N85 13877

DEVELOPMENTS IN

SPACE POWER COMPONENTS

FOR

POWER MANAGEMENT AND DiSTRIBUTiON

David D. Reuz

NASA Lewis Research Center

Cleveland, Ohio

PRF'_"_"G PACE BL.a.N.K NO7' _-_L:,_ D

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https://ntrs.nasa.gov/search.jsp?R=19850005568 2018-07-08T06:00:39+00:00Z

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Power Electronic Co_ponent Developmentat Levis Research Center

Advanced power electronic component development for space applications hasbeen goius on at NASA Levis for more Chart a decade (Fig. 1). A wid_ range of

development york has been done, includin 8 transformers and induccors, semi-conductor devices such as transistors and diodes, remote pmaer controllers,and supporting electrical materials developtent, l_:esent power component

capability for space applications is about 25 kW. Work in the early andmiddle 1980's should raise this capability up ¢o lO0 k_ and begin _ork towarda megawatt.

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MAGNETICS

THYRISTORSo

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DIELECTRICS/CAPACITORS

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D60T Trans:I_tor

Against the backdrop of a circuit diagrau £o_ a solid-state remote povercontroller a technician holds a D60T (Fig. 2) ready £or assembly in s studpackage (ref. 1). In her right h=nd the interdiE_tated silicon wa£er may beseen inside the base. The emitter-base contacts are visible in the ceramic-

co-metal top held in her le£t hand. To the left of the picture are shmm

three package _ype_. From the top are a special £_t base paclmEe (a modi-f_.aCion o£ cbe scud package), a scud package and a dJ__c-cype package. ThJ.seranslstor is raced at 400 to 500 volts, i00 amperes contlnuo_ (200 A peak)

collector currents w_,th s_rltchln 8 frequency of 20 to 50 kHz. Thls devlcecan be used in DC-DC inver_ers, DC-AC converters_ DC motor controllers and

remote power conCrollers.

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High Current Power Switching Transistor

Figure 3 shows _e Westinghouse D7ST (ref. 2), which is now being marketed

as a direct transfer of technology fro= a research contract supported anddirected by NASA LeRC. The two package types available are shown in the center

photograph. Surrounding the picture are listed the features and applicationsof the DTST. The primary benefit of the new transistor to NASA is the

extension of the power handl_ng capabil_ty to 50 kW without paralleling of

transistors. This opens new areas of application and directions for future

space ;)over system design.

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AugnentedPmaerTransistor Specifications

Figure 6 shows the ratings and main characteristics of a research contractnow undervay st Westinghouse Cref. 3). Transistors from this pro_rau are nowavailable. The t_o sisnificant develol_ents of this program were the

demonstration of slass passivation of the va£er to provide hermetic sealing of

the juoctions and a hey package that isolates the thermal and electrical inter-faces.

VOLTAGE: 800 TO 1000 VOLTS

CURRENT: 70 TO 112 AMPERES (GAIN OF lO)400 AMPERES PEAK

POWER HANDLING: 75 KILOWATTS

POWER DISSIPATION: 1.25 KILOWATTS AT 750C

RISE AND FALL TIMES: 0.5 MICROSECOND

STORAGE TIME: 2,5 MICROSECONDS

373

Fast l_ecovez_, High Voltage Power Diode

Figure 5 shoos the benefits to NASA, the features and general applications

of a newly developed 50 smpere, 1200 volt fast recovery pouer diode (ref. 4).

Power Transistor Company developed the new diode on contract to NASA LeRC.

Because of the large demand for such a device co==erc£ally in motor

controllers, Power Transistor Company is already marketing the product astheir PTC 900 series Power Rectifier. A 150 ampere device (ref. 5) has also

been developed but is not shown.

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120 VDC, 30 Amp, Solid State Remote Pover Controller

Figure 6 shows the 30 ampere version of the 120 VDC solid state KPC (re£.

6) developed for NASA LeRC by Westinghouse Aerospace Division. This version

incorporates I2t trip characteristics rather than current limitin@. It _ay

be noted that this version has a single layer substance 6 x 7 cm end weighsabout 7 ounces.

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NASA High Voltage, Ei_ Pover Circuits

Figure 7 shovs an SCR switched solid state circui_ breaker breadboard forI000 volts DC and 25 amperes (ref. 7). This is an early model developed for

use with ion thruster power supplies by John Sturaan of Lewis Research

Center. With the development o£ the 1000 volt 07 size transistor, atransistorized version is nov available as symbolized by the circuit schematic

on the right. Three advantages are listed, also. Solid state circuitbreakers at high voltage DC have othe_ significant advantages overconventional electromechanical circuit breakers. These include: artless

circuit interruption, long life (no contact wear), reliability, 99%

efficiency, and universal source, load, computer interface compatibility.

