Introduction of Electric Powertrain
E-power train System is the final stage of the motor generated power before it hits the wheels. The whole system is responsible to connect motor and wheels, driving and alter the output shaft rotation to a desired speed/torque ratio, allowing a wide range of speed and better performance as the engine has its own RPM limit and maximum torque.
This report will go into further depths of the actual engineering analysis and formulation of the E-power train. The contents describe the formal equations that describe our concept generation as well as the layouts and explanations of the final system. Below we have generated a gear ratio from our given constraint, reasonable assumptions and our goal speed and torque.
1.1 Component of the E-power Train:
Baja vehicle utilize many on board systems that allow the vehicle to operate fully. These systems include the motor, controller, differential etc.
- BLDC Motor
BLDC motor works on the principle similar to that of a conventional DC motor, i.e., the Lorentz force law which states that whenever a current carrying conductor placed in a magnetic field it experiences a force. As a consequence of reaction force, the magnet will experience an equal and opposite force. In case BLDC motor, the current carrying conductor is stationary while the permanent magnet moves.
Figure 1: Principle of motor
When the stator coils are electrically switched by a supply source, it becomes electromagnet and starts producing the uniform field in the air gap. Though the source of supply is DC, switching makes to generate an AC voltage waveform with trapezoidal shape. Due to the force of interaction between electromagnet stator and permanent magnet rotor, the rotor continues to rotate.
- CV Joint
CV stands for Constant Velocity. It's a type of axle which is used on front wheeled drive vehicles which allows power to still be transmitted to the front tires even while wheel is turned. It is called "constant velocity" due to the way it's designed. No matter which way the outer section is turned, it will remain at the same speed as the inner section. This allows for smooth power to be transmitted. U-joints don't work the same, as speed actually varies as the yokes are turned over the u-joint. Here's an image of a typical CV axle:
Figure 2: CV joint and Half shaft assembly
The automotive differential is designed to drive a pair of wheels while allowing them to rotate at different speeds. A locking differential is designed to overcome the chief limitation of a standard open differential by essentially "locking" both wheels on an axle together as if on a common shaft. This forces both wheels to turn in unison, regardless of the traction (or lack thereof) available to either wheel individually.
When the differential is unlocked (open differential), it allows each wheel to rotate at different speeds (such as when negotiating a turn), thus avoiding tire scuffing. An open (or unlocked) differential always provides the same torque (rotational force) to each of the two wheels, on that axle. So although the wheels can rotate at different speeds, they apply the same rotational force, even if one is entirely stationary, and the other spinning. (Equal torque, unequal rotational speed).
Traction is one of the most important aspects of both steering and getting the power to the ground. The ideal tire has low weight and low internal forces. In addition, it must have strong traction on various surfaces and be capable of providing power while in puddles.
The Rims shall be made up of Aluminum to minimize unsprung weight. By reducing the width of the rim the inertia will be directly decreased and subsequently this will also reduce the overall weight. The diameter of all four rims will be 8 inches. To make our Design cost effective.
Figure 3: Tire & Rim
- Battery (Li-ion)
Lithium-ion batteries (LIB) are a family of rechargeable batteries having high energy density and commonly used in consumer electronics. The life cycle & efficiency of li-ion battery is more as compare to other type of rechargeable battery.
Figure 4: Battery (Top view)
- Kelly Controller
A motor controller is a device or group of devices that serves to govern in some predetermined manner the performance of an electric motor. A motor controller might include a manual or automatic means for starting and stopping the motor, selecting forward or reverse rotation, selecting and regulating the speed, regulating or limiting the torque, and protecting against overloads and faults.
- Kill Switch
These kill switches are able to cut off all the electrical connections including ignition system and are rigidly mounted near the driver seat where the driver can easily control it. Second kill switch is placed on right side of vehicle & perpendicular to the firewall.
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.
© 2020 TOUSIF HUSAIN QURESHI