Hybrid Horsepower: Hybrid/EV Racing Technology

Jan. 1, 2020
Electric motors have a distinct advantage in racing. They make all their power instantly or with the push of a button. Hybrid and electric vehicle (EV) power sources are used in drag racing,

Electric motors have a distinct advantage in racing. They make all their power instantly or with the push of a button. Hybrid and electric vehicle (EV) power sources are used in drag racing, Formula 1, and other popular motorsports. Let’s take a look at the technology involved and compare it to that offered by OEMs to consumers.

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DC Motors have brushes that wear out

There is a relatively new technology that is gaining widespread acceptance in Formula 1 and GT racing called the Kinetic Energy Recovery System (KERS). Indy car racing is considering using the KERS technology in a “Push-to-Pass” system. Although hybrid and EV technology constantly is evolving in racing and in production vehicles, there are some common systems that are used. Each system has its advantages and disadvantages.

Energy Storage Devices
Let’s start by looking at different batteries and systems found in today’s vehicles used in Kinetic Energy Recovery Systems.

First there are Electro-Chemical Batteries. Lithium-Ion (Li-Ion) batteries are the most

CD Motor field coils are wire wound and can carry large amounts of current

commonly used battery in KERS systems, in drag racing, as well as new EVs, hybrid-electric vehicles (HEV) and plug-in hybrid vehicles (PHEV).

Li-Ion Battery systems have a high power density kW (ability to absorb or provide a large amount of energy), and have a very high energy density kWh (can accept or supply energy for a very long time duration). Lithium-ion batteries are used as storage devices for some KERS systems because of their lightweight as compared to ultra-capacitors.

There are several chemical variations of lithium-ion batteries used in today’s racecars as well as consumer vehicles as the technology keeps improving.  Ford, General Motors, Honda, Nissan, Tesla, Toyota and Hyundai all use Lithium-ion technology in their latest HEVs, PHEVs and EVs.

Induction motors are light weight and powerful

A new variation of Formula 1 racing will begin in 2014 called Formula E Racing. These are all electric racecars that will be using a variation of a lithium-ion battery for about 25 minutes of racing. I assume they will be swapping out the battery pack in a pit stop to continue racing.

Next are flywheel systems, which some race teams currently use as part of the KERS in racing.  They have a very high power density kW (ability to quickly absorb or provide a large amount of energy), but have a very low energy density kWh (cannot accept or supply energy for a very long time duration).

Flywheel systems use very strong permanent magnets mounted to a high-speed (up to 40,000 rpm) flywheel to convert rotational energy into electrical energy to propel the vehicle for a few additional seconds as needed. A set of permanent magnets is mounted around the inside circumference of the flywheel. The flywheel rotates around a set of field coils (much like an alternator, but with the rotor and field coil positions swapped). 

When the racecar is decelerating or braking, the kinetic

Induction Motor rotor contains no permanent magnets

energy of the vehicle is converted into electrical energy by the spinning the electric drive motor(s) attached to the engine or axle. The electric motor acts as a generator and supplies three-phase AC current to the flywheel system where the energy is stored as rotational energy; this increases the speed of the flywheel.

When additional power is needed for acceleration or to pass another racecar, the driver presses a boost button. The boost process turns the high-speed flywheel into a three-phase AC generator to create power for the electric drive motor(s). The motors help the engine crankshaft to rotate or drives the electric motor(s) in the front axle to provide additional power. As the flywheel delivers power to the drive motors, its rotational speed decreases.

Induction Motor Field coils are precisely controlled to vary motor speed.

The boost phase provides additional horsepower (regulated to a maximum of 60 kW (80 hp) in Formula One, and 150 kW (203 hp) in GT Racing) for a approximately seven seconds.

Finally, some race teams use ultra-capacitor systems as part of the KERS in racing. Ultra-capacitors have a very high power density kW (ability to instantly accept a large charge or to discharge), but have a very low energy density kWh (can not accept or supply energy for a very long time duration). They use very high capacitance capacitors, rated at hundreds or even thousands of Farads, to store electrical energy.

