Note: Descriptions are shown in the official language in which they were submitted.
12~50~7
BAr~CROUND OF INVENTION
This invention was made at the Center for Electron
mechanics of the University of Texas at Austin with support
from the Department of the Army
The present invention relates to pulsed power supply
systems; and more particularly it relates to high-energy
(multi-MJ), high current MA), pulsed power supply systems
using inertial energy storage with homopolar conversion.
Inertial energy storage with homopolar conversion is
known to be useful as a pulsed power supply. Such a home-
polar generator HUG is shown, for example, in US. Patent
No. 4,246,507. however, HUG power supplies have tended to
be large, rather bulky, fixed laboratory installations.
An HUG, because it models electrically as a capacitor,
admits to application as a power supply for electromagnetic
(EM) propulsion systems for accelerating projectiles. Such
EM propulsion systems include rail guns and launchers. In
such applications, particularly rail guns, the power supply
must be compact, and desirably is field portable. Prior HUG
power supplies due to their relatively large physical
dimensions are not satisfactory.
Allis
SUMMARY OF THE INVENTION
The present invention provides a compact pulsed power
supply system utilizing a homopolar venerator. By reason
of its compactness, the power supply is field portable
The power supply system provides a high-energy (multi-
MY), high-current mealtime) pulsed electrical output. The
power supply is suitable for powering rail guns and the
like The power supply utilizes a homopolar generator
(HUG) comprising a rotor split into halves insulated from
one another and having a recess formed in the periphery.
A stators and a field coil, for producing a magnetic field
are disposed within the recess in the rotor. Further
included in the HUG is means for collecting electrical
discharge current from the rotor. An auxiliary supply and
drive system it further included in the power supply. The
auxiliary system comprises a prime mover for providing
operating power, and includes a means for motoring the HUG
to speed. A control system coupled to the HUG and the
auxiliary supply system controls the operation of the HUG
to obtain pulsed electrical power therefrom.
The control system includes a logic controller for
executing a prescribed sequence of steps including turning
on the prime mover, initiating motoring of the HUG, ever-
giving the field coil, and initiating discharge of electric
eel current.
The motoring means for the HUG includes a hydraulic
motor coupled to the rotor. A hydraulic circuit, include
in a hydraulic supply pump driven by the prime mover,
~2c
controls the operation of the motor To permit tree-
wheeling of the motor during discharge of the HUG, thy
hydraulic circuit includes a relief valve bypassing the
output of ho supply pump.
The HUG may also include a bearing system to facile-
late rotation ox the wrier The auxiliary supply and
drive system may further include a bearing lubrication
system.
The current collecting means in the HUG may be brush
mechanisms pneumatically actuated into contact with the
rotor The auxiliary supply and drive system may further
include a pneumatic control circuit for controlling the
bra so mechanisms.
With particular reference to the subject matter claimed
herein, the invention in one broad aspect pertains to a brush
mechanism for a rotating electrical machine having a slip ring
surface from which electrical current can be collected,
comprising a brush for contacting a slip ring surface to collect
current, and a brush strap having the brush attached to one
end, for supporting the brush with respect to the slip ring
surface, the brush strap comprising a plurality of laminations.
Another aspect of the invention pertains to a homopolar
generator, comprising a stators for producing a magnetic field,
a rotor having a slip ring surface defined thereon, for rotation
within the stators magnetic field to generate an electrical
potential, and a brush for contacting the rotor slip ring
surface to collect current therefrom. Means are provided for
repeatedly actuating the brush into contact with the rotor
~S~97
slip ring, and there is a brush strap having the brush attached
thereto, for transferring current and for lifting the brush
clear of the rotor slip ring after actuation. The brush strap
comprises a plurality of laminations.
A still further aspect of the invention comprehends a
homopolar generator, comprising a support structure with a
stators assembly inwardly disposed within the support structure
for producing a stators magnetic field. A shaft is mounted
in the support structure and a rotor is carried on the shaft,
the rotor including two mating rotor halves together defining
a recess in the peripheral surface of the rotor, for fitting
around the stators assembly to enclose the same. An inner brush
mechanism is disposed within the recess in the rotor, for
contacting a surface of the rotor defined by the recess to
collect discharge current, and an outer brush mechanism is
disposedwithln the support structure, for contacting the
peripheral. surface of the rotor adjacent the recess to collect
discharge current.
The invention also comprehends a brush assembly for a
rotating electrical machine including a stators having a field
coil for producing a magnetic field, a rotor for rotation within
the stators magnetic field to produce electrical current, and
a slip ring surface on the rotor. The assembly includes a
brush pad comprising a plurality of adjacent brush pad blocks,
for making contact with the rotor slip ring surface, and a
brush strap connected to the brush pad, for biasing the brush
pad blocks toward a retracted position away from the rotor
slip ring surface. An actuator is provided for causing
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S`V97
deflection of the brush strap to simultaneously place the brush pad blocks in contact with the slip ring surface, the actuator
including an elongated core structure having a passage
there through for fluid communication, and an inflatable
diaphragm comprising a synthetic rubber body molded around
the core and bonded only to the top and sides thereof, whereby
a diaphragm cavity is defined. Means are provided for
introducing pressurized gas through the passage in the core
and into the diaphragm cavity, to expand the diaphragm against
the back of the brush strap and force the brush pad blocks
into contact with rotor slip ring surface.
Various other aspects of the invention will become apparent
from the more detailed disclosure which follows in conjunction
with the appended claims.
