EV Engines are the heart of every electric car conversion, but which one will suit your personal, financial, and performance needs? Today we are going to dive into this world of EV Engines.
Internal combustion engines (ICEs), which have dominated transportation for more than a century, are being replaced by electric vehicles as a preferred green transportation option. Electric vehicles work with a battery-powered electric motor. For electric vehicles, a variety of motor types are used. This article examines the EV motor types that are most frequently utilized from the inside out.
Quick Overview
Electric vehicles employ traction motors that can send torque to the wheels. The two main categories of electric motors are DC and AC motors. Both kinds are applicable to EV applications. DC motors are reliable and offer straightforward control. Both brushed and brushless DC motors can be produced. A well-established technology, brushed DC motors offer low cost, strong torque at low speed, and simple speed regulation. These characteristics are crucial for traction motors. However, due to their drawbacks, such as their size, inefficiency, and need for frequent maintenance because of the brush and collector arrangement, brushed DC motors are not commonly utilized in EVs. High efficiency, reduced maintenance, improved dependability, and regenerative capability, which allows braking energy to be transferred back to the batteries, are all advantages of AC motors over DC motors.
EV Engine Must-haves
Because lost power must be made up for, an EV’s motor and electronics efficiency directly affect the battery weight. Battery power is increased by 1% for every 1% decrease in efficiency (meaning more batteries). The electrical motor’s specs have a direct impact on how well the EV performs. The torque-speed and power-speed characteristics of the traction motor determine the motor’s performance.
The maximum speed and grade ability are crucial factors in these curves. High torque at low speed is necessary for the required motor grade ability, allowing for proper starting and acceleration.
According to the graph (Torque and power curves of an electric motor), the EV motor must have a large speed range in the constant power area as well as high power at high speed. For a smooth start and uphill drive at low speed, the constant torque operating region is crucial.
The maximum EV speed on flat surfaces is determined by the constant power region.
The EV motor achieves its rated power limit when the base speed is reached, and the torque of the EV motor drops proportionally to the square of speed. Beyond base speed, in the range from base speed to maximum motor speed, the constant power area begins. This range varies between motor types and is a crucial factor in choosing the right EV motor type. Additionally, by utilizing the appropriate control drives, the motor operation range can be modified.
Finding the right balance between acceleration performance and wide speed range in the constant power area is difficult when choosing an EV motor’s output characteristic. The power needed for acceleration performance decreases when the constant power zone is expanded. The amount of torque required rises, affecting the motor’s size and final cost.
The EV Engines Comparison
You really have to be smart about the engine you will select. This is why we will compare the sort of EV Engines available on the items below:
- Efficiency
- Instant power
- Torque response
- Power density
- Low cost
- Acceleration
- Robustness
The DC Motor – Direct Current Motor
The sturdy design and easy operation of DC motors in EVs are their main benefits. Due to their proper torque-speed properties, DC motors can generate a lot of torque at low speeds. Their primary drawbacks include their size, poor performance, poor dependability, high maintenance requirements, and slow speed due to friction between brushes and collectors. Brushless and brushed DC motors are two different types of DC motors. The latter is being inhibited more and more as power electronics develop.
The PM BLDC Motor – Permanent Magnet Brushless DC Motor
Permanent magnets are used in PM BLDC motors in place of the rotor windings. Their efficiency is greater than that of inductive motors since they do not account for rotor losses. Due to a stator field weakening the permanent magnet field, PM BLDC motors have a limited constant power operation zone. Conduction angle control can be used to increase the constant power region needed for EVs, which can increase the speed range to three to four times the base speed.
The motor torque is also restricted by the permanent magnets. The high temperature has a substantial impact on the magnets, which lowers the remaining flux density and, as a result, the motor torque capacity. The primary drawbacks of this kind of motor are the mechanical forces and magnet costs. Due to the potential for the magnets to break, the increased centrifugal forces brought on by faster motor rotation rates can provide safety concerns.
The IM Motor – Induction Motor
Due to its straightforward design, excellent dependability, robustness, ease of maintenance, low cost, and functioning in many environmental conditions, this motor type is widely used in EVs. If the inverter fails, IMs can naturally de-excite, giving EVs a significant safety benefit. Industrial standards exist for IMs’ field-oriented vector control.
As opposed to PM motors, IMs have slightly lower efficiency, larger power losses (due to increased cage losses), and a relatively low power factor. In the constant power operating area, the speed range can be increased by weakening the flux. Dual inverters can also be used to expand this area. Careful motor design can help cut down on rotor losses.
