Note: Descriptions are shown in the official language in which they were submitted.
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COMPACT HIGH POWER ALTERNATOR
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims priority to U.S. provisional application no.
60/775,904, filed
February 22, 2006, in the name of Charles Y. Lafontaine et al. and claims
priority to and is a
continuation of U.S. patent application no. 11/347,777, filed February 2,
2006, which claims
priority to U.S. provisional application no. 60/649,720, all of which are
incorporated herein by
reference in their entirety for all purposes.
DESCRIPTION OF THE INVENTION
The present invention relates to voltage and current control systems for
machines for
converting between mechanical and electrical energy, such as brushless AC
generators, and in
particular to a control system for a compact permanent magnet high power
alternator, such as a
compact permanent magnet high power alternator suitable for automotive use.
BACKGROUND OF THE INVENTION
An alternator typically comprises a rotor mounted on a rotating shaft and
disposed
concentrically relative to a stationary stator. The rotor is typically
disposed within the stator.
However, the stator may be alternatively positioned concentrically within the
rotor. An external
energy source, such as a motor or turbine, commonly drives the rotating
element, directly or
through an intermediate system such as a pulley belt. Both the stator and the
rotor have a series
of poles. Either the rotor or the stator generates a magnetic field, which
interacts with windings
on the poles of the other structure. As the magnetic field intercepts the
windings, an electric field
is generated, which is provided to a suitable load. The induced electric field
(which is commonly
known as a voltage source) is typically applied to a rectifier, sometimes
regulated, and provided
as a DC output power source. The induced current is typically applied to a
rectifier, sometimes
regulated, and provided as a DC output power source. In some instances, a
regulated DC output
signal is applied to a DC to AC inverter to provide an AC output.
Conventionally, alternators employed in motor vehicle applications typically
comprise: a
housing, mounted on the exterior of an engine; a stator having 3-phase
windings housed in the
housing, a belt-driven claw-pole type (e.g. Lundell) rotor rotatably supported
in the housing
within the stator. However, to increase power output the size of the
conventional alternator must
be significantly increased. Accordingly, space constraints in vehicles tend to
make such
alternators difficult to use in high output, e.g. 5 KW, applications, such as
for powering air
conditioning, refrigeration, or communications apparatus.
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In addition, the claw-pole type rotors, carrying windings, are relatively
heavy (often
comprising as much as three quarters of the total weight of the alternator)
and create substantial
inertia. Such inertia, in effect, presents a load on the engine each time the
engine is accelerated.
This tends to decrease the efficiency of the engine, causing additional fuel
consumption. In
addition, such inertia can be problematical in applications such as electrical
or hybrid vehicles.
Hybrid vehicles utilize a gasoline engine to propel the vehicle at speeds
above a predetermined
threshold, e.g. 30 Kph (typically corresponding to a range of RPM where the
gasoline engine is
most efficient). Similarly, in a so-called "mild hybrid," a starter-generator
is employed to provide
an initial burst of propulsioii when the driver depresses the accelerator
pedal, facilitating shutting
off the vehicle engine when the vehicle is stopped in traffic to save fuel and
cut down on
emissions. Such mild hybrid systems typically contemplate use of a high-
voltage (e.g. 42 volts)
electrical system. The alternator in such systems must be capable of
recharging the battery to
sufficient levels to drive the starter-generator to provide the initial burst
of propulsion between
successive stops, particularly in stop and go traffic. Thus, a relatively high
power, low inertia
alternator is needed.
In general, there is in need for additional electrical power for powering
control and drive
systems, air conditioning and appliances in vehicles. This is particularly
true of vehicles for
recreational, industrial transport applications such as refrigeration,
construction applications, and
military applications.
For example, there is a trend in the motor vehicle industry to employ
intelligent electrical,
rather than mechanical or hydraulic control and drive systems to decrease the
power load on the
vehicle engine and increased fuel economy. Such systems may be employed, for
example, in
connection with steering servos (which typically are active only a steering
correction is
required), shock absorbers (using feedback to adjust the stiffness of the
shock absorbers to road
and speed conditions), and air conditioning (operating the compressor at the
minimum speed
required to maintain constant temperature). The use of such electrical control
and drive systems
tends to increase the demand on the electrical power system of the vehicle.
Similarly, it is desirable that mobile refrigeration systems be electrically
driven. For
example, driving the refrigeration system at variable speeds (independently of
the vehicle engine
rpm) can increase efficiency. In addition, with electrically driven systems
the hoses connecting
the various components, e.g. the compressor (on the engine), condenser
(disposed to be exposed
to air), and evaporation unit (located in the cold compartment), can be
replaced by an electrically
driven hermetically sealed system analogous to a home refrigerator or air-
conditioner.
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Accordingly, it is desirable that a vehicle electrical power system in such
application be capable
of providing the requisite power levels for an electrically driven unit.
