Tag Archives: EV

New Circuit Protection Technologies

A wide variety of vehicle models is entering the EV market these days. The demand is for decreased charging times and increased range. This is heightening not only the challenges towards electrical system performance but also towards better circuit protection.

For instance, decreasing the charging times requires systems using higher voltages and higher currents. This has necessitated the shift from the 400 V system to the 800 V, bringing with it major challenges to the design of circuit protection, especially on the battery side. That is because manufacturers must now consider increased fault currents that the protection components must handle.

With motor currents and power ramping up, circuit protection and switching devices also face higher stresses. They now need to withstand not only the higher operating currents but also the higher cycling requirements. Increased range means higher fault currents.

Therefore, circuit protection requirements are moving in several directions simultaneously. SiC MOSFET switches, acting as solid-state resettable transistor switches, address the high-voltage, low-current subsystems.

The power distribution box in the vehicle is still using the conventional system architecture of a coordinated fuse and contactor. Coordination between the two is necessary to ensure they cover the full range of possible faults from a range of underlying causes including different states of charge of the battery.

Another circuit protection technique is the pyrotechnic approach. This comes into play in events of a catastrophic nature, such as in crashes, when it is necessary to physically cut the busbar. These systems are mostly triggered by circuits that deploy the airbag and work to quickly isolate the battery from the rest of the vehicle. This helps to protect the driver, the passengers, and the first responders from fire and explosion from short circuits through the body of the vehicle.

The above are leading to the development of newer types of protection, such as with breaktors, fully coordinating circuit protection, and switching. Its design allows the breaktor to trigger passively or it can actively interrupt in case of power loss, thereby improving the functional safety of critical protection systems. Moreover, it has the ability to reset itself.

Another is an automotive precision bidirectional eFuse, which is increasingly becoming a common device in a vehicle. Traditional automotive fuses can be low in accuracy and slow to react. This can be a safety issue, as the safety of the system is indirectly proportional to the response time of a fuse. An eFuse not only has high accuracy but also a low response time, which increases the safety of the system.

However, there is a durability issue related to fuses and contactors that vehicle manufacturers use. The solution for this is the pyrotechnical switch. This is a protection device based on a trigger-able circuit similar to the functioning of an airbag. It produces a controlled explosion to sever a conducting busbar. Pyrotechnical switches, while solving the challenge of coordination, must rely on accurate triggering rather than on the passive reaction of fuses. Additional components are necessary to ensure a reliable triggering.

All the above protection systems require a trade-off between speed and durability. While a big fuse can be slow to operate, a smaller one may be faster but may suffer from a fatigue risk.

Standard Connectors for EV Charging

With EVs or electric vehicles becoming a trend for both individuals and commercial operations, more people are opting for them for commuting to work, school, and moving around the town. While there are tax benefits to using EVs, they also reduce our dependence on fossil fuels. Moreover, with the maturing of battery technologies, EV performance is comparable to those of vehicles with traditional internal combustion engines.

With the increasing number of EVs in use, their fundamental and foremost requirement is charging the battery. This aspect has led to a spurt in the growth of electric vehicle charging stations. Manufacturers of electric vehicles produce a range of vehicles that they base on their specific design specifications. However, charging devices need a uniform design so that any make or model of an electric vehicle can hook up for charging. At present, there are two categories of electric vehicle chargers—Level 1 and Level 2.

Level 1 chargers are available with the vehicle. They have adapters that the user can plug into a standard mains 120-Volt outlet. Manufacturers make these chargers common for use in home charging outlets.

Level 2 chargers are standalone types and separate from electric vehicles. They have adapters to plug into a 240-Volt outlet. These chargers are typically available in offices, parking garages, grocery stations, and other such locations. Homeowners may also purchase Level 2 chargers separately.

To allow any model or make of EV to connect to any Level 2 chargers, it is necessary for both the EV and the charger to use a standard connector. At present, the standard charger connector for Level 2 chargers is the SAR J1772. All the latest electric vehicles using plug-in charging use the standard SAE J1772 plug, while the charger connectors use the standard SAE J1772 adapters. These are also known as J plugs. J1772_201710 is the most current revision for the J plug specifications.

While SAE was originally an acronym for the Society of Automobile Engineers, presently they are known as SAE International. They often come up with recommended practices that the entire automobile industry accepts as standards. With the use of the standard SAE J1772 plugs, a customer purchasing an electric vehicle from any manufacturer can charge it using the same charging connector. Public electric charging stations also use the SAE J1772 chargers, and these are compatible with plugs in most vehicles from different manufacturers.

Each SAE J1772 charger has a standard coupler control system consisting of AC and DC residual current detectors, an off-board AC to DC high power stage, an auxiliary power stage, an isolation monitor unit, a two-way communication system over a single wire, contactors, relays, service and user interface, and an energy metering unit. Charging stations with J1772 connectors use a cable for charging the electric vehicle, and the rating of this cable is EVJE for 300 Volts or EVE for 600 Volts.

The EVJE/EVE cable consists of a thermoplastic elastomer jacket and insulation around a center conductor made of copper. The cable usually has two conductors of 18 AWG wire, one conductor of 10 AWG, and another conductor of 16 AWG.