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~2'~5Q~7
BRIEF DESCRIPTION OF TOE DRYNESS
A written description setting forth the best mode
presently known for carrying out the present invention
and of the manner of implementing and using tip is pro-
voided by the following detailed description of an thus-
trative HUG power supply embodiment shown in the attached
drawings wherein:
Figure 1 is a schematic diagram illustration of the
HUG power supply;
Figure 2 is a graph of current and voltage versus
time for the HUG power supply output upon charging of a
specified load;
Figure 3 is a cross-sectional view of the single
rotor HUG used in the HUG power supply;
Figure 4 is a cross-sectional view of the rotor
assembly of the HUG power supply, including illustration
of rotor hydraulic fitting;
Figure 5 is a plan view of the support structure for
the rotor assembly;
Figure 6 is a side view of the support structure
shown in Figure 5;
Figure 7 is a cross-sectional illustration of the
thrust bearing assembly shown in Figure 3;
Figure 8 is a cross-sectional view of the stators
assembly of the PUG power supply;
Figure 9 is a sectioned end view of three of the
inner brush mechanisms used in the HUG power supply;
5{J I
Figure 10 is sectioned side view of one of the
inner brush mechanism in the PI power supply;
Figure 11 it a sectioned end view of two of the outer
brush mechanisms used in the PUG power supply;
Figure 12 is a sectioned side view of one of the outer
brush mechanisms used in the HUG power supply;
Figure 13 is an illustration of the conductor cross-
ovens for electrically connecting the two rotor halves in
series;
Figure 14 it a schematic diagram of the air supply
for the pneumatic brush mechanisms shown in Figures 9-12;
Figure 15 is a schematic diagram of the bearing
lubrication system;
Figure 16 is a schematic diagram of the motoring
system for bringing the PUG to speed;
Figure 17 is an illustration of the auxiliary and
drive package for the HUG;
Figure 18 is a diagram of the control system; and
Figure 19 is a flow chart of the control sequence
for the HUG power supply (Figures aye & lob).
so
DETAILED DESCRIPTION OF
ON ILLUSTRATIVE EMBODIMENT
A. HUG Power Supply General Configuration
In Figure 10 there is presented a diagrammatic thus-
traction of a homopolar generator (HUG) power supply system
10 providing in a compact, field-portable package, a high-
energy mealtime, high-current (multi-MA) pulsed power
supply.
HUG power supply system 10 comprises a homopolar
generator (HUG) 12 in a single rotor configuration.
Output pulsed power from HUG 12 is available at terminals
I HUG power supply 10 further includes auxiliary supply
and drive package 15 for driving HUG 12 to speed and for
supplying the required auxiliaries to HUG 12. An incitory-
mentation and control system 18 provides control for the
various components of the system 10 and disarms HUG 12 if
a fault occurs
The drive package 16 and HUG 12 are preferably mounted
on a skid 13~ The control system is preferably provided in
a standalone cabinet and connected by cable to the HUG and
drive package.
By HUG Power Supply Operating Parameter
As a sinqle-rotor machine and for an operating outer
slip ring speed of 220 m/s (6,200 rum the electrical
characteristics of HUG 12 are as summarized in Table I.
--6--
~12:~.5~
TALE I
stored Energy 6.2 Jo
Rotational Speed 654 Rudy
Capacitance 4,960
Internal Resistance 7.5
Internal Inductance OWE H
Voltage 50 V
Magnetic Flux Density 2 T
yield Coil 70,000 A-t
lo Armature Current 750,00U A
Referring now to Figure 2, calculated curves of
current and voltage versus time for HUG 12 when used to
charge a load consisting of-a 5.4 micro henry, 27 micro-
ohm inductive coil are shown
C. Homopolar Generator Description
1. General
Referring to Figure 3, HUG 12 is shown in cross-
section. HUG 12 includes several major subassemblies,
including: rotor-shaft assembly 20; stators 22; support
structure 24; bearing systems 26, 28; inner brush mock-
anises 30; outer brush mechanisms 32; and field coil 34.
Also shown is motor 36 for driving HUG 12 up to speed.
The rotor is the primary element of the machine; it
stores the energy inertial and converts it to electric
eel energy upon demand. lost of the fabrication labor
involved in building this machine is applied to the stators
assembly, which includes the field coils, brush mechanisms,
I
~51:)~7
conductor, ferromagnetic twitter, and the support try-
sure mounting the stators assembly relative to the rotor
assembly The brush mechanisms are subjected to exterior
dinarily difficult duty. The brushes must contact the
rotor at its full diameter and thus at maximum surface
speed. They must conduct extremely high currents at low
voltage drop or maximum efficiency and minimum brush
heating, They must operate in a relatively high magnetic
field and thus are subjected to high J x forces during
discharge. The outer brushes are the making switch for
the machine and must simultaneously contact the rotor
while remaining completely clear of the rotor before being
actuated. Finally, the brush mechanisms must minimize and
reject heating due to friction, interface voltage drop,
and joule losses in order to minimize brush wear. Require-
mints for the rotor assembly are that it be sufficiently
stiff to allow operation at speeds up to 8,500 rum without
encountering a critical frequency while being lightweight
and compact. Because HUG power supply 10 is to be field
portable, rolling element bearings, with minimal hydraulic
power requirements are preferred. These bearings mutt be
stiff; they are sub jetted to impact loads during a disk
charge and might have to operate in stray magnetic fields
that could cause electrical pitting.
Auxiliaries for HUG 12 include motoring supplies,
lubrication systems, field-coil power supplies, and brush
actuation.
The total weight of HUG 12 is approximately 3,500 lobs,
and the machine fits into a 0.86 m diameter, O.g1 m long
cylinder, a volume of O . 53 my
I 97
2. Rotor
Rotor 24 in HUG 12 of thy field portable power supply
being described is suitably 68 I in diameter, 40 cm
thick, and shaped for a constant area magnetic flux path.
Rotor 24 it preferably made of steel, and weigh about
1j500 lobs. Rotor 24 is supported radially by heavy-duty
needle bearings and axially by angular contact ball
bearings, which bearings are provided in bearing systems
26, 28.
The stators support structure 25 houses the stators
22, the inner brush mechanism 30 and the field coils 34
(Figure 3). Therefore to assemble the machine, the rotor
20 must be split into halves and fitted around the stators
In addition, the ability to take the rotor halves apart at
any time it needed to perform maintenance on either the
field coils or the inner brush mechanism. Furthermore,
the rotor halves must be insulated from each other to per-
mix two voltage generating passes through the externally
applied magnetic field.
