{"id":9782,"date":"2015-03-30T10:10:47","date_gmt":"2015-03-30T17:10:47","guid":{"rendered":"http:\/\/cafe.foundation\/blog\/?p=9782"},"modified":"2015-03-30T10:10:47","modified_gmt":"2015-03-30T17:10:47","slug":"making-siemens-motor-light-powerful","status":"publish","type":"post","link":"http:\/\/cafe.foundation\/blog\/making-siemens-motor-light-powerful\/","title":{"rendered":"Making the Siemens Motor Light and Powerful"},"content":{"rendered":"

Siemen\u2019s recently-announced 260 kilowatt (348.5 horsepower) motor has brought several comments, \u00a0one from a skeptical blog reader who asked some interesting questions.<\/span><\/p>\n

\u201cVO\u201d or \u201cVolker\u201d comments on Siemen\u2019s claims for the motor, and throws in speculation as to the company\u2019s veracity.\u00a0 (Note to readers who submit comments: please don\u2019t attribute conclusions not intended by the editor, as in the last sentence of VO\u2019s comment, and avoid speculating on the honorable intentions of those who announce new concepts or projects.)<\/p>\n

\"Dr.<\/a>

Dr. Frank Anton and associates examine 50 kilogram, 260 kilowatt motor. \u00a0Streamlining the installation should be easy and elegant<\/p><\/div>\n

\u201cThe first three you mention are kind of concepts but with reasonable or high efficiency. What is the efficiency of the Siemens motor? And whose tech are they using? They have been circling the makers you mentioned for years. Did they license something or steal again? On most you mention, I could find efficiency numbers (Emrax with a whopping 98%?) and more or less detailed specs. I don’t know. Looks like a marketing ploy.<\/p>\n

\u201cTypically, you would see boasting with efficiency in an aircraft app. Also which tech is it? AC induction, Sync PM, is it axial flux or not?<\/p>\n

\u201cAs you pointed out, it does not seem to be a release of accurate info, so claiming world records is a bit irresponsible.\u201d<\/p>\n

VO is correct in thinking Siemens might employ a \u201cmarketing ploy.\u201d\u00a0 Your editor wrote technical white papers, sequences of operations, operations manuals and other detailed, dry bits of prose, but also turned out many proposals, marketing brochures, and scripts that called for a more poetic temperament.\u00a0 That doesn\u2019t make the former more correct than the latter \u2013 just different in approach and selected audience.<\/p>\n

In a March 24 press release<\/a>, Siemens explains that their earlier efforts with an electric hybrid drive in 2011, \u201coptimized\u201d in 2013, had a power\/weight ratio of \u201caround 5 kilowatts per kilogram, which at that time was unsurpassed, but it only delivered a relatively modest 60 kilowatts of continuous power \u2014 enough for a single-engine light aircraft at most.\u201d<\/p>\n

Part of the weight reduction that allowed Siemens to make its power\/weight ratio claim for its 260 kW unit was \u201coptimizing\u201d the motor\u2019s end shield, cutting the weight from 10.5 kilograms to 4.9 kilograms.\u00a0 (Your editor\u2019s manager discouraged the use of \u201coptimized\u201d numbers since that implied that one couldn\u2019t do better.\u00a0 Since statements made in press releases and advertising copy can be interpreted as legal contracts with a potential client, such hyperbole is reined in by many tech editors.)<\/span><\/p>\n

This aluminum component \u201csupports the motor bearing and the propeller, which is fixed to a continuous drive shaft without a gearbox in between.\u201d\u00a0 Dr. Frank Anton, head of electric motor development at Siemens, explains, \u201cIt\u2019s subject to very large forces whenever the nose of the aircraft moves up or down, so it\u2019s an absolutely vital component for the safety of the aircraft.\u00a0 That\u2019s why, in the past, it was always pretty solid and therefore correspondingly heavy.\u201d<\/span><\/p>\n

Using the Siemens computer aided engineering (CAE) program NX Nastran, engineers performed a finite element analysis on the end shield, identified the elements that are barely subject to stress and are therefore dispensable.\u00a0 Dr. Anton explains, \u201cNature designs our bones in a similar manner.\u00a0 Their structure follows the lines of stress from external forces. Using this iterative process, we end up with a solution an engineer would never have been able to work out by means of theory.\u201d<\/p>\n

Departing from the aluminum filigree structure that they crafted, Siemens\u2019 researchers are now working with a carbon-fiber reinforced polymers end shield \u201cthat weighs a mere 2.3 kilograms, less than a quarter of the conventional component.\u201d<\/p>\n

Siemens engineers took on the electromagnetic design of the motor, using a cobalt-iron alloy in the stator for high magnetizability.\u00a0 They arranged permanent magnets in the rotor in a Halbach array, with four magnets \u201cpositioned next to one another in such a way that the orientation of each field is in a different direction.\u201d\u00a0 Magnetic flux can reach high levels with a minimum use of materials. \u00a0This might help them attain the 97-percent efficiency goal they note in their press release.<\/p>\n

\"Difference<\/a>

Difference between Halbach and more conventional arrangement of magnetic flux<\/p><\/div>\n

Cooling uses \u201cdirect-cooled conductors\u201d and \u201can electrically non-conductive cooling liquid.\u201d Siemens uses silicon oil or Galden<\/a>.\u00a0 The Solvay Plastics web site explains, \u201cGalden\u00ae PFPE is a line of high-performance, inert, fluorinated fluids used as heat transfer and for various high-tech applications in the Electrical & Electronics and Semiconductors markets.\u201d<\/p>\n

The Halbach array is not a new idea, and is in use in LaunchPoint motors.\u00a0 The fact that two different companies have developed motors using this technology is not an indicator of skullduggery on either\u2019s part \u2013 no more so than that they both use electricity to power the motor.<\/p>\n

Dr. Anton will be at the ninth annual Electric Aircraft Symposium<\/a> in Santa Rosa, California on May 1st and 2nd, along with Michael Ricci of LaunchPoint Technologies. \u00a0\u00a0Attendees will be able to compare the two company\u2019s approaches, a benefit of an open forum and an exciting opportunity to hear about the latest in technological breakthroughs in motors.\u00a0 (Now, that approaches hyperbole \u2013 but one within legitimate bounds.)<\/p>\n

Doubtless, <\/span>Dr. Anton will expand on this idea<\/a>: \u201cOnly a very few companies have such detailed understanding of converters and motors, not to mention decades of experience working with them in very different and sometimes very extreme environments.\u00a0 What\u2019s more, at Siemens we\u2019re committed to the idea of electrically powered flight and have the staying power to develop the new drives.\u201d<\/span><\/p>\n

\"First<\/a>

First in electric flight: Tissandier Brothers fly their Siemens motor-powered aerostat in 1883<\/p><\/div>\n

History is on his side in the matter of decades of experience.\u00a0 The Tissandier brothers used a Siemens motor on their electrically-powered aerostat in 1883, a world first.<\/p>\n