Electronic systems and components are often exposed to high temperature environment in space-based applications, nuclear power facilities, and geothermal energy extraction fields. A key requirement for these systems is, therefore, to withstand the high temperature exposure while maintaining efficient and reliable operation. Efforts were taken to design and develop a high temperature power inverter capable of 200 C operation. A 1 kW, 20 kHz Mapham inverter was designed and evaluated as a function of temperature at different load levels. The inverter system, excluding its input, control, and logic circuits, was characterized at temperatures from ambient to 200 C at 0%, 50%, and 100% resistive loading. With an applied input voltage of 75 VDC, the inverter produced an output of 250 VAC. The results obtained, which indicate good operational characteristics of the inverter up to 200 C, are presented and discussed

Bauman, Eric

Bercaw, Robert

Gerber, Scott

Hammoud, Ahmad

Myers, Ira

Overton, Eric

English

NASA Technical Reports Server

NASA-TM-107027 19960007618
NASA Technical Memorandum 107027
Development of a 1kW, 200°C
Mapham Inverter
Ahmad Hammoud and Scott Gerber
NYMA, Inc.
Brook Park, Ohio
Eric Baumann, Eric Overton, Ira Myers, and Robert Bercaw
Lewis Research Center
Cleveland, Ohio
Prepared for
Power Conversion and Intelligent Motion/Power Quality '95
sponsored by Intertec Intemational, Inc.
Long Beach, California, September 10-15, 1995
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https://ntrs.nasa.gov/search.jsp?R=19960007618 2020-06-16T05:17:22+00:00Z