As the rotor is brought Jo speed in an HUG, the inner
diameter (ID) of the rotor expands due to centrifugal
forces. The shaft of the machine also experiences eon-
trifugal growth, but not as much as the rotor ID. Cons-
until a relative growth is present between the shaft and
rotor ID at operating speeds; this growth increases with
the square of machine speed. Therefore, an initial inter-
furriness button the shaft and rotor is required in order
to Anton contact at operating conditions.
97
heretofore, in most HUG machines, this initial inter-
furriness is obtained by a thermal shrink fit of the shaft
into the rotor. For shrunk fitting, the swat diameter
is machined larger than the ID of the rotor to obtain the
necessary interference. The shape is chilled reducing it
diameter, while the rotor is heated; then the shaft it
inserted into the rotor bore. When the ma trials return
to room temperature (i.e., when there is no longer a
thermal gradient), the interference between the rotor bore
lo and shaft is established. However, in HUG 12, the rotor
cannot be assembled solely by this method, since once the
shrink fix is completed, the rotor cannot readily be
separated from the shaft.
In view of these rotor assembly restrictions, the
thermal gradient technique is used to fit one rotor half
into place while using a hydraulic technique to fit the
other rotor half into place. The thermal shrink fit is
intended to be permanent, while the hydraulic fit can be
disassembled. A drawing of the rotor assembly appears in
Figure 4.
At the design speed of 220 m/s (6~242 rip the
relative diametral growth between rotor bore and shaft
is 0.0060 in Using a 100 percent factor of safety, the
required initial interference is 0.0120 in. This is a
conservative design that allows the machine to be run at
speeds in excess of the design goals if desired. (At 300
so approximately 3,000 psi interference pressure will
still be present between the shaft and rotor bore)
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lS~9'Y
The 0.012-in. interference produces an interference
pressure of approximately 44,000 psi at the contacting
surfaces. The maximum combined stress resulting rum this
pressure occurs at the inner diameter of the rotor and is
7B,250 psi. At the design speed of 2~0 m/s this stress
increases to a maximum value of 81~750 Sue This is a
clear advantage of the interference fit; the maximum
stress remains fairly constant over the operating speed
range of the machine. The mechanism for this phenomenon
is such that, at zero speed, the stresses present are due
entirely to the initial interference between the shaft and
rotor bore. As the machine speed increases, the inter-
furriness is decreased, lowering the stress level due to the
interference pressure. Concurrently, the stresses due to
centrifugal effects in the rotor increase with speed,
keeping the total maximum stress level fairly constant.
This effect is particularly advantageous from a fatigue
standpoint because the cyclic stresses are minimized.
In order to shrink the right side AYE of the rotor
onto shaft 21 a temperature differential large enough to
offset the inn interference is required. For a 4-in
diameter shaft, assuming that 0.001-in. clearance is surf-
fishnet for assembly, the required temperature differential
between shaft and rotor is 542F. This differential can be
obtained by chilling the shalt, by heating the rotor, or
by a combination of both.
To hydraulically assemble the left side of 20B of the
rotor, the shalt 21 and rotor surfaces are not separated
thermally as in a shrink fit, but by hydraulic pressure
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Sue
supplied by an external pup. Thy pressure it introduced
to the await rotor interface through a port 38 and oil
grow 40~ ~ig~-pres~ure oil seal 42, 44 on both side
of toe oil groovy prevent leakage frown the ends of the
rotor. Once the pressure it applied, the rotor bore
expand, thy shaft diameter shrinks, and a hydraulic
pusher 46 is used to push the rotor half 20B onto the
tapered shaft 21. A port 48 and oil groove 50 provided on
the shrink-fi~ side AYE of the rotor enable disassembly
lo of this rotor lye it necessary. Since seal are not
required for rotor disassembly, they are omitted on the
shrin~-fi~ side
The hydraulic pressure necessary Jo separate the
shaft and rotor born it the same as the final interference
pressure (44,000 pal). A hand-operated pump pressure
Prvduc~ Industries Model No. OH-102-60) and high pressure
fitting manufactured by Sno-Trik) may be used; this
pumping system it rated at a working pressure ox 60,000
psi. In addition, the seal for the system comprise
Parker Pulp Type B seals (material: 90 dormitory Molt
thanT~-4615)~ and Parker Modular backup rings (material
Palmetto z-4652).
The hydraulic pusher 46 it designed to force the
rotor onto the shaft while the rotor and shaft surface
are separate by the high pressure hydraulic system. The
inner cylinder of the pusher attaches to the shaft; the
outer cylinder, actuated by a low-pressure pump (South-
western Controls twiddle No. SC-40-500-3, maximum pressure
5,000 psi), presses against the rotor face and provide
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:121~i~97
the force to push Abe rotor onto thy shaft. an ester
ally applied pressure of 44,000 pi a thy ~haft-rotor
int~rfa~e, the force required Jo push the rotor onto the
shaft 77,500 lb tithe shaft an rotor interface ha a 1
per side taper). At the present hydraulic pusher dummy
swoons the low-pressure pump will have to produce 3~800
pi to achieve the 77,500-lb force.
In order to have two voltage generating passes
through the motion externally applied magnetic yield,
the rotor halves must be insulated from one another. The
scheme to accomplish this it illustrated in Figure JO
On the -shrink fit rotor half AYE, a ceramic material
52 will insulate between that rotor half and the shaft.
In addition, the ceramic will be used to insulate between
rotor face. Because the ceramic will insulate between
the shaft and rotor on one side, it will have Jo with-
stand some demanding mechanical tresses Kit will undergo
the full interns pressure) without sacrificing it
required electrical properties.
The ceramic coating may be aluminum oxide, such a
Allah available prom Norton Industrial Ceramics Division.
