42-volt electrical system
Encyclopedia
In automobile
s, a 42-volt electrical system was a proposed electrical power standard in the late 1990s intended to allow more powerful electrically driven accessories, and lighter automobile wiring harnesses. Electric motor
s were proposed to be used for power steering
or other systems, providing more compact installations and eliminating the weight of drive belt
s or large wires for high-current
loads. Although investigated as early as 1988, 42-volt electrical components are now used in only a few automotive applications, since incandescent light bulb
s work well at 12 volts and switching of a 42-volt circuit is more difficult.
The proposed new standard was triple the voltage of existing "12 volt" systems. Lead-acid batteries produce around 12.6 volts while discharging, while automotive alternator
s produce 13.5 to 14.5 volts during normal charging operation. 42 volts is an approximation of the output of the new standard's charging system. The higher voltage was selected to provide greater power capacity for wiring and devices on one hand, and to stay under the 50 volt limit used as a guideline for electric shock
hazard.
Although many manufacturers were predicting a switch to 36-volt (lithium ion battery) / 42-volt (charging voltage) electrical systems, the changeover has not occurred, and the plans appear to have been canceled. The availability of higher-efficiency motors, new wiring techniques and digital controls, and a focus on hybrid vehicle systems
that use high-voltage starter/generators has largely eliminated the push for switching the main automotive voltages. Applications that once were thought to require higher voltages, such as electrical power steering, have now been achieved with 12 volt systems.
The European auto manufacturer Daimler-Benz
proposed a 42V brand name for the conversion.
, the first "Workshop on Advanced Architectures for Automotive Electrical Distribution Systems" was held at the Massachusetts Institute of Technology Laboratory for Electromagnetic and Electronic Systems (MIT/LEES) in Cambridge, Massachusetts
USA. with the aim of defining the architecture for a future automotive electrical system. From the outset, the participants in this workshop included suppliers as well as the automobile companies Daimler-Benz
, Ford and General Motors
.
In September 1995, various electrical systems architectures were compared at MIT using the tool "MAESTrO", and in December 1995, in the "Conclusions" of this study, a future voltage level of approx. 40V was defined.
In early 1996, the "Consortium on Advanced Automotive Electrical and Electronic Systems" was set up. At the ensuing workshop in March 1996, the future nominal voltage of 42V was confirmed.
In August 1996, IEEE Spectrum published the paper "Automotive electrical systems circa 2005".
On the occasion of the October 1996 Convergence in Detroit, Professor John G. Kassakian (MIT) gave a talk entitled "The Future of Automotive Electrical Systems" as part of the "IEEE Workshop on Automotive Power- Electronics".
On March 24, 1997, Daimler-Benz
presented the MIT with a "Draft Specification of a Dual Voltage Vehicle Electrical Power System 42V/14V".
, the former SICAN GmbH held its first "Forum Bordnetz" (Vehicle Electrical System Forum) in Hanover
for German automobile companies. Here too, suppliers were invited to participate at a very early stage, together with all European vehicle manufacturers.
On February 15, 1996, the introductory paper "Bordnetzarchitektur im Jahr 2005" (Automotive electrical system architecture for the year 2005) was agreed, and on June 4, 1996, BMW
presented the "Tabelle heutiger und zukünftiger Verbraucher im Kfz" (Table of present and future loads in the motor vehicle) and the "42V/14V-Bordnetz" (42V/14V PowerNet).
On September 13, 1996, at the 7th International Technical Meeting for Vehicle Electronics in Baden-Baden
, considerable interest was raised by the paper "Neue Bordnetz- Architektur und Konsequenzen" (New Automotive Electrical System Architecture and Consequences), presented by Dr. Richard D. Tabors (MIT).
On March 6, 1997, BMW
presented the "Spezifikationsentwurf für das Zwei-Spannungsbordnetz 42V/14V" (Draft Specification of a Dual Voltage Vehicle Electrical Power System 42V/14V) in Hanover
.
