Electrified motor vehicles demystified

TO understand how a hybrid electric vehicle (HEV) operates, you should think of a conventional car with an internal combustion engine (ICE), with the addition of a small battery pack operating together to provide an efficient power train system.

The ICE is connected to a high-voltage generator that is used to generate electrical power to charge the battery pack within this type of application, which is extending the range of the battery pack.

The generator is also used to provide electrical power to the electric drive motor.

The electric drive motor and internal combustion engine combine different level of torque at given different road speeds and loads for vehicle propulsion.

Utilising an ICE to generate power for a hybrid vehicle allows the HEV to have a comparable range to a conventionally powered vehicle.

HEVs are a necessary intermediate step in the conversion of automobile from a petroleum-powered vehicle, to a fully electric one.

Prior to the hybrid vehicles, the automobile was a series of different systems that somewhat worked together to allow the vehicle to operate properly.

This worked well enough throughout the years, with the electrical and mechanical systems working with little interaction.

Each system operating independently of the others did not prove to be an optimal or efficient setup.

Prior HEVs, vehicle powertrain systems did not work efficiently together.

A lot of these inefficiencies are related to varying speeds at which the engine and vehicle operate at, along with chemical conversion of gasoline or petrol to mechanical motion.

This energy conversion creates a lot of wasted heat that is released to the surrounding air.

Controlling this waste of energy is key in creating efficiency within a vehicle.

The strategy of powertrain control module (PCM) on an HEV is to control revolutions per minute (RPM), with the main purpose of generating power instead of propelling vehicle.

The vehicle drive wheels are connected to electric motors and the engine through the planetary gear set, which provides the output torque to propel the vehicle.

Having an engine that maintains constant RPM is useful, because it can be set to operate at the most efficient RPM for that design.

Without fluctuations of the conventional ICE, the HEV increases the efficiency of the ICE by maintaining a constant RPM.

This constant RPM operator comfort issues and decreases wear on engine components.

To help minimise wasted energy, the HEV a regenerative braking strategy to recapture some of the energy that was lost during acceleration.

Regenerative braking simply recaptures energy expended, and uses that energy to recharge the battery pack.

This only happens under the right conditions; when the vehicle is coming to a stop, the high-voltage controller changes the drive motor to a generator by orienting (retarding) the stator magnetic field to a slower frequency than the RPM of the rotor.

Using the generator magnetic fields, vehicle braking will be applied to the vehicle, by using negative torque on electric machine rotor, and a drive unit/transmission axle.

The kinetic energy from the vehicle rotates the electric machine rotor, which permits regenerative (magnetic) energy and negative torque to be produced, which reduces vehicle speed.

 

The weight of the vehicle helps move the rotor within the generator field to generate electricity.

Power generation is variable based on the potential sensed by the high-voltage controller, which is developed by the speed of the vehicle, by the braking requested by the driver, and by the type of system on the vehicle.

After the HEV, the next transition to a pure battery electric vehicle (BEV) is a plug-in hybrid electric vehicle (PHEV).

The PHEV has all of the same components as the HEV, but has much larger battery pack that can be plugged into the utility power for recharging.

In the USA, where I did most of my hybrid and electric vehicles training, the average driver travels 29 miles or 46 kilometres a day.

Many PHEVs have an average of 21 miles or 33 kilometres, before the internal combustion engine (ICE) even has to start.

Minimising the operation of the ICE will further lessen the impact a vehicle has on the environment.

PHEV emulates those on the HEV.

Adding the charging element from home alternating current (AC) power allows the PHEV to operate primarily on high voltage battery, while also allowing the vehicle to drive past the battery capacity.

The PHEV is a crucial step transitioning drivers to plug in their vehicles on a regular basis.

As vehicles transition to being fully electric, drivers have to change the way they operate their vehicles.

Planning out trips to take advantage of charging opportunities and looking for areas with higher population of charging stations will progressively become part of the public’s mindset.

The issue that most drivers have with a PHEV is the premium cost of a vehicle that still has an internal combustion engine (ICE) to maintain.

This dual-purpose vehicle costs more to maintain and repair than a typical battery electric vehicle (BEV).

As the battery electric vehicle (BEV) increases its market share within the automotive market, both consumers and technician must change the way they approach them.

A BEV application eliminates the ICE completely and relies on the high voltage battery pack for propulsion power.

Eliminating the ICE decrease the vehicle’s weight and its need for regular maintenance.

With the increased room, the vehicle can now have larger electric motors, larger battery packs, and more room to situate those components in the ideal locations.

Issues with BEVs come down to the range capacity of the battery pack.

Without the availability of the ICE to generate power any time it is needed, the vehicle must become more efficient than it was previously.

To help increase this efficiency, the whole vehicle is integrated together; the systems all work together and regenerative braking increases to help increase or maintain the battery pack’s state of charge.

*Taurayi Raymond Sewera is ASE and AutoCate Association-certified World Class Master Technician with 39ASEs, ASE Advanced Level Specialist L1, L2, L3 and L4, AMI-Accredited Master Electric Vehicles and Master Automotive Manager, and ACDC-certified Master Hybrid and Electric Vehicles Technician. He is the founder and CEO of TauRay Automotive. He can be contacted on: +263772341193, +263772357296 or rtsewera@ gmail.com