The coating it preferably applied by a flame-spraying
technique such as that conducted by the F. W. Garter Co.,
3805 Lamar, Houston, Texas. After application, the ceramic
coating it impregnated with silicon resin such as General
Electric SR182S the resin it allowed to sure and is then
around to dimension.
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~2~5(:~7
3. Support Structure and Bearings Systems
The PUG 12 support structure 24 is shown in detail in
Figures 5 and 6. The support structure provide alignment
and structural integrity needed for the rotor. The sup-
port structure also provides a mounting attachment for the
stators assembly.
Support structure 24 is made entirely of aluminum and
comprises a one-inch thick aluminum ring 54. Preferably,
the ring 54 is shrunk fit onto the stators 22. A plurality
of T-shaped crossbars 56 are welded to ring 54. Two conic
eel end plates say 60 are bolted to the crossbars, and
carry stainless steel bearing housings 62, 64.
Bearing system 28 (Figure 3) is a non-thrust bearing,
whereas bearing system 26 in housing 62 it a thrust bear-
in. Roth bearing systems have radial bearings of heavy-
duty needle bearings which are suitably Torrington No.
HJ-445628 bearings. These bearings include both the inner
and outer race and a cage to accurately guide the bearing
rollers. In Figure 7, there is a cross-sectional view of
the thrust bearing system 26, showing both the needle
roller radial bearing 64 common to the non-thrust bearing
system 28 and the duplex angular contact ball thrust bear-
in 66~
Needle bearings are used because of their inherently
high stiffness. because the rolling elements (the needles)
are radially thin and are relatively long axially, they
are much stiffer than comparable ball bearings. In add-
lion, the fact that the rollers have line contact with
each race (rather than point contact as in ball bearings)
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SUE
also adds kiwi their 'siphon. The calculated ~iffnes~
for each of the joy bearing. I 7.23 x 10~ lb/in at
a reload provided by like rotor weight.
It us important hut the bearings in the HUG 12
machine be preluded to prevent skidding at high speed.
In the radial bearing this reload it provided by the
weight of the rotor approximately 800 lb per Bering
The radial bearing have a catalog-ra~ed maximum steed of
6,150 rum however overspending of rolling element bear-
lo ins is an acceptable practice provided they receive
adequate lubrication and cooling The radial bearings
have a calculated h-10 life of 1,850 hour a continuous
operation at 6,300 rip
Referring to Figure 7, the thrust bearing system 26
it shown in pagan with shaft 21 inserted therein
Additionally, figure 7 shows stainless steel bearing
housing 62 bolted to conical end 58 of thy support struck
lure I by bolts 68. Conical end 58 is further shown to
inlay a steel mounting sleeve 70 pressed therein. Con-
netted by bolt 72 it a bearing housing cap 74.
The angular contact ball bearing 66, suitably SO
No. 7411 B, art duplex mounted back-to-bacX on one end
of the machine. Attaining sufficient stiffness from the
annular contact bull bearings I is accomplished by pro-
loading, To prowled these bearings, a shim can be placed
between the outer races of the two back-to-back bearing.
Then by clamping the two bearings together on the shaft
with a nut, the reload can be established. The amount of
reload attained can be adjusted by the thickness of the
-15-
slough
hi between ho bearing. The tradeoff to be made forth thrust bearing it Tiffany versus luff Increasing
the reload increase the stiffness while depressing the
bearing Lowe. At an 8,000-lb reload (8.5 x 106 lb/in
s~iffnesR~, the calculated L-10 life of the thrust bearing_
pair is 97 his. Thy rated speed limit of the bearing it
approximately 5,100 rum; however, overspending is accept
able when adequate lubrication and cooling are provided.
Lubrication and cooling is provided by an injection
lo of oil into the bearing rolling element. Oil flow is
provided through lubrication oil inlet 75 to oil injection
passage 76 in bearing housing 62 and housing cap 74. At
the end of each pa sage is a nozzle 78, which may suitably
TM
be a 0.055-in-diameter fluid restructure (Lee Plug Jet Part
No. 187002-005)~ A shown, there are two ox is provided
for each wide of etch set of bearing roller elements Jo
that the bearing will receive lubricant in case of a
clogged restructure Also in bearing housing 62 and housing
cap 74 are oil jump passages 80 leading to a lubrication
oil sup outlet 82. Preferably, the lubrication oil will
be passed through at a total flow rate ox 10 gal/min. Oil
scavenging is at 25 gamin to prevent oil from pooling in
the beaning housing and keep viscous friction losses to a
m~nimumr
There further shown in Figure 7 a clamping nut 84
on the end of shaft 21 and a drive coupling 86. Driving
motor 36 figure 3) it partially shown coupled through
mounting flange 88 and spacer 90 to housing caps 74 and
d r ivy coup i no 8 6 .
--16--
I. Stutter Assumably
The talon assembly for PUG 12 it shown it detail in
Figure 8. the stators assumably my be regraded a including
the ferromagnetic stutter ring 22, the field coil 34, and
the aluminum T-bar3 56 figure S) for connecting the pharaoh
magnetic stators rings to the support structure. Addition-
ally, the stators assembly include inner brush ring 92 and
outer brush ring 94. Connecting to the inner brush ring
are current collecting conductors AYE and 968.
lo The ferromagnetic stators 22, preferably of A-36 steel,
conducts the magnetic field from one rotor face to the
other Since the inner brush mechanisms are air-actuated,
as will be described, an air manifold 98 is provided
through staSor ring 22 and in communication with brush air
inlet 100. A noted in the ascription relating to the
support structure 24 shown in Figures S and it, aluminum
ring 54 is shrunk onto stout ring 22. Additionally, the
aluminum ring 54 is pinned to the Starr by steels studs 102.
As shown in Figure 8J the T-bars 56 are bolted by stainless
steel bolts 104 to the aluminum ring 54. The bolts 104 are
modified so as Jo register with and have inserted in Tao
end thereof the steel stud 102. To further enhance the
connection of the T-bar 56 to aluminum ring 54, dowel pin
106 are inserted. through the T bar and into ring 54. Bolts
104 are preferably I inch in diameter, and dowel pins 106
are preferably 3~8 inch in diameter. It is also preferred
that compensating conductor go be held firmly to the steel
stators ring by, for example nylon fathead screws (not
shown).