NASA Technicat
3 1176 01422 9323
DEVELOPMENT OF A 1 kW, 200°CMAPHAM INVERTER
Ahmad Hammoud, Scott Gerber
NYMA, Inc.
NASA Lewis Research Group
Cleveland, OH 44135
w
Eric Baumann, Eric Overton,
Ira Myers and Robert Bercaw
NASA Lewis Research Center
Cleveland, OH 44135
ABSTRACT
Electronicsystemsand componentsare often exposed to high
temperatureenvironmentin space-basedapplications,nuclearpower
facilities, and geothermal energy extraction fields. A key
requirementfor these systemsis, therefore,to withstandthe high
temperature exposure while maintaining efficient and reliable
operation. Efforts were taken to design and develop a high
temperaturepower inverter capable of 200°Coperation. In this
work, a 1 kW, 20 kHz Mapham inverterwas designedand evaluatedas
a functionof temperatureat differentload levels. The inverter
system, excluding its input, control and logic circuitries,was
characterizedat temperaturesfrom ambientto 200°Cat 0%, 50%, and
100% resistiveloading. With an applied input voltage of 75 VDC,
the inverterproducedan outputof 250 VAC. The results obtained,
which have indicated good operational characteristicsof the
inverterup to 200°C,are presentedand discussed.
INTRODUCTION
Future challenges of advanced power systems comprise
increasing packaging density, improving reliability, and surviving
hostile environment. High temperature constitutes one of the harsh
stresses where power systems and components will be exposed to
during their lifetime. These applications include deep space
exploration, communications satellites, and supersonic transport
vehicles. Others include engine and brake-mounted sensors and
electronics in the auto industry, and control and instrumentation
in well logging fields. For space-based applications, there is an
enormous demand for increasing the energy densities and raising the
power levels of the power systems and associated components with
• the objectives to reduce size and weight, and to further improve
efficiency and reliability. These requirements, however, will
certainly result in raising the operating temperature of the power
0 system and will create, among other things, thermal stresses that
well exceed the withstanding or normal operating level of the
presently available devices and components. Improvement in the
current designs and processes, and the identification of new
1
materials and components capable of providing reliable and
efficient operation at high temperature, thus, play important role
for future needs of space power systems to be met. In addition to
meeting the requirements of hostile environment survivability and .
endurance, other benefits that can be gained from the availability
of reliable components and systems with high temperature capability
include reduced launch cost, simplified system design, and improved
thermal management. It has been reported, for example, that high
temperature components can make significant improvement in
reliability for satellite mission on the order of a hundred years
[i].
A program to develop lightweight, reliable 200°Cpower inverter
for aerospace applications is being performed at NASA Lewis
Research Center. As part of this effort, an existing 1 kW Mapham
inverter designed to operate at room temperature was modified to
investigate potential 200°C operation. Modification of the system
included circuit design and the utilization of in-house developed
high temperature components. The inverter was characterized at
0o, and 100%high temperature from ambient to 200°C at 0%, 5
resistive loading. In this paper, the experimental procedure and
the results obtained are discussed.
EXPERIMENTALPROCEDURE
As was mentionedearlier,an existingpower inverterdesigned
for room temperatureoperationwas modified in order to explore
high temperaturecapability. The original inverteris generally
known as a Mapham invertercapableof providing1 kW with a 125 VDC
input. It uses a resonant tank circuit in an H-bridge
configurationto develop a sinusoidalvoltage acrossthe resonant
capacitor with a fundamental output frequency of 20 kHz [2].
Modificationof the inverterincludedcircuitreconfigurationand
utilization of high temperature power components that were
developedeitherin-houseor throughcollaborativeresearchefforts
[3-5]. The basic circuit diagram of the inverter is shown in
Figure 1 with the dashedblock representingthe sectionwhich was
exposed and thus evaluatedat high temperatures. A list of the
high temperaturecomponentsused is given in Table 1 [3-5].
Evaluationof the inverterwas preformedat high temperature
with various load levels. A bias of 75 VDC was suppliedto the
input stage of the inverterwhich resultedin an outputvoltage of
250 VAC at about 20 kHz. A Hewlett-PackardModel 4030Apower supply
was used for the inputwhile SystronDonnerTL8-3 furnishedpower
for the control logic. A hotpack oven was used as the heating
chamberand thermocoupleswere mounted on the individualswitches,
inductors,capacitors,and on the center and end of the coaxial
transformerusing a Duralco 4525 epoxy. The temperaturesof the
chamber and the componentswere monitoredby a Keithley740 System .
Scanning Thermometer and a Doric Trendicator. At a given load
level, the inverter circuit was characterizedas a function of
temperaturefrom ambientto 200°Cin 25°Cincrements.A soakperiod
2
of 30 minutes was allowed at each test temperature to allow thermal
stabilization. The temperature rise and variations of the various
components were recorded. In addition, the values and the
• waveforms of many monitored signals were obtained using Tektronix
DSA 602A Waveform Analyzer. The measured signals included the
voltages and currents of the input source, switches, inductors,
capacitors, and the transformer primary and secondary windings.
' Besides the high temperature characterization, the effect of
loading on the measured properties was also determined as the
inverter was subjected to 0% (open-circuitsecondary), 50% (145 _),
and 100% (72 n) resistive loading at a given test temperature.
RESULTS AND DISCUSSIONS
The operational characteristics of the inverter were
investigated by monitoring and recording the temperature variation
of the inverter components as well as the current and voltage
levels and waveforms of several variables. During the course of
