Rapid and widespread adoption of Electric vehicles has been impeded by consumers’ anxiety over the reliability of batteries, limited autonomous options, and many other issues. In 2020, highly advanced technologies will be integrated into EVs to address these issues and entice consumers.
Electric vehicles are a growing market for new car purchases with more and more people making the switch from the petrol station to an electrical outlet to fuel their vehicles. Electric car charging stations have been growing at an exponential rate. With every manufacturer planning to make the eventual transition towards electric vehicles, throwing up infrastructure has become a potentially lucrative investment. This trend toward electric vehicles is expected to continue, especially with the billions of dollars that auto manufacturers are investing in these new vehicles.
The year 2020 would be remembered as the one that gave vitality to the electric vehicle revolution in India. The Auto Expo 2020 saw the birth of dozens of EVs of different sizes and prices from a wide section of automakers. With this new wave of electric vehicles, there is a desire for constant innovations in the electric car industry requiring a need for more infrastructure to accommodate the consumer demand. Seeing an electric car on the road will become as common as driving past a traffic light.
Types of Electric Vehicles: BEV, PHEV and HEV
There are three main types of electric vehicles (EVs), classed by the degree that electricity is used as their energy source. BEVs, or battery electric vehicles, PHEVs of plug-in hybrid electric vehicles, and HEVs, or hybrid electric vehicles. Only BEVs are capable of charging on a level 3, DC fast charge.
Battery Electric Vehicles (BEV)
Battery Electric Vehicles, also called BEVs, and more frequently called EVs, are fully-electric vehicles with rechargeable batteries and no gasoline engine. Battery electric vehicles store electricity on board with high-capacity battery packs. Their battery power is used to run the electric motor and all on-board electronics. BEVs are charged by electricity from an external source. Electric Vehicle (EV) chargers are classified according to the speed with which they recharge EVs battery. BEV Examples that can charge on DC Level 3 Fast Chargers are Tesla Model 3, BMW i3, Chevy Bolt, Chevy Spark, Nissan LEAF, Ford Focus, Electric, Hyundai Ioniq, Karma Revera, Kia Soul, Mitsubishi i-MiEV, Tesla Model S, Tesla X, Toyota Rav4 and Volkswagen e-Golf.
Plug-in Hybrid Electric Vehicle (PHEV)
Plug-in Hybrid Electric Vehicles or PHEVs can recharge the battery through both regenerative braking and “plugging in” to an external source of electrical power. While “standard” hybrids can (at low speed) go about 1-2 miles before the gasoline engine turns on, PHEV models can go anywhere from 10-40 miles before their gas engines provide assistance.
Hybrid Electric Vehicles (HEV)
HEVs are powered by both gasoline and electricity. The electric energy is generated by the car’s own braking system to recharge the battery. This is called ‘regenerative braking’- a process where the electric motor helps to slow the vehicle and uses some of the energy normally converted to heat by the brakes.
HEVs start off using the electric motor, then the gasoline engine cuts in as load or speed rises. The two motors are controlled by an internal computer, which ensures the best economy for the driving conditions.
Electric Vehicle Battery Charging:
Charging your EV requires plugging into a charger connected to the electric grid, also called electric vehicle supply equipment (EVSE). There are four major categories of chargers, based on the maximum amount of power the charger provides to the battery from the grid:
- Level 1– Home Charging: Provides charging through a 120 V AC plug and does not require installation of additional charging equipment. Can deliver 2 to 5 miles of range per hour of charging. Most often used in homes and workplaces.
- Level 2– Home and Public Charging: Provides charging through a 240 V (for residential) or 208 V (for commercial) plug and requires installation of additional charging equipment. Can deliver 10 to 20 miles of range per hour of charging. Used in homes, workplaces, and for public charging.
- Level 3– DC Fast Charge: Provides charging through 480 V AC input and requires highly specialized, high-powered equipment as well as special equipment in the vehicle itself. They typically provide up to an 80% charge in just 20-30 minutes. Used most often in public charging stations, especially along heavy traffic corridors.