1 KV. 25 A D.C.SOLID STATE

BREAKER

DRIVE CIRCUIT

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Heat Pipe Cooled Transfor=er

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Using heat pipe cooling permits about a 30Z reduction in transformer

weight in the transformer sho_n (ref. 8). Lifetime is also probably improved,

as [he maximum temperature rise above baseplate is only half as much. The

transformers shown in Figure 8 have a nom_al 2.2 kWpower rating and a power

density of 0.6 kg/kW at an operating frequency of I0 kHz.

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Comparison o£ Space-Type and Commercial Transformers

The significant weight and •size reductions which can be reaXized by goingto high frequency operation and unique the_l control techniques are clearlyillustrated in Figure 9. Of maj@r _mportance also is the face that the 25 kVAspace-type transformer (ref. 9) is more than 1Z more efficient and has a35°C lower temperature rise than the eoDerclal transformer. The specific

weight of the space-type 25 kVA. 20 kl_z transformer is 0.28 lb/kVA, while that

of the conmercial 25 kVA, 60 Hz transformer is 16 lb/kVA. The very good

maintainability and easy serviceability o£ the space-type transformer areadditioual outstanding features. The advanced technology which the space-type

transformer exemplifies is not limited to power transformers but should beapplicable to other power maEnetLc components. Power systems utilizin E this

type of magnetic components should show marked improvement in system weight,size, ef£icieucy and reliability,

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25 kVA Space-Type Transformer

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Shown in Figure 10 is a close up photograph of the 25 kVA high frequency

transformer shown on the previous page. Pie or pancake-type coils bonded to

metallic conduction plates are the basic building blocks for constructing the

primary and secondary windlnEs. Very low leakage inductance is possible by

placing a primary pie coil on one face of the metallic conduction plate and

the secondary pie coil on the opposite face. Good thermal control is realized

since the coil's 12R loss is uniformly transmitted directly to the metal

coil plates which _hen conduct the hear dlrectly To the heat sink baseplate.

In this transformer, the 8 primary pie coils for a 200 V input are connected in

parallel and the ends of each pie-coil terminate on copper tabs which become

an integral part of the primary bus bars located on top of the transformer.

The 8 secondary pie coils for a 1500 V output are connecued in series, and

again the ends of each pie-coil terminate on copper tabs which become an

integral part of the secondary bus bars located below the primary bus bars.

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High Power High Frequency Lightweight Capacitor

The smaller capacitor is a ncquinal microfarad, 600 vclt capacitor with a

maximum current capability of 125 A at 40 kHz (ref. i0). The dielectric is

potypropytene. The losses at maximum operating conditions are 22 watts, which

may be compared to the 75 kVA rating of the capacitor. The small capacitor

developed for NASA applications as sho_-n in Figure 11 is compared to a typical

commercial &0 kHz capacitor, which has a ratlng of 1.8 kVAR per pound. The

NASA capacitor, as developed by Maxvetl Laboratories, inc., has a power density

of II kVARper pound. This represents a decrease in size and weight by a

factor of seven.

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Lightweight Filter Using Heat Pipe Cooled Inductor

Fiaure 12 shows a factor of _do reduction in veisht resulting from the use

of heat plpe cooled inductors (ref. 8) in the first stage input filter in a

DC-DC converter. Both capacitor and inductor weights are reduced, because the

lightweiSht inductor allows the u_e of a larEe inductance value, and therefore

a smaller capacitance.

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Power Processor for Ion Rockets, Functional Node]

The power processor for a pair of 30 cm ion thrusters (re£. ll) is shorn

in Figure 13 in its package form. Included in this functional model is Lewisdeveloped ne_ technology in both circuits and electronic components. Circuitdevelopment includes the series resonant inverter, which throush zero currentturn oft and turn on of swltc6es allows low stress long life operation.Components developed st Lewis and incorporated in this model include heat pipe

cooled lightweight transformers and inductors, polyvinylideue fluoridecapacitors, and gate assisted turn-off thyristors. The power level is _bout6 kW.

