How electronics has been changing motoring
Jul 10, 2019
No doubt about it. Cars have changed the world in the past hundred years. Even so, the trend towards ever faster and bigger models seems to have been bucked. Climate change and diminishing resources have forced us to rethink. Electron power has replaced horsepower in defining a car’s performance, with fascinating applications emerging for modular converters.
The Formula Student Electric (FSE) racing car developed at the University of Munich has six highly isolated RECOM DC/DC converters on each wheel supplying the power electronics (Photo: MunicHMotorsport)
Anyone that expects a quick shift towards e-cars in Germany with a graduate physicist at the levers of power will be disappointed. The political scene originally forecast a million e-cars by 2020, but last year only saw fifty thousand – and that’s including half the number of “hybrid compromises.” All the political and environmental activists seem to be campaigning for the same, so why has the transition been so sluggish? There’s a host of reasons.
With this in mind, enthusiasm for e-mobility is unsurprisingly lukewarm. It’s almost as if the time hasn’t quite come for battery-powered motoring – especially considering that a battery with 400km range weighs in at 600 kilos. This weight needs to be moved along with the car, decreasing efficiency. It comes as little consolation that electric motors are lighter than conventional car engines – even if some of the power can be recovered during braking.
How voltage transformers come into the picture
Charging circuitry is required to convert AC power from the grid into high DC voltage while monitoring and controlling the charging process before an e-car can set off with a fully charged battery. A conventional 230V socket is enough to charge a small e-car in the garage overnight. The car comes with its own charging circuitry. The charging process will take hours at the maximum 2.3kW power available from a domestic power outlet.
Public and fast-charging stations are quicker as they pull more than 100kW and take an hour or so to charge up an 85kWh battery. Ultra-high-power stations still under development can handle up to 400kW. This would speed up the charging process to around a quarter of an hour, which would easily fit in with quick breaks planned in every few hundred kilometres.
Fig. 1: Voltage converters in charging stations provide the high levels of isolation needed.
All major charging stations use DC voltage to charge up e-car batteries. Voltages of 400V are currently standard, but this could rise to 800V sometime in the future. Voltages of this scale are deadly on contact even if DC voltage is thought of as safe in a home environment. Demands on the reliability of the whole system are correspondingly high.
This needs mechanically robust plug connections as well as a reliable electronic safety system. To this end, the battery management system in the car keeps constant communication with the charging station. The power only flows with the charger plug securely seated in the charging socket and the battery charger transmitting a constant “ok” signal. The charging station instantly disconnects on any interruption to the signal.
The RECOM RAC05-xxSK/480 was developed for this monitoring task (Fig. 2). The AC/DC converter operates at input voltages of up to 528V AC, and therefore easily operates between two phases in the three-phase system. Isolated for voltages of up to 4kV, the 5W converter converts three-phase power into low DC voltages of 5 or 12V DC for the monitoring electronics. The AC/DC converter’s auxiliary power powers the handshaking system that only allows power to flow if everything else is in good order.
Fig. 2: The RECOM RAC05-xxSK/480 converts 480V three-phase power into 5 or 12V DC. The 5W converter operates at temperatures of 40°C minus to 80°C plus.
Not only charging stations need thorough monitoring; the battery itself requires constant observation. Advanced lithium-ion batteries are usually arranged into several modules. Current, voltage and temperature in each module need to be monitored separately to ensure a charging process that preserves the battery. It has to be possible to switch off individual modules if they fail while continuing to supply power to the healthy modules. A complex electronic system is vital in battery life maximisation and failure protection for individual cells.
RECOM has already developed a series of 1W DC/DC converters used for battery management in e-cars. Each battery module needs its own DC/DC converter to isolate monitoring electronics equipment operating at various floating voltages from the CAN bus. RECOM converters are isolated for voltages of 5.2kV DC and hi-pot-tested.
Highly isolated DC/DC converters are also used for controlling power semiconductors in charging stations. This involves using IGBT, SiC or Si MOSFETs or GaN FETs controlled by gate drivers, which require a positive and negative voltage each to accelerate the switching process and avoid misfires.
The power switches have high floating voltages, so the driver’s voltage supply needs very effective isolation. RECOM has developed dual “reinforced” isolated DC/DC converters with output voltages of +15V/-9V (IGBT), +15V/-3V and +20V/5V (SiC) and +6V/+9V (GaN) for the purpose. These converters have especially low coupling capacities to ensure long system service life.
Fig. 3: Highly isolated DC/DC converters with dual outputs supply IGBT, SiC or GaN drivers with floating voltage.
