HYBRID ELECTRIC VEHICLE

1. Chapter 7
Sizing the drive system
SM
AP, EED, SurTech

2. Matching the electric machine and the
internal combustion engine (ICE)
• Matching the electric machine and the internal combustion engine
(ICE) depends on several factors, including the power output
required, the torque curve of the ICE, the available space and weight
budget, and the desired fuel efficiency. Here are some general
considerations:

3. Matching the electric machine and the
internal combustion engine (ICE)
1. Power output: The electric machine should be able to provide enough power to complement
the power output of the ICE. The power output of the ICE can be estimated from its
displacement, number of cylinders, and maximum RPM. The power output of the electric
machine depends on its voltage, current, and efficiency.
2. Torque curve: The electric machine should provide torque at low RPMs to assist the ICE during
acceleration. The torque curve of the electric machine should complement the torque curve of
the ICE to provide a smooth and seamless driving experience.
3. Available space and weight budget: The electric machine and ICE should be sized appropriately
to fit within the available space and weight budget of the vehicle. The size and weight of the
electric machine and ICE depend on their power output, cooling requirements, and other
factors.
4. Fuel efficiency: The electric machine should be able to provide enough power to reduce the
load on the ICE during cruising and low-load conditions. This can help improve the fuel
efficiency of the vehicle.
• Overall, the matching of the electric machine and ICE is a complex process that requires careful
consideration of many factors. It is typically done by the vehicle manufacturer during the design
phase of the vehicle.

4. Sizing the propulsion motor
• Sizing the propulsion motor for a given application typically involves determining the required torque and speed
for the motor based on the performance requirements of the system. Here are the basic steps for sizing a
propulsion motor:
1. Determine the requirements of the system: To size the motor, you need to know the requirements of the
system you are designing. This includes the speed and torque required to propel the vehicle or machine, as well
as any other performance criteria that are important for the application.
2. Calculate the required torque: Once you know the speed and other performance requirements, you can
calculate the required torque using the following equation: Torque (T) = Power (P) / Angular velocity (ω)
3. where Power (P) is the power required to drive the system, and Angular velocity (ω) is the rotational speed of
the motor.
4. Select an appropriate motor: After calculating the required torque, you can select a motor that is capable of
providing the necessary torque and speed. You will need to consider factors such as the motor's maximum
torque and speed, efficiency, and weight.
5. Check for safety factors: When sizing a motor, it's important to consider safety factors to ensure that the motor
is not overloaded during operation. This includes taking into account any variations in torque or speed that may
occur during use, as well as any other factors that may affect the motor's performance.
6. Test the motor: Once you have selected a motor, it's important to test it to ensure that it meets the
performance requirements of the system. This includes testing the motor under various operating conditions to
ensure that it is capable of providing the necessary torque and speed.

5. Sizing the power electronics
• Sizing the power for electronics involves calculating the amount of electrical power that the electronic device or
circuit requires to operate effectively and safely.
• To size the power for electronics, you need to consider the following factors:
1. Voltage: Determine the voltage required by the device or circuit. This may be specified in the device's
datasheet or in the circuit design.
2. Current: Determine the current required by the device or circuit. This may also be specified in the datasheet or
in the circuit design.
3. Power rating: Calculate the power rating required by the device or circuit by multiplying the voltage and
current. For example, if the voltage required is 12V and the current required is 1A, the power rating required is
12W.
4. Safety margin: Add a safety margin to the calculated power rating to ensure that the device or circuit operates
reliably and safely. The amount of safety margin to add depends on the specific application and the level of risk
involved.
5. Power supply: Choose a power supply that can provide the required voltage and current with the appropriate
safety margin. The power supply should also be able to handle any fluctuations in voltage or current that may
occur during operation.
• By properly sizing the power for electronics, you can ensure that the device or circuit operates effectively and
safely, with a lower risk of damage or failure.