There is also a particular need for a "remove and replace" high power
alternator to retrofit
existing vehicles. Typically only a limited amount of space is provided within
the engine
compartment of the vehicle to accommodate the alternator. Unless a replacement
alternator fits
within that available space, installation is, if possible, significantly
complicated, typically
requiring removal of major components such as radiators, bumpers, etc. and
installation of extra
brackets, belts and hardware. Accordingly, it is desirable that a replacement
alternator fit within
the original space provided, and interfaces with the original hardware.
In general, permanent magnet alternators are well known. Such alternators use
permanent
magnets to generate the requisite magnetic field. Permanent magnet generators
tend to be much
lighter and smaller than traditional wound field generators. Examples of
permanent magnet
alternators are described in US Patents 5,625,276 issued to Scott et al on
April 29, 1997;
5,705,917 issued to Scott et al on January 6, 1998; 5,886,504 issued to Scott
et al on March 23,
1999; 5,929,611 issued to Scott et al on July 27 1999; 6,034,511 issued to
Scott et al on March 7,
2000; and 6,441,522 issued to Scott on August 27, 2002.
Particularly light and compact pennanent magnet alternators can be implemented
by
employing an "external" permanent magnet rotor and an "internal" stator. The
rotor comprises a
hollow cylindrical casing with high-energy permanent magnets disposed on the
interior surface
of the cylinder. The stator is disposed concentrically within the rotor
casing, and suitably
comprises a soft magnetic core, and conductive windings. The core is generally
cylindrical width
an axially crenellated outer peripheral surface with a predetermined number of
equally spaced
teeth and slots. The conductive windings (formed of a suitably insulated
electrical conductor,
such as varnished copper motor wire), are wound through a respective slot,
outwardly along the
side face of the core around a predetermined number of teeth, then back
through another slot.
The portion of the windings extending outside of the crenellation slots along
the side faces of the
core are referred to herein as end turns. Rotation of the rotor about the
stator causes magnetic
flux from the rotor magnets to interact with and induce current in the stator
windings. An
example of such an alternator is described in, for example, the aforementioned
US Patents
5,705,917 issued to Scott et al on January 6, 1998 and 5,92,611 issued to
Scott et al on July 27
1999.
The power supplied by a permanent magnet generator varies significantly
according to
the speed of the rotor. In many applications, changes in the rotor speed are
common due to, for
example, engine speed variations in an automobile, or changes in load
characteristics.
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Accordingly, an electronic control system is typically employed. An example of
a permanent
magnet alternator and control system therefore is described in the
aforementioned US Patent
5,625,276 issued to Scott et al on Apri129, 1997. Examples of other control
systems are
described in US patent 6,018,200 issued to Anderson, et al. on January 25,
2000. Other
examples of control systems are described in commonly owned co-pending U.S.
Patent
Applications No. 10/860,393 by Quazi et al, entitled "Controller for Permanent
Magnet
Alternator" and filed on June 6, 2004 and No. 11/347,777 by Faber man et al
(including the
present inventors), entitled "Controller for AC Generator" and filed February
2, 2006. The
aforementioned commonly owned applications are hereby incorporated by
reference as if set
forth verbatim herein.
The need to accommodate a wide range of rotor speeds is particularly acute in
motor
vehicle applications. For example, large diesel truck engines typically
operate from 600 RPM at
idle, to 2600 RPM at highway speeds, with occasional bursts to 3000 RPM, when
the engine is
used to retard the speed of the truck. Thus the alternator system is subject
to a 5:1 variation in
RPM. Light duty diesels operate over a somewhat wider range, e.g. from 600 to
4,000 RPM.
Alternators used with gasoline vehicle engines typically must accommodate a
still wider range of
RPM, e.g. from 600 to 6500 RPM. In addition, the alternator must accommodate
variations in
load, i.e., no load to full load. Thus the output voltage of a permanent
magnet alternator used
with gasoline vehicle engines can be subject to a 12:1 variation. Accordingly,
if a conventional
permanent magnet alternator is required to provide operating voltage (e.g. 12
volts) while at idle
with a given load, it will provide multiples of the operating voltage, e.g.
ten (10) times that '
voltage, at full engine RPM with that load, e.g. 120 volts. Where the voltage
at idle is 120 V, e.g.
for electric drive air conditioning, or communications apparatus, the voltage
at full engine RPM
would be, e.g. 1200 volts. Such voltage levels are difficult and, indeed,
dangerous to handle. In
addition, such extreme variations in the voltage and current may require more
expensive
components; components rated for the high voltages and currents produced at
high engine RPM
(e.g. highway speeds) are considerably more expensive, than components rated
for more
moderate voltages.
The stator of a conventional high current motor vehicle alternator is
constructed with
conductors of large cross sectional area effectively connected in series. More
particularly, coil
groups, one associated with each phase (the A, B and C Phase) are
conventionally employed.
The respective Phase coil groups, (A, B and C) are connected together
(terminated) as a`WYE'
or `Delta' at one end. The opposite ends of the coil groups are arranged by
phase so that each
phase is isolated and then terminated to both collect and exit the alternator
to a voltage control.
