FIELD
[0001] This application relates to the field of alternators, and more specifically, a
5 dual axis alternator for a flywheel of an engine.
BACKGROUND
[0002] An engine-generator set, which may be referred to as a generator or a
genset, may include an engine and an alternator or another device for generating electrical
energy or power. One or more generators may provide electrical power to a load through a
10 power bus. The power bus, which may be referred to as a generator bus or common bus,
transfers the electrical power from the engine-generator set to a load.
[0003] The generator may include a rotating part, rotor, and a stationary part stator.
The armature, which can be part of the rotor or the stator, is the electric producing portion
(e.g., coils of wire) for producing time varying voltage. The field produces a magnetic field
15 that causes the time varying voltage to be produced when the rotor moves relative to the
stator. The field may be in either the rotor or the stator and opposite to the armature.
[0004] A separately excitable generator also includes an exciter generator for
producing a field current for the magnetic field. The separate exciter generator takes up
space. Depending on the design and package, the exciter may extend the length of the
20 genset from 5-30%. In many applications, this space is not available this space could be
used in other ways.
3
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] Exemplary embodiments are described herein with reference to the following
drawings.
[0006] FIG. 1 illustrates an example side view of a dual axis generator.
[0007] FIG. 2 illustrates an example exploded view of an engine including 5 a dual axis
generator.
[0008] FIG. 3 illustrates an example exploded view of an engine including a dual axis
generator.
[0009] FIG. 4 illustrates an example cross section of a dual axis generator.
10 [0010] FIG. 5A illustrates a stationary portion of a dual axis generator.
[0011] FIG. 5B illustrates a moving portion of a dual axis generator.
[0012] FIG. 6 illustrates an axial embodiment of a dual axis generator.
[0013] FIG. 7 illustrates a cross section of a rotor portion of the axial embodiment.
[0014] FIG. 8 illustrates a side view of a rotor portion of the axial embodiment.
15 [0015] FIG. 9 illustrates a cross section of a stator portion of the axial embodiment.
[0016] FIG. 10 illustrates a side view of a stator portion of the axial embodiment.
[0017] FIG. 11 illustrates a coolant system of a dual axis generator.
[0018] FIG. 12 illustrates another embodiment of a coolant system of a dual axis
generator.
20 [0019] FIG. 13 illustrates a heat exchanger for a coolant system of a dual axis
generator.
4
[0020] FIG. 14 illustrates an example field current supply devicefor the dual axis
generator.
[0021] FIG. 15 illustrates an example electrical diagram for the dual axis generator.
[0022] FIG. 16 illustrates a dual axis generator with the access cover removed.
[0023] FIG. 17 illustrates example operating modes for the generator 5 controller.
[0024] FIG. 18 illustrates an example speed profile plot.
[0025] FIG. 19 illustrates an example controller.
[0026] FIG. 20 illustrates a flow chart for the controller.
DETAILED DESCRIPTION
10 [0027] Controlled-field synchronous generators include an exciter for generating a
field current. As the exciter armature is rotated in a magnetic flux, a time varying voltage is
induced in the windings of the exciter armature. The output from the exciter armature is
connected to the main field portion of generator. The connection may be made without
brushes and slip rings. The field current of the output of the exciter provides a magnetic
15 field in rotor field of the generator. As the field portion of the alternator is rotated relative
to the stator, a magnetic flux is passed through and across the alternator stator windings
producing time varying voltage.
[0028] The field current from the exciter armature output may be rectified or
otherwise controlled. The generator may include various modes of control for the field
20 current. The controlled field generators are flexible in electrical operation but require
significant space. The exciter portion and the main portion may be supported and rotated
5
by a common shaft. The exciter portion and the main portion may be spaced axially apart
on the common shaft. This design requires significant space to allow for the exciter portion
and the main portion to be spaced axially apart.
[0029] Other designs improve on the space requirements. A permanent magnet
generator(PMG) has a rotor field that is provided by permanent magnets. 5 The rotating part,
or rotor, rotates about the center of the generator, and the stationary part, or stator,
includes coils for generating voltage when the rotor is rotated relative to these coils. The
generator is described as synchronous generator because the frequency of the electrical
output is directly proportional to the angular speed (e.g., revolutions per minute) of the
10 rotor.
[0030] The permanent nature of the permanent magnets in the PMG leads to
several disadvantages. First, because the magnets cannot be “turned off,” safety issues
arise during assembly or maintenance of the PMG. More significantly, the PMG design is
less flexible than other designs. The following embodiments provide the space advantages
15 of the PMG in combination with the control flexibility of controlled field generators.
