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WORKSHOP Generator designs including choices for hybrid vehicles Time: 14:00 to 15:00 Presenter James R. Hendershot Life Fellow IEEE Edited by Prof. Ernie Freeman, FREng. Fellow Royal Academy of Engineering (1987) Copyright 2016 Motorsolver 1 Workshop Abstract: Bosch Generator designs including choices for hybrid vehicles ENERCON Never before in history have generators of electricity been more important to societies around the world. Every principal method of creating electricity except solar and fuel cells requires a rotating electro-magnetic machine called a generator. There are three or four favorite machine types used for generating electricity when rotated by some prime mover. Each has its pros & cons, some relating to their performance and others relating to manufacturing methods and cost. Choices of generators are reviewed with respect to a few important applications like hybrid vehicles,” more electric ship propulsion”, “more electric aircraft,” “wind turbines” and “flywheel batteries”. Very large generators for power plants are best served by wound field synchronous generators with practically no other option so this application is not studied. A comparison of permanent magnet synchronous, reluctance synchronous, switched reluctance and Induction asynchronous machines are discussed and compared for the current popular generator applications. Some important design features are discussed in addition to cooling requirements. Copyright 2016 Motorsolver 2 Workshop Presenter: James R Hendershot Jim has over 40 years experience in practical hands-on PM & SR brushless motor design, manufacturing and development. With past key employments at United Technologies, General Motors, Clifton Precision, Berger Lahr & Pacific Scientific, he has designed hundreds of brushless motors for computer disc drives, servo systems, high speed machine tool spindles, traction drives, hybrid vehicles, micro-turbine and diesel generators. He has written numerous technical papers, publications and presented tutorials on many different electric motor topics. Hendershot is the co-author with Professor TJE Miller for two of the leading design books on Permanent books on Permanent Magnet Motor and Generator Design (ISBN 1-881855-03-1, 1994 & ISBN 978-0-9840687-0-8, 2010). Jim teaches detailed motor design training courses (including workshops) at public venues, conferences and custom designed workshops tailored on-site for companies around the World. Jim Hendershot holds a B.S in Physics from Baldwin Wallace University in Berea Ohio along with additional E.E. & M.E. engineering studies at Cleveland State University as well as graduate courses at Case-Western University in Cleveland Ohio. He specializes in the design, analysis, sourcing, manufacturing and teaching of both electro-magnetic and permanent magnetic devices. In addition to continuing studies in magnetics and electric machines. Jim has enjoyed a long and rich association with Dr. Tim Miller, founder of the SPEED Consortium at the University of Glasgow combining Jim’s practical hands-on motor design skills with TIM’S theoretical knowledge and research For the past few years Jim has also been associated with Infolytica Corp, Prof. Dave Lowther (of McGill University), Prof. Ernie Freeman retired from Imperial College, London and their staff for continued development and research involving the design and research for electric motors and generators. Jim Hendershot developed a Dyno-Kit for teaching electric motor drives used by over 120 US Universities and Colleges for Prof. Ned Mohan of the University of Minnesota. These are used for the lab portion of their Electric Drive Courses. Jim Hendershot has created a series of 36 electric machine design lectures for the University of Minnesota, funded by the US Navy Research Labs that are available on YouTube. (9 to 10 hrs. of lectures covering all aspects of practical electric machine design). Copyright 2016 Motorsolver 3 Introduction: Most electric machine discussions center