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On the exiting termination end, the coil ends of like phases are soldered in
groups to insulated
motor lead wire. These motor lead wires may then in turn be soldered in groups
to even larger
gauge motor lead wire culminating in three separate conductors for each phase,
A, B and C. The
lead wires are then secured to the stator by lashing the conductors to the end
turns of the stator.
Lashing conductors to end turns reduces the amount of exposed copper to
cooling fluid passing
through the alternator, in effect acting as an insulating blanket and
hindering cooling of the end
turns and lead wires. Several additional problems can exist with this winding
method. For
example: because of the low number of turns (in some instances only a single
turn) per pole
phase coil, it is difficult or impossible to make a small change in design
output voltage by
changing the number of turns of the phase pole coil; the large cross sectional
area of the
conductors make the stator difficult to wind; and a short circuit between
coils will typically burn
out the entire stator and may stall the alternator, resulting in possible
damage to the drive system
or overloading the vehicle engine.
In general, permanent magnet alternators incorporating a predetermined number
of
' independent groups of windings, wound through slots about predetermined
numbers of teeth
where the power provided by each group is relatively unaffected by the status
of the other groups
are known. For example, such an alternator is described, together with a
controller therefor, in
US patent 5,900,722 issued to Scott et al. on May 4, 1999. In the alternator
described in patent
5,900,722, the number of groups of windings was equal to an integer fraction
of the number of
poles, and the controller circuit selectively completed current paths to the
individual groups of
windings to achieve a desired output.
However, there remains a need for a compact high power alternator wherein a
desired
output voltage can be achieved by changing the number of turns of the phase
pole coil, that is
relatively easy to wind, and minimizes the consequence of short circuits,
while at the same time
facilitating cooling.
SUMMARY OF THE INVENTION
In accordance with various aspects of the present invention, the stator
winding is wound
with a predetermined number of pole phase coils, preferably equal to the
number of magnetic
poles. Each pole phase coil is wound with enough turns to generate the
required output voltage
of the alternator and a fraction of the output current equal to I divided by
the number of
magnetic poles. These individual pole phase coils are then connected in
parallel.
In accordance with another aspect of the present invention, a respective
conducting phase
ring corresponding to each output phase is installed within the alternator
with each coil
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corresponding to the associated phase electrically connected to the conducting
phase rings to
facilitate cooling and grouping and transmission of output phases to the
control
In accordance with another aspect of the present invention the conducting
phase rings are
held in place by a non-conducting support structure.
In accordance with another aspect of the present invention the conducting
phase rings are
disposed to provide an efficient cooling by exposure to the cooling fluids
e.g. air, passing over
the conducting phase rings and end turns.
BRIEF DESCRIPTION OF THE DRAWING
The present invention will hereinafter be described in conjunction with the
figures of the
appended drawing, wherein like designations denote like elements (unless
otherwise specified).
Figure 1 is a block schematic of a system for converting between mechanical
and
electrical energy.
Figure 2A is a side view of the exterior of an alternator in accordance with
various
aspects of the present invention.
Figure 2B is a sectional view along A-A of the alternator of Figure 2A.
Figure 2C is a simplified sectional view along B-B of the alternator of Figure
2A
showing the relative placement of the conducting phase rings within the
alternator.
Figure 2D is simplified sectional view of a terminal in the alternator of
Figure 2A.
Figure 2E is a diagram showing an alternative.embodiment of a conducting phase
ring.
Figure 2F is a simplified perspective view of the stator core, and the
conducting phase
rings of the alternator of Figure 2A, illustrating the connections between the
conducting phase
rings and respective groups of windings (winding end turns omitted).
Fig. 2G is a block schematic wiring diagram of an alternator utilizing phase
rings in
accordance with the present invention adapted to produce a DC voltage output.
(Figures 2A - 2G are collectively referred to as Figure 2).
Figure 3A is a side view of the exterior of an alternative embodiment
alternator in
accordance with various aspects of the present invention.
Figure 3B is a sectional view along C-C of the alternator of Figure 3A.
Figure 3C is a simplified perspective view of the stator core, and the
segmented
conducting phase rings of the alternator of Figure 3A, illustrating the
connections between the
segmented conducting phase rings and respective groups of windings (winding
end tums
omitted)_
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Fig. 3D is a block schematic wiring diagram of an alternator utilizing
segmented
conducting phase rings in accordance with the present invention adapted to
produce a D.C.
voltage output. (Figures 3A - 3D are collectively referred to as Figure 3).
Figure 4A is a top view of the exterior of an alternative embodiment
alternator in
accordance with various aspects of the present invention.
Figure 4B is a sectional view along D-D of the alternator of Figure 4A.
Figure 4C is a simplified perspective view of the stator core, and the multi-
segmented
conducting phase rings of the alternator of Figure 3A, illustrating the
connections between multi-
segmented conducting phase rings and respective groups of windings (winding
end turns
omitted).
Fig. 4D is a block schematic wiring diagram of an alternator utilizing multi-
segmented
conducting phase rings in accordance with the present invention adapted to
produce a D.C.
voltage output. (Figures 4A - 4D are collectively referred to as Figure 4).
