design for similar material content. For example, the bar-wound machine will require more copper and steel to reach the same short circuit and motor-starting capability of a similarly rated wire-wound machine. Usually, the reactances of a wire-wound machine will be relatively lower than those of a similar-sized bar-wound machine, reflecting this physical distance.

■ To summarize, bar-wound generator designs typically offer greater mechanical strength than wire-wound designs and greater dielectric strength, but they provide less performance in terms of voltage waveform quality, motor-starting performance and short circuit performance.

Application recommendationsThe physical characteristics and performance differences in the two basic generator designs lead to the following recommendations for their use:

Bar-wound designs are generally more desirable for medium-voltage applications. In these situations the ability to provide better turn-to-turn insulation will result in a more reliable machine, with relatively minor sacrifices in cost.

Bar-wound designs are also generally desirable for prime power applications that need the more rugged mechanical strength of the bar-wound design. In particular, applications that use continuous, repeated surge loads to the machine are usually best served with a bar-wound design. The surge loads result in magnetic reactions in the windings, particularly in the end turns of the stator, that tend to deform the windings, or even break them over time. With a rigid, heavily braced design, the impact of these mechanical stresses can be more easily mitigated.

A common situation of this type occurs in oil-field applications, where drilling operations put continuous sudden loads on the generator set. Wire-wound designs tend to provide the best performance in terms of voltage waveform quality, resistance to waveform distortion, short circuit performance, and motor-starting performance. Thus they are almost always the best choice for line voltage applications in emergency/standby situations. This is particularly true in situations where there are large motor loads or when good waveform quality is important, such as due to the presence of non-linear loads in the system.

Applications such as uninterruptible power supply (UPS) for data centers, water treatment or sewage lift can often benefit from a wire-wound generator. These applications have heavy concentrations of rectifier-based loads. They are different from, say, drilling applications in that loads are applied to the generator in a relatively gradual process to minimize voltage sags and swells, whether operating on the utility service or generator set power.

For example, UPS will ramp loads onto a generator set after a power failure, and it will draw reserve power from a battery supply when a sudden load is applied to its output. These loads on the generator set are much less mechanically stressful than those from drilling applications. Consequently, there is no clear need for the bar-wound design, and the greater efficiency of the wire-wound design may be desired.

Both bar-wound and wire-wound designs need special protection when used in harsh environments such as coastal areas or where they could suffer from corrosion.

ConclusionThe bottom line is that there are no applications that absolutely require one generator design over another. In general, for similar-sized machines, the bar-wound machine is best suited to high-voltage applications and cases where the loads subject the generator to severe mechanical stresses. The wire-wound machine, properly constructed, will provide the best service in applications where motor-starting capability and the best resistance to waveform distortion are important.

From the customer’s perspective, the objective is to buy a product that satisfies their functional requirements and has the

best quality price ratio.

Bar-wound VersusWire-wound Generators

Figure 1

Winding and slot size comparison shows that for similar

winding size, the slot size of a wire-wound machine

(above right) will be much smaller, resulting in lower

harmonic distortion in voltage produced

1211


Coupling the STAMFORD generator to the engine at

SCHNELL’s headquarters in Amtzell, Germany

New biogas powerplant

Case Study:German Farmers Set-up CHP Plant

Enhanced Efficiency Option for Reciprocating Power Plants

A local consortium of farmers required four generating sets for a brand new biogas power plant in northern Germany. SCHNELL Motoren AG was commissioned for the design and installation, who specified four industrial STAMFORD HC4 generators, rated at 350kVA each.

The founders of the power plant supply agricultural matter, which is then fermented to create biogas. The gas is converted into electricity and supplied to the grid, whilst the waste heat is captured and used to heat a nearby commercial greenhouse and the regional SCHNELL company building.

When SCHNELL began work on the biogas plant in Rodewald, Germany, they turned to Cummins Generator Technologies to supply STAMFORD AC generators. Having been a long standing customer, SCHNELL knew they could rely on highly efficient, reliable STAMFORD HC4 generators to deliver on this brand new project.