[0031] The following embodiments include a dual axis generator. In a dual axis
generator, the exciter generator and the main generator are arranged concentrically in the
same plane around the common shaft. Because the exciter generator and the main
generator are arranged concentrically, the amount of space required in the axial direction is
20 much less. Because the generator has a controlled field, the dual axis generator provides
control flexibility in a space similar to a PMG.
6
[0032] FIG. 1 illustrates an example side view of a dual axis generator. A shaft 22
supports a rotor frame 23. A stator frame 21 is supported by a fixed member that provides
the frame of reference for the rotating rotor. The fixed member may be an engine block or
skid or other fixed member. The rotor frame 23 rotates with the shaft. The rotor frame 23
supports a rotor field device 24a and an exciter armature device 24d. Thus, 5 the rotor field
device 24a and the exciter armature device 24d may be rigidly mounted together or
integrally formed. The stator frame 21 supports an exciter field device 24c, and a main
stator device 24b. Thus, the exciter field device 24c and the main stator device 24bare
rigidly mounted in the same frame of reference relative to the rotor or may be integrally
10 formed. Either or both of the stator side and the rotor side may be formed of cast iron or
steel or laminated silicon steel or other magnetically permeable materials
[0033] An exciter air gap 25a is maintained between the exciter field device 24c and
the exciter armature device 24d. The exciter field device 24c is energized by a voltage
regulator or another power source to generate an exciter magnetic field in the exciter air
15 gap 25a. The exciter armature device 24d is configured to rotate with respect to the exciter
field device 24c and impart a first time varying voltage in a set of coils in the exciter
armature across the exciter air gap 25a. In one alternative, the exciter field device 24c may
include permanent magnets. In another alternative, the exciter field device may include
coils or another magnetic field generating device.
20 [0034] A main air gap 25b is maintained between the rotor field device 24a and the
main stator device 24b. The main stator device 24b including a second set of coils. The rotor
7
field device 24a is configured to be energized by the first current in the first set of coils and
generate a main magnetic field that imparts a second time varying voltage in the coils of the
main stator device 24b across the main air gap 25b.
[0035] As illustrated in FIG. 1, the main stator device 24b and the exciter field device
24c lie in on a common plane normal to an axis of rotation of the shaft 5 22. In a first
embodiment, only the main stator device 24b and the exciter field device 24c lie in on the
common plane with the rotor field device 24a and the exciter armature device 24d lying in
an adjacent plane. In this example, the adjacent plane including the rotor field device 24a
and the exciter armature device 24d are axially spaced from the main stator device 24b and
10 the exciter field device 24c. In this embodiment, the main air gap 25b and the exciter airgap
25a lie in adjacent planes or a common plane normal to the shaft. In a second embodiment,
the main stator device 24b, the exciter field device 24c, the rotor field device 24a and the
exciter armature device 24d lie in the common plane. In this embodiment, the main air gap
25b and the exciter air gap 25a may be concentrically aligned parallel to the axis of the
15 shaft 22 with all or part of the cylindrical exciter air gap 25a contained within the cylindrical
main air gap 25b. Note combinations of the first and second embodiments are possible and
contemplated.
[0036] The exciter armature device 24d is inwardly spaced from the exciter field
device 24c, main stator device 24b, and the rotor field device 24a. In other words, the
20 exciter armature device 24d is closer to the shaft 22 than the exciter field device 24c, the
main stator device 24b, and the rotor field device 24a. As shown in the embodiment of
8
Figure 1, the exciter armature device 24d is closest to the shaft, followed by the exciter field
device 24c, then the main stator device 24b, and finally the rotor field device 24a. Thus, the
rotor field device 24a is radially and outwardly spaced from the exciter armature device
24d, the exciter field device 24c, and the main stator device 24b. Embodiments where the
rotor field device 24a is inwardly spaced from the main stator device 5 24b are also
contemplated.
[0037] FIG. 2 illustrates an example exploded view of an air cooled engine 10
including a dual axis generator. The engine 10 includes a flywheel 11, a backing plate 12, an
ignition module 13, a flywheel washer 14, a flywheel screw 15, a debris screen 16, a fan 17,
10 and electrical connector 18. FIG. 3 illustrates an example exploded view of a liquid cooled
engine 100 including a dual axis generator. Additional, different, or fewer components may
be included.
[0038] Either flywheel 11, 111 is mechanically coupled to a prime mover of the
engine 10 or 100, respectively. The flywheel 11, 111 stores energy produced by the engine
15 10. The engine includes one or more pistons that perform a series of strokes. The flywheel
11, 111 stores energy from the prime mover, through momentum and inertia, from one or
more of the series of strokes and delivers to energy to the prime mover in another one or
more of the series of strokes.