Figure 5 is a schematic wiring diagram illustrating three individual windings
of a three
phase pole group of the stator used in each of the embodiments of this
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to Fig. 1, a power conversion apparatus, such as an alternator
102, in
accordance with various aspects of the present invention, suitably cooperates
with a rectifying
control system 100 and a source of mechanical energy (e.g. drive) 104, e.g. an
engine or turbine,
a load 106, such as a motor and, if desired, in energy storage device 108,
such as a battery,
capacitor, or flywheel.
Rectifying control system may be any system suitable for rectifying the AC
signal from
alternator 102, i.e. converting it into a DC signal, and regulating the
voltage of that signal at a
predetermined level, e.g. 28V. In the preferred embodiment, system 100
comprises a controller
110 and a switcliing bridge 112 such as described in commonly owned US patent
application No.
11/347,777 by Faber man et al (including the present inventors), entitled
"Controller for AC
Generator" and filed February 2, 2006. If desired, an inverter (sometimes
categorized as
comprising part of load 106) can also be provided to generate an AC signal at
a constant
predetermined frequency and amplitude (e.g. 60 Hz, 120V).
In general, alternator 102 generates AC power in response to mechanical input
from
energy source 104. Alternator 102 preferably provides multi-phase (e.g. three-
phase, six-phase,
etc.) AC output signals, e.g. phase A (11S), phase B (120), and phase C (122).
Those output
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signals are typically unregulated and may vary significantly in accordance
with drive RPM
(source 104).
The AC phase signals from alternator 102 are applied to system 100, preferably
through
input fuses 128. System 100 rectifies the AC signal from alternator 102, i.e.
converts it into a
DC signal and regulates the voltage of that signal at a predetermined level,
e.g. 28V. In the
preferred embodiment, switching bridge 112 selectively, in response to control
signals from
controller 110, provides conduction paths between the various phases of the AC
signal from
alternator 102 and a load 106. Exemplary switching bridges 112 are shown in
commonly owned
co-pending U.S. Patent Application No. 11/347,777 by Faber man et al
(including the present
inventors), filed February 2, 2006.. Controller 110 selectively generates
control signals to
switching bridge 112 to produce a regulated output signal at a predetermined
voltage. Controller
110 suitably samples the regulated output either locally at input 114, or
remotely at input 140
and adjusts the signals to bridge 112 to maintain the proper output.
Additionally, the output
current is sensed at input 116 to further modify the control signals to bridge
112.
The regulated DC signal Voltage Regulated Output (VRO) is then applied,
suitably
through an output fuse 136, to load 106 and energy storage device 108. Load
106 may be any
device that uses power, such as, e.g. lights, motors, heaters, electrical
equipment, power
converters, e.g. inverters or DC-to-DC converters. Energy storage device 108
filters or smoothes
the output of control system 110 (although, in various embodiments, controller
110 may itself
incorporate or otherwise provide adequate filtering).
If desired, other outputs, 150, and 160, may be provided by system 100. In
addition, a
suitable crowbar circuit 142 may be provided for system protection.
Alternator 102 is preferably an alternator generally of the type described in
commonly
owned co-pending U.S. Patent Application No. 10/889,980 by Charles Y.
Lafontaine and Harold
C. Scott, entitled "Compact High PowerAlternator" and filed on July 12, 2004,
but includes for
each pole, a respective group of windings (including at least one winding
corresponding to each
phase) with all of the windings corresponding to a given phase connected in
parallel. The
aforementioned Lafontaine et al application is hereby incorporated by
reference as if set forth
verbatim herein.
In accordance with one aspect of the present invention, a parallel connection
between
coils corresponding to the same phase is effected through a corresponding
conducting phase ring
138, and includes fusible links 124, disposed between the conducting phase
rings 138, and the
output terminals 262 of the alternator. The output of each individual coil is
collected by its
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respective conducting phase ring 138, which is in turn attached to its
respective output
terminal 126.
As the total number of poles in alternator 102 increases, so too do the number
of
individual coils. The conventional method of gathering coils involves
soldering the motor wire
to conventionally insulated motor lead wire. As the rated output of the
alternator increases, a
corresponding increase in the load carrying capacity of the motor lead wire is
also required.
Increasing load demand on the lead motor wire is typically met by increasing
the cumulative
gauge of the wire, either by increasing the gauge of a single wire or by using
multiple wires in
parallel. The net effect is increasingly large cross sectional areas of motor
lead wire. When
considering the total number of coils and their respective end turns along
with the lead wire and
its associated insulation, the resulting stator assembly with conductor and
motor lead wire tied
together insulate the end turns, detrimental to cooling. The resulting
assembly also restricts the
only available coolant flow (e.g., airflow) over the end turns further
reducing cooling.
