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Sumitomo Electric Develops Liquid Nitrogen Cooled Superconducting Motor for EVs

The prototype motor. Click to enlarge.

Sumitomo Electric Industries Ltd. (SEI) unveiled an electric vehicle equipped with a prototype superconducting motor cooled by liquid nitrogen and built using SEI’s high-temperature superconducting (HTS) wires.

High-temperature superconducting wires, cooled to about -200° C, can reduce electrical resistance to almost zero. The EV can run about 13% longer than an electric vehicle using a conventional copper wire motor, the company said.

In September, 2007, a Japanese research group coordinated by IHI Corporation and including SEI unveiled a 365 kW HTS motor cooled by liquid nitrogen and using SEI’s DI-BSCCO superconducting wire. SEI’s bismuth-based superconducting material is made of bismuth - strontium - calcium - copper - oxygen (Bi-Sr-Ca-Cu-O).

Cutaway of the 365 kW HTS motor announced in September 2007. Click to enlarge.

In 2005, the Japanese research group developed a flux collector based on the idea of applying a large current to the coil while reducing the magnetic flux, and completed the world’s first practical-level liquid-nitrogen cooled HTS motor using this flux collector and SEI’s DI-BSCCO superconducting wire. The group then worked to improve motor capacity and developed the practically applicable 365 kW HTS motor.

The 365 kW HTS motor has the following three main features:

  • In other HTS motors, only the field coil (DC coil) have HTS wires wound around it. However, the research team applied a low AC-loss design to the armature windings (AC coil) by adopting a flux collector.

  • When HTS coils were set in a parallel configuration, non-uniform current distributions occur in the coils. In order to solve this problem, the operating current for each coil was precisely controlled.

  • Earlier HTS motors were required to have a mechanism that allows coolant to circulate through the shaft. However, the HTS motor designed by the Japanese frontier research group has the fixed superconducting armature windings and is without the cooling system using a shaft. This new design enables two motors to be connected in tandem using both ends of the shaft and thus improve the motor’s capacity.

The group is constructing a superconducting propulsion unit for directly driving a contra-rotating propeller by connecting the newly developed 365 kW HTS motor in tandem with a 50 kW HTS motor developed in 2006.

SEI expects larger powered applications of this HTS system to be developed, up to 2,500 kW, for marine applications.

The group included, in alphabetical order: Fuji Electric Systems Co., Ltd.; Hitachi, Ltd.; IHI Corporation; Nakashima Propeller Co., Ltd.; Niigata Power Systems Co., Ltd.; Sumitomo Electric Industries, Ltd.; Taiyo Nippon Sanso Corporation; and University of Fukui (Prof. Hidehiko Sugimoto).

The EV with prototype HTS motor. Click to enlarge.

Sumitomo is also downsizing the applications of the HTS motor system for application in light duty vehicles. The company said that it will continue to work to improve the performance of the prototype EV motor, which is targeted for application in light-duty passenger vehicles. Applications of superconducting motors for buses and large trucks are also underway. The company sees the motor as being practical within 10 years.



Do we need to supercool a electric motor to get just 13% increase?


"The EV can run about 13% longer than an electric vehicle using a conventional copper wire motor, the company said."

Can we assume that they take into account losses to the cooling system? Keeping something at -200C isn't "free" in terms of energy.

One of the great advantages of using an electric motor is that you can potentially mount them in the wheel hub which allows for some pretty unique designs and some weight saving (no transmission, axles, or differentials). I do not see this as being possible with this sort of motor.


Also, does anyone care to speculate about the power density of such a motor? I'd imagine that it is pretty high.


I really don't see the practical application for this in EV, the need to cryogenics makes it useless there (unless there is a liquid hydrogen economy) Sure the power density has been increased and the efficiency has been brought up from 85-90% to 99% oh woop dee doo.


What is the N2 boil off rate for the motor and how does this impact the perceived efficiency gains? Total energy cycle needs to be considered here. More power to them if it is an net efficiency gain. As a reference, liquid H2 requires something like 30% of the H2's heating value to perform the liquefaction process (http://www1.eere.energy.gov/hydrogenandfuelcells/storage/hydrogen_storage.html#liquid).


Why would it be Liquid Nitrogen Cooled rather than Liquid Hydrogen Cooled, with the Hydrogen being used in a fuel cell to provide power for the motor?

It seems that integrating the systems would make sense.


This is pure research. But the naysayers have to immediately downplay their efforts. Hope the naysayers aren't from America showing disregard for basic knowledge advancement.



You have a good idea for PHEVs with a small fuel cell as genset.

A 13% improvement in efficiency (specially on a motor already (85% to 90%) efficient is something to be proud of.

If somebody would have done the same to our famous inefficient ICE motors, (i.e. from 17% to 30% efficiency) many would have rejoiced.

Are we being anti-something here?


any reason it has to be an open cooling system? A single cylinder stirling engine could keep this thing cool provided it doesn't eat up too much energy.

Paul F. Dietz

Liquid nitrogen is much easier to handle than liquid hydrogen and is much less expensive. Liquid hydrogen tanks and lines have to be vacuum insulated, since otherwise air will condense, or even freeze, on them.