around motors Faraday first discovered the generator in 1831 Tesla did not invent the Induction motor until 1887 Today only two electricity sources do not require a generator Fuel Cell & Solar All others require either a linear or a cylindrical generator (Batteries& capacitors are used for storage not generating) Generators convert mechanical input power into electrical output power. Lets have a look at the current electricity generation choices Copyright 2016 Motorsolver 4 Sun can produce electric power Solar Panels NO SUN, NO POWER! Mirrors focus suns heat to produce steam for electric turbine generators Betaray >70 % Copyright 2016 Motorsolver 5 Fuel cells require no energy conversion generator Toyota cell UK Carbon Trust Ballard Bus Fuel Cell Toyota Fuel Cell Fueled by Hydrogen or Natural Gas Copyright 2016 Motorsolver 6 Wind energy produces electric power Copyright 2016 Motorsolver 7 Power must be stored when No Sun and No Wind Hydro Energy storage Chemical battery storage Chemical battery storage Flywheel battery New Tesla Battery pack Copyright 2016 Motorsolver 8 Historical generating systems for electricity Copyright 2016 Motorsolver 9 Model of Faraday’s Generator National Museum of Nature and Science, Tokyo, Japan. CIRCA 1831 It consists of a copper disk between the poles of a horseshoe magnet. When the disk is turned with the crank, a current of electrons flows radially from the center of the disk to the rim, due to Faraday’s law of induction. This is picked up by a springy contact pressed against the rim of the disc. The current flows through an external circuit & returns to the center of the disc through the axle Copyright 2016 Motorsolver 10 Steam engines and steam turbine driven DC generators Edison Copyright 2016 Motorsolver 11 Prof. A. Binder TECHNISCHE UNIVERSITÄT DARMSTADT Copyright 2016 Motorsolver 12 Three Gorges Dam power plant in China (32) 700 megawatt generators Hydro-Electric Copyright 2016 Motorsolver 13 Power plant generators, Air, Water or Hydrogen cooled Air Cooled to 335 MVA Hydrogen cooled to 630 MVA Water cooled to 800 MVA Copyright 2016 Motorsolver Normally driven by coal fired steam turbine 14 MORE POWER PLANT GENERATORS Copyright 2016 Motorsolver 15 Wound field synchronous generator (brushless exciter) (48) slot stator, with (2) coils/pole/phase (8) pole wound rotor, with brushless exciter Copyright 2016 Motorsolver 16 TYPICAL STAND-BY GENERATOR Copyright 2016 Motorsolver 17 AC Induction motor with (3) phase wound rotor Large versions used for Wind Turbine generators (MW size) ranges) Copyright 2016 Motorsolver 18 Cut-A-Way of a synchronous generator with PM brushless exciter Copyright 2016 Motorsolver 19 Wound rotor AC Induction machines Rotor wound with three phase windings connected to three slip rings and brush assemblies More expensive than caged rotors Lower slot fills than caged rotors Torque vs speed vs rotor resistance Used in the past for lifting heavy loads requiring high starting torques Used for wind turbine generators Copyright 2016 Motorsolver 20 21st Century generating systems for electricity including renewables Copyright 2016 Motorsolver 21 Turbine driven generator Copyright 2016 Motorsolver 22 Switched Reluctance startergenerator for 20,000 rpm gas turbine engine (4) pole rotor (6) pole fuel cooled stator General-Electric & Sundstrand Copyright 2016 Motorsolver 23 Switched Reluctance seem to be popular for large off road machine 5900 liter Hybrid front end loader Copyright 2016 Motorsolver 24 Copyright 2016 Motorsolver 25 Combined Cycle Natural Gas & Renewables like Wind & Solar Copyright 2016 Motorsolver 26 Copyright 2016 Motorsolver 27 Tidal and ocean wave generation Copyright 2016 Motorsolver 28 Generating Electrical Power from Tidal Energy Copyright 2016 Motorsolver 29 Most three most common wind turbine generators Doubly fed AC induction machines with slip rings (1500 to 1800 rpm)with step up (3) stage gearing Direct drive permanent magnet (5 to 20 RPM) Medium speed permanent magnet with single or two stage gearing (100 to 500 rpm) There