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so
Field coil 34 comprise two coil Hoyle AYE and 34~,
preferably designed for 70,000 amp-turns a a magnetic air
yap of 0.5 inch. Because of it interior location, field
coil 34 mutt be as thin as possible radially. Accordingly,
the coy pulsed rather Han steady state. Each field
coil half ha 156 turns of 0.23 inch square solid copper
conductor insulated with a heavy coat of armored polyp
thermalized insulation.
The terminals 108 of the coil are plug-in-Multilam
connectors located between the two coil halves AYE and
34B. Terminal access is through the center of the stators
which minimize field dissymmetry. The coils can be run
either in series or in parallel and require a 30-V, 417-amp
power supply per coil at the 70,000 amp-turn level. In
parallel the 30-V requirement is very nearly compatible with
an Army 28-V generator.
The field coil is fabricate a follows. The square
conductors art half-lap-wrapped with 0.OOS-inch thick, 1/2-
inch wide fiberglass tape. Then the two conductors are wound
separately onto the two halves of a vacuum impregnation
mold. the terminals are then brazed into place, the two
halve are bolter together, an the entire structure it
vacuum impregnated with a low viscosity, 250F, elevated-
temperature-cure epoxy.
JO Brush mechanisms
Collection and transfer of current from the high-
surface-speed slip rinse is accomplished in PUG 12 by the
inner brush mechanism Sheehan in r issues 9 and 10 and the
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L5~97
outer brush mechanism shown in Figures 11 and 12. This
is a demanding task, and because ox the A-I-R configure-
lion of the machine additional constraints are placed on
the inner brush mechanism in regard to radial height.
That is the radial height must be minimized because the
brush and its actuator directly reduce the flux-cutting
area of the rotor, which in turn reduces the generated
machine voltage. In HUG 12, the outer brush mechanism
is also subject to additional considerations since it is
lo being used as the current mixing switch.
Referring first to Figures 9 and 10, the inner brush
mechanism 30 is shown in position relative to the stators
and the rotor In Figure 9, the brush mechanism is shown
in an end view (along with two other brush mechanisms 31
and 33). In Figure 10, brush mechanism 30 is shown in a
side view
The inner brush mechanisms are shown in Figures 9 and
10 connected to the inner brush current collecting conduct
ion ring 92 by fathead screws 110. The brush pads 112
which make contact to the rotor inner slip ring surface
19, are preferably 1/8 inch thick by 3/4 inch long by 7/16
inch wide sistered copper-graphite blocks. Each brush pad
is attached by silver brazing to a brush strap 114 that
carries the current to the brush ring.
The brush straps must conduct extremely high currents
without becoming excessively hot. They must operate in a
relatively high magnetic field and thus are subjected to
high electromagnetic forces during a current pulse. The
strap must provide sufficient elastic spring force to lift
-lo-
~2~51~9~
the brush clear of the slip ring. Finally and most
important, the strap must provide a dynamically stable
brush mount sufficiently soft radially Jo allow the brush
to track the slip ring but 5uffi~iently stiff axially and
circumferential to ensure that the brush return to
exactly the same orientation on the rotor after each
actuation
As brush 112 wears away with use, it is desirable to
compensate for this wear so that the brush is retracted
the same distance from the rotor slip ring surface through-
out its useful lifetime, ensuring consistent brush actual
lion times and down forces Unfortunately for compact,
high packing factor brush assemblies that require short
brush straps, the bending stress in the solid copper strap
is exceeded during brush actuation, causing the brush
strap to yield in the "brush down position and resulting
in a 108s of ability to retract the brush. Conventionally
hardened copper (hardened by cold working or rolling)
cannot be used to raise the yield strength of the brush
strap since it will be annealed during the process of
brazing the brush strap to the brush.
As a solution, brush straps 114 are laminated.
laminated brush strap is both dynamically stable and
stiff in the axial and circumferential planes. This means
that the brush will swing through the same arc and maze
contact in the same location with each actuation. This it
important because as the brush wears it makes better con-
tact, but it must make contact in the same orientation
with the slip ring during each cycle. The brush strap
-20-
mutt radially soft because whatever mechanist is act-
axing the brush must overcome the strap stiffness as well
as provide adequate down forte of thy brush onto ho slip
ring however, the strap must be thick enough to conduct
the current without an excessive temperature rise. ~150
it must be strong enough to lift the brush clear of the
slip ring; thus it should not yield during actuation.
These problems were resolved by laminating the brush
strap. By maying the laminations different thicknesses
and out of different types of copper (i.e., beryllium, ETA
110, or dispersion strengthened copper, which is not
annealed during brazing 9 various combinations of stiff-
news, cross-sectional area and strength can ye obtained.
A typical example is a strap made of two 0~031-inch-thick
ETA 110 copper straps and one 0.031-inch-thick dispersion
strengthened copper strap all 7/16 of an inch wide.
Laminated brush straps 114 will each conduct 3,000
amperes for 0.25 seconds with a 15F~temperature rise.
It take approximately S pounds to move the brush 1/16 of
an inch, which provides a lift force of approximately 4.5
pounds. Each strap 114 is approximately one inch long.
The discharge currents in the brush straps 114 react
with each other and wit the excitation magnetic field to
lift the brushes off the slip ring during a discharge.
Therefore current compensating straps 116 are provided to
counteract these of cats. Straps 116 increase the brush
down force as the current magnitude increases because the
currents flowing in opposite directions repel each other.
This guarantees maximum gown force at peak current.
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So
Spacer 118 are alto shown on screws 110 between adjacent
compensating straps.