[0039] Consider an example in which a compression cycle of the engine 10 includes
20 an intake stroke, a compression stroke, a power stroke, and an exhaust stroke. During the
intake stroke, the piston moves from the top of the cylinder to the bottom of the cylinder. A
9
fuel and air mixture is drawn into the cylinder. Next, during the compression stroke, the
piston moves back to the top of the cylinder, compressing the fuel and air mixture against
the cylinder head. Next, during the power stroke, the compressed fuel and air mixture is
ignited by a spark plug, compression, or heat source. The piston is pushed back down
toward the bottom of the cylinder by the pressure generated from combustion. 5 Finally,
during the exhaust stroke, the piston returns to the top of the cylinder to expel the spent or
combusted fuel and air mixture through an exhaust valve.
[0040] During the power stroke, the flywheel 11, 111 receives momentum from the
crankshaft. As the piston ends the power stroke, the flywheel 11, 111 provides momentum
10 to continue through the exhaust stroke, intake stroke and compression strokes. The
flywheel 11, 111 reduces fluctuations in the speed of the engine by resisting both
acceleration during the power stroke, and deceleration during the other strokes. The inertia
of the flywheel 11, 111 may also reduce fluctuations in the speed of the engine 10, 100
when the load varies.
15 [0041] The engine 10, 100 may require a flywheel 11, 111to provide a moment of
inertia at a predetermined level. Requirements for moments of inertia for the flywheel 11,
111may vary according to the firing frequency of the engine, the number of cylinders or
other characteristics of the engine. The exciter armature device 24d and the rotor field
device 24a may be integrated in the flywheel 11, 111 of the engine 10, 100 while the exciter
20 field device 24c and the main stator device 24b may be contained within the flywheel 11,
111. Because the dual axis alternator may be integrated with the flywheel 11, 111, the
10
moment of inertia of the flywheel 11, 111 may be different than in other types of engines.
The moment of inertia may be increased with greater mass from the exciter armature
device 24dand the rotor field device 24a. A dual purpose may be achieved in decreasing the
torque variation of the engine 10, 100 via the flywheel 11, 111including the moment of
inertia of the rotor field and exciter armature laminations and coils. The 5 rotor field and
exciter armature may also be wound on a casting of the flywheel 11, 111, which may be
formed cast iron, steel, or another magnetically permeable material.
[0042] In the air cooled example, an ignition module 13 may use a pickup to
generate energy and a signal from the passing of a magnet for generating an electric spark
10 to one or more cylinders of the engine 10 at an appropriate time. The ignition module 13
may be spaced by a distance from the rotor field on the flywheel 11 in order to prevent
interference between the rotor field and the ignition magnet. The ignition module 13 may
be in a different place than the flywheel 11. The flywheel 11 may be secured to the engine
10 by the flywheel washer 14 and the flywheel screw 15 fastening to the backing plate 12.
15 The fan 17 is driven by the flywheel and forces air onto the flywheel 11 and or other
components of the engine 10 in order to cool the engine 10. The debris screen 16 catches
any foreign matter from being blown by the fan 17 into the engine 10.
[0043] The liquid cooled engine 100 may include an engine block 101, cylinder heads
102, intake manifold 103, throttle body 104, crank angle sensor 105, ignition module 106,
20 starter motor 107, starter solenoid 108, flywheel cover 109, access cover 110, and flywheel
11
111. Other embodiments may not include the starter motor 107 or starter solenoid 108, if
the dual axis generator is used to crank the engine.
[0044] The liquid-cooled engine 100 may reduce the temperature of the engine
block, cylinder head, and other components of the engine by exchanging heat into a liquid
coolant. The liquid coolant can be pumped to convey the heat away 5 from the engine
components and into another heat exchanger to be dissipated into another cooling fluid or
heat sink. The liquid coolant may be a glycol-water mixture, alcohol, water, or another
coolant. The other heat exchanger may include a liquid to air heat exchanger (e.g. a
radiator), a liquid to liquid heat exchanger (e.g. a seawater heat exchanger), or a large metal
10 heat sink (such as the keel or hull of a ship).
[0045] FIG. 4illustrates an example cross section including the magnetic material of a
radial air gap dual axis generator. Because of the layout of the machine, the power density
is optimized. That is the main (field and stator) devices are larger than the exciter devices.