A Chevrolet Volt 360V Lithium-ion Battery

When the racecar is decelerating or braking, the kinetic energy of the vehicle is converted into electrical energy by driving the electric drive motor(s) attached to the engine or axle(s). The electric motor acts as a generator and supplies three-phase AC current to an AC-to-DC converter where it is converted into DC current and stored in the Ultra-capacitor system (Charging the capacitors). When additional power is needed for acceleration or passing another racecar, the driver presses a boost button. The boost cycle discharges the Ultra-capacitors through a DC-to--AC Inverter to provide three-phase power for the electric drive motor(s). The motor(s) help the engine crankshaft to rotate or drives the electric motor(s) in the front axle to provide additional power.

The boost phase provides additional horsepower (regulated to a maximum of 60 kW (80 hp) in Formula One, and 150 kW (203 hp) in GT Racing) for a little less than 7 seconds.  During the boost phase, the capacitors are discharging.

The following table shows a comparison of the three different energy storage systems.

 

Lithium-Ion Batteries

Flywheel Systems

Ultra-Capacitors

Financial Cost

High

High

High

Package Weight

low

Low

Medium

Package Volume (size)

Large

Small

Large

Optimum Operating Temperature

70 degrees F

Any

Any

Energy Density - The ability to store large amounts of energy

High

Low

Medium

Power Density - the ability to quickly add or remove energy over a period of time

Low

Medium

High

Charge Rate – The ability to accept a maximum charge without overheating

Low

Medium

High

Discharge Rate– The ability to provide a maximum charge without overheating

Low

Medium

High

Life Cycles – The approximate number of full charges and discharges before serious performance degradation occurs

1,000

100,000

1,000,000

Crash Safety Concerns – The risk of fire or personal injury caused by a crash.

High

Medium

Low

Environmental Impact – Required proper disposal to prevent environmental damage.

Yes

No

No

All Kinetic Energy Recovery Systems, electric drag racing vehicles, electric vehicles, hybrid-electric vehicles, and plug-in hybrid vehicles utilize one or more electric motors to help propel or to propel the vehicle. Although electric motor technology is slowly evolving in racing and in production vehicles, there are some common motor types that are used. Each motor type has its advantages and disadvantages.

A Buick Lacrosse 115V Lithium-ion Battery

Electric Motor Types
Direct Current (DC) Motors utilize brushes to transfer current to the motor armature. In racing, there is one commonly used type of DC motor, wire wound motors. The armature and the field coils are wire wound. This requires the current to travel through the field coils and the motor armature (through the brushes) at precise intervals to cause the motor to rotate.

In modern wire wound DC motors, there are separate external electrical connections for the field coils and also for the armature. This allows for maximum control of the magnetic fields and allows variable speeds by means of a special motor controller unit.

Wire wound DC motors are very heavy but provide instant torque. This instant torque is an amazing thing to experience since there is no delay in acceleration. They are a low cost, high power solution for many racing applications; however, any motor that utilizes brushes will eventually have durability and maintenance issues due to the fact that the brushes and the armature’s commutator to wear out as you use them.

The field coils of Permanent Magnet motor from a 2006 Toyota Prius

Wire wound DC motors have a relative low operating temperature and are typically air-cooled. Racing applications of DC motors can cause high operating temperatures and require an upgraded cooling system.

There are no modern production vehicles for the typical consumer to purchase that utilize a wire wound DC brush type motor.

Alternating current motors do not use brushes because the armature (rotor) is spun by other methods. These AC motors are sometimes referred to as brushless DC motors. In racing there are two commonly used types of AC motors: permanent magnet synchronous AC motors and induction motors (both three-phase AC).

The rotor with the magnets removed from a 2006 Toyota Prius

In Permanent Magnet Synchronous AC motors, the rotor contains many evenly spaced high strength permanent magnets; the field coils are wire wound in a wye formation. This configuration requires the current to travel through the field coils at precise intervals to rotate the motor.  The rotor is pulled (rotated) by the magnetic attraction of the activated field coils. The position and speed of the rotor can be controlled by the field coils with great precision by means of a special motor controller unit typically housed in an inverter-converter assembly.

These motors are very heavy but provide instant torque. These motors are a high cost, high power solution for many racing applications. Although these motors cost more money than DC motors, they are very durable and reliable with few maintenance concerns. The high cost is due partly to the materials from which the permanent magnets are made.

