Mitsubishi Electric develops EV motor system with built-in silicon carbide inverter
08 March 2012
|
|
| New EV motor system with built-in silicon carbide inverter. Click to enlarge. |
Mitsubishi Electric Corporation has developed a prototype electric vehicle (EV) motor system with a built-in silicon carbide inverter. The EV motor system is the smallest of its kind, measuring just half the dimensions of Mitsubishi Electric’s existing motor system that uses an external inverter, and loss is below half that of silicon-based systems.
The new motor system is expected to enable manufacturers to develop EVs offering more passenger space and greater energy efficiency. The company plans to commercialize the motor system after finalizing other technologies for motor/inverter cooling, downsizing and efficiency.
The global demand for EVs and hybrid EVs (HEVs) has been growing in recent years, reflecting increasingly strict regulation of fuel efficiency and growing public interest in saving energy resources and reducing carbon dioxide emissions. As EVs and HEVs require relatively large spaces to accommodate their battery systems, there is a strong need to reduce the size and weight of motor systems and other equipment to ensure sufficient room in passenger compartments, Mitsubishi reasons.
Mitsubishi Electric’s existing system—comprising separate motors and inverters driving the motors—requires more space for these components and their wiring. The newly developed cylinder-shaped inverter matches the diameter of the motor, enabling them to be connected coaxially within a chassis, resulting in a substantial downsizing of the motor system.
Silicon chips have been widely used in power devices for inverter switching. Silicon carbide, however, is now recognized as a more suitable material for chips owing to its electrical characteristics, including a breakdown electric field that is 10 times greater compared to silicon chips. This greater breakdown electric field enables thinner chips, which reduces electrical resistance and lowers loss.
All power chips in the inverter are silicon carbide-based, resulting in a more than 50% reduction of loss compared to the company’s silicon-based inverter system.
The motor is a permanent magnet motor that uses a neodymium magnet. Mitsubishi Electric’s proprietary dense-winding structure enabled the company to utilize its Poki-Poki motor production technologies that essentially entail wrapping coils around an extended core to enable higher density and using a joint lapping technique (earlier post) to reduce the size of the motor.
(Mitsubishi has developed the Poki-Poki motor manufacturing technology since 1993 and has applied it to various motors used in such products as information devices, industrial equipments, electrical household appliances, motor vehicles and elevators.)
The size and configuration of the stator and rotator poles were optimized using Mitsubishi Electric’s high-level magnetic-design technology. As a result, magnetic efficiency was increased and power output was improved by 5% over previous motors.
Another EV advancement.
Posted by: kelly | 08 March 2012 at 05:27 AM
This is all good. It's not clear what is the efficiency gain from the "more than 50% reduction of loss". For, example, will the loss reduction move the inverter efficiency from 90% to 96% or is it from 80% to 91%?
The size reduction and ability to coaxially mount the inverter are also good steps forward. Now, how about those batteries ....
Posted by: NorthernPiker | 08 March 2012 at 05:33 AM
An added advantage of combining the motor and controller in 1 package is that they can share the cooling system. This simplifies the use of that waste heat for heating the passenger cabin.
Electric cars miss the 'advantage' of an ICE car of ample waste heat. They must scavenge for waste heat to limit electric consumption in winter.
Posted by: Arne | 08 March 2012 at 06:23 AM
The total inverter-motor-generator efficiency is probably close to 94% to 96%. The 4% to 6% waste + the batteries waste heat could be retrieved to heat the cab. A very high efficiency heat pump could also help to ensure passenger comfort year round.
Posted by: HarveyD | 08 March 2012 at 06:56 AM
Another big savings for EVs, and much less copper wiring is needed.
Perhaps the old design was really bad?.. inverters have been 95% efficient for many years now.
The motor/inverter pictured must be tiny, or the coolant inlets are 2" in diameter.
Posted by: Herm | 08 March 2012 at 08:46 AM
The new Renault ZOE is using a heat pump, 3kW of heat from 1kW of electricity.. pretty nice!
Posted by: Herm | 08 March 2012 at 08:48 AM
That would see a better increase of efficiency if it's installed in a electric hydrogen fuelcell car or truck then in a battery car because an hydrogen tank plus a fuelcell is lighther less costly and more powerful then a battery. Also fuelcell are constant impedance contrary to batteries that are unstable impedance so they can optimise the size of the motor and inverter and if it's installed in a battery car they will have difficulty to power the motor and they will have to overbuild all the components and reduce the power and decrease the range for safety and longevity.
Battery only is the hardest and most complicated way and even if they study this from more then a hundred years they are still not on the market or to say the least it's been rejected by consumers right now. Fuelcell cars and trucks on the other hands are fully devellop and ready but goverments, bloggers and big oil , union worker associations, journalist own by high financial circles and gasoline technicians are impeding the hydrogen infrastructure to protech their jobs that is related to petrol sales.
Posted by: A D | 08 March 2012 at 08:50 AM
The other advantage of SiC is its high operating temperature. Power dissipation that would require liquid cooling for silicon devices can use air cooling instead, making the systems cheaper, simpler and more reliable.
I'm hoping that applications such as this expand the market for SiC devices and bring prices down. There is too much promise there that's been unfulfilled.
Posted by: Engineer-Poet | 08 March 2012 at 09:20 AM
Thank you Herm for the info on the Renault Zoe on-board heat pump. It may be a first in the industry. Using pre-heated air from the battery pack + controls etc it could probably work well in cold climate areas too. It would be more efficient than current A/C units, specially in electrified vehicles.
Posted by: HarveyD | 08 March 2012 at 01:46 PM
Yes, thanks for the Zoe information, it looks like a good little car.
Posted by: SJC | 08 March 2012 at 05:38 PM
Gizmag has the full story of the Zoe the most exciting new car announcement this yoer IMO. Take note at price and range. Much better than the Leaf.
http://www.gizmag.com/renault-zoe-electric-car-geneva-premiere/21755/
Posted by: Account Deleted | 09 March 2012 at 02:56 AM
@Engineer-Poet: Would not GaN technology be a better long-term option for inverters, since as LED lighting takes off, GaN material should improve (fewer LEDs per light) and more importantly get much cheaper than Si-C?
Posted by: NorthernPiker | 09 March 2012 at 05:01 AM
Just look at under-the-hood pictures of the new Focus BEV, its a nightmare of coolant hoses. Simplicity is good.
Posted by: Herm | 09 March 2012 at 06:22 AM
Good article at Gizmag. I am convinced with enough quick chargers in enough places, this could take off.
Think of every shopping center, coffee shop and fast food place with 2-3 quick chargers. Just bluetooth paypoint or mag card, 15 minutes and you have 40 miles more range, no more anxiety.
Posted by: SJC | 09 March 2012 at 08:31 AM
Tesla has already integrated the motor and inverter in the Model S sedan. It's a larger system than the Mitsu, but also much more powerful.
Posted by: JRP3 | 11 March 2012 at 08:19 AM
@Henrik,
When you add in the cost of the battery lease you find that after about 5 years of ownership the smaller Zoe costs the same as the larger LEAF. Not such a great bargain.
Posted by: JRP3 | 11 March 2012 at 08:22 AM