For example, the exciter field device 24c is larger than the exciter armature device 24d, and
15 the rotor field device 24a is larger than the main stator device 24b. The main stator device
24b and the exciter armature device 24d have a high number of teeth (e.g., 24), and the
rotor field device 24a and the exciter field device 24c have a low number of teeth (e.g., 8).
Each tooth may support a winding.
[0046] This is an optimized machine topology because the rotor field device 24a and
20 the main stator device 24b may require more air gap area to generate output current to the
12
load relative to the current provided by the exciter field device 24c and the exciter
armature device 24d to the rotor field device 24a.
[0047] FIG. 5B illustrates a stationary portion of a dual axis generator. The rotor field
device 24a and the exciter armature device 24d may be rigidly mounted together or
integrally formed as the stationary portion. FIG. 5Aillustrates a moving 5 portion of a dual
axis generator. The exciter field device 24c and the main stator device 24b are rigidly
mounted together or integrally formed as the moving portion.
[0048] FIG. 6 illustrates an axial embodiment of a dual axis generator. The axial dual
axis generator includes a stator frame 35 and a rotor frame 32. A shaft 39 supports the
10 rotor frame 32. The stator frame 35 is attached to a fixed member. The rotor frame 32
rotates with the shaft 39. The rotor frame 32 supports a rotor field device 31a and an
exciter armature device 31d. Thus, the rotor field device 31a and the exciter armature
device 31d may be rigidly mounted together or integrally formed.
[0049] The stator frame 35 supports an exciter field device 31c and a main stator
15 device 31b. Thus, the exciter field device 24c and the main stator device 24b are rigidly
mounted together or integrally formed. Either or both of the stator side and the rotor side
may be formed of cast iron or steel or other magnetically permeable material. The coils may
be wrapped on the cast iron, or, in an alternative embodiment, the coils may be integrated
in a printed circuit board.
20 [0050] An exciter air gap 33a is maintained between the exciter field device 31c and
the exciter armature device 31d. The exciter field device 31c generates an exciter magnetic
13
field in the exciter air gap 33a. The exciter armature device 31d is configured to rotate with
respect to the exciter field device 31c and impart a first time varying voltage in a set of coils
at the exciter air gap 33a.
[0051] A main air gap 33b is maintained between the rotor field device 33a and the
main stator device 31b. The main stator device 31b includes a second set of 5 coils. The rotor
field device 31a is configured to be energized by the first current in the first set of coils and
generate a main magnetic field that imparts a second time varying voltage on the main
stator device 31b at the main air gap 33b.
[0052] As illustrated in FIG. 6, the main stator device 31b and the exciter field device
10 31c lie in on a first common plane normal to an axis of rotation of the shaft 39. The
common plane extends in directions normal to the shaft 39. The rotor field device 31a and
the exciter armature device 31d are in a second common plane axially spaced (e.g., in the
longitudinal direction of the shaft 39) from the main stator device 31b and the exciter field
device 31c in the first common plane. In the axial dual axis generator, the exciter armature
15 device 31d is inwardly spaced, toward the center of rotation, from the exciter field and the
rotor field device 31a. In addition, the exciter field device 24c in inwardly spaced from the
main stator device 31b.
[0053] FIG. 7 illustrates a cross section of the rotor frame 32 of the axial
embodiment, and FIG. 8 illustrates the side view of only the rotor frame 32. The rotor frame
20 32 rotates with the shaft 39. The rotor frame 32 supports a rotor field device 31a and an
14
exciter armature device 31d. Thus, the rotor field device 31a and the exciter armature
device 31d may be rigidly mounted together or integrally formed.
[0054] FIG. 9 illustrates a cross section of stator frame 35 of an axial embodiment,
and FIG. 10 illustrates a side view of the stator frame 35 of the axial embodiment. The
stator frame 35 supports the exciter field device 31c and the main stator 5 device 31b. The
axial embodiment may reduce the overall length of the machine. Cooling may be improved
because the iron is directly connected to the engine block. If less iron is between the engine
block and the windings, heat may be dissipated more efficiently. The axial embodiment may
be easier to manufacture because it can be wound from one end with rotating the machine.
10 Finally, less permanent magnet material may be required in cases where the exciter utilizes
a permanent magnet field.
[0055] FIG. 11 illustrates a coolant system 50 of a dual axis generator. While
illustrated with the example of FIG. 1, the coolant system 50 may also be applied to any of
the examples described herein including the axial embodiment. The coolant system 50 may
15 include a coolant passage 51. As shown by the arrows, a coolant flows from an input end
52a to an output end 52b of the coolant passage 51. The coolant may be any type of gas or
fluid such as air, water, seawater, antifreeze, methanol, ethyl alcohol, nitrogen, or another
coolant. The coolant passage 51 may carry the coolant to a cavity 53 that is in contact with
the exciter field device 24c and/or the main stator device 24b. In other examples, the
20 coolant passage 51 and/or the cavity 54 may be in contact with the exciter armature device
24d and/or the main stator devices 24a.