Brush pads 12 are downwardly actuated to contact
with thy lip ring of the rotor and a down force it
applies to maintain brush contact. Actuation of each
brush 112 it by a brush actuator 120. The actuator come
proses an inflatable diaphragm that forces the brush
down. As indicated, one actuator provides simultaneously
a down force to a row of brushes ( F inure 1 0 ) The die-
frog 122 is suitably synthetic rubber neoprene) molded
around a metal brass) core 124, and bonded by a vulcan
Nissan process to the top and sides thereof but not to
the bottom.
The diaphragm t22 is secured by fathead screws 126
to a fiberglass dovetail mount 128. The mount engages
a mating mount t30 carried on the end ox screws 110.
Pressurized gas at about 90 psi is introduced
through a hole in the metal core and into the diaphragm
cavity. This expands the diaphragm against the back
of strap 114 and forces brush pad 112 into contact with
the rotor slip ring. The pressurized gas is introduced
via inlet tube t32.
Referring now to Figures 11 and 12, outer brush
mechanism 32 and adjacent brush mechanism 35 are shown
connected by screws 134 to conductor ring 94 and in
position adjacent rotor outer slip ring surface 29. Each
brush mechanism comprises a brush pad 136 for awaking
contact with the rotor slip ring surface. The brush pads
are preferably sistered copper-graphite blocks having
-22-
ISSUE
dimension of I inch in thickness by 3/4 inch in length
by 7/16 inch in width. Each brush pad is attached by
silver brazing Jo a laminated brush strap 138. Brush
straps 138 are a composite famine ion of two 1/32 inch
thick annealed copper straps and one 1/32 inch thick disk
pension strengthened copper strap.
To prevent discharge currents in brush straps 138
from reacting with each other and with the excitation
magnetic field t current compensating straps 140 are
provided. Straps 140 extend between adjacent screws 134,
and spacers 142 are placed between the straps on each
screw.
Deflection of brush straps 138 to place brush pads
136 in contact with the slip ring surface 29 is by await-
atop devices 144 carried on the ends of screws 134. The
actuator devices comprise a neoprene diaphragm t46 that
inflates when pressurized, forcing the brush pads down.
As shown in Figure 12, each actuator provides a down force
simultaneously to a row ox brush pads 1360 The diaphragm
146 is molded around a metal (brass) core 148. The metal
core is further connected to a manifold 150 having Ann
inlet 152 therein. Pressurized gas (air) at 90 psi it
suitable for actuating brush actuator devices 144. Actual
lion time is on the order of about three millisecond.
The down force applied is about 4-1/2 to 5 lobs.
To electrically connect the two rotor halve in
series, which effectively doubles the HUG open-circuit
voltage, conductor cross-over structure is required
Referring to Figure 13, there is shown a portion of thy
--23--
:iL2~1LS~97
exterior of HUG 12u pa view art oros~-sv~r bars 154 9
along with arrows inditing discharge current. Each
cross over bar arrangement empower two copper Brie 5~8
inch thick by 1-3/8 inch wide It bar 154 are nested
between the aluminum T-bars 56. The bars 154 are attached
to conductors 94 and 96 (Figure 8) by silver brazing.
Terminals 156 are also shown in Figure 13
D. Auxiliary Supply an Drive System
The auxiliary supply and drive system include the
lo brush actuator air supply (Figure 14), the bearing Libra-
cation system figure 15), and the motoring system (Figure
US). These subsystems are shown in Figure 17 in an
arrangement on a skid mount. All subsystem are powered
by a prime mover, e.g., any motor, engine, or turbine
capable of 200 ho a 1800 rum. Suitably, a squirrel-cage
induction motor such as Lineguar3M445T is used. It is a
drip proof motor with service factor of 1.15 and varnished
windings requiring one 460v three-phase lingo Its full-
I load speed it 1,780 rum, and its full-load torque is 600
f tubs .
1. Brush Air Supply
Brushes 30, 32 figure 3) for HUG 12 are actuated by
compressed air. The pneumatic control circuit shown it
Figure 14 will supply the brush actuators with 90 pus
compressed air The air volume of the inner brush mock
anise 30 is approximately 100 in, roughly 1/2 gal. The
--24--
2 So I
volume of the outer brush mechanist 32 it approximately
190 in, roughly one gal, The total ye I idea to
handle up to 150 pi, although normal operation it antic-
pawed in thy vote of 90 psi.
A single stage two-cylinder air comparer pump 160
in Figure 14 it belt-driven from the prime Dover 162~ The
compressor 160 (Spiders) is rated to t50 pi
maximum pressure and delivers 5.70 aim fret air at 100 pal
and 735 rum. At 1 no psi this corresponds to 6.25 gamin
compressed air. This means the accumulators 172, 174 con
be charged to 100 pi in under one minute. The compressor
require up to 2 ho when not unloaded.
Once the accumulators have been charged the compressor
will be unloaded (outlet vented to atmosphere) by a con-
Tony run unloader control 164. The unloader Control
Device 55X709 us rated to 250 psi maximum pressure at 20
efmO Control pressure are adjustable to 135 psi. The
unloader also act a a check valve. Down line from the
unloader is a SO pi air filter 166 to prevent compressor
oil from entering the brush mechanisms. The air filter
Speedair~M2Z328 go razed a 110 aim with 40-micron lit-
traction.- After filtration, two 125 psi pressure Wrigley-
tars 16B, 170 provide control of accumulator pressure.
The regulator SpeedaiTM lZ~38 it rated at 250 pi maximum
pressure at 18 aim. Compressed air is stored in two 3-gal
accumulator 172, 174. Brush air pressure control it
accomplishes with your 300 psi normally closed, two-way
solenoid valves 176, 17~t 180, 182. These valve have a
l-in port, assuring quick pressurization and venting.
-25-
US
Thy valve are ~kkom~tic ~S430-~ semi direct lift solenoid
equipped with manual opening h~ndwheel~.
I Bearing Lubrication System
The rolling eleven Byron 26, 28 (Figure 3) used
in the HUG 12 require oil jet for proper lubrication and
cooling. Sufficient scavenging capacity it required to
prevent accumulation of lubricant in the bearing and sup
covet.