Thus, there is a need for a compact high power alternator wherein a desired
output
voltage can be achieved by changing the number of turns of the phase pole
coil, that is relatively
easy to wind, and minimizes the consequence of short circuits, while at the
same time facilitating
cooling. In accordance with various aspects of the present invention this is
achieved by
employing a predetermined number of pole phase coils, preferably equal to the
number of
magnetic poles, with pole phase coil wound with enough turns (of a relatively
small diameter
wire) to generate the required output voltage of the alternator and a fraction
of the output current
equal to 1 divided by the number of magnetic poles and connecting the
individual pole phase
coils in parallel, preferably employing conducting phase rings (collectors)
138. Use of
conducting phase rings 138 not only greatly simplifies assembly of alternator
102, but also
facilitates cooling of the windings.
More particularly, alternator 102 preferably comprises: a shaft 202,
preferably including
a tapered projecting portion 204 and a threaded portion 206; a rotor 208; a
stator 210; a front
endplate 212; a front bearing 214; a jam nut 216; a rear endplate 218; a rear
shaft retaining ring
220; a rear bearing 222; a rear jam nut 224; an outer casing 226 and
respective tie rods (not
sliown). Rotor 208 is mounted on shaft 202 for rotation with the shaft. Stator
210 is closely
received within rotor 208, separated from rotor 208 by a small air gap 228.
Front endplate 212,
front bearing 214, rear bearing 222, rear endplate 218, outer casing 226 and
tie rods cooperate as
a support assembly to maintain alignment of shaft 202, rotor 208, and stator
210. Shaft 202 is
maintained by bearings 214 and 222, which are mounted on front endplate 212
and rear endplate
218, respectively, and rotatably maintain and align shaft 202 concentric and
perpendicular with
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the endplates. Rotor 208 is mounted for rotation on shaft 202, positively
positioned by
cooperation with tapered shaft portion 204. Rear endplate 218 mounts and
locates stator 210 so
that it is disposed within rotor 208 properly aligned with shaft 202 and rotor
112. Outer casing
226 has end faces perpendicular to its axis (is preferably cylindrical) and is
disposed between
front endplate 212 and rear endplate 218. Tie rods compress endplates 218 and
212 against outer
casing 226, keeping the components squared and in alignment.
In a typical automotive alternator application, a pulley 230 is mounted on the
end of shaft
202. Power from an engine (e.g., 104, not shown in Fig. 2) is transmitted
through an appropriate
belt drive (not shown) to pulley 230, and hence shaft 202. Shaft 202 in turn
causes rotor 208 to
rotate about stator 210. Rotor 208 generates a magnetic field, which interacts
with the windings
on stator 210. As the magnetic field intercepts the windings, an electrical
current is generated,
which is provided to a suitable load.
Rotor 208 preferably comprises an endcap 232, a cylindrical casing 234 and a
predetermined number (e.g. 16 pairs) of alternatively poled pertnanent magnets
236 disposed in
the interior side wall of casing 234. Rotor endcap 232 is suitably
substantially open, including a
peripheral portion 238, respective cross-arms (not shown) and a central hub
240 to provide for
connection to shaft 202. Respective coolant (e.g., air) passageways 242 are
provided through
endcap 234, bounded by peripheral portion 238 adjacent cross arms (not shown),
and central hub
240.
Stator 210 suitably comprises a core 244 and conductive windings (shown
schematically)
280. Core 244 suitably comprises laminated stack of thin sheets of soft
magnetic material, e.g.
non-oriented, low loss (lead free) steel, that are cut or punched to the
desired shape, aligned and
joined. Core 244 is generally cylindrical, with an axially crenellated outer
peripheral surface, i.e.,
includes a predeterinined number of teeth and slots. Core 244 is preferably
substantially open,
with a central aperture, and suitably includes crossarms with axial through-
bores to facilitate
mounting to rear endplate 218.
Front endplate 212 is suitably generally cylindrical, including: a centrally
disposed hub
246, including a coaxial aperture that locates front bearing 214; a peripheral
portion and
including respective tapped holes (not shown) disposed at predetermined radial
distances from
the central aperture, distributed at equal angular distances, to receive tie
rods (not shown); and
respective (e.g., 4) crossarms (not shown) connecting peripheral portion 248
to hub 246, and
defining respective coolant (e.g., air) passages 250
Rear endplate 218 carries and locates rear bearing 222, and mounts and locates
stator
core 244. Rear endplate 218 suitably includes a stepped central hub 252 having
a forward
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reduced diameter portion 254 and central aperture 256 there through, and is
general-ly cylindrical
preferably having the same outer diameter as front endplate 212, connected to
hub 252 by
respective crossarms (not shown). Rear endplate 218 also suitably includes
respective coolant
(e.g., air) passageways 258, bounded by adjacent crossarms (not shown), outer
portion 260, and
hub 252.
The output from stator windings 280 is collected by phase rings 138 and
provided at
respective output terminals 262. More particularly, output terminals 262 (one
for each phase) are
suitably provided in rear endplate 218. Terminals 262 are suitably
electrically connected through
fusible links 124, to associated conducting phase rings (collectors) 138.