The work at SICAN GmbH was given decisive impetus by the cooperation between BMW
and Daimler-Benz
, as witnessed in their joint definition of the European "Load List 2005" and the jointly authored "Draft Specification of a Dual Voltage Vehicle Electrical Power System 42V/14V".
The limiting factor for direct voltages is a shock-hazard protection limit of 60V, which must not be exceeded even during voltage fluctuations caused by extreme conditions. This limit eliminates the option of an automotive electrical system with a nominal battery voltage of 48V, because at low temperatures the charging voltage of the battery can attain 60V. Also, the price, weight and volume of batteries are influenced by the number of cells, which must therefore be kept to a minimum.
New battery technologies for automotive applications would not have been available at affordable costs for the 42V/14V PowerNet. Lead-acid batteries are low-priced and have a very "compliant" charging/discharging characteristic. Therefore, lead-acid batteries would have been used optimised for energy and service life at the lower voltage and optimised for power at the higher voltage.
Another important criterion for a new architecture was that it should offer extensive migration possibilities, i.e. the loads should if necessary be converted to the higher voltage only gradually as a function of actual requirements.
The present nominally 12V automotive electrical system usually operates around 13.8 volts, so 14V is descriptive. Literature on 42 volt electrical systems often refers to systems powered with a 6-cell lead-acid battery as nominally 14 volts. Depending on operating conditions, the vehicle electrical system voltage today can vary between 6.5 and 16V, with a varying degree of ripple superimposed on this value. In a 42V/14V system, the 14V branch should have been freed of higher-power loads and should operate within much narrower limits.
Power electronics is becoming increasingly important in the automotive sphere and will be a decisive factor in the price of future vehicles. This criterion was therefore especially important when selecting the most suitable higher voltage level. Despite the considerable upward trend of power electronics in automotive applications, its share of the market will decline, because growth rates in other market segments are even higher. For that reason alone, a specific manufacturing technology for automotive use is inconceivable.
In intensive discussions with the major semiconductor manufacturers, a voltage of approx. 40V was found to be advantageous. Many arguments are summarised in the paper "Intelligente Leistungshalbleiter für zukünftige Kfz-Bordnetze" ("Intelligent Power Semiconductors for Future Automotive Electrical Systems") presented by the former Siemens Semiconductors now Infineon at the 17th "Elektronik im Kraftfahrzeug" (In-Car Electronics) conference on June 3/4, 1997 in Munich.
Other arguments for a higher voltage included the reduction of weight in the wiring system and the improved stability of the automotive electrical system, including by means of reduced voltage drops. With three times the voltage, thick conductors can be reduced to a third of the cross-section, and at the same time the relative voltage drop can also be reduced to a third. For the same cross-section, the relative voltage drop is now no more than one ninth.
The voltage level resulting from these comprehensive arguments was so close to three times the present voltage that 42V became the automatic choice for the second voltage level.
Automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...
s, a 42-volt electrical system was a proposed electrical power standard in the late 1990s intended to allow more powerful electrically driven accessories, and lighter automobile wiring harnesses. Electric motor
Electric motor
An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...
s were proposed to be used for power steering
Power steering
Power steering helps drivers steer vehicles by augmenting steering effort of the steering wheel.Hydraulic or electric actuators add controlled energy to the steering mechanism, so the driver needs to provide only modest effort regardless of conditions. Power steering helps considerably when a...
or other systems, providing more compact installations and eliminating the weight of drive belt
Belt (mechanical)
A belt is a loop of flexible material used to link two or more rotating shafts mechanically. Belts may be used as a source of motion, to transmit power efficiently, or to track relative movement. Belts are looped over pulleys. In a two pulley system, the belt can either drive the pulleys in the...
s or large wires for high-current
Electric current
Electric current is a flow of electric charge through a medium.This charge is typically carried by moving electrons in a conductor such as wire...
loads. Although investigated as early as 1988, 42-volt electrical components are now used in only a few automotive applications, since incandescent light bulb
Incandescent light bulb
The incandescent light bulb, incandescent lamp or incandescent light globe makes light by heating a metal filament wire to a high temperature until it glows. The hot filament is protected from air by a glass bulb that is filled with inert gas or evacuated. In a halogen lamp, a chemical process...
s work well at 12 volts and switching of a 42-volt circuit is more difficult.