HTSC motors might be useful in trains or large trucks, and very likely in ship. The US Navy has been funding work in that area for years, since electric drive adds design flexibility, and also allows the electrical power to be diverted as needed to advanced weapons systems like rail guns, very high power microwave transmitters, or laser and particle beams.



While were at it, why not use the nitrogen the boils off to run a compressed air motor, like the MDI car has?

I remember a company years ago at the Toronto Autoshow, that had a motor that ran on compressed nitrogen, supplied by boiling off liquid nitrogen.

As for infrastructure, liquid nitrogen is already shipped by tanker truck, like gasoline.


13% of 375kw is 49kw.. that 49kw would otherwise turn into heat in the motor, besides the monetary waste it would require lots of forced cooling in the motor, usually with water.. now scale this up to 2500kw.

49kw in a small motor could instantly self destruct if the cooling fails..

I would imagine the nitrogen is not vented, just re-liquefied.

probably too much motor for an 18 wheeler, but that 13% difference in fuel consumption could make a big difference for profitability.

I read somewhere the US Navy has a superconducting motor installed in a destroyer.. tiny thing for the power it produces. 50,000 kw maybe?


If my comment came across as "naysaying," I apologize. The question was meant to spark some critical thinking about what was being proposed and what may need to be improved upon in order for the technology to make sense (from an energy balance perspective). If a superconducting electric motor can provide net energy savings despite the inherit energy penalty in cryogenic coolants, then this has immediate potential. If the current technology can't provide benefits, is there anything that can be done to improve the scenario.
The potential to use liquid hydrogen does have some intriguing dimensions since the requirement for evaporating the liquid fuel can be used to gain propulsion efficiency and thus extend the vehicle’s range. The case for liquid hydrogen would become stronger. However, if the technology is applied to a BEV, PHEV, or HEV, where a cryogenic liquid is not already available, then I doubt there is much benefit in applying the technology. Here’s the kernel of my comment… Analysis is needed to quantify the total energy cycle implications (e.g. more research is needed).

Henry Gibson

Glad to see something working made out of superconductors.

Hydraulics are likely to be better and cheaper for many vehicles. See the UPS van and the INNAS proposed HYDRID series hybrid car. The digital controlled hydraulic motors might be efficient enough too. ..HG..


Next step is to have other portions of the motor superconducting...magnets/magnetic matierals have always been a problem when superconducting.


Hmmm.... so if the motor is 99% efficient, 1% goes to waste heat. In the case of this 365kw motor, that's 3.65kw of heat. Anyone care to speculate as to how much power would be necessary to keep something emitting 3.65kw of heat at -200C? I suppose you need to know the surface area and R factor of the casing....


Harvey, you're making a miscalculation. Improving the efficiency of an ice from 17% to 30% is not the same as increasing the efficiency by 13%. Your example amounts to an efficiency increase of (30/17 - 1) * 100% = 76%. Furthermore, this 13% comes at a high price in terms of cooling, which costs energy too. That's why the response is lukewarm at best.

My guess is that superconducting motors will be limited to large applications, ships and perhaps trains. The relative cost of heating is much lower then. Firstly because of the size and secondly because they are in near continuous operation. A car is parked 95% of its life.

Aren't current state of the art electric motors above 90% efficiency? So how they get to 13% more distance is anybody's guess. Superconducting electronics?

And finally, don't forget that this motor does not work at all when it is not cooled to -200 C. It will not revert to an 'ordinary electric motor' mode when you run out of liquid nitrogen. The superconductor looses any conductivity at room temperature and the motor will not work. So that creates an extra headache of 'liquid nitrogen logistics' for the motorist.

I'm sorry, but it turns out I am a naysayer too. Looks more like the brain child of the marketing department.


Isn't most of the heat coming from resistance(s) which is now very low so derate the requirement to cool he motors waste heat.
Imagine using thermoelectric(one day) to supply energy to directly cool the nitrogen from the remaining heat and It makes more sense.

arnold .

Superconducting grid feeds has been studied and described in the past and that beggars beleif, but hey some people still use the back of the fingernail for checking domestic voltages.
This sounds tame by comparison.



Sorry. I thought it was (real) percentage points. I agree with you that, as you approach 100% efficeincy, percentage points and percent increases are almost the same, but from a low base of 17% it is two very different ball games.

I stand corrected


A question for the engineers among our number as follows:

Is it possible to configure a per wheel motor/super efficient hydrogen storage tank combination where the motor is inside the tank for super cooling. Can the per wheel fuel cell also be included such that hydrogen out gassing feeds the fuel cell and combines the gaseous O2 from air without that air freezing. Would this configuration have any advantages to outweigh its disadvantages?


-200 degrees. Hmmmm. sounds like this technology would be useful for deep space missions or or here in northern Canada.


Too cold now, just have patience.
You only have to wait a few years and you can use a pool in your back yard in winter.

Andrey Levin

Some day into the future, liquid nitrogen won’t be necessary. Nanotubes (carbon and metallic) already demonstrate room-temperature superconductivity properties. One example:


@Andrey Levin

Those nanotubes do everything but make the bed; don’t they?

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