15
[0056] The dual axis generator may include a variety of coolant passages. The
coolant passages may pass through the interior of the flywheel. The coolant passages may
pass through the laminations of the dual axis generators. The coolant passage may pass
through any combination of the exciter field device 24c, the main stator device 24b, the
exciter armature device 24d and/or the rotor 5 field device 24a.
[0057] FIG. 12 illustrates another example of a coolant system 50 of a dual axis
generator. The coolant passage 51 in this example, carries the coolant from a coolant
source 57 to the cavity 53 that is in contact with the exciter field device 24c and/or the
main stator device 24b and then to a coolant reservoir 55. A return line 58 may return the
10 coolant from the coolant reservoir 55 to a coolant source 57. The return line 58 may be
plumbing such as a pipe or plastic tubing. The return line 58 or the coolant passage 51 may
include a pump for pumping the coolant to or away from the dual axis generator.
[0058] In one example, the arrangement of the coolant system 50 in FIG. 12 may be
the coolant system of the engine 100. In other words, the engine 100 includes a coolant
15 system for passing coolant through any combination of a radiator, a pump, an engine
blocks, and cylinder heads of the engine 100. The coolant passage 51 may be part if this
coolant route. Thus, the engine 100 and the dual axis generator may include a common
coolant passage with the engine 100.
[0059] In one example, the coolant system of the engine 100 may be independent
20 from the coolant system 50 of the dual axis generator. That is, none of the plumbing of the
coolant system of the engine 100 is connected to the plumbing of the coolant system 50 of
16
the dual axis generator. The coolant system of the engine 100 may include a first reservoir,
and the coolant system 50 of the dual axis generator may include a second reservoir.
[0060] In one example, the arrangement of the coolant system 50 in FIG. 12 may
utilize an external source. For example, the coolant source 57 may be a source of coolant
outside of the dual axis generator and the engine 100. In one example, 5 the dual axis
generator is used in a marine application, and the coolant source 57 is an ocean, lake, or
river. In this example, the coolant may be freshwater or seawater. The freshwater or
seawater may be delivered from the coolant source 57 to one or more components of the
dual axis generator and then return directly or indirectly through the coolant reservoir 55 or
10 the return line 58.
[0061] FIG. 13 illustrates a heat exchanger 60 for a coolant system of a dual axis
generator. The heat exchanger 60 includes a secondary conduit 61 and a primary conduit
63. In one example, a set of conductive supports 65 may conduct heat from the exciter field
device 24c and/or the main stator device 24b to the secondary conduit 63. In another
15 example, the secondary conduit 63 may be exposed to the exciter field device 24c and/or
the main stator device 24b. In other examples, the heat is transferred through a
compressed interface between the exciter field device 24c and the main stator device 24b
and through the engine block to the secondary conduit 63, which may be contained in the
engine block.
20 [0062] The primary conduit 63 may include any of the fluids described above (e.g.,
water, seawater, or another fluid), which may be referred to as a first coolant. Heat is
17
absorbed from the exciter field device 24c and/or the main stator device 24b through the
conductive supports 65 to the primary conduit 63, or alternatively directly from the first
coolant to the exciter field device 24c and/or the main stator device 24b. Heat from the first
coolant may be absorbed from a second coolant in the secondary conduit 61. The coolant in
the secondary conduit 61 may be released into the environment and 5 sourced from the
environment. In one example, the coolant in the secondary conduit 61 is seawater from a
nearby body of water. The heat exchanger 60 prevents the seawater from contaminating or
damaging the dual axis generator or the engine 100. The seawater may have a temperature
lower than other coolants regulated by a thermostat. An example maximum temperature
10 for seawater may be 35 C and an example maximum temperature for other coolants may
be 110 C. The exciter field device 24c and the main stator device 24b may have passages for
either coolant that may be lined with a thermally conductive and corrosion resistant
material.
[0063] FIG. 14 illustrates an example field current supply device 71 for the dual axis
15 generator. The field current supply device 71 may be a rectifying device configured to
convert the first current in the first set of coils of the exciter armature device 24d into a
rectified signal supplied to the rotor field device 24a. The field current supply device 71 may
be a controlled rectifier with digital logic or circuitry to convert the signal of the exciter
armature device 24d to be suitable for the rotor field device 24a. The field current supply
20 device 71 may convert the alternating current in the exciter armature device 24d to a
rectified or direct current suitable for the rotor field device 24a.