The proposed new standard was triple the voltage of existing "12 volt" systems. Lead-acid batteries produce around 12.6 volts while discharging, while automotive alternator
Alternator
An alternator is an electromechanical device that converts mechanical energy to electrical energy in the form of alternating current.Most alternators use a rotating magnetic field but linear alternators are occasionally used...
s produce 13.5 to 14.5 volts during normal charging operation. 42 volts is an approximation of the output of the new standard's charging system. The higher voltage was selected to provide greater power capacity for wiring and devices on one hand, and to stay under the 50 volt limit used as a guideline for electric shock
Electric shock
Electric Shock of a body with any source of electricity that causes a sufficient current through the skin, muscles or hair. Typically, the expression is used to denote an unwanted exposure to electricity, hence the effects are considered undesirable....
hazard.
Although many manufacturers were predicting a switch to 36-volt (lithium ion battery) / 42-volt (charging voltage) electrical systems, the changeover has not occurred, and the plans appear to have been canceled. The availability of higher-efficiency motors, new wiring techniques and digital controls, and a focus on hybrid vehicle systems
Hybrid electric vehicle
A hybrid electric vehicle is a type of hybrid vehicle and electric vehicle which combines a conventional internal combustion engine propulsion system with an electric propulsion system. The presence of the electric powertrain is intended to achieve either better fuel economy than a conventional...
that use high-voltage starter/generators has largely eliminated the push for switching the main automotive voltages. Applications that once were thought to require higher voltages, such as electrical power steering, have now been achieved with 12 volt systems.
The European auto manufacturer Daimler-Benz
Daimler-Benz
Daimler-Benz AG was a German manufacturer of automobiles, motor vehicles, and internal combustion engines; founded in 1926. An Agreement of Mutual Interest - which was valid until year 2000 - was signed on 1 May 1924 between Karl Benz's Benz & Cie., and Daimler Motoren Gesellschaft, which had...
proposed a 42V brand name for the conversion.
USA – Consortium on Advanced Automotive Electrical and Electronic Systems
In 1994, at the initiative of Daimler-BenzDaimler-Benz
Daimler-Benz AG was a German manufacturer of automobiles, motor vehicles, and internal combustion engines; founded in 1926. An Agreement of Mutual Interest - which was valid until year 2000 - was signed on 1 May 1924 between Karl Benz's Benz & Cie., and Daimler Motoren Gesellschaft, which had...
, the first "Workshop on Advanced Architectures for Automotive Electrical Distribution Systems" was held at the Massachusetts Institute of Technology Laboratory for Electromagnetic and Electronic Systems (MIT/LEES) in Cambridge, Massachusetts
Massachusetts
The Commonwealth of Massachusetts is a state in the New England region of the northeastern United States of America. It is bordered by Rhode Island and Connecticut to the south, New York to the west, and Vermont and New Hampshire to the north; at its east lies the Atlantic Ocean. As of the 2010...
USA. with the aim of defining the architecture for a future automotive electrical system. From the outset, the participants in this workshop included suppliers as well as the automobile companies Daimler-Benz
Daimler-Benz
Daimler-Benz AG was a German manufacturer of automobiles, motor vehicles, and internal combustion engines; founded in 1926. An Agreement of Mutual Interest - which was valid until year 2000 - was signed on 1 May 1924 between Karl Benz's Benz & Cie., and Daimler Motoren Gesellschaft, which had...
, Ford and General Motors
General Motors
General Motors Company , commonly known as GM, formerly incorporated as General Motors Corporation, is an American multinational automotive corporation headquartered in Detroit, Michigan and the world's second-largest automaker in 2010...
.