The lubricant preferred is æ parafinic ~ineral-based
lo oil with foam suppressant having a viscosity of 100 SO
at 150-F. This lubricant will carry away a significant
portion of bearing and seal drag heat output. Bearing
losses are emoted at 7.7 ho total; seal losses are east-
mated at 7.2 ho total. These losses are nearly linearly
dependent on speed and represent worst-case figures
A schematic of the bearing lubrication system it shown
in Pure 15. The supply and scavenge pumps are belt-
driven by the prime mover 162. The bearing oft supply
pressure is provided by three 3.2-gpm Gyrate pumps A
noble H3H3 GerotoTMdouble pump 184 supplies pressure to
the thrust duplex pair 183 and the thrust end radial
bearing 185. Redundant rut assure lubricant flow to
both bearings in case of failure of either pump. The oil
pressure for the non-thrust-end radial bearing 1~1 is
provided by one 3.2-gpm pump of a Double A H3H3Dl Gyrate
triple pump 186. This pump is driven by a through shaft
from pump 1 a through a flexible coupling. The other
3.2-gpm pump is used to scavenge the outer non-thrust-end
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US
jump 187~ Thy small 1-gpm pump it used to sieving thy
inner hru~t-end sup 189.
Thy third pump 188 it by driven by thy prime Dover.
The Double ~5~5 Juror double pump scavenge both
middle jump 191 192 with a keep of 5.0 gyp each.
Driven from the third pump through a flexibly coupling,
the fourth pup 190 it a Double A ~12D1 Jury doubly
pump. The 13-gpm pump scavenges the outer throned
sup OWE The 1-gp~ pump scavenges the non-thrust~end
lo inner sup 195.
overall supply flow is 9.6 gyp while overall scavenge
flow it 28.2 gym. This result in a scavenge-to-supply
ratio of 2,9.
Flow from the scavenge pumps it directed to a toggle
reservoir 192 for deforming. From the res~rvoirD oil it
pulled through an oil cooler 194 and filter 196 ho the
supply pumps. The Perfex SUB I oil cooler it rated at 20
hp/100~ITD at 9.6 gym. The cooler has minimal pressure
drop at this low flow. The yoke DEFY 330 oil filter it
rated for 46 pi at JOY pi and provides 5-micron
ration. Should the pressure drop of these components
cause cavitation in the supply pumps, they can be moved to
the scavenge to reservoir line. This location would be
undesirably as tooling capacity will drop due to air
entrapment in the oil cooler. However, the system should
be able to maintain the machine at speed indefinitely
. Motoring System
wow hydraulic motor AYE, 36B figure 3), one on each
end of the shaft, will be used to bring the A-I-R HUG 12
Sue
to speed. VolvoMF11~-19 hydraulic motor are preferred to
obtain a motoring time ox approximately 2 yin Jo reach
6,300 rip the design speed. The hydraulic ~lrcuit, shown
schematically in Figure 16~ must supply each hydraulic
motor with 32 gal of OWE psi hydraulic fluid per min.
In the schematic, new ANSI fluid power symbols are used to-
identify the compo~ent5.
The hydraulic motor AYE, 36~ in Figure 1 it, have
1.16 in3/rev displacement, a maximum continuous operating
lo pressure of 5,000 psi, and a listed maximum operating
speed ox 7,500 rum. They have a constant output torque of
922 in-lb~ each and require 31~6 gamin each at 6,300 rip
before mechanical and volumetric efficiencies are included.
Estate mechanical efficiency is 90 percent and estimated
volumetr~e efficiency is 99 percent.
The hydraulic supply pump 198 is a ~ydromati~ AVOW 16~
DRY variable displacement, flange-mounted, bent axis, axial
piston pump. It has displacement of 164 crave, Max-
mum speed of 2,000 rum, adjustable constant pressure con-
trot, and mechanical stroke limiter. It has a theoretical output of 77.t gym at 1, 780 rum, which becomes 74.8 go
with 3 percent displacement losses. Thus thy hydraulic
circuit ha a 15 percent martin of safety including menu-
lecturers losses, for motoring to 6,300 rum.
A separate cooling and filtering circuit will cool
the hydraulic fluid during motoring and idling. The
cooling pump 200 it 40 gym flange-mounted gear pump.
The HydrecBM2025 fixed displacement pump it rated for
1, 800 rum and 750 psi although system pressure it limited
--28
I 097
it 100 pal by on nine relief valve 202. This Rowley
valve protect ho oil cooler 204 and filter 206 Roy o'er
pressures during syrup The Circle Siam in-line
relies Allah 202 it rated for 40 gym an 1,200 pi Mom
The rocking prowar it adjustable from 85 pi to 120
psi. The Pere~MS~-6~ oil cooler 2~4 way sized to disk-
pate the heat generated from the hydraulic braking valve
at 75 hp/100 vindicated temperature difference). It ha
an estimated pressure drop of 40 psi, a maximum operating
lo pressure of 150 psi, and a maximum flow of 72 gyp The
GreseTMF401 filter 206 provide 10-micron filtration. The
filter it rated for 75 gym at 200 psi and ha a 15 psi
bypass spring.
After motoring to speed the pilot-operated relief
valve 20~, ~10 will be opened to the reservoir by two-way
solenoid valve 212, 214. This will allow freewheeling of
the hydraulic motors and will bypass the main supply pump
output to the reservoir during discharge or idling condo-
lions. The Victor Fluid Powe~FMVR323105 pilvt-operated
relief valves 208, 21~ operate as a 6,000 psi relief valve
until vented my the wow solenoid valve. The valve
rated at 10,000 psi maximum pressure at 50 gym flow The
Circle Sea~MSV460 two-way solenoid valves 212, 214 ore
rated at 6,000 psi maxim pressure. They have a I of
0.64 which assures very low vent pressure. These valve
are normally open so that in the event of loss of power
the relief v21ves will fail open.