Output terminals 262
and fusible links 124 are positioned radially about conducting phase rings
138. The respective
phase rings 138 collect, e.g. are electrically connected to, through, e.g.,
conductors 276, each of
the individual coils with the associated phase. Respective individual
conducting cables (e.g. 294
in Fig. 2G) are attached to terminals 262 to transmit phase output to the
control 100.
Conducting phase rings 138 are made of a suitable conductive material e.g.
plated copper.
Phase rings 138 are suitably uninsulated or minimally insulated (e.g. with
varnish) to facilitate
cooling and sufficiently stiff or rigid to facilitate isolation from each
other once mounted and
subjected to environmental forces/acceleration. The conducting phase rings may
be formed of
rod stock or punched from a sheet of appropriate material. In the embodiment
of Fig. 2,
conducting phase rings 138 are each continuous e.g. a single piece rod stock
with it ends
connected by e.g., soldering or brazing, to form a continuous conducting ring.
Use of solid continuous phase rings 138 are particularly advantageous in that
dual current
paths to fusible link 124 permits use of lower gauge (and thus lighter and
less expensive)
material for phase rings 138. When a solid, a continuous phase ring 138 is
utilized, the current is
effectively split at a point 180 degrees opposite the point at which fusible
link 124 is attached.
All current produced by conductors 276 on one half of the phase ring exit to
fusible link 124
effectively remains on that half, current produced on the opposite half
follows that path to
fusible link 124. The result is a phase ring approximately half the gauge of a
conductor with only
a single path to fusible link 124.
The respective rings 138 are disposed in the coolant flow path, electrically
isolated and
spaced apart from each other and from rear endplate 218. Conducting phase
rings 138 are
suitably mechanically fastened to endplate 218 using a non-conducting
conducting phase ring
mounting structure 264 preferably made of a high impact resistant and
chemically stable material
e.g. polyamide-imide, so that each conducting phase ring, one for each phase
output, are
physically spaced apart and isolated electrically from each other and rear
endplate 218.
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Conducting phase rings 138 are positioned in coolant (e.g., air) passage 258
to maximize
exposure to coolant (e.g., air) flow produced by alternator 102. The ekposure
to airflow is further
maximized by progressively varying the diameter of adjacent phase rings. For
example, the
phase ring 138 associated with phase A (terminal 118) is disposed closest to
the interior of
endplate 218, but of a relatively large diameter (suitably approaching the
outer diameter of
coolant (e.g., air) passage 258 in endplate 218). The phase ring 138
associated with phase B
(terminal 120) is suitably coaxially disposed but offset rearwardly, and with
a smaller diameter
(the outer diameter of the phase B ring suitably less than the inner diameter
of the phaseA ring
by a predetermined amount). The phase ring 138 associated with phase C
(terminal 122) is
likewise suitably coaxially disposed but offset rearwardly from the phase B
ring 138, and with a
smaller diameter (the outer diameter of the phase C ring suitably less than
the inner diameter of
the phase B ring by a predetermined amount). This alignment, made possible by
phase ring
mounting structure 264, presents each ring to cooling air flow at close to
ambient inlet
temperature as possible. Preferably, the rings farthest from the ambient inlet
have the larger
diameters.
Referring to Fig. 2D, output terminal assembly 126 suitably comprises a
threaded
conducting stud 266, preferably a highly conductive corrosion resistant
material (e.g. plated
copper) along with an electrically non-conductive bushing 268, preferably a
high impact resistant
and chemically stable material (e.g. polyamide-imide), to electrically isolate
the output terminal
from alternator rear endplate 218. The threaded conducting stud 266 in the
preferred embodiment
has an incorporated shoulder 270, to act as a seat from inside alternator rear
endplate 218 to
which nut 272 can be tightened, capturing the assembly in rear endplate 218.
Fusible link 124 is made of a suitable material e.g. a calculated diameter and
length of
wire (preferably plated copper) that will melt when subjected to loads
calculated to be
destructive to alternator 102, control 100 or electrical systems being powered
by said equipment.
In the preferred embodiment fusible link 124 is soldered or brazed to both the
threaded
conducting stud 266 and conducting phase ring 138. An alternate method to
secure the fusible
link is to attach a suitable lug to the end of fusible link 124 which is then
fastened to stud 266
mechanically by means of a threaded nut.
Referring particularly to Figs. 2B and 2C, conducting phase rings 138 are
fastened to
structure 264. Conducting phase rings 138 are disposed in the coolant path,
exposed to coolant
flow (e.g., airflow) 274, cooling conducting phase rings 138 as well as
conductors 276
(connecting the coil windings to phase rings 138). Ring mounting structure 264
is positioned to
produce a gap between phase rings 138 and the stator end turns (not shown).
This gap exposes
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the rear stator end turns to cooling fluid that would not be available in a
conventionally wound
stator.
Coolant (e.g. cooling air) continues through the alternator and impinges upon
winding
end turns 280 of stator 210 cooling the end turns. Airflow then divides and
proceeds through
stator core 244 and into cavity 278 at which point it cools the far end turns
of stator 210. The
other divided airflow passes between rotor casing 234 and outer casing 226
cooling rotor casing
234 and magnets 236. The divided airflow rejoins in air passageway 250 and
leaves the
alternator to centrifiigal fan 282.
