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 3 rd 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 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 battery 36-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

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 Payoff Power/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 Payoff Lower life cycle costsLower 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 operationReduced acoustical noise signature for improved survivability

18 Benefits to components for transitioning to a 28/42V electrical system. Component Benefit Integrated 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 Benefit Electronic 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.