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Controlled Power Technologies Heading to Commercialization of Switched-Reluctance Motor Systems for Vehicle Efficiency

Design evolution of the production-ready VTES. Click to enlarge.

Controlled Power Technologies (CPT), a UK startup working with switched reluctance motor technology to deliver cost-effective CO2-reducing solutions for vehicles (earlier post), is progressing toward commercialization of three initial products: Variable Torque Enhancement System, VTES, an electric supercharging system; SpeedStart12, an integrated belt-driven starter generator system; and TIGERS (earlier post), an exhaust turbine-driven generator system.

All three products, acquired from Visteon, employ switched reluctance motors. Controlled Power Technologies secured an exclusive license from Switched Reluctance Drives Limited to develop its electric motor technology for the automotive sector. SR Drives is a UK company based in Harrogate and wholly owned subsidiary of Emerson Electric Company.

VTES schematic. Click to enlarge.

VTES is the closest to commercialization, and is ready for high-volume production, according to CPT. Guy Morris (formerly of Visteon), the company’s engineering director and chief technical officer presented VTES to the Advanced Charging & Downsizing Concepts Congress in Stuttgart, Germany, earlier this month.

VTES is a compact, forced induction torque enhancement system using a compressor driven by an air-cooled switched reluctance motor, which achieves high power density to deliver high airflow and efficiency. The motor operates using existing 12-volt electrical systems.

The fully programmable product is designed for integration into both gasoline and diesel engines. The design has been optimized to achieve effective engine boosting when used on its own or in conjunction with a standard turbocharger.

VTES offers maximum boost pressure of 0.45 bar, with a maximum speed of 70,000 rpm.

When optimized, VTES can dramatically increase the engine air charge density over the first 10 combustion cycles of a low speed transient operation, hence enabling real improvements in both torque and emissions performance, where it matters most.

Looking ahead, this technology also has the potential for energy recovery during throttled operation of gasoline engines. The motor can switch to generator mode almost instantly, the compressor can be configured as a ‘cold air’ induction turbine with efficiencies of more than 50 percent being possible, while power levels greater than 150W can be readily generated at 14 volts.

For fuel cell applications we’re looking at a 2-stage high voltage (240+ volts) concept delivering approximately 4kW of stabilised power offering a more compact, lower mass and lower noise system than other solutions.

—Guy Morris

The SpeedStart12 starter generator system. Click to enlarge.

SpeedStart12 is not quite ready for application, according to CPT, but not far behind VTES in development. SpeedStart12 is a fully integrated belt-driven starter generator system, including all control and power electronics, featuring a liquid-cooled switched reluctance motor.

SpeedStart12 is optimized to use standard 12V vehicle architecture. To ensure compatibility with most modern European powertrains, production intent hardware has been carried out predominantly on a European 2-liter common rail diesel engine, although the product is designed for integration into both gasoline and diesel engines.

CPT is targeting a 5% reduction in CO2 on the NEDC from stop-start functionality, with an additional 3-5% reduction from optimized high-power regeneration during decelerations. Nominal cranking power is 2.2 kW, and continuous generation power is 2.7 kW. Low engine speed generation power is 2.0 kW, and typical generation efficiency is 80%.

Design scheme for TIGERS. Click to enlarge.

TIGERS—Turbo-generator Integrated Gas Energy Recovery System—has been under development since 2004 and was partly funded by the UK government Foresight Vehicle initiative to establish a proof-of-concept.

In the TIGERS system, a small switched reluctance turbo-generator is installed in a by-pass waste pipe fitted just below the engine exhaust manifold. A valve linked to the engine’s management control system allows some of the high-energy exhaust gases to pass through a turbine to drive the generator, depending on engine load conditions.

Typically the 800º C exhaust gases have a velocity of 60m/s and a mass flow rate of 0.05 kg/s, providing enough energy to spin the generator at up to 80,000 rpm and create electrical power of up to 6kW—sufficient to handle the car’s electrical systems.

So far, CPT has met a number of milestones with TIGERS, including engine and vehicle simulation; system concept designs; control system design and simulation; proof of concept detail design and component manufacture as well as engine baseline testing.




It looks like they have several excellent products at exactly the right time.


that motor in the TIGERS will run hot.. not a bad idea if they can get it to work.


Now they just need to combine TIGERS with VTES and they would have something. I am not sure that VR for BAS is the way to go.

Rafael Seidl

@ Herm -

I expect the stator coils would be water-cooled, since the turbine volute has to be anyhow. TIGERS was designed for naturally aspirated gasoline engines in mind. The rotor in a switched reluctance motor does not contain permanent magnets and is therefore more tolerant of high temperatures. Thermal expansion would change the air gap, though, which has to be very small for SR to work.

@ Sjc -

SR motors exhibit torque ripple, as does the crankshaft. The belt's elasticity dampens both of them out but the part needs to be stronger than usual to support cold cranking. It's more difficult to get SR machines to do that, but apparently CPT has licked that problem - at least for the small displacement engines that make up the bulk of the European market.

Note that Valeo stuck with a conventional claw pole machine for its STaRS stop-start system. Those are quite inefficient but their windings can take a lot of amperage, generating a lot of torque at low RPM - just what you want to cold-crank a mid-sized diesel engine in the middle of a harsh winter.


It probably is lower cost, but I usually associate SR with higher RPMs. It makes sense in the turbo and it might be lower cost than PM for the starter/generator.


The rotor in the TIGERS can run hotter than PM materials, but is still limited by the Curie temperature.

I see the interesting possibility of the combination of TIGERS with Speedstart (electric turbocompounding).  The TIGERS could easily produce an excess of power beyond vehicle needs, which has to go somewhere; the VTES in generator mode would add to this.  What better than to dump it to the Speedstart and thence to the output shaft?  But to make this work, the Speedstart would need to be big enough to absorb that much power at continuous duty.

If this could be made larger and the TIGERS run as a second-stage turbine after a turbocharger, this would appear to have immediate possibilities for diesel trucks.


Oh yeah...this is beginning to look like the heat recovery that I have been thinking about for hybrid trucks. Anytime you can recover wasted energy you can get more mileage.


I thought I would pass this along to those interested. This company has developed what they call a Rankine-Microturbine. As best I can figure, it is a combined cycle power plant that claims 40% efficiency.

Henry Gibson

I have watched Emerson and Switched Reluctance drives waste ten years when they had enough money to convert the flywheel in any production automobile to an integrated starter generator hybrid car. Compression relief mechanims would give full electric operation, and regeneration was always possible. Capstone turbine has had air lubricated turbogenerators for ten years why not tiny ones for car and truck exhaust. The big WWII propellor engines had exhaust turbines geared into the main shaft with the final exhaust giving some jet thrust too....hg...

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