Conductors 276, comprising an A phase 118, B phase 120 and C phase 122
component of
a single three-phase pole group, as will be described later, exit stator 210
and are soldered or
brazed to their respective associated conducting phase rings 138. Conductors
276 in the preferred
embodiment are exposed to airflow 274. In certain cases it may be desirable to
sheath conductors
276 with a thin walled electrically isolating material e.g. Nomex to protect
against grounding.
Referring now to Fig. 2 E. an alternate method of producing conducting phase
ring 138 is
accomplished by forming it of rectangular stock such that suitable surfaces
are presented for
drilling and tapping holes 284. The end of fusible link 124 can, in this
embodiment, be attached
with a suitable lug 286 for fastening by, e.g. a tlireaded fastener 288 to
conducting phase ring
138. Equally, conductor 276 can also be equipped with a similar lug and
fastened to conducting
phase ring 138 using fastener 290. Conducting phase ring 138 is in turn
secured in a similar
manner to rear endplate 218 using an appropriate structure similar to 264.
Alternatively slots 292
may be cut into each phase ring at regular intervals in which individual
conductors exiting the
stator can be soldered. This method of assembly has a major advantage over
previously
described methods of fastening conductors 276 to phase rings 138 in that
automation of assembly
can be implemented by modifing existing ultrasonic soldering equipment used to
terminated
conductors in electric motor manufacturing.
Referring now to Fig. 2F, stator 210 is shown, for clarity, without coils, and
with
individual conductors 276 in greatly reduced detail. In this particular
embodiment, the
respective phase rings 138 associated with each of the three A, B and C phases
are continuous
either by soldering, brazing or machined from a single piece of un-insulated,
corrosion resistant
conductive material e.g. plated copper. Terminals 126, represented
graphically, correspond to A
phase 118, B phase 120 and C phase 122. The output of each pole group is
collected within the
alternator through the phase rings 138 and exits the alternator via three
conductors that that
representing all three phases to control 100.
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Referring now to Fig 2G. individual conductors 276 from the respective A
phase, B phase
and C phase windings 118, 120, and 122 are terminated on respective collection
phase rings 138
which then in turn are carried to control 100 via conductors 294. The output
from control 100
results in a voltage regulated output or VRO, of an application specific
voltage e.g. 28 VDC.
Conductors 294, coupled between output terminals 264 and control 100 are
suitably of
sufficient gauge to adequately carry the current. As the gauge of a wire or
cable increases, it
becomes increasingly difficult to route cables due to the larger bend radius
found in large gauge
wire. As a result it is difficult to use very large gauge wire or cable in
many applications. As
will be discussed, in applications in which very large conductors may not be
appropriate it is
possible then to segment phase rings into multiple sections in which each
phase ring section is
assigned an appropriately sized conductor to carry the reduced current
produced by that specific
section.
For example, current requirements may be reduced by employing phase rings
split into a
plurality of groups. Referring now to figure 3A - 3D, an alternator 302
employing two sets of
phase rings 306 with corresponding terminals 126 and fusible links 124,
cooperate with
associated controls 308 and 310. Phase rings 310 are separated electrically at
point 312 and 314.
Each group carries respective A phase, B phase and C phase components each
leading to their
respective controls 308 and 310. Rear end plate 304 is similar in all respects
to end plate 218 in
all but one feature in that it is machined to accept a second set of terminals
126.
Referring now to figure 3D, phase ring portions 306 each receive their
respective
conductors 276 from stator 210. Phase ring portions 306 are electrically
connected via terminals
126, conductors 316 to controls 308 and 310. When terminal 126 is connected in
the middle of
phase ring portion 306, the current is effectively split at the point at which
fusible link 124 is
attached. All current produced by conductors 276 on one half of the phase ring
portion exit to
fusible link 124 effectively remains on that half, current produced on the
opposite half follows
that path to fusible link 124. The result is a phase ring portion
approximately half the gauge of a
conductor with only a single path to fusible link. The gauge of conductors 316
can be sized
according to application specific requirements. Modern engine compartments
have very little
space to offer when considering, for example, the size of conductor required
to properly conduct
600 amps of power at 28 VDC. By halving the current carried by conductors 316
in very high
output applications, routing of cables becomes much more manageable. There is
a corresponding
benefit in the controls as well. As amperage increases the size and cost of
components increases,
but not in a linear fashion. Tlierefore by halving the current carried by the
conductors and the
control components as well, a savings in space and cost is achieved.