18
[0064] In another example, the field current supply device 71 is an analog circuit.
The analog circuit may accept a single phase or three phase input from the exciter armature
device 24d. The analog circuit may provide a DC voltage to the rotor field device 24a. An
example of the analog circuit may be a diode rectifier, and another example for the analog
circuit may be a controlled rectifier. The controlled rectifier may include 5 one or more
thyristor, field effect transistor, insulated gate bipolar transistor, or another active
component.
[0065] FIG. 15 illustrates an example electrical diagram for the dual axis generator.
The electrical diagram includes the electrical components that for the dual axis generator
10 for the interaction between the main stator device 24b, the exciter field device 24c, the
rotor field device 24a and the exciter armature device 24d. The electrical diagram includes
an exciter field component 93 for the exciter field device 24c, an exciter armature
component 94 for the exciter armature device 24d, a diode network 95 for the field current
supply device 71, a rotor coil 96 for the rotor field device 24a, and a stator component 97
15 for the main stator device 24b. The exciter field 93, rotor field 96, exciter armature 94, and
stator 97 may be a single-phase coil or poly-phase coils. The rotor field supply device 95
may be an inverter to drive the rotor field 96.
[0066] FIG. 16 illustrates a dual axis generator with the access cover 72 removed.
The field current supply device 71 is protected by an access cover 72, which may be sealed
20 with a gasket, o-ring, or other sealant to prevent exposure of the field current supply device
71 to moisture. The placement of access cover 72 allows for easy access to the field current
19
supply device. In addition, the access cover 72 may contain a transparent window 73 that
allows for optical communication between a stationary communication assembly and the
field current supply device 71. The transparent window 73 may be formed of plastic or
glass. The transparent window 73 may be replaced by an opaque or other type of protective
color. The transparent window 73 may be selectively transparent to certain 5 wavelengths of
light but not transparent to other wavelengths.
The field current supply device 71 receives power from the exciter armature through exciter
armature leads 74, 75, 76 and provides power to the rotor field using field leads 77, 78 in
slots 79. The slots 79 may be covered or remain open. Alternatively, the field current supply
10 device 71 may receive power through bolts connecting it to the exciter armature leads 74,
75, 76 and supply power through bolts to field leads 77 and 78. The bolts may also hold the
field current supply device 71 to a rotating member.
[0067] The output voltage of a given generator depends primarily on two factors, the
speed that the alternator is rotating and the magnetic flux generated by the rotating field.
15 In a permanent magnet generator, the magnetic flux is determined by the properties of the
permanent magnets, so the generator outputs a voltage that is primarily determined by the
speed of the engine. Because the field current can be controlled on a dual-axis generator,
the output voltage of the alternator is dependent on both factors and the output voltage
can be controlled independently of the engine speed.
20 [0068] Because the output voltage can be controlled independently of engine speed,
the dual-axis generator allows for different engine speed versus load profiles while
20
producing a given output voltage. A permanent magnet generator typically increases speed
when load is applied to offset internal voltage drop due to inductance and resistance on the
stator windings and armature reaction flux, but the dual-axis generator permits operation in
a variety of speed versus load scenarios.
[0069] FIG. 17 illustrates example operating modes for the generator 5 controller and
the dual axis generator. The operating modes are illustrated by plots including a plot for
each of a fuel efficiency mode 81, a constant speed mode 82, a sound mode 83, a power
quality mode 84, and a zero dip mode 85. Additional modes not illustrated are possible. For
example, a vibration minimization mode may avoid speeds that induce resonant vibration in
10 the engine or nearby objects. The design of the dual axis generator permits these operating
modes because the output voltage of the generator is not completely determined by the
speed of the engine. The area below each of the mode plots represents the operating range
of the dual axis generator in that mode. The red line limiter 80 illustrates that maximum
operation of the dual axis alternator. Various embodiments may include any combination of
15 the fuel efficiency mode 81, the constant speed mode 82, the sound mode 83, the power
quality mode 84, and the zero dip mode 85. One or modes may include an increased speed
as load increases (e.g., the fuel efficiency mode 81 and the sound mode 83), one or more
other modes may include a decreased speed as load increases (e.g., power quality mode),
one or more modes may include a combination of increasing and decreasing speed with
20 increasing load, and one or more other modes may include a substantially constant speed
21
as load increases (e.g., zero dip mode 85). A substantially constant speed may be a speed
within a set percentage (e.g., 1%, 5%, or 10%).