6. Selecting the energy storage technology
• Selecting the appropriate energy storage technology depends on
several factors, including the application requirements, energy
density, power density, cycle life, cost, safety, and environmental
impact. Here are some key considerations when selecting an energy
storage technology:

7. Selecting the energy storage technology
• Application requirements: Consider the specific application, including the required
energy and power capacity, operating temperature range, and charging and discharging
rates. Different applications may require different energy storage technologies with
varying performance characteristics.
• Energy density: Energy density refers to the amount of energy that can be stored per unit
of volume or weight. For applications that require a high amount of energy storage in a
small space, such as in mobile devices or electric vehicles, high energy density storage
technologies like lithium-ion batteries or solid-state batteries may be preferred.
• Power density: Power density refers to the amount of power that can be delivered per
unit of volume or weight. For applications that require high power output, such as in
grid-scale energy storage or electric vehicle acceleration, high power density storage
technologies like supercapacitors or flywheels may be preferred.
• Cycle life: Cycle life refers to the number of charge and discharge cycles a battery or
energy storage system can undergo before its performance degrades. For applications
that require long-term use, such as in renewable energy storage, batteries with a high
cycle life, such as lithium-ion or flow batteries, may be preferred.

8. • Cost: The cost of an energy storage technology is an important consideration, especially
for large-scale applications like grid-level energy storage. Different technologies may
have varying costs for their production, installation, and maintenance, and the overall
cost may vary depending on the application's specific requirements.
• Safety: Safety is a critical consideration for energy storage technologies. Some
technologies, such as lithium-ion batteries, may have safety concerns related to
overheating or fire risks. Choosing a technology with a proven safety record and
implementing appropriate safety measures can help reduce these risks.
• Environmental impact: The environmental impact of energy storage technologies,
including their production, disposal, and use, is also an important consideration. Some
technologies, like lead-acid batteries, can have a significant environmental impact due to
the materials used and disposal requirements. Choosing a technology with a low
environmental impact, such as lithium-iron-phosphate batteries or hydrogen fuel cells,
can help reduce the overall environmental footprint of the application.
Selecting the energy storage technology

9. Communications
• In a driving system, communication plays a crucial role in ensuring smooth and safe operation. The driving
system can include various components such as the engine, transmission, braking system, and steering
system. Effective communication among these components is essential for the proper functioning of the
vehicle.
• One example of communication in a driving system is between the engine and the transmission. The engine
generates power that is transmitted through the transmission to the wheels. The transmission must be able
to communicate with the engine to determine how much power to transmit and when to shift gears.
• Similarly, the braking and steering systems must be able to communicate with each other and with the
engine and transmission to ensure safe and effective braking and steering. For example, if the vehicle's
speed is too high, the engine and transmission must communicate with the braking system to slow the
vehicle down.
• Modern driving systems also incorporate electronic control units (ECUs) that communicate with various
components of the vehicle to ensure optimal performance and efficiency. These ECUs use sensors to gather
data about the vehicle's speed, acceleration, braking, and other factors, and communicate with the engine
and transmission to make adjustments as needed.
• Overall, communication is essential in a driving system to ensure safe and efficient operation, and modern
technologies such as ECUs are increasingly being used to enhance communication and performance in these
systems.

10. Supporting Subsystem
• In addition to the main components of the driving system (engine, transmission, braking system, steering system), there are
also several supporting subsystems that play important roles in ensuring safe and efficient operation. Some examples of these
subsystems include:
1. Electrical System: The electrical system in a vehicle is responsible for powering all of the electronic components, such as
lights, audio system, and instrumentation. It also includes the battery and charging system.
2. Fuel System: The fuel system is responsible for delivering fuel from the tank to the engine. It includes components such as
the fuel pump, fuel filter, and fuel injectors.
3. Cooling System: The cooling system is responsible for regulating the temperature of the engine and preventing it from
overheating. It includes components such as the radiator, coolant, and thermostat.
4. Suspension System: The suspension system is responsible for maintaining the vehicle's stability and handling by absorbing
shocks and vibrations from the road. It includes components such as the shock absorbers, struts, and springs.
5. Exhaust System: The exhaust system is responsible for removing exhaust gases from the engine and reducing emissions. It
includes components such as the catalytic converter and muffler.
6. Safety Systems: Safety systems in a vehicle include components such as airbags, seat belts, and anti-lock brakes (ABS) that
are designed to protect the occupants in the event of an accident.
• Overall, these supporting subsystems work together with the main components of the driving system to ensure safe and
efficient operation of the vehicle