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F_ta_ Power Transformer

Two studies were conducted by General Electric for Levis Research Center. _.¢'_

The first study des£Ened e I00 kW rotar 7 trmmformer (ref. 11) which had an _:_

axial gap (axial sy_uetric) and utilized four .25-kW modules placed alone the

shaft axis. The second study (ref. 12) was to InvestiKate a radial gap(vertical gap) rotary transformer and compare Its characteristics with those of

the axial gap configuration. The conclusion of the study was that the radial i

gap rotary transformer is the most feasible method for transferring electricalpower of 100 kW or more across a rotary joint. The rotary transformer programis shown in Figure 14.

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STLE)IES

A) 103 _ (GEHE]W_ELECTRIC)

B) > 100 i_ (I_[M_eL ELECTTLIC)

2 k_,. 2 ki'lz _-'_ DB'IIL_'i']_ r.llD_

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B) 20 kttz

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_oll Ring

The Roll Ring is s device chat transfers electrical power across arotating joint through rotating flexures between concentric conductors (Fig.15). The advantages of the Roll &inS over the slip ring are the elimination

of sliding friction and the low torque needed to rotate the device. The RollRing can transfer both AC and DC power and will be more efficient than therotary transformer. Lewis Research Center is purchasing a mulcl-kilowstt

device .from Sperry Flisht System, Phoenix, Arizona for in-house componenttestin E. Each power circuit will be capable of conducting 200 amperes at 500volts DC.

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Transmission Lines

Lewis Research Center is presently preparing sn _ for 8 high power, h£ghfrequency transmission line. The spe¢i£icatinns of the line will be 1000volts, I00 amperes 8c 20 kHz. The output of the contrac_ will be a 50 metercransmisslon line rJhar viii be tested to de_ermine the line cbarac_erlstics.

Fig. 16 shows two possible con£iguracions of 8 high £requency transmissionline.

XJGN-POWERHIGH-FREOUENC¥

TRANSRISSIOWLINE

COAXIAL LINE

PARALLEL PLATE LINE

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Power HanaEemenc

For the last 15 years, Lewis Research Center has been developinE powerprocessors for space flishts. The current development is a 25 kW seriesresonant DC/DC converter which is at the prototype level (ref. 13). _ith

today's component technology, the power level of space power processors couldreach 50 kW. These 50 kWmodules could then be paralleled, which could

increase the power system size to 250 kW or larger (Fig. 17).

STATUS: 25 kW DC/DC CONVERTER - PROTOTYPE

TODAY'S TECHNOLOGY: 50 kW POWER PROCESSORS (AC OR DC)(USING N_ POWER COMPONENTS)

SYSTER SIZE: BY USING 25 TO 50 kW MODULES IN PARALLEL, SYSTEMSIZES >250 kW ARE REASONABLE

FiE. 17

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References !i. Hower, P. L.; and Chu, C. K.: Development and Fabrication of Improved

Power Transistor Switches. NASA CR-159524, 1979.

2. Rower, P. L.: High-Current, Fast-Switching Transistor Development.

NASA CR-165372, 1981.

3. Gelsler, M. J.; Hill, F. E.; and Ostop, 3. A.: Development and Fabrication

of an Augmented Power Transistor. NASA CR-168262, 1983.

4. Berman, A. H.; Balodls, V.; et el.:

Fast Recovery, High Voltage Power Diode.

5. Berman, A. H.; Balod_s, V.; et el.:

Rlgh Current, Fast Recovery Power Diode.

Development and Fabrication of aNASA CR-165411, 1981.

Development and Fabrication of a

NASA CR-168196, 1983.

6. M/tchell, J. T.: Aerospac 9 Technology Development of Three Types of

Solid State Remote Power Controllers For 120 VDC With Current Ratings of Five

and Thirty Amperes, One Type Having Current Limiting. NASA CR-135216, 1977.

7. Mitchell, J. T.: Kilovolt DC Solid State Remote Power Controller Development.

NASA CR-168041, 1982.

8. Chester, M. S.: Heat Pipe Cooled Power Magnetics. NASA CR-159659, 1979.

9. Welsh, J. P.: Design and Development of Multi-kW Power Electronic Trans-

formers -- for Lon E Duration Space Applications. NASA CR-168082, 1983.

I0. White, C. W.; and Hoff_an, P. S.: High Frequency, HiEh Power Capacitor

Development. NASA CR-168035, 1983.

Ii. Welnberger , S. M.: Prellmlnaz7 Design Development of I00 kW Rotary Power

Transfer Device. NASA CR-165431, 1981.

12. Welnberger, S.M.: Design Study of a Rish Power Rotary Transformer.

NASA CE-168012, 1982.

13. Hughes Aircraft Company: 25-EW Serles-Eesonant de/de Power Converter.

NASA t_-168273, 1984.

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