The power plant was commissioned by a consortium featuring ten farmers from local surrounding villages. The plant consists of four dual fuel 265 kW generating-sets running 24 hours a day, 7 days a week providing dependable continuous power. Agricultural matter is used to fuel the plant: 40% animal slurry and 60% fermented biomass consisting of corn, rye and grass, among others.

This project is a great example of a CHP plant; in addition to producing electricity to sell to the public grid, energy typically wasted is captured and used to heat the SCHNELL company building and a commercial greenhouse nearby, home to a family-run horticulture business. The generating-sets reach industry leading electrical efficiencies of 47% by using additional efficiency enhancements, thus providing a maximum return on investment for the customer, which is expected withineight years.

The generating-sets used in this power plant were assembled at SCHNELL’s headquarters in Amtzell, southern Germany, where the four STAMFORD HC4 generators were coupled with Scania-SCHNELL engines.

Confidence in STAMFORD generators to provide great value over the lifetime of this project is clear. As a customer of Cummins Generator Technologies, SCHNELL benefitted from having highly trained, knowledgeable engineers at their disposal, a dedicated account manager, as well as the assurance of our premium after sales support service to support the entire product lifecycle.

With natural resources becoming scarcer and scarcer and ever increasing environmental demands by governments, efficiency in reciprocating power plants is becoming a key issue for our customers. To support our wide base of customers operating in this field, Cummins Generator Technologies, under the AvK brand, will be launching a high efficiency version of the popular DIG 167 range.

Although customers have attested good to very good efficiencies on the machines so far, Cummins Generator Technologies saw a further demand for even better performance. Based on the use of a higher grade electrical steel lamination the DIG 167 can now be offered with losses that have been reduced by 7 to 12%!

This might not seem massive, but at outputs of up to 16,700kVA per machine and power plants consisting of 18 such units, the savings quickly add up. Depending on the point of view, the customer can either reduce the amount of fuel burnt to generate a fixed amount of power or generate a higher output while keeping fuel consumption at the same level.

To demonstrate, at 0.10$ per kWh, a power plant consisting of a single generating-set, running in continuous mode would be modeled as follows.

Typical efficiency values of a higher efficiency AvK DIG 167 versus a competitor generator:

Operational profile of a typical continuous duty power plant:

The savings for the DIG 167 e/8 versus the competitor generator would be:

As you can see this is a substantial benefit. If one now considers higher sales prices for energy during peak hours, as one sees in deregulated markets like Texas, USA, the benefit will be considerably higher. We believe this to be a competitive benefit for our customers thus enabling them to be more successful, in turn, we expect to see this as a key driver in the coming years and are expecting significantly higher volumes in this range.

The AvK DIG 167 high efficiency range is now available and can be offered with the usual suite of options, from different AVRs to water cooled versions. DIG 167 is offered in all standard MV ranges from 3.3kV to 13.8kV in 8 and 10 pole versions. Typical engines that can be fitted with these machines are made by all major players.

Having been a long-standing customer,SCHNELL knew they could rely

on STAMFORD AC generators to deliveroutstanding value on this brand

new project.

Actual load / Sn 25% 50% 75% 100%

Competitor 94.65% 96.54% 96.98% 97.03%

DIG 167 e/8 95.05% 96.80% 97.20% 97.60%

Annual Load Rating (ALR)

= load range / rated load

ALR = 0(not in use)

0 < ALR ≤ 37.5%

37.5% < ALR ≤ 62.5%

62.5% < ALR ≤ 87.5%

87.5% < ALR ≤110%

Typical characteristics

for power plant

(operating hours per

year)

500 250 750 1,500 5,760

Additional energy 125,594 kWh per year

Additional money 12,559 $ per year

Additional money 62,795 $ in a 5-year-period

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Engine Electrification for Leaner, Greener Vehicles · world’s first self-regulating generator...

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Transcript of Engine Electrification for Leaner, Greener Vehicles · world’s first self-regulating generator...