[0070] For a permanent magnet generator, flux is determined by the properties of
the permanent magnets and is not controlled. For a given speed, flux passes coils at a set
rate, which creates a specific output voltage. If the output voltage is to 5 be determined with
fluctuations in the load, an armature reaction must be offset. When there is a load
connected to the armature windings, there is current flowing through the armature
windings. This creates an additional mutual flux linkage component that is in opposition to
the flux component from the field winding; this flux linkage is denoted as armature
10 reaction. Thus, as the load on the alternator is increased, the speed of the engine is
increased to maintain the output voltage in a permanent magnet design.
[0071] However, in the wound field designs described herein, there is more flexibility
to counter the armature reaction. Similar to the permanent magnet design, the speed of
the engine may be increased. However, a second option is to increase the field current to
15 the main rotor field device 24a using an exciter mechanism to cause voltage to increase.
Thus, through the generator controller 71, the field current is controller to control the
output of the generator. The field control may offset signal drooping from load fluctuations.
Because the speed profile is flexible, various modes may be realized.
[0072] The power quality mode 84 may include a first droop setting. In first droop
20 setting, when there is a load transient, the dual axis generator reacts quickly because the
22
speed of the engine is higher in a no load condition and has room to dip as the load is
applied.
[0073] A load transient is a change in load over time. The load may go up and down,
but generally generator output responses are described in terms of increasing loads.
[0074] The fuel efficiency mode 81 may include a second droop 5 setting. In the
second droop setting, when there is a load transient, there is less response by the dual axis
generator because fuel efficiency is optimized. That is, for the highest fuel efficiency, the
engine should be run at the lowest speed that provides adequate output for the load. The
fuel efficiency mode 81 may have a slow response time or lag time, which may cause lights
10 to dim or other problems when load transients occur.
[0075] The constant speed mode 82 may include a third droop setting that is at or
near zero, which effectively targets a constant speed. As load is applied, the throttle of the
engine is opened to maintain the speed of the engine sufficient to provide the rated output
of the generator. The output speed may not correspond to a typical output speed for a
15 synchronous alternator (e.g., 1800 RPM). In addition, the output speed target is determined
a required power output of the generator and not by the required frequency of the output
of the generator.
[0076] In a zero dip mode or a motor starting mode 85, when there is a load
transient, there is no, or very little, response to the output voltage of the dual axis
20 generator. The zero dip mode 85 may include a profile that is inverted. For example, the
23
engine may run at a speed (e.g., 2200 rpm) that is faster than normal speed (e.g., 1800 rpm)
so that any load transients are absorbed without causing a disruption in the output voltage.
[0077] FIG. 18illustrates an example sound versus speed curve 99 for the sound
mode 83. Typically, an engine is quieter as speed is lowered. However, at certain low
speeds, engines may experience resonant frequencies of components 5 or other anomalies
that cause the engine to shake and produce more sound at lower speeds. Some low
resonant frequencies may be below the range of vibration dampeners (e.g., vibromounts).
Therefore, the speed curve for the sound mode 83 may overlap the fuel efficiency mode 81
at higher speeds or powers but run at higher speeds than the fuel efficiency mode 81 at
10 lower speeds. The generator controller 91 is configured to access the speed profile and
control the speed of the engine to depend on both the load on the generator and the speed
profile in order to minimize the sound. Human ears receive different sounds at different
sensitivity levels. A perceived sound level may vary disproportionately to sound level. The
sound versus speed profile 99 may be modified to account for this phenomenon.
15 [0078] FIG. 19illustrates an example generator controller 91. The following
description may also be applied to other implementations of the field current supply
device71 besides the generator controller 91. The generator controller 91 may include a
processor 300, a memory 352, and a communication interface 353. The generator controller
91may be connected to a workstation 359 or another external device (e.g., control panel)
20 and/or a database 357 for receiving user inputs, system characteristics, and any of the
values described herein. Optionally, the generator controller 91 may include an input device
24
355 and/or a sensing circuit 311. The sensing circuit 311 receives sensor measurements
from as described above. Additional, different, or fewer components may be included. The
processor 300 is configured to perform instructions stored in memory 352 for executing the
algorithms described herein. The processor 300 may identify an engine type, make, or
model, and may look up system characteristics, settings, or profiles based 5 on the identified
engine type, make, or model.
[0079] FIG. 20 illustrates a flow chart for generator mode and performance profile
selection for the dual axis generator. Additional, different of fewer acts may be included.