- Wireless battery management system (wBMS):Automotive Industry’s First Wireless Battery Management System for Electric Vehicles introduced by Analog Devices Inc. It enables automotive manufacturers increased flexibility to scale their electric vehicle fleets into volume production across a wide range of vehicle classes. It will debut on General Motors’ production vehicles powered by Ultium batteries like Chevrolet, Buick, GMC, Cadillac, Holden, Baojun and Wuling.
The implementation of ADI’s wBMS eliminates the traditional wired harness, saving up to 90% of the wiring and up to 15% of the volume in the battery pack, as well as improving design flexibility and manufacturability, without compromising range and accuracy over the life of the battery.
ADI’s wBMS includes all integrated circuits, hardware and software for power, battery management, RF communication, and system functions in a single system-level product that supports ASIL-D safety and module-level security building upon ADI’s proven industry leading BMS battery cell measurement technology. Additional system features enable batteries to measure and report their own performance, increasing early failure detection, and enabling optimized battery pack assembly.
Types of plugs
Most modern chargers and vehicles have a standard connector and receptacle, called the SAE J1772. Any vehicle with this plug receptacle can use any Level 1 or Level 2 EVSE. All major vehicle and charging system manufacturers support this standard, so your vehicle should be compatible with nearly all non-fast charging workplace and public chargers.
Fast charging currently does not have a consistent standard connector. SAE International, an engineering standards-setting organization, has passed a standard for fast charging that adds high-voltage DC power contact pins to the SAE J1772 connector currently used for Level 1 and Level 2. This connector enables use of the same receptacle for all levels of charging, and is available on certain models like the Chevrolet Spark EV. However, other EVs (the Nissan Leaf and Mitsubishi i-MiEV in particular) use a different type of fast-charge connector called CHAdeMO.
Fortunately, an increasing number of fast chargers have outlets for both SAE and CHAdeMO fast charging. Lastly, Tesla’s Supercharger system can only be used by Tesla vehicles and is not compatible with vehicles from any other manufacturer. Tesla vehicles can use CHAdeMO connectors through a vehicle adapter.
Electric Vehicle Motor Technology
The core element of the EV, apart from Electric Vehicle Batteries, which replaces the Internal Combustion engines is an Electric motor. The rapid development in the field of Power electronics and control techniques has created a space for various types of electric motors to be used in Electric Vehicles. The electric motors used for automotive applications should have characteristics like high starting torque, high power density, good efficiency, etc. The five types of motors used for EVs:
- DC Series Motor
High starting torque capability of the DC Series motor makes it a suitable option for traction application. It was the most widely used motor for traction application in the early 1900s. The advantages of this motor are easy speed control and it can also withstand a sudden increase in load. All these characteristics make it an ideal traction motor. The main drawback of DC series motor is high maintenance due to brushes and commutators. These motors are used in Indian railways. This motor comes under the category of DC brushed motors.
- Brushless DC Motors
It is similar to DC motors with Permanent Magnets. It is called brushless because it does not have the commutator and brush arrangement. The commutation is done electronically in this motor because of this BLDC motors are maintenance free. BLDC motors have traction characteristics like high starting torque, high efficiency around 95-98%, etc. BLDC motors are suitable for high power density design approach. The BLDC motors are the most preferred motors for the electric vehicle application due to its traction characteristics. BLDC motors further have two types:
- Out-runner type BLDC Motor:In this type, the rotor of the motor is present outside and the stator is present inside. It is also called as Hub motors because the wheel is directly connected to the exterior rotor. This type of motors does not require external gear system. In a few cases, the motor itself has inbuilt planetary gears. This motor makes the overall vehicle less bulky as it does not require any gear system. It also eliminates the space required for mounting the motor. There is a restriction on the motor dimensions which limits the power output in the in-runner configuration. This motor is widely preferred by electric cycle manufacturers like Hullikal, Tronx, Spero, light speed bicycles, etc. It is also used by two-wheeler manufacturers like 22 Motors, NDS Eco Motors, etc.
