1

Army Transition To 42-V Vehicular Electrical Power System

Mr. Barry Gilbert*, Dr. M. Abul Masrur**, Mr. John Monroe**, Mr. Rakesh Patel**, Mr. Mike Smith*

* DCS Corporation ** U.S. Army TACOM

NDIA 3rd Annual Intelligent Vehicle Systems Symposium

June 9 – 12, 2003

2

Objectives of this presentation

The purpose of this paper is to show the: • Advantages in transitioning to a dual 28/42V

electrical system that will overcome the current 28V drawbacks

• Need to rapidly develop a new power system capable of supporting integration of new technologies.

3

Electrical System Trends

• Both military and commercial vehicles electrical power needs have increased substantially over the past years.

• The automotive industry is transitioning to a 42V electrical system that dramatically increases available power for technical advances with less space and weight in the existing 12V vehicles.

• Military vehicles should follow the same trend• The current 28V system meets only 40% of the Future

Combat System (FCS) needs for power generation, energy storage and power distribution.

• A prototype 28/42V military vehicle does not yet exist and it is imperative that a prototype vehicle electrical system be investigated

4

Background – Voltage Evolution

Evolution of voltage for commercial and military

vehicles

Commercial– 6 volts (7 v charging) to 12 volts (14 v charging) in the

1950’s for passenger vehicles

– 12 volts (14 v charging) to 24 volts (28 v charging) since the 1950’s for trucks

– On the way from 12 volts (14 v charging) to 36 volts (42 v charging) since the 2002 for passenger vehicle

Military– Followed commercial vehicles until the late 1940’s

– 24 v (28 v charging) used in most military since the late 1940’s

5

Power Needs

• 3 Kw or 3.5 Kw (with an anticipated 5 Kw or higher later on) in commercial automobiles in the near future.

• About 5 Kw (with an anticipated 15 Kw) in military vehicles in the near future.

* The above and other pictures in this presentation are from various open literature and open websites of non-govt. and govt. sources.

6

     ELECTRICAL POWER SYSTEM REQUIREMENTS FOR MILITARY VEHICLES

• LAV -- Alternator 28 v dc, 245/280 amps ( 7.5 Kw)

• HMMWV – Alternator, 28 v dc, appx. 100 amps in a particular variant ( 2.8 Kw)

7

     ELECTRICAL POWER SYSTEM REQUIREMENTS FOR MILITARY VEHICLES

• FMTV -- Alternator, 14/28 dual volt dc, appx. 100 amps in a particular variant (200 amps option) ( 2.8 Kw)

• Abrams Tank – 28 v dc, 650 amps ( 18 Kw)

8

     ELECTRICAL POWER SYSTEM REQUIREMENTS FOR MILITARY VEHICLES

• UGV – Similar to above depending on the platform chosen

• Robots – As low as 30 watts to 1500 watts @ 12 v or 24 v, Current: about 3 amps to 100 amps, depending on the voltage.

9

Needs in Military

• Improved mission effectiveness implying– Increased silent watch time– Managed dynamic power allocation, enabled use of advanced

technologies to maximize combat performance, and reduced logistical footprint.

• More electrical power will be required so the latest technologies can be incorporated

• Primary 28/42V transition objectives become: – Increase available power and energy storage, – Reduce fuel consumption, – Implement X-by-wire (X represents steer, brake, suspension,

engine management, etc.) – Replace bulky mechanical components with smart and lighter

electrical components, including reduction of wiring harness weight

– Improve mission effectiveness

10

Needs in Military

- Belt-less engine operation for most components (safety and reliability)

- Better design packaging (components do not have to be located on the belt system). - A prototype 28/42V military vehicle does not yet exist and it is imperative that a prototype vehicle design and build be started to demonstrate the advantages of transitioning to a higher voltage system.

11

Typical 42/28 dual-voltage architecture

24-volt

loads

24-volt

battery36-volt

loads

36-volt

battery

42-volt

starter

Alternator

42 to 28 volt conversion system (DC/DC converter)

AC

DC

12

 

Military Vehicle Power Demand Versus Time Trend

Time

Automotive Loads Voice Radios Analog Electronics

Electronic Architecture Digital Electronics Advanced Sensors Fire Control and NBC Digital C2 and SA Silent Watch Drive-by-Wire

Hybrid Engine High Power Weapons High Power Protection

First GenerationSystems

Legacy/Interim/SmallRobotic Systems

Objective force

PowerDemand

13

Components affected by voltage shift to 42 v (commercial vehicles)

• Starter (few hundred amps for short duration amperage draw)

• Alternator

• Cooling fan (13 A)

• A/C blower motor (22 A) • Windows motor (8 amps )• Vacuum pump (7 amps)• Power seat (7 amps) • Wiper (4 amps)Less affected --• Washer (3 amps) • Idle speed (0.6 amps)• Door lock (1.5 amps)

14

Practical issues

• Beyond certain size, can’t reduce motor winding gauge due to manufacturing constraints

• Similarly, in the wiring harness only the wires carrying > 3 amps can be reduced in size

• Implies that only 34% of the wiring harness will be benefited by the introduction of 42-volt system (24% total copper savings), compared to 14 volts.

15

Components affected by voltage shift to 42 v (military vehicles)

More affected -• Starter , alternator , climate control systems,• Thermal power unit (20 amps)• Motors for certain armor systems (4 amps) • Cooling fan • Washer (3 amps)

Less affected --• Idle speed motor (0.6 amps)

16

Benefit claim and payoff for transitioning to a 28/42V.