In September 1995, various electrical systems architectures were compared at MIT using the tool "MAESTrO", and in December 1995, in the "Conclusions" of this study, a future voltage level of approx. 40V was defined.
In early 1996, the "Consortium on Advanced Automotive Electrical and Electronic Systems" was set up. At the ensuing workshop in March 1996, the future nominal voltage of 42V was confirmed.
In August 1996, IEEE Spectrum published the paper "Automotive electrical systems circa 2005".
On the occasion of the October 1996 Convergence in Detroit, Professor John G. Kassakian (MIT) gave a talk entitled "The Future of Automotive Electrical Systems" as part of the "IEEE Workshop on Automotive Power- Electronics".
On March 24, 1997, Daimler-Benz
Daimler-Benz
Daimler-Benz AG was a German manufacturer of automobiles, motor vehicles, and internal combustion engines; founded in 1926. An Agreement of Mutual Interest - which was valid until year 2000 - was signed on 1 May 1924 between Karl Benz's Benz & Cie., and Daimler Motoren Gesellschaft, which had...
presented the MIT with a "Draft Specification of a Dual Voltage Vehicle Electrical Power System 42V/14V".
Europe
At the same time as the activities in the USA, in 1994, again at the initiative of Daimler-BenzDaimler-Benz
Daimler-Benz AG was a German manufacturer of automobiles, motor vehicles, and internal combustion engines; founded in 1926. An Agreement of Mutual Interest - which was valid until year 2000 - was signed on 1 May 1924 between Karl Benz's Benz & Cie., and Daimler Motoren Gesellschaft, which had...
, the former SICAN GmbH held its first "Forum Bordnetz" (Vehicle Electrical System Forum) in Hanover
Hanover
Hanover or Hannover, on the river Leine, is the capital of the federal state of Lower Saxony , Germany and was once by personal union the family seat of the Hanoverian Kings of Great Britain, under their title as the dukes of Brunswick-Lüneburg...
for German automobile companies. Here too, suppliers were invited to participate at a very early stage, together with all European vehicle manufacturers.
On February 15, 1996, the introductory paper "Bordnetzarchitektur im Jahr 2005" (Automotive electrical system architecture for the year 2005) was agreed, and on June 4, 1996, BMW
BMW
Bayerische Motoren Werke AG is a German automobile, motorcycle and engine manufacturing company founded in 1916. It also owns and produces the Mini marque, and is the parent company of Rolls-Royce Motor Cars. BMW produces motorcycles under BMW Motorrad and Husqvarna brands...
presented the "Tabelle heutiger und zukünftiger Verbraucher im Kfz" (Table of present and future loads in the motor vehicle) and the "42V/14V-Bordnetz" (42V/14V PowerNet).
On September 13, 1996, at the 7th International Technical Meeting for Vehicle Electronics in Baden-Baden
Baden-Baden
Baden-Baden is a spa town in Baden-Württemberg, Germany. It is located on the western foothills of the Black Forest, on the banks of the Oos River, in the region of Karlsruhe...
, considerable interest was raised by the paper "Neue Bordnetz- Architektur und Konsequenzen" (New Automotive Electrical System Architecture and Consequences), presented by Dr. Richard D. Tabors (MIT).
On March 6, 1997, BMW
BMW
Bayerische Motoren Werke AG is a German automobile, motorcycle and engine manufacturing company founded in 1916. It also owns and produces the Mini marque, and is the parent company of Rolls-Royce Motor Cars. BMW produces motorcycles under BMW Motorrad and Husqvarna brands...
presented the "Spezifikationsentwurf für das Zwei-Spannungsbordnetz 42V/14V" (Draft Specification of a Dual Voltage Vehicle Electrical Power System 42V/14V) in Hanover
Hanover
Hanover or Hannover, on the river Leine, is the capital of the federal state of Lower Saxony , Germany and was once by personal union the family seat of the Hanoverian Kings of Great Britain, under their title as the dukes of Brunswick-Lüneburg...
.