The boost button from a Porsche GT3 R Hybrid racecar with KERS

These motors allow for regenerative braking in a typical hybrid or electric vehicle and in the KERS in racecars. These motors have a relative high operating temperature and are typically liquid-cooled. The large majority of modern production EV, PHEV, and HEV vehicles for the typical consumer to purchase utilize Permanent Magnet Synchronous AC motors.

In Induction Motors, the rotor contains no permanent magnets; instead it contains many sets of laminated coils of copper or aluminum and the field coils are wire wound in a wye formation. This configuration requires the current to travel through the field coils at precise intervals to rotate the motor.

The rotor is pulled (rotated) by the magnetic attraction of the activated field coils in relation to the rotor’s magnetic field created by induction from the field coils. The speed of the rotor can be controlled by the field coils with good precision by means of a special motor controller unit typically housed in an inverter-converter assembly.

The front axle permanent magnet drive motors from a Porsche GT3 R Hybrid racecar with KERS

These motors are very lightweight and provide good torque. Although these motors cost more money that DC motors, these motors are very durable and reliable with few maintenance concerns.

These motors allow for regenerative braking in a typical hybrid or electric vehicle and possibly in the KERS in racecars. These motors have a relative high operating temperature and are typically liquid-cooled.

Small numbers of modern production EV, PHEV, and HEV vehicles for the typical consumer to purchase utilize Induction AC motors. I expect to see more of these lower cost solutions to be utilized in the future.

The following table compares two racecars to two production vehicles available to consumers.

Specifications

Formula 1 Racecar with KERS

Formula E Racecar

2013 Tesla Model S Performance

2013 Nissan Leaf

Top speed:

362 km/h (225 mph)

220 km/h A
 (137 mph)

210 km/h (130 mph)

150 km/h (93 mph)

Acceleration:

0 to 100 km/h 2.6 seconds

0 to 100 km/h 3 seconds


0 to 100 km/h 4.4 seconds


0 to 100 km/h 9.9 seconds


Power:

559 kW (750 hp)

180 kW
 (241 hp)

310 kW (416 hp)

80 kW (110 hp)

Weight:

640 kg (1411 lb)

780 kg
 (1720 lb)

 

2108 kg (4647 lb)

1521 kg (3354 lb)

Gearbox:

 

7 gears

2 gears


1 Speed Electric Motor

1 Speed Electric Motor

Batteries:

 

Lithium ion
 - (Li-Ion)

Lithium ion
 - (Li-Ion)

85 kWh Lithium ion
 - (Li-Ion)

24 kWh Lithium ion
 - (Li-Ion)

Range:

About 7 seconds

About 25 minutes

300 Miles @ 55 mph = 5.4 hrs

117 miles at 65 mph = 1.8 hrs

Charging time (fully depleted):

About 7 seconds

About 90 minutes

9.5 hrs

8 hrs

The Flywheel Motor Generator from a Porsche GT3 R Hybrid racecar with KERS

Standards and Regulations
As this new technology evolves and progresses, standards and rules need to be established to insure uniformity, reliability, and safety. All racing bodies as well as consumer vehicles have or will have standards established.

Formula 1 regulates the KERS systems used in racing with several rules: They have strict guidelines pertaining to the maximum amount of electrical energy which can be stored, used during acceleration, and used per lap. The National Electric Drag Racing Association also has rules established for electric drag cars, trucks and motorcycles, while the National Fire Prevention Association (NFPA), the Society of Automotive Engineers (SAE) and the International Standards Organization (ISO) all establish many standards for consumer vehicles (including a common charge port connector independent of vehicle manufacturer)

The Flywheel System Overview of a Porsche GT3 R Hybrid racecar with KERS

Summary
I think it is very interesting and exciting to watch the evolution and changes made by progress in new technologies. Many of these technologies are highly controversial and many people have their opinion of whether or not this technology should be used at all. I personally believe this is a step in the right direction towards improving fuel economy, becoming less dependent on petroleum-based products, and promoting a cleaner-greener environment.

There will always be those that resist this change, but once the racing world fully accepts it, makes it look cool, and has it perform as well or better than conventional racecars or consumer vehicles, it will be easier for the general public to accept it.

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