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Application of Commercial Resources to

Military Needs for Electronic Power Sub-Systems

Ed Mabe TRW, Space and Electronics Group, Avionics
System Division, Kettering, OH

Marvin Soraya, Air Force Research Laboratory, Wright
Patterson Air Force Base, OH

Carlos Gonzalez, Raytheon,
El Segundo, CA

Abstract

To reduce the costs of military power supply
and distribution systems, the Electronic Power Specification Standardization
(EPSS) activities, supported and driven by coalitions of the industry,
is developing two interrelated reference documents: 1) Specification
Language, and 2) Building Codes.  Specification Language imparts
integrity to the power system specification process and the resulting
products.   Building Codes are based on available high-end
commercial products, and indicate their expected performance. 
The EPSS strategy is to provide the rational for the commercial power
supply manufacturers to conform to these developing industry standards. 
Military power supply users will be able to confidently select needed
resources from the commercial suppliers that conform to these EPSS standards. 
EPSS is sponsored by the Open Systems Joint Task Force from the Office
of the Secretary of Defense.

Overview

Across military and commercial market places and applications,
electronic power systems perform the same basic service of providing
regulated power required by the functional electronic systems. 
This basic service is an indispensable part of all electronics. 
However, high costs are an acute problem to the DOD and industry. 
The salient reason for this problem is the lack of a consistent broadly
accepted set of standards that is applied in the development and application
of electronic power systems.  Specifically, this prevents generic
product development and the resultant cost savings.  By developing
standards that are based on best commercial practices, the military
industry and DOD can maximize the effective use of high-end commercial-off-the-shelf
(COTS) products. The objective of the Electronic Power Specification
Standardization (EPSS) activities is to develop the vehicles that enable
the effective use of such products.  Government and industry have
been supporting and participating in the development of these vehicles.
The EPSS strategy is to provide the rational and the incentive for the
commercial power supply manufacturers to adopt these standards in describing
their products.  The standards will enable military power supply
users to confidently select and utilize commercial-off-the-shelf (COTS)
products conforming to the EPSS standards.

EPSS is developing two interrelated products: 1) Specification
Language, and 2) Building Codes.  Specification Language development
began in 1997.  The development has been driven by the EPSS Working
Group, which is comprised of industry personnel.  This Group developed
the draft IEEE P1515 document that is currently undergoing the balloting
process leading to an IEEE standard.  IEEE P1515 is scheduled for
final approval in March 2000.  Building Codes development began
in Q4 1998 and has been a separate effort performed by the EPSS Consortium. 
The Consortiums work is in preliminary draft condition.  Since
these two activities are complementary, many EPSS contributors have
participated in the development of both documents.

The EPSS activities are sponsored by Open System Joint
Task Force (OS-JTF)1 from the Office of the Secretary of
Defense.  The DODs Open Systems Architectures/System Engineering
Process is driven by an integrated technical and business strategy. 
The EPSS goal conforms to that of OS-JTF, that is to reduce systems
acquisition costs through advancing the use of commercial-off-the-shelf
(COTS) standards, products, services, and processes.  Both DOD
and the Institute of Electrical & Electronics Engineers (IEEE) have
recognized the benefit of developing an electronic power specification
standard, and are actively supporting the EPSS activities.  Power
Sources Manufacturers Association (PSMA) also has a forum for Government
and Industry to address problems such as those that are being addressed by
EPSS.

EPSS Standards

Presently the focus of the EPSS activities is on electronic
power systems for digital and low-power RF electronics.  The range
of power systems covered includes single phase and three phase systems,
with power levels up to 20KW, voltage levels up to 600 V, and frequencies
up to 1 kHz.  However, this language can be applied to systems
outside this range. 

Specification Language

Specification Language, in the form of IEEE P1515
Recommended Practice for Electronics Power Distribution Systems, contains
definitions, test methods and test conditions for the parameters used
to characterize power products.  Use of Specification Language:
1) enables manufacturers to unambiguously specify their products based
on EPSS definitions, test methods and test conditions, and 2) increases
the confidence level of the potential users to select the products of
the conforming manufacturers.  By applying the Specification Language,
manufacturers can reliably specify their products as tested to the EPSS
specified test method and test condition.  The objective is to
have the parametric features to be defined and tested in the same way
and under the stated conditions across all contending manufacturers. 
This standard method of product definition and characterization imparts
integrity to the conforming products.  Users can purchase conforming
products with the confidence that parameters were tested using the conforming
test methods and conditions.  Manufacturers will have the basis
to specify their products, test methods, and test conditions in order
to have a conforming product.

Specification Language was considered to be a good
starting point for the EPSS activities since it is difficult to compare
products that are specified and tested differently.  Different
manufacturers specify power products differently.  For example,
different performance parameters are referred to using the same descriptor. 
Also, performance testing is done in different ways and under different
conditions.  The P1515 Specification Language provides corresponding
definitions, test methods, and test conditions that if used, can enable
product consistency among manufacturers. 

Building Codes

Power supply architecture can be modeled as shown
in Fig.1 Power System Architecture.  Building Codes only address
the boundary between the electronic power system and its external surroundings. 
The power system is considered a black box whose internal contents
are of no concern to the EPSS architectural model.  The boundary
must be defined such that under a set of specified inputs, outputs can
be predicted.  The boundary, as depicted in the model, is divided
into four interfaces: electrical, mechanical, environmental, and system
effectiveness, see Fig. 2 Power System Interfaces.  Each interface
can be defined by a set of parameters.

Fig.1
Power System Architecture

Fig.
2 Power System Interfaces

For example,
the electrical interface has parameters for Vin, Vout, Voltage Ripple,
etc.  Each parameter is constrained by common sense rules or
Building Codes that are based on the capabilities of available high-end
commercial products.  For example, the electrical interface parameter
input voltage might be constrained to commonly available input voltages,
including but not limited to 12Vdc or 115Vac.

The objective of the Building Code
development is to identify and compile the capabilities of available
high-end COTS power system products.  A set of Building Codes will
allow the military power system designer to select from the commonly
available products, to optimally meet the system requirements. 
Commercial producers, with the knowledge of the typical military power
usage, could tailor their specifications to conform to EPSS.

Application of
EPSS Standards

A scenario describing the use of EPSS products
begins with a power engineer tasked with configuring a power system
for a digital rack.  The digital card designers determine power
requirements for the digital rack equipment.  Requirements include
input and output voltages, power required at each voltage level, acceptable
amounts of electrical noise, and other information that has been referred
to as electrical parameters and Building Codes.  Systems engineering
allocates a location and volume available for the power system in addition
to other pertinent mechanical, system effectiveness, and environmental
parameters and Building Codes.

The power engineer can then perform a make
or buy analysis for a power system configuration that meets the requirements
of the digital rack system.  As part of the make or buy analysis,
power products from various manufacturers, specified to EPSS standards,
are