testing, however, there was little deviation in the operation of
the inverter and insignificant change in many of its measured
parameters whether by applying different test temperature or
changing the load level. Therefore, only selected data will be
presented.
The switch and output capacitor current and voltage waveforms
with no load applied at 25°C and 200°Care shown in Figures 2 and 3,
respectively. These waveforms are also shown in Figures 4 and 5
with 100% resistive load connected to the inverter output. It can
be clearly seen that no major variations were exhibited by these
parameters due to change in test temperature or load level. For
both cases, no load and full load conditions, it should be pointed
out, however, that slight increase in the switch (IGBT-diode)
voltage turn-off overshoot occurs as the test temperature was
increased to 200°C. It is believed that this overshoot is most
likely due to the increase in diode reverse recovery time with
temperature [5]. Initially, 150°Crated diodes were used but they
failed to operate for any significant time at 200°C. These diodes
were then replaced by 175°Crated units and, as a result, extended
operation at 200°Cwas achieved.
Figure 6 depicts the difference between the case temperature
of one of the inductors and that of the chamber as a function of
chamber temperature for three load levels. At a given test
temperature, the inductor case temperature had an average of 20° _T
higher than that of the test chamber. Similar trend was observed
for all inductors. Unlike the inductors, the _T in the case
• temperature of the switches amounted only to about 15°C, as shown
in Figure 7. It is important to note that the higher _T
experienced by the inductors was due to the fact that the
, thermocouple mounted on the inductor winding was wrapped with
teflon tape for mechanical support. This insulation layer might
have affected thermal distribution and interfacial equilibrium.
CONCLUSIONS
Key design requirements for advanced spacebased power systems
include higher energy densities, larger power levels, and better
harsh environment survivability. The development of high
temperature components is therefore necessary to meet these goals
and to further improve on the mission's thermal management design,
durability and cost effectiveness. In this work, a 1 kW Mapham '
inverter utilizing some high temperature components as its output
and switching stages was evaluated at three load levels in the
temperature range of room to 200°C. The preliminary results
indicate that the power inverter operated successfully over the
entire temperature range and at various load levels without any
noticeable change in its characteristic behavior. In fact, the
inverter showed good stability in its overall performance although
some of the individual components exhibited slight variation in
their properties with temperature. Although the present work
demonstrated 200°Coperation of the power inverter, more testing is
required to fully characterize the reliability of the system and to
determine its potential for long term use in high temperature
environments.
ACKNOWLEDGEMENTS
This work was supported by NASA Lewis Research Center,
Contract #NAS3-27186, Task Order #5430-04, "High Temperature Power
Electronics."
REFERENCES
[i] J. Burnham, "Leakage Current-Voltage Characteristics of Solid
Tantalum Capacitors at Very High Temperatures," Proceedings of the
24th Electronic Components Conference, Washington, DC, May 13-15,
1974.
[2] E. D. Baumann, I. T. Myers, and A. N. Hammoud, "Electrical
Characterization of a Mapham Inverter Using Pulse Testing
Techniques," 25th Intersociety Energy Conversion Engineering
Conference, Reno, Nevada, August 12-17, 1990.
[3] A. N. Hammoud, E. D. Baumann, I. T. Myers, and E. Overton,
"High Temperature Power Electronics Program," NASA LeRC Internal
Program Review, November 1993.
[4] D. M. Divan, D. W. Novotny, and N. H. Kutkut, "High
Temperature Co-axial Winding Transformers," University of
Wisconsin, Wisconsin Power Electronics Research Center, Interim
Report, February 1993.
[5] J. Bromstead, B. Weir, R. M. Nelms, R. W. Johnson, and R.
Askey, "Silicon Device Performance Measurements to Support
Temperature Range Enhancement," Auburn university - CCDSP, Final
Report, January 1994.
4
TIN --_
+ , l_., x
IQI,_INPUT VIN
I DR1 _ DR2--
_. L1 "rc----) =)19
PulseGenerator _ DR2 04 _l *_'J=
._ltv_ _- + ._IL & _
DR4 DR4_r.J Vsec DR3
ISeC _<)
LOAD
Figure 1. Basiccircuitof the MaphamInverter
Table i. High Temperature Components Specifications
[3-5].
Component Specification
Capacitor Capacitance: 1.0 uF
Voltage: 125 VAC
Frequency: 20 kHz
Dielectric: film
Inductor Inductance: 13 uH
Core: MPP
Frequency: 20 kHz
Current: 25 A
Transformer Power: 2.5 kVA
• Voltage: 125/250 VAC
Frequency: 20 kHz
Core: 80% Nicke! tape
i
Switch Device: IGBT TA9796
Voltage: i000 V
Current: 34 A
5
200 2OO
150 150
loo loo
0 ......... " - -
3o 30 I ] [ I 1 I I [ [
2O 2O
_ 10 10
8 °
_o -I -10
-20 -20
-30 "3O
200 20C
150 150
100 100
:_ o _
o
o -50 _
f._ -100 -10C
o150 -15C
°200 -20C4o _ ] ] I 1 I 1 I I I
"E 10 1€
-1 -1¢
-20 -2(
-30
-40 -4€
1o 2o 3o 4o 5o 6o _o 8o 9o _oo lo 20 _o 40 5o 60 7o 8o ,o loo
"l_me(US) Time (US)
Figure2: Switch(Q4)and outputcapacitor Figure3:Switch(Q4)and outputcapacitor
currentsandvoltageswithnoload currentsandvoltageswithnoload
at 25°(3. at 200"C.
6
2OO 2OO
150 150
& (_ 0 ...... 0
i
-5o203o_I _---_.-_--.I1 I :! "5°2o30
10 10
(3
._ -I0 -10
U)
-20 -20
-30 -3O
200 [ 1 [ I I [ I ] I 200
150 150
100 100
O) 5O 5O
(2.
f,_ -100 -100
-150 -150
-200 -200
40 40
3O 3O
_- 2o 2o
10 10
(3 0
"_ -1 -10
-20 -20
•30 -3O
•.40 -40
0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100
Time (us) Time (us)
Figure 4: Switch (Q4) and output capacitor Figure 5: Switch (1214)and output capacitor
currentsandvoltageswithfullload currentsandvoltageswithfullload
at 25_C. at 200_.
ii
30- 30-
0 _
.o :_- 8 °°°°° o 2°- o o o o °°°°°
_ 0@_l _ _5- o o D Do °°"_ Is- 0 n
0 0 0 0 d0 0 0 0 0 om
I0- 0 100%Load _ 10- 0 100%Load
D 50% Load [3 50% Load
5- 5-
0 0%Load 0 0%Load
O- i i i i i i i 0 i J 715 i i i i l0 215 50 75 100 125 1,50 175 200 25 ,50 100 125 150 17S 200
Oven Temperature (°C) Oven Temperature (°C)
Figure 6: Inductortemperatureriseabovethat Figure7: Switchtemperatureriseabovethat
ofthe chamberat variousloads, ofthe chamberatvariousloads.
8