are many variations of the PMGs Copyright 2016 Motorsolver 30 Direct drive PM synchronous generator Unexpected high down times Copyright 2016 Motorsolver 31 Most common wind turbine generating system Proven design with long history and lowest cost to install. (Unexpected least down time) Copyright 2016 Motorsolver 32 Wind Turbine PMG, medium speed with gear box Perhaps the most promising wind turbine generator concept, medium single or double stage gear box & much lower magnet cost. Copyright 2016 Motorsolver 33 Enercon E 126 direct drive wind turbine with no magnets 6.5 MW Copyright 2016 Motorsolver 34 Copyright 2016 Motorsolver 35 Enercon 6.5 MW stator winding Copyright 2016 Motorsolver 36 Enercon 6.5 MW Rotor Windings Includes Slip Rings and Brush Rigging @ 10 to 20 rpm Copyright 2016 Motorsolver 37 Enercon 6.5 MW Rotor & Stator Coils Copyright 2016 Motorsolver 38 Thermal-acoustic power generator Voice coil in a PM field attached to a titanium diaphragm generates electricity when exposed to heat or noise Titanium Diaphragm Copyright 2016 Motorsolver Fellows Pat. # 6910332 39 THERMAL LINEAR GENERATORS Copyright 2016 Motorsolver 40 Thermal-acoustic power generator Paul Riley, University of Nottingham Copyright 2016 Motorsolver 41 Linear PM Generator driven with two cylinder IC Engine Prof. Valeri Golovitchev Copyright 2016 Motorsolver 42 TRANSVERSE FLUX PM GENERATOR CAN BE GANGED UP ON A SHAFT FOR DIRECT DRIVE WIND TURBINE. Copyright 2016 Motorsolver 43 Toyota free piston engine linear generator Copyright 2016 Motorsolver 44 Generating electric power for vehicles, cars, trucks, buses, delivery vans farm tractors & off road equipment Copyright 2016 Motorsolver 45 Copyright 2016 Motorsolver 46 Conventional alternators have limited output for newer vehicles Typical “claw” rotor High powered alternator Added magnets Patent # 6,903,485 Copyright 2016 Motorsolver 47 Claw Pole alternator (0ver 80 million produced in 2014 not counting trucks) Copyright 2016 Motorsolver 48 Copyright 2016 Motorsolver 49 Multiple alternator installations for more E - power Copyright 2016 Motorsolver 50 Hi performance Switched Reluctance IC engine generator Off road vehicles& Semis require greater than 2.3 to 3.0 kW from heavy duty claw pole alternators Copyright 2016 Motorsolver PAT # US 7755308 51 Homopolar Hybrid generator (PMHH) High power density brushless PM generator with no bearings (coupled directly to IC engine crankshaft) USED FOR MILITARY VEHICLES Copyright 2016 Motorsolver 52 Electric machine choices for generators & some design tips Some of the following slides display output results taken from th MotorGenerator simulation tool used by this author called MOTORSOLVE with new generator simulation features, by Infolytica.com Copyright 2016 Motorsolver 53 Generators with (3) different rotor configurations using similar stators and three phase windings. IM RSM SRM SR machines can be used as generators but the regulation of the voltage more complex than the other machine types. Copyright 2016 Motorsolver All three machines typically utilize boost converters for voltage, frequency & power regulation. IPM or SPM 54 ELECTRIC MACHINE POWER DENSITY COMPARISONS TESLA 4.5 kw/kg (225 kw peak for 30 sec??) New TESLA 4.34 kw/kg (300 hp 115 lbs peak) BMW i3 = 2.5 kw/kg (at 125 kw max) Siemens 5 kw/kg Aero PM motor (260 kw @ 50 kg) Copyright 2016 Motorsolver 55 How does one choose the best machine for a generator application? The selection has a lot to do with the application but don’t forget the following points: The highest peak & continuous power efficiency is achieved with a Permanent Magnet Synchronous machine (motor or generator). Some applications cannot support the cost of magnets Increasing speed reduces machine size & increases power density Slip rings and brushes can be acceptable if rpm is very low Copyright 2016 Motorsolver 56 Maximum flux densities of materials limit performance No matter which machine you choose for a generator its torque density is limited by two important magnetic materials. 