- In-runner type BLDC Motor:In this type, the rotor of the motor is present inside and the stator is outside like conventional motors. These motor require an external transmission system to transfer the power to the wheels, because of this the out-runner configuration is little bulky when compared to the in-runner configuration. Many three- wheeler manufacturers like Goenka Electric Motors, Speego Vehicles, Kinetic Green, Volta Automotive use BLDC motors. Low and medium performance scooter manufacturers also use BLDC motors for propulsion.
- It is due to these reasons it is widely preferred motor for electric vehicle application. The main drawback is the high cost due to permanent magnets.Overloading the motor beyond a certain limit reduces the life of permanent magnets due to thermal conditions.
- Permanent Magnet Synchronous Motor (PMSM)
This motor is also similar to BLDC motor which has permanent magnets on the rotor. Similar to BLDC motors these motors also have traction characteristics like high power density and high efficiency. The difference is that PMSM has sinusoidal back EMF whereas BLDC has trapezoidal back EMF. Permanent Magnet Synchronous motors are available for higher power ratings. PMSM is the best choice for high performance applications like cars, buses. Despite the high cost, PMSM is providing stiff competition to induction motors due to increased efficiency than the latter. PMSM is also costlier than BLDC motors. Most of the automotive manufacturers use PMSM motors for their hybrid and electric vehicles. For example, Toyota Prius, Chevrolet Bolt EV, Ford Focus Electric, zero motorcycles S/SR, Nissan Leaf, Hinda Accord, BMW i3, etc use PMSM motor for propulsion.
- Three Phase AC Induction Motors
The induction motors do not have a high starting toque like DC series motors under fixed voltage and fixed frequency operation. But this characteristic can be altered by using various control techniques like FOC or v/f methods. By using these control methods, the maximum torque is made available at the starting of the motor which is suitable for traction application. Squirrel cage induction motors have a long life due to less maintenance. Induction motors can be designed up to an efficiency of 92-95%. The drawback of an induction motor is that it requires complex inverter circuit and control of the motor is difficult.
In permanent magnet motors, the magnets contribute to the flux density B. Therefore, adjusting the value of B in induction motors is easy when compared to permanent magnet motors. It is because in Induction motors the value of B can be adjusted by varying the voltage and frequency (V/f) based on torque requirements. This helps in reducing the losses which in turn improves the efficiency.
Tesla Model S is the best example to prove the high performance capability of induction motors compared to its counterparts. By opting for induction motors, Tesla might have wanted to eliminate the dependency on permanent magnets. Even Mahindra Reva e2o uses a three phase induction motor for its propulsion. Major automotive manufacturers like TATA motors have planned to use Induction motors in their cars and buses. The two-wheeler manufacturer TVS motors will be launching an electric scooter which uses induction motor for its propulsion. Induction motors are the preferred choice for performance oriented electric vehicles due to its cheap cost. The other advantage is that it can withstand rugged environmental conditions. Due to these advantages, the Indian railways has started replacing its DC motors with AC induction motors.
- Switched Reluctance Motors (SRM)
Switched Reluctance Motors is a category of variable reluctance motor with double saliency. Switched Reluctance motors are simple in construction and robust. The rotor of the SRM is a piece of laminated steel with no windings or permanent magnets on it. This makes the inertia of the rotor less which helps in high acceleration. The robust nature of SRM makes it suitable for the high speed application. SRM also offers high power density which are some required characteristics of Electric Vehicles. Since the heat generated is mostly confined to the stator, it is easier to cool the motor. The biggest drawback of the SRM is the complexity in control and increase in the switching circuit. It also has some noise issues. Once SRM enters the commercial market, it can replace the PMSM and Induction motors in the future.
Conclusion:
With the foundation laid for both electric vehicles and their infrastructure, driving electric is becoming the new norm. The concerns of the past – speed, driving distance and fueling time, to name a few – are quickly diminishing. Purchase prices also continue to decrease and are expected to reach parity with petrol vehicles in the next few years.
Improving and more cost-effective batteries will further reduce the price of electric vehicles, and technology continues to enhance their durability. Those developments, coupled with the spread and progress of charging stations, paint an optimistic picture for the electric vehicle future.