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Current requirements can be further reduced by splitting the phase rings into
a plurality of
portions. For example, referring to Figs. 4A -4D, the phase rings can be
broken into four
sections 406, electrically separated at points 416, 418, 420, and 422. An
associated set of
terminals 118, 120, 122 is provided for each phase ring segment, connected to
respective
controls 408, 410, 412, and 414. As with phase ring portions 306, terminal 126
is connected in
the middle of phase ring portion 406, the current is effectively split at the
point at which fusible
link 124 is attached. All current produced by conductors 276 on one half of
the phase ring
portion exit to fusible link 124 effectively remains on that half, current
produced on the opposite
half follows that path to fiisible link 124. The result is a phase ring
portion approximately half
the gauge of a conductor with only a single path to fusible link The outputs
of controls 408, 410,
412, and 414 are coiinected in parallel to provide outputs VRO+ and VRO-.
As previously noted, stator core 210 is generally cylindrical with an axially
crenellated
outer peripheral surface having a predetermined number of equally spaced teeth
and slots. The
conductive windings (formed of a suitably insulated electrical conductor, such
as varnished
copper motor wire), are wound through a respective slot, outwardly along the
side face of the
core around a predetermined number of teeth, then back through another slot.
Referring now to
Fig. 5, stator core 210 includes a predetermined number of slots, e.g. 36
(shown schematically in
figure 5, indicated by numerals 1- 36). The conductive windings include a
predetermined
number of individual phase coils (A phase, B phase, and C phase) corresponding
to each
magnetic pole in the rotor. Individual pole phase coils of a three phase
alternator comprise an A
pole phase coil 518, B pole phase coil 520 and C pole phase coil 522 which
collectively make up
a pole phase coil group 526. There is one pole phase coil group for each pole
of an alternator
(e.g. 12 pole phase coil groups in a 12-pole alternator) cooperating in a
"Wye" connection 524.
The pole phase coil conductors 526 of a 12 pole alternator are attached to
their respective
conducting phase ring 506, 508 and 510.
For example, an individual pole phase coil 522 (C phase of pole group 1) is
wound
around slots #36 and #3 of stator 210. The number. of turns of conductor 526
comprising coil
522 is equal to the number of turns required to generate the rated output
voltage of one phase of
the alternator. The output current portion of the individual phase coil is
equal to 1 divided by the
number of magnetic poles of the alternator. Thus, the individual pole phase
coil is made up of a
relatively large number of turns of relatively small wire.
This construction results in a number of advantages, both during construction
of the
alternator and during operation of the alternator.
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Because each individual pole phase coil is made up of a relatively large
number of turns,
small changes in design voltage can be accomplished by changing the number of
turns. For
example, a particular 12 pole alternator wound in a conventional manner with
all of the pole
phase coils connected in series may require 1.0417 turns of conductor equal to
wire gage 6.285
to produce 14 VDC (after proper rectification), 300 amperes at 1940 rpm.
Neither the number of
turns nor the equivalent wire gage is practical numbers for production. By
constructing the
example alternator with the pole phase coils connected in parallel, each
individual pole phase
coil would be 12.5 turns of 17 gage wire. (As a note, half turns can be
constructed by
terminating one end of the individual pole phase coil, say the start, on one
side of the stator
lamination stack, and the other end, say the finish, at the other side of the
stator lamination stack.
This construction is illustrated in Figure 18A) Further to this example,
increasing the original
design to 1.0833 turns (again, an impractical number) would reduce the rpm to
1894. This could
be accomplished in the alternate construction by increasing each parallel pole
phase coil to 13
turns. The relatively small cross sectional area of the conductors provides
for easier winding of
the coils.
A short circuit between turns of an individual pole phase coil results in most
of the power
being generated in the alternator flowing in the shorted coils. Because the
coils are constructed
of a relatively large number of turns of relatively small cross sectional area
conductors, the
shorted turns will very quickly melt and clear the short circuit. The decrease
in output power
resulting from one pole phase coil opening up is approximately 1/(number of
magnetic poles +
number of phases). For example the power output reduction of a 12 pole, three-
phase alternator
with one pole phase coil shorted and then self cleared is approximately 3%.
For example, a short circuit between turns of an individual pole phase coil
will typically
clear in less than two seconds. Damage to the alternator drive system is
eliminated, the engine
continues operation with no additional load and the alternator continues to
produce power to the
connected load. Conducting phase rings 138 are individually identified as A
ring 506, B ring
508 and the C ring 510. Three individual pole phase coil conductors, A phase
512, B phase 514
and C phase516 are schematically illustrated for clarity. Each of the three
pole phase coils that
make up a pole phase coil group is, in this illustration connected in a "Wye"
connection 524. As
noted earlier, the use of a "Delta" connection can also be implemented using
phase collector
rings.
The individual phase coil conductors are gathered in an efficient manner that
does not
impede cooling. With phase coil conductors leaving the phase coil end turn at
90 degrees to the
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face of stator 210, the end turns are exposed to the greatest air flow
possible which in turn offers
the best possible cooling of said end turns.
Although the present invention has been described in conjunction with various
exemplary
embodiments, the invention is not limited to the specific forms shown, and it
is contemplated
that other embodiments of the present invention may be created without
departing from the spirit
of the invention. Variations in components, materials, values, structure and
other aspects of the
design and arrangement may be made in accordance with the present invention as
expressed in
the following claims.