1-Hard materials (permanent magnets) can only produce a maximum flux density of 1.4 tesla 2-Soft materials (electrical steels) become saturated at maximum flux densities in the range of 2.1 to 2.4 Tesla I offer each of you a challenge to invent new materials A new material with a negative permeability would be a good start, then higher temperature super conductivity materials Copyright 2016 Motorsolver 57 Stator diameter vs number of poles (Fixed rotor diameter) When number of poles is doubled, the back iron flux is cut in half. Example below is with fixed rotor diameter which reduces the stator OD Yoke thickness & stator O.D. increases with decreasing pole numbers with a fixed stator slot depth & rotor OD Copyright 2016 Motorsolver 58 AC Induction machine with either aluminum or copper shorted turn rotor Rotor & stator cross section Three phase winding layout Copyright 2016 Motorsolver 59 Wound rotor AC Induction machines Rotor wound with three phase windings connected to three slip rings and brush assemblies More expensive than caged rotors Lower slot fills than caged rotors Torque vs speed vs rotor resistance Used in the past for lifting heavy loads requiring high starting torques Used for wind turbine generators Copyright 2016 Motorsolver 60 Doubly fed Induction generator Rotor Details Rotors with ducts for cooling Copyright 2016 Motorsolver Slip Rings & Brushes 61 Torque vs. speed of AC Induction machine (constant voltage and frequency) Motoring Generating Copyright 2016 Motorsolver 62 AC Induction motor pole number greatly influences motor size and mass (under ~ 1700 Nm) Also applies to RSM motors (JRH) Drip-proof force ventilated Totally enclosed blower cooled Drip-proof force ventilated Totally enclosed blower cooled Copyright 2016 Motorsolver ~1700 NM 63 Reluctance Synchronous generators Standard AC Induction stator laminations Standard AC induction phase windings Manufactured with existing AC machine machinery & tooling Synchronous performance with no rotor slip Driven with existing AC Induction inverters (with software modification) No expensive permanent magnets in rotor Only change is a new rotor design Copyright 2016 Motorsolver 64 RSM rotor examples Copyright 2016 Motorsolver 65 Reluctance Synchronous machine Copyright 2016 Motorsolver 66 Reluctance synchronous phase windings Copyright 2016 Motorsolver 67 2010 Toyota Prius PM Synchronous Generator Copyright 2016 Motorsolver 68 2010 Toyota Prius generator components Resin Encapsulated stator IPM rotor ass’y (8 pole) Copyright 2016 Motorsolver 69 Generator output voltage and power The internally generated voltage emf in a single phase of a synchronous machine is not usually the voltage appearing at its terminals. It equals to the output voltage V only when there is no armature current in the machine. The reasons that the open circuit voltage is not equal to the output voltage V are: 1. Distortion of the air-gap magnetic field caused by the current flowing in the stator (armature reaction) 2. Self-inductance of the armature coils 3. Resistance of the armature coils Copyright 2016 Motorsolver 70 Two rotor configurations of Permanent Magnet Generators Copyright 2016 Motorsolver 71 4PH SR 8-6 3PH SR 6-4 Copyright 2016 Motorsolver 3PH SR 6-8 72 More PM Synchronous Generator configurations Inside Rotors Ring Magnet Spoke IPM Outside Rotors Bread-loaf SPM Radial Arcs V-Pole IPM Parallel Arcs Copyright 2016 Motorsolver 73 IPM brushless machine mounted to IC engine Vehicle traction and assist 24 slot stator concentric coils Replaces alternator for battery charging Replaces engine starter by quickly & quietly cranking engine during stops (18) poles Also used to dampen crankshaft vibrations of IC engine leading to smoother ride. Copyright 2016 Motorsolver 74 Chevy Volt Motor and generator Copyright 2016 Motorsolver 75 We are not going to be able to get along without generators for electricity so lets learn more about their possibilities and capabilities. Thank you for attending JRH Copyright 2016 Motorsolver 76 Copyright 2016 Motorsolver 77 Copyright 2016 Motorsolver 78