Motor racing generates innovation
Motor racing provides an effective general barometer of technological change. Additional electric power plays an essential role in winning at formula racing. Formula E has been growing from strength to strength and runs on electricity. The race can be completed on one battery charge now compared to a year ago, when the car had to be changed mid-race.
Universities are also working hard on the future. Students at the University of Munich University are working together with municHMotorsport on an electrically powered racing car to run in the Formula Student Electric (FSE) race. The four three-phase motors in the wheel hubs are equipped with a total of twenty-four isolated DC/DC converters from the RECOM RxxP2xx family to power the control electronics. The racer exhibited at the RECOM booth of the electronica 2018 trade fair runs at 174 bhp and goes from 0 to 100 km/h in less than two seconds.
Outlook
Researchers across the world are working hard on improving e-mobility technology – not least in China. Whether or not lithium-ion batteries will be the last word remains to be seen. Researchers at the Institute for Energy and Climate Research see a lot of potential in developing a new type of solid-state battery. All the components are manufactured from phosphate compounds. There doesn’t seem to be any lack of resources for these. No fluids are used, so they should be safer and more durable than lithium-ion batteries.
Hydrogen-powered fuel cells are also considered promising. The Friedrich Alexander University of Erlangen is researching safe “fuels” with hydrogen organically bound in oil. These liquid organic hydrogen carriers (LOHCs) are neither flammable nor toxic and can be used the same way as conventional fuel in normal fuel tanks. Cars would need around the same amount of LOHC fuel as normal car fuel to cover a distance of 600–800 km. The existing service station network could also be used for filling up with LOHC fuel.
Even so, the drive will definitely be electric with electronic control, monitoring and communication. This will require a variety of innovative voltage converters – one reason for RECOM to focus specifically on e-mobility.
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Anyone that expects a quick shift towards e-cars in Germany with a graduate physicist at the levers of power will be disappointed. The political scene originally forecast a million e-cars by 2020, but last year only saw fifty thousand – and that’s including half the number of “hybrid compromises.” All the political and environmental activists seem to be campaigning for the same, so why has the transition been so sluggish? There’s a host of reasons.
- Range and lack of charging stations: The lithium-ion batteries available barely have enough capacity for a carefree start to the weekend. That especially applies to the summer and winter months calling for a climate-controlled interior. Apart from that, quick-charging stations are still very thin on the ground in Germany – especially in rural areas. And once found, it’s still almost an hour’s wait for the battery to charge up enough for a couple of hours of driving. This means that pure e-cars only make sense as second cars for driving around town.
- E-cars are still too expensive: E-cars are still too expensive for the mass market despite state subsidies. The price of electricity is also especially high in Germany, saving just 30% compared to diesel at at 30 cents/kWh. These savings might pay off for long-distance journeys, but hardly for a city runabout next to the family car.
- Limited battery life: E-cars save on maintenance costs such as oil changes, but the heavy cost of replacing a worn-out battery looms large after a few years. An e-car’s value could be expected to depreciate to a few thousand euros with the original battery fitted as potential buyers will need to factor in the cost of a new battery.
- E-mobility is not as clean as its reputation: Even without an exhaust pipe, e-cars are not nearly as clean as their reputation. The raw materials used in lithium-ion batteries include lithium, cobalt and nickel, which are mined in countries where environmental protection is not high on the priority list. Apart from that, manufacturing emissions average more than a hundred kilos of carbon dioxide per kilowatt-hour of battery capacity. On top of that, the electrical power needed to charge the battery is only free of emissions if it comes from renewable sources.
- The raw materials are not available in unlimited quantities: Nobody knows how long lithium deposits and other resources will last in amounts high enough to meet the needs of global e-mobility. As resources dwindle, the price of batteries may well rise rather than fall, especially as the battery will have to be replaced at least once over the lifetime of the e-car. The raw materials can to some extent be recovered by recycling, but this process is time-consuming and expensive.
With this in mind, enthusiasm for e-mobility is unsurprisingly lukewarm. It’s almost as if the time hasn’t quite come for battery-powered motoring – especially considering that a battery with 400km range weighs in at 600 kilos. This weight needs to be moved along with the car, decreasing efficiency. It comes as little consolation that electric motors are lighter than conventional car engines – even if some of the power can be recovered during braking.
How voltage transformers come into the picture
Charging circuitry is required to convert AC power from the grid into high DC voltage while monitoring and controlling the charging process before an e-car can set off with a fully charged battery. A conventional 230V socket is enough to charge a small e-car in the garage overnight. The car comes with its own charging circuitry. The charging process will take hours at the maximum 2.3kW power available from a domestic power outlet.