The hydraulic braking valves 216, 218 are 2,500 pus
pilot-operated relief valves vented by normally open
-29-
solenoid valve Swahili o the frill relief valve.
The Tickers CT5-10 ~ol~no~d-controlled relief valve
combine both in one unit. These valves were selected for
their low venter pressure drop of 25 psi at 35 gym.
higher pressure drop would adversely aft the hydraulic
motors These valves will be open except during emergency
shutdown situation. When closed, these braking valves
will stop the rotor in less than 3 mix from 6,300 rum.
The hydraulic fluid reservoir 220 has two deforming
lo plates and a capacity of 10 gal. It will be constructed
from welded aluminum pipe and sheet stock. The high-
pressure feed hose 222 will be 1.00-in ID, 1.91-in ODE
sprawler double-armored hydraulic hose. It is rated
at 5,000 psi working pressure and 20,000 psi minimum burst
pressure. the return hove 224 will be 1.25-in-ID, 1.91-in
ODE 4-spiral-wire, double-armored hydraulic hose. It is
rated at 3,000 psi working pressure and 12,000 psi minimum
burst pressure. The cooling circuit hose 226 will be
1.38-in ID, 1.75-in ODE single-wire braid hydraulic hose.
it it rated at 500 psi worming pressure and 2,000 pus
minimum burst pressure. The hydraulic medium chosen for
the system is Rondo Oil HD32. It is a high-grade mineral-
based hydraulic fluid with a viscosity of 152 SUE at
150-F, the projected operating temperature.
4. Auxiliary System Mounting Arrangement
Referring now to figure 17, the mounting arrangement
of the supply subsystems on a skid frame 228 is diagramed
The prime mover 162 is securely located between the rails
-30-
~ZJ~S~97
of fray 2280 To one en of ho prize mover I hydraulic
supply pump 1980 flexible coupling 230 it owe inter-
ensuing the prize mover and pup OWE Drive belt 232
sonnet thy prim over to Berlin oil supply double pup
184 an bearing oil scavenge double pump 18B. Bearing owl
supply pump I driven by pump 18~. Similarly, bearing
oil scavenge pump 190 it driven by pump 188. Reservoir
192 which receives flow from the scavenge pump it shown
in the forward part of the skid frame. Thy owl from the
lo reservoir it pulled through cooler 194 located aft of
prime mover 162.
hydraulic cooling circuit pump 200 is mounted on the
skid adjacent pump 188 and driven by prime mover The
hydraulic owl filter 206 it mounted aft on the slid frame
The hydraulic relief valves 208, 210 art shown in position
in the forward portion of the skid frame, along with
braking valve ~16, 218. Hydraulic fluid reservoir 220 is
mounted just behind valves 216, 218 and adjacent the oil
reservoir. The high pressure hydraulic feed hoses 222 are
carried in the forward end of the skid frame as are the
hydraulic return hose 224. A hydraulic air cooler 2~3
for prime mover 162 it mounted to the aft end of the skid.
Alto mounted on the skid it field golf generator 23~.
This generator, belt-driven from prime mover 162, energizes
the PUG field coils. the air compressor 160 for the brush
actuator Siam is mounted on the opposite side ox the
skid from generator 23~, and is also belt-driven from the
prime mover. HUG 12, though not shown, also mounted on
the skid frame.
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l~LS097
En Control System
The control system 18 (Figure 1) junctions to control
the various system of the HUG power supply, and to disarm
ho machine if a fault occurs The PUG power supply it
controlled by an operator through a control panel 240
shown in Figure 18. Thy control system further include a
logic controller 242, an L~C-40 device, interconnected with
the control panel and HUG 12. Instrumentation, including
a signal analyzer 244, an integrator 246, and an oscillo~
lo graph 248 are also provided and receive control signal
inputs from the logic controller. The instrumentation
provides information useful to monitor machine performance.
For example, the following my be monitored: discharge
current, rum, voltage, rotor runt, and bearing signature
analysis.
The control panel 240 with which the operator inter-
faces has four push buttons for controlling HUG 12 include
in power on Sutton 250, shut down button 252, ready to
motor button 254, and ready to discharge button 256.
digital tachometer 258 is provided, and there are a series
of fault-indicating lights 260. The fault lights indicate
the following:
Low Brush Pressure -- two pressure switches with a
low point set at 90 Sue
Lowe Bearing Oil Pressure -- one pressure switch
set at a low point of 50 psi and a high point
of 125 psi.
jot Bearing Oil -- a temperature switch set at 20GF~
-32-
Low Motoring Oil pressure -- a pro sure switch set
at 2,500 pi.
owe Motoring Oil -- a temperature switch sot at 250~.
Rotor Vibration -- a vibration alarm switch set a
1-g lateral acceleration.
Long rotor Time -- LDC I controller provide a timer.
Low Alternator Voltage -- a millimeter with an
adjustable sex point connected in series
with a shunt across terminals of alternator
jot Field Coil - a temperature switch set at 220'F.
Brush Dragging -- a millimeter with an 8-10-V set
point connected across terminal of A-I-R PUG
No PUG Voltage -- same as Brush Dragging
No HO Current -- a Rogues coil set to trip a
latching relay.
Overfeed Pi set point on digital tachometer.
The operating control sequence carried out by logic
controller 242 is set forth in the flow chart of Figure
19. Default mode indicated on the controller flow chart
are:
LEVEL 1 - Stand by
- Light up fault indicating on control
panel
- Hold until clear
LEVEL 2 hydraulic motor braze. When stopped,
go to Level 1
LEVEL 3 - Reduced field discharge
LEVEL 4 - Full field discharge
5V9~
The foregoing description of the invention has been
directed to a particular preferred embodiment for purposes
of explanation and illustration It will be apparent
however, to those skilled in this art that many modifica-
lions and changes in both the illustrated apparatus and
the methods taught may be made without departing from the
invention. It is applicants' intention in the following
claims to cover all equivalent modifications and variations
as fall within the scope of the invention.
I
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