The PMSM Motor – Permanent Magnet Synchronous Motor
PMSMs have permanent magnets in the rotor, just like BLDCs. PMSMs features a sinusoidal back electromotive force (EMF), in contrast to BLDC motors, which have a trapezoidal back EMF waveform. They are suitable for use as traction motors because of their straightforward design, high efficiency, and high power density (common in hybrid vehicles, EVs, and buses). Comparatively speaking, PMSM motors are more efficient than IMs. High prices eddy current loss in PMs operating at high speeds, and a reliability risk due to the potential for magnet breakage are disadvantages of this design. Surface-mounted permanent magnet (SPM) and interior permanent magnet (IPM) synchronous motor drives are the two types of PMSM motors. IPM motors work better than SPM motors, however, the drawback is their intricate construction.
The SRM Motor – Switched Reluctance Motor
The advantage of SRMs is their high torque component, which makes it possible for them to be used in numerous applications such as wind energy, gas turbine engine generator starter systems, and high-performance aerospace applications. Additionally, their durability, ease of control, high efficiency, wide constant power operation zone, fault tolerance, and efficient torque-speed characteristics are benefits of EV Engines. The maintenance of SRMs is very easy and efficient because they don’t have brushes, collectors, or magnets, and their cost is very reasonable.
The issue with mechanical forces is solved by the absence of magnets, allowing the motor to run at a high speed. Due to the lack of use of the motor’s windings, there are no copper losses in the rotor, resulting in a lower rotor temperature than with other motor types. SRM motors can continue to run even if one of the phases disconnects since the phases are not linked. Compared to other motor types, SRM rotors have reduced inertia. This motor type’s disadvantages include higher acoustic noise and vibration. High torque ripple is also a result of the salient-pole rotor and stator architecture. Because of the high rotor inductance ratio, sensorless control is possible. High speeds can be operated thanks to the wide constant power operation region provided by an appropriately designed motor. SRMs are very applicable for an EV Conversion.
Scoring the EV Engines
This column will provide you with a nice overview of how the different EV Engines score.
It is obvious that the IM motor type possesses all the traits necessary for EVs. Safety is one of the most crucial factors in this application, and the SRM and IM kinds ensure driving safety. The rated speed of IM is, however, somewhat slow. In the low-speed sector, PM has a better power factor and efficiency.
The SRM type requires less maintenance because it does not employ brush collectors and magnets. In comparison to other varieties, this type also has smaller power losses. This is a result of their overall length and short winding ends. One of the key benefits of SRM-type motors is the low rotor temperature and simple cooling provided by the lack of conductors in the rotor.
SRM enables exceptionally high-speed operation and runs at high speeds over a large constant power zone. In addition, the motor is lightweight, affordable, and efficient. SRM is the motor type that EVs should use the most when all factors are taken into account. BLDC motors are not frequently employed in EV applications despite having a reasonably high power density and efficiency. This is mostly due to their limited constant power range.
So where to harvest what?
Traditional IMs are used by the Model S and Model X from Tesla. A switched reluctance motor (SRM) known as an internal permanent magnet switched reluctance motor is used in the Model 3. (IPM-SRM). Tesla also offered dual-motor models; the Model 3 has an IM up front and an IPM-SRM in the back. For the Model S and Model X, the situation is the opposite. The magnets used in the PMSM in the GM Chevrolet Bolt are housed inside the rotor. The Toyota Prius, Nissan Leaf, and BMW i3 all make use of this particular motor type. Each producer uses their methods and technology to provide propulsion that is as effective as possible, and they create numerous variations of the same motor type. There will be many more available in the next years since more EV cars will mean more chance of a wrecked EV for your to harvest a nice EV Engine from. Next to that, there are 9 other fundamentals you could check out before you start! Read all about it.
References:
https://www.engineering.com
Dorrell, D.G., Popescu, M., Knight, A.M., Evans, L., Staton, D., A., “Comparison of Different Motor Design Drives for Hybrid Electric Vehicles”, IEEE, pp. 3352-3359, 2010.
Z., Mounir, El Hachemi Benbouzid, M., Senior Member, Diallo, D., “Electric Motor Drive Selection Issues for HEV Propulsion Systems: A Comparative Study”, IEEE, vol. 55, no. 6, pp. 1756-1764, November, 2006