Public and fast-charging stations are quicker as they pull more than 100kW and take an hour or so to charge up an 85kWh battery. Ultra-high-power stations still under development can handle up to 400kW. This would speed up the charging process to around a quarter of an hour, which would easily fit in with quick breaks planned in every few hundred kilometres.
Fig. 1: Voltage converters in charging stations provide the high levels of isolation needed.
All major charging stations use DC voltage to charge up e-car batteries. Voltages of 400V are currently standard, but this could rise to 800V sometime in the future. Voltages of this scale are deadly on contact even if DC voltage is thought of as safe in a home environment. Demands on the reliability of the whole system are correspondingly high.
This needs mechanically robust plug connections as well as a reliable electronic safety system. To this end, the battery management system in the car keeps constant communication with the charging station. The power only flows with the charger plug securely seated in the charging socket and the battery charger transmitting a constant “ok” signal. The charging station instantly disconnects on any interruption to the signal.
The RECOM RAC05-xxSK/480 was developed for this monitoring task (Fig. 2). The AC/DC converter operates at input voltages of up to 528V AC, and therefore easily operates between two phases in the three-phase system. Isolated for voltages of up to 4kV, the 5W converter converts three-phase power into low DC voltages of 5 or 12V DC for the monitoring electronics. The AC/DC converter’s auxiliary power powers the handshaking system that only allows power to flow if everything else is in good order.
Fig. 2: The RECOM RAC05-xxSK/480 converts 480V three-phase power into 5 or 12V DC. The 5W converter operates at temperatures of 40°C minus to 80°C plus.
Not only charging stations need thorough monitoring; the battery itself requires constant observation. Advanced lithium-ion batteries are usually arranged into several modules. Current, voltage and temperature in each module need to be monitored separately to ensure a charging process that preserves the battery. It has to be possible to switch off individual modules if they fail while continuing to supply power to the healthy modules. A complex electronic system is vital in battery life maximisation and failure protection for individual cells.
RECOM has already developed a series of 1W DC/DC converters used for battery management in e-cars. Each battery module needs its own DC/DC converter to isolate monitoring electronics equipment operating at various floating voltages from the CAN bus. RECOM converters are isolated for voltages of 5.2kV DC and hi-pot-tested.
Highly isolated DC/DC converters are also used for controlling power semiconductors in charging stations. This involves using IGBT, SiC or Si MOSFETs or GaN FETs controlled by gate drivers, which require a positive and negative voltage each to accelerate the switching process and avoid misfires.
The power switches have high floating voltages, so the driver’s voltage supply needs very effective isolation. RECOM has developed dual “reinforced” isolated DC/DC converters with output voltages of +15V/-9V (IGBT), +15V/-3V and +20V/5V (SiC) and +6V/+9V (GaN) for the purpose. These converters have especially low coupling capacities to ensure long system service life.
Fig. 3: Highly isolated DC/DC converters with dual outputs supply IGBT, SiC or GaN drivers with floating voltage.
Motor racing generates innovation
Motor racing provides an effective general barometer of technological change. Additional electric power plays an essential role in winning at formula racing. Formula E has been growing from strength to strength and runs on electricity. The race can be completed on one battery charge now compared to a year ago, when the car had to be changed mid-race.
Universities are also working hard on the future. Students at the University of Munich University are working together with municHMotorsport on an electrically powered racing car to run in the Formula Student Electric (FSE) race. The four three-phase motors in the wheel hubs are equipped with a total of twenty-four isolated DC/DC converters from the RECOM RxxP2xx family to power the control electronics. The racer exhibited at the RECOM booth of the electronica 2018 trade fair runs at 174 bhp and goes from 0 to 100 km/h in less than two seconds.
Outlook
Researchers across the world are working hard on improving e-mobility technology – not least in China. Whether or not lithium-ion batteries will be the last word remains to be seen. Researchers at the Institute for Energy and Climate Research see a lot of potential in developing a new type of solid-state battery. All the components are manufactured from phosphate compounds. There doesn’t seem to be any lack of resources for these. No fluids are used, so they should be safer and more durable than lithium-ion batteries.
Hydrogen-powered fuel cells are also considered promising. The Friedrich Alexander University of Erlangen is researching safe “fuels” with hydrogen organically bound in oil. These liquid organic hydrogen carriers (LOHCs) are neither flammable nor toxic and can be used the same way as conventional fuel in normal fuel tanks. Cars would need around the same amount of LOHC fuel as normal car fuel to cover a distance of 600–800 km. The existing service station network could also be used for filling up with LOHC fuel.
Even so, the drive will definitely be electric with electronic control, monitoring and communication. This will require a variety of innovative voltage converters – one reason for RECOM to focus specifically on e-mobility.
RECOM: We Power your Products
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