The work at SICAN GmbH was given decisive impetus by the cooperation between BMW
BMW
Bayerische Motoren Werke AG is a German automobile, motorcycle and engine manufacturing company founded in 1916. It also owns and produces the Mini marque, and is the parent company of Rolls-Royce Motor Cars. BMW produces motorcycles under BMW Motorrad and Husqvarna brands...
and Daimler-Benz
Daimler-Benz
Daimler-Benz AG was a German manufacturer of automobiles, motor vehicles, and internal combustion engines; founded in 1926. An Agreement of Mutual Interest - which was valid until year 2000 - was signed on 1 May 1924 between Karl Benz's Benz & Cie., and Daimler Motoren Gesellschaft, which had...
, as witnessed in their joint definition of the European "Load List 2005" and the jointly authored "Draft Specification of a Dual Voltage Vehicle Electrical Power System 42V/14V".
Choice of voltage
After extensive preparatory work, resulting in the "List of Loads in the Automobile of the Year 2005", various automotive electrical system architectures were compared using the tool "MAESTrO" (12V, 12V/24Vdc, 12V/48Vdc and 12V/60Vac) in the September 1995 workshop at the Massachusetts Institute of Technology (MIT/LEES). The finding of this study was that the highest possible direct voltage was the best alternative.The limiting factor for direct voltages is a shock-hazard protection limit of 60V, which must not be exceeded even during voltage fluctuations caused by extreme conditions. This limit eliminates the option of an automotive electrical system with a nominal battery voltage of 48V, because at low temperatures the charging voltage of the battery can attain 60V. Also, the price, weight and volume of batteries are influenced by the number of cells, which must therefore be kept to a minimum.
New battery technologies for automotive applications would not have been available at affordable costs for the 42V/14V PowerNet. Lead-acid batteries are low-priced and have a very "compliant" charging/discharging characteristic. Therefore, lead-acid batteries would have been used optimised for energy and service life at the lower voltage and optimised for power at the higher voltage.
Another important criterion for a new architecture was that it should offer extensive migration possibilities, i.e. the loads should if necessary be converted to the higher voltage only gradually as a function of actual requirements.
The present nominally 12V automotive electrical system usually operates around 13.8 volts, so 14V is descriptive. Literature on 42 volt electrical systems often refers to systems powered with a 6-cell lead-acid battery as nominally 14 volts. Depending on operating conditions, the vehicle electrical system voltage today can vary between 6.5 and 16V, with a varying degree of ripple superimposed on this value. In a 42V/14V system, the 14V branch should have been freed of higher-power loads and should operate within much narrower limits.
Power electronics is becoming increasingly important in the automotive sphere and will be a decisive factor in the price of future vehicles. This criterion was therefore especially important when selecting the most suitable higher voltage level. Despite the considerable upward trend of power electronics in automotive applications, its share of the market will decline, because growth rates in other market segments are even higher. For that reason alone, a specific manufacturing technology for automotive use is inconceivable.
In intensive discussions with the major semiconductor manufacturers, a voltage of approx. 40V was found to be advantageous. Many arguments are summarised in the paper "Intelligente Leistungshalbleiter für zukünftige Kfz-Bordnetze" ("Intelligent Power Semiconductors for Future Automotive Electrical Systems") presented by the former Siemens Semiconductors now Infineon at the 17th "Elektronik im Kraftfahrzeug" (In-Car Electronics) conference on June 3/4, 1997 in Munich.
Other arguments for a higher voltage included the reduction of weight in the wiring system and the improved stability of the automotive electrical system, including by means of reduced voltage drops. With three times the voltage, thick conductors can be reduced to a third of the cross-section, and at the same time the relative voltage drop can also be reduced to a third. For the same cross-section, the relative voltage drop is now no more than one ninth.
The voltage level resulting from these comprehensive arguments was so close to three times the present voltage that 42V became the automatic choice for the second voltage level.
External links
- Paper by Emilian Ceuca:
- Halbleiter im 42V-Bordnetz Dr. Alfons Graf Infineon Technologies, Munich October 2001