Overcoming Poor Power Quality in Small Spaces

For years, the adoption of electric vehicles (EVs) has been marred by a slow diffusion of innovation among consumers. Probably the most obvious problem is that buyers have been apprehensive of the high initial cost of buying EVs, as well as the total cost of owning an electric vehicle over the course of its lifetime compared to traditional petrol and diesel-powered vehicles.

However, in its annual Electric Vehicle Outlook 2017 report, Bloomberg New Energy Finance (BNEF) brought to light recent data showing that this is changing faster than ever before. According to the report, in the third quarter of 2016, global sales of electric vehicles rose 63 per cent compared to the same period last year, and it projects that total annual sales will exceed one million units for the first time.

Government policy aside, one of the truest indications that we are experiencing a paradigm shift towards clean transport is the response from big oil. Traditional bastions of fossil fuel such as BP, Shell and ExxonMobil are making moves to alter the fundamental make-up of their oil-heavy portfolios. Whether it's investment in straightforward alternative energies such as wind and solar, or research into microalgae-based biofuels, it's clear that EVs are inspiring far-reaching changes.

Soon, all cars will need to be capable of zero-emission driving. Battery-electric and hybrid cars are leading the way to more efficient and sustainable driving, but automotive manufacturers are under significant pressure to design components as robust as those designed for internal combustion vehicles.

This is greatly down to the modern motor vehicle being a far cry from the crude, greasy and heavy electromechanical systems of old. Yet, despite the advancement in nearly every other area of engineering, sitting in a car today, you would be unlikely to tell that the vehicle is being propelled by largely the same internal combustion technology that was invented 159 years ago.

Internal combustion engines (ICEs) as we’ve known them for the past hundred years have been chosen over alternatives like the steam engine because they're relatively well-suited to powering automobiles. Now that the environmental cost is clear, however, the UK Government has announced plans to stop sales of pure ICE vehicles from 2030, with The Road to Zero Strategy.

While sales of electric vehicles are rising, manufacturers are profiting and governments are considering the burgeoning EV market, there are still various challenges that could hamper innovation and development in the market.

According to Toyota, the average car is made up of 30,000 components. In EVs, the number of components is a great deal less, especially when considering the number of moving parts.

To explain more clearly, for an internal-combustion engine (ICE), there is typically the crankshaft, fuel pumps and fuel injectors. In addition to this, there will be two valves per cylinder, or at least four valves per cylinder in the latest more economic engine designs. Outside of the engine, there are even more moving parts including a multiple-speed manual or an automatic transmission.

In comparison, EVs have been created to have the simplest architecture possible. Take the Nissan Leaf for example, which has been manufactured with no clutch or torque converter, but features a simple reduction gearbox, with a single gear ratio and the motor itself has just one moving part.

While the number of components may differ, the design principles for these components are virtually identical. For example, each of these parts must be able to withstand repeated bouts of acceleration and braking, as well as low and high-speed driving over smooth and rough areas. The same parts must be able to perform in a variety of extreme environmental conditions, from hot and humid to cold and wet.

At REO UK, we’ve identified one of the key constraints for EV components to be poor power quality because of issues like electromagnetic interference (EMI). While electrical and electronic components provide a much more efficient transfer of energy, having so many parts operating in close proximity makes the vehicle susceptible to electrical noise.

EMI, if unaddressed can result in overheating, efficiency losses and even interference with the vehicle’s data communication systems. When looking to integrate features that can mitigate issues like EMI, design engineers are also faced with the problem of having the limited space of fitting more electrical components into a vehicle that already has high component density.

This is compounded by the fact that the same lines used to deliver power to the electric vehicle are also used for data signaling to provide the battery management control system with information on variables like charge status, temperature and voltage. A failure to address EMI can result in overheating, efficiency losses and potential radio frequency issues that interfere with the vehicle's data communication systems.

To meet this challenge, REO has built on its extensive experience in railway electrification and developed a variety of inductive and resistive components for electric vehicles and their charging systems. EVs have some equivalent subsystems to those found in their internal combustion counterparts. The powertrain consists of batteries combined with an electric motor to generate propulsion and the drivetrain uses electric motors to drive the wheels.

For the EV charging systems, this takes the form of a single-phase transformer and electromagnetic compatibility (EMC) filter. As transformers get bigger for higher frequency applications, the proportion of losses and eddy currents rises. To keep these at bay, it's preferable to keep the size of the transformer small. REO achieves this by using better core materials such as amorphous cores, nanocrystalline cores and ferrite cores.

Automotive manufacturers should also look to integrate inductive and resistive components to supress EMI. EVs, much like petrol ICE vehicles, feature an inverter and a DC-DC converter, using high frequency switching, to manage power conversion. By using high frequency components like REO’s transformers, filters and choppers, engineers can protect any sensitive semiconductor power electronics in the vehicle.

For example, our chokes have been designed to eliminate electrical noise in the inverter and can effectively store and discharge magnetic energy from the core. This is regardless of whether its core is made from a ferrite, amorphous or nanocrystalline material.

According to the Department of Energy, petrol or diesel cars can only convert between 14 to 26 per cent of the battery’s energy. EVs, however, can convert up to 80 per cent of the battery’s energy. This is because vehicles traditionally use friction to convert mechanical braking energy into heat and wear on the brake pads. In an EV, braking choppers are responsible for converting any energy created as a result of high speed changes.

Components like inverters are also at risk of overheating. As we’ve discussed, design engineers are already limited on space and so traditional air-cooling methods, that involve using a fan to dispel any heat generated, are not viable. Instead manufacturers must integrate liquid-cooling systems to manage the thermal properties of the electrical components while allowing them to meet the space constraints in the vehicle.

As EVs become increasingly mainstream, it’s important that design engineers and automotive companies keep pace with consumer demand and not at the cost of reducing efficiency, by using poor quality or the wrong components. Instead, automotive manufacturers should look to assemble their future models with the latest components that address prominent issues for EVs, like poor power quality.
 

REO UK

http://www.reo.co.uk