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August 1995 Technical Memorandum
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Developmentof a 1kW, 200°C Mapham Inverter
6. AUTHOR(S) WU-233-01--0C •
Ahmad Hammoud, Scott Gerber, Eric Baumann,Eric Overton,
Ira Myers, andRobert Bercaw
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION
REPORT NUMBER
National Aeronautics and SpaceAdministration
Lewis Research Center E-9843
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AGENCY REPORT NUMBER
National Aeronautics and SpaceAdministration
Washington, D.C. 20546-13001 NASA TM- 107027
11. SUPPLEMENTARY NOTES
PreparedforPowerConversionandIntelligentMotion/PowerQuality'95sponsoredby IntertecInternational,Inc.,LongBeach,
California,September10-15,1995.AlamadHammoudandScottGerber,NYMA,Inc., 2001AerospaceParkway,BrookPark,Ohio
44142(workfundedby NASAContractNAS3-27186);ErieBaumann,ErieOverton,IraMyers,and RobertBercaw,NASALewis
ResearchCenter.Responsibleperson,ErieOverton,organizationcode5430,(216)433-8189.
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13. ABSTRACT (Maximum 200 words)
Electronic systems and componentsare often exposed to high temperatureenvironment in space-based applications,
nuclear power facilities, and geothermal energy extraction fields. Akey requirement for these systems is, therefore, to
withstand the high temperature exposure while maintainingefficient andreliable operation. Efforts were taken to design
and develop a high temperature power inverter capable of 200°C operation. In this work, a 1kW, 20 kHz Mapham
inverter was designed and evaluated as a function of temperatureat different load levels.The inverter system, excluding
its input, control and logic circuitries, was characterizedat temperatures from ambient to 200°C at 0%, 50%, and 100%
resistive loading. With an applied input voltage of 75 VDC, the inverterproduced an output of 250 VAC. The results
obtained, which have indicated good operationalcharacteristics of the inverter up to 200°C, are presented and discussed.
14. SUBJECT TERMS 15. NUMBER OF PAGES10
High temperature; Inverter; Power components 16. pRICECODE
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