Advanced Solutions for Electric Vehicles

Although EVs or electric vehicles have existed in some form or the other for many hundred years now, it is only in the past few decades that technology has advanced and companies have found success. With concern over the effects of air pollution, climate change, and an ever-diminishing supply of fossil fuel, more and more people are considering changing over to EVs.

Consumer demand constitutes the basis of the growing popularity of EVs. The role of governments also helps by tightening their regulations and mandates in reducing carbon emissions with an effort towards reducing global warming.

The rapidly increasing rate of growth of EVs is presenting a huge opportunity not only for EV manufacturers alone, but also for OEMs, and suppliers of aftermarket parts. Although there has been a significant advancement in EV technologies and solutions over the past few decades, there are still a few challenges that must be overcome, and which can quickly become hindrances. Manufacturers must develop new and innovative ways of addressing these challenges if they want to continue on the path to success.

At present, there are three important considerations that most consumers stipulate manufacturers must overcome—range anxiety, performance, and cost.

Even among modern EVs, many could not go very far without their batteries needing a recharge. For most people, this range was too small to seriously consider a changeover to fully electric vehicles. Although battery and motor technology have advanced significantly, range anxiety is still a factor.

Even two decades ago, EVs were struggling to match the performance and power of fossil-fuel-powered vehicles.

As with any new technology, EVs were initially expensive. Typically, modern EVs were far beyond the reach of most people, or what people were willing to pay for them.

Although car manufacturers are actively addressing the above challenges, an EV that is affordable enough for most consumers and does not compromise on performance, and one that requires only a single charge a month, is still only a mirage. Right now, manufacturers are busy balancing tradeoffs between range, performance, and cost. For instance, improving the performance affects range and cost, while cutting costs can severely compromise range and performance.

Fortunately, manufacturers are finding enhancing efficiency to be the key to the solution. For instance, the primary bottleneck to improving range is the capacity of the battery. Although the obvious solution is to use a bigger battery, that complicates matters further. Not only do bigger batteries cost more, but they also weigh more. Therefore, a bigger battery while increasing the vehicle’s cost can also decrease its performance.

Therefore, manufacturers are looking for ways to use the existing battery more efficiently. They are reducing the energy losses occurring naturally in the power-conversion system of the vehicle. This is mainly as lost energy in the form of heat in the EV’s motor, powertrain, and the power-electronics systems in the vehicle.

Weight is another factor affecting performance—a lightweight vehicle has superior performance. Therefore, manufacturers are trying for higher power density, where they add more power to the vehicle without increasing its weight. With lighter batteries and power-conversion systems, the vehicle can achieve better performance and speed.

Advanced Materials for Magnetic Silence

High-performing advanced magnetic materials are now available that help to handle challenges in hybrid/electrical vehicles. These are challenges related to conducted and radiated electromagnetic interference. Automotive engineers are encountering newer challenges with fully electric vehicles or EVs and hybrid electric vehicles or HEVs become more popular.

The above challenges are so intriguing, engineers now have a fundamental discipline for it, noise vibration and harshness or NVH engineering. Their aim is to minimize NVH for ensuring not only the stability of the vehicle but also the comfort of the passengers.

With electric vehicles becoming quieter, several NVH sources that the noise of the internal combustion engine would mask, are now easily discernible. Engineers divide the root cause of the NVH problems in electric vehicles into vibration, aerodynamic noise, mechanical noise, and electromagnetic noise.

For instance, cabin comfort is adversely affected by electromagnetic noise from auxiliary systems such as the power-steering motor and the air-conditioning system. This can also interfere with the functioning of other subsystems.

Likewise, there is electromagnetic interference from the high-power traction drive system. This interference produces harmonics of the inverter switching and power supply frequencies. Moreover, the interference also induces electromagnetic noise within the motor as well.

With the battery frequently charging and discharging when the EV is in operation, combined with various electromagnetic noises like radiated noise, common-mode noise, and differential noise move through the transmission lines.

All the above reduce the cabin comfort in the vehicle while interfering with systems that help manage the combustion engine in an HEV.

As with many engineering projects, NVH issues are also specific to particular platforms and depend on the design of several structural components, the location of subsystems related to one another, and the design of isolating bushes and mountings. Engineers must deal with most NVH issues related to EMI by applying best practices in electrical engineering for attenuating high-frequency conducted and radiated interference as they couple onto cables and reach various subsystems. Engineers use cable ferrites for preventing long wires from acting as pickups or radiating aerials. They also use inline common-mode chokes for attenuating EMI entering signal and power lines by conduction.

For automotive applications, such cable chokes and ferrites must meet exacting criteria.  Major constraints for these components are their weight and size. Common-mode chokes must provide noise suppression through excellent attenuation properties while using a small physical volume. Additionally, they need to suppress broadband noise up to high operating temperatures, while maintaining high electrical and mechanical stress resistance.

To help with manufacturing such as maintaining high levels of productivity, there are further requirements of robustness and easy handling on assembly lines. This ensures each unit reaches customers in perfect condition. New materials meet the above requirements while offering enhanced characteristics.

The new class of materials is Nanocrystalline cores that engineers classify as metals and they help with eliminating low-frequency electromagnetic noise. Cable ferrites and choke cores made of these materials are much smaller than those made from conventional materials like ceramic ferrites. They also deliver superior magnetic performance, presenting a viable solution for challenging automotive and e-NVH issues.