Benefit Claim PayoffPower/Energy Management • Better performance to improve mission

effectiveness such as, increased silent watch time• Autonomous control of vehicle power distribution based on the vehicle state and mode• Permit graceful degradation of loads

Meet Force Transform Objective Provide something better than what currently exists

Increased power • Less electrical distribution loss due to better efficiencies• Permit support of new electrical equipments for changing mission needs• Improve cold start requirements

Lower space and weight claim (better packaging) • Permit addition of new electrical equipments for changing mission needs• Cable weight reduction on circuits carrying >3 amps.

More efficient processes • Reduced fuel consumption (Army Key Performance Parameter)• Lower crew workload to reduce personnel fatigue for longer-duration missions.

Smart electrical components • Replacement of bulky and inefficient mechanical/hydraulic systems to improve efficiencies and reliability• Reduced parasitic loss• Current control circuitry for power management and built in test for diagnostics/maintenance

17

Benefit claim and payoff for transitioning to a 28/42V -- continued

Benefit Claim PayoffLower life cycle costs Lower Unit of Action Operation and Maintenance

(O&M) costs through greater reliability and lower maintenance

Incorporation of latest technologies • Reduces the prospect of technical obsolescence• Increases service life• Convenience and comfort features available to reduce crew work load and fatigue

Dual voltage • Backward compatible with 28V legacy systems• Permit introduction of selected advanced technologies in legacy systems

Quieter operation Reduced acoustical noise signature for improved survivability

18

Benefits to components for transitioning to a 28/42V electrical system.

Component BenefitIntegrated Starter Generator (ISG) • Optimized design by consolidating starter and

generator in a single unit provides space claim advantage• Allows engine cut off during slow down• Short delay in engine restart with non-perceivable lag Implementation of brake regeneration possible when ISG placed in line with the crankshaft• Can add power to the system during high torque demands• Potential fuel consumption reduction by 6-12 %, as demonstrated in the automotive industry

Source Power Converter • More compact design at 42V • Allows backward compatibility with 28V legacy systems

Constant power mechanical loads driven by electricity

• More efficient at 42V• Advanced brushless dc and switched reluctance motor drive technology can be implemented

Higher power generator/alternator • Compact design due to increase in voltage from 28V to 42V • Better efficiency at 42V with optimized magnetics

19

Benefits to components for transitioning to a 28/42V electrical system -- continued

Component BenefitElectronic power modules Compact size due to change from 28V to 42V.

Pump and fan loads • Operate on demand• Reduces/eliminates parasitic operation found in belt driven implementation

Electric valves • Provides variable timing options not available with mechanical implementation• Precise control and ability to monitor operation

Electrical conductors • Smaller cross section wire leading to lighter cable harnesses• Space claim advantage due to smaller size

Batteries • Energy density increase of 80 percent• Life increase of 2x• Status and state of charge feedback

20

JUSTIFICATION OF 42 V SYSTEM

Advantages• Overall gain in electrical system efficiency (even without new

functionalities, e.g. X-by-Wire, ISG etc.)• Packaging advantages due to the introduction of new

functionalities by replacing mechanical elements• 42 v system leads to improved packaging compared to 14 or 28

v Issues• Higher lamp filament voltage for lighting can be overcome by

use of LED technology• Load dump and high voltage transients• Arcing due to higher voltage

21

Transition Plan

The path to 42V transformation includes:

• Compatibility with current/emerging industry practices• Compatibility with legacy vehicles• Use of emerging standards such as, 42V PowerNet • Compatibility with Army fielding process• Endorsement by Army users and leading industry players• Acceptance as formal Army standard.

22

Transition Plan -- continued

The existing Advanced Mobile Power System (AMPS) STO is focused towards the development of the configurable power system, which is :

• Capable of supporting electrical power and power management requirements to integrate Vetronics, C4ISR (Command, Control, Communications, Computers, Intelligence, Surveillance and Reconnaissance, and embedded simulation capabilities into FCS platforms, including robotic Unmanned Ground Vehicles (UGV).

• The success of the AMPS STO can easily be extrapolated to any future military vehicular platform as well.

 

23

Summary

• The current 28V vehicle electrical system is inefficient, bulky, and less cost effective for the rapidly increasing power demands caused by new vehicle electrical loads such as, high power directed energy weapons, self protection (countermeasures) computers, multimedia, displays, communications, drive by wire, etc.

• Mission needs are changing and requiring greater flexibility of vehicles.

• As time passes, new technologies must be introduced to improve mission effectiveness.

• The added features in military vehicles have exhausted the operating margin in the current 28V electrical system.

• The military vehicles must follow the automotive industry to a higher voltage electrical system, such as 42V

• The payoff is significant in terms of flexibility, improved mission effectiveness, and decreased logistics burden.

24

CONCLUSIONS

• Beneficial for the military to embrace and phase in a 42-volt (single-voltage) electrical system architecture by starting with a dual 28/42 volt system.

• Dual 14/42-volt for commercial and 28/42 volt for military will benefit from better packaging, weight reduction, and improved efficiency, even if X-by-wire or ISG is not incorporated.

• Fuel economy will be improved by integrating components such as, integrated starter alternator (hybrid operation), electrical brake and steering systems, which are difficult to package using the existing 14 and 28 volt technologies.

• Fuel economy will also result from several improvements working together, e.g. reduced size and weight of wiring harness, brake regeneration, integrated starter generator (hybrid operation), parasitic loss reduction, etc.

• In terms of lamps use of new technologies like incandescent HID, LED’s, or PWM technology based lamps will be beneficial.