[0080] At act S101, the processor 300 receives a user selection for generator mode
10 from the input device 355. The mode may be any of the fuel efficiency mode 81, the
constant speed mode 82, the sound mode 83, the power quality mode 84, and the zero dip
mode 85. The user selection may be made on a keypad, touch screen, push button, or
another input.
[0081] At act S103, the processor 300 accesses a performance profile from the
15 memory 352 based on the selected generator mode from the user selection. The
performance profile may be stored in memory 352. A different profile may be stored for
each of the fuel efficiency mode 81, the constant speed mode 82, the sound mode 83, the
power quality mode 84, and the zero dip mode 85.
[0082] At act S105, the processor 300 may set a field current or an engine speed
20 based on the performance profile. The processor 300 accesses the appropriate profile
which may be a lookup table that associates target engine speeds with load values. The
25
sensing circuit 311 may calculate a load value based on output power, voltage, or current.
In one example, the load value may be inferred from a change that occurs in the field
current.
[0083] The processor 300 may include a general processor, digital signal processor,
an application specific integrated circuit (ASIC), field programmable 5 gate array (FPGA),
analog circuit, digital circuit, combinations thereof, or other now known or later developed
processor. The processor 300 may be a single device or combinations of devices, such as
associated with a network, distributed processing, or cloud computing.
[0084] The memory 352 may be a volatile memory or a non-volatile memory. The
10 memory 352 may include one or more of a read only memory (ROM), random access
memory (RAM), a flash memory, an electronic erasable program read only memory
(EEPROM), or other type of memory. The memory 352 may be removable from the network
device, such as a secure digital (SD) memory card.
[0085] In addition to ingress ports and egress ports, the communication interface
15 303 may include any operable connection. An operable connection may be one in which
signals, physical communications, and/or logical communications may be sent and/or
received. An operable connection may include a physical interface, an electrical interface,
and/or a data interface.
[0086] The communication interface 353 may be connected to a network. The
20 network may include wired networks (e.g., Ethernet), wireless networks, or combinations
thereof. The wireless network may be a cellular telephone network, an 802.11, 802.16,
26
802.20, or WiMax network. Further, the network may be a public network, such as the
Internet, a private network, such as an intranet, or combinations thereof, and may utilize a
variety of networking protocols now available or later developed including, but not limited
to TCP/IP based networking protocols.
[0087] While the computer-readable medium (e.g., memory 352 or 5 database 357) is
shown to be a single medium, the term "computer-readable medium" includes a single
medium or multiple media, such as a centralized or distributed database, and/or associated
caches and servers that store one or more sets of instructions. The term "computerreadable
medium" shall also include any medium that is capable of storing, encoding or
10 carrying a set of instructions for execution by a processor or that cause a computer system
to perform any one or more of the methods or operations disclosed herein.
[0088] In a particular non-limiting, exemplary embodiment, the computer-readable
medium can include a solid-state memory such as a memory card or other package that
houses one or more non-volatile read-only memories. Further, the computer-readable
15 medium can be a random access memory or other volatile re-writable memory.
Additionally, the computer-readable medium can include a magneto-optical or optical
medium, such as a disk or tapes or other storage device to capture carrier wave signals such
as a signal communicated over a transmission medium. A digital file attachment to an email
or other self-contained information archive or set of archives may be considered a
20 distribution medium that is a tangible storage medium. Accordingly, the disclosure is
considered to include any one or more of a computer-readable medium or a distribution
27
medium and other equivalents and successor media, in which data or instructions may be
stored. The computer-readable medium may be non-transitory, which includes all tangible
computer-readable media.
[0089] In an alternative embodiment, dedicated hardware implementations, such as
application specific integrated circuits, programmable logic arrays 5 and other hardware
devices, can be constructed to implement one or more of the methods described herein.
Applications that may include the apparatus and systems of various embodiments can
broadly include a variety of electronic and computer systems. One or more embodiments
described herein may implement functions using two or more specific interconnected
10 hardware modules or devices with related control and data signals that can be
communicated between and through the modules, or as portions of an application-specific
integrated circuit. Accordingly, the present system encompasses software, firmware, and
hardware implementations.
15
28
We Claim : 1. An apparatus comprising:
an exciter field device generating an exciter magnetic field in a first air gap;
5 an exciter armature device configured to rotate with respect to the exciter
magnetic field and impart a first voltage in a first set of coils at the first air gap;
a main stator device including a second set of coils; and
a rotor field device configured to be energized by the first current in
the first set of coils and generate a main magnetic field that imparts a second
10 voltage on the main stator device at a second air gap,
wherein the main stator device and the exciter field device lie in on a
common plane normal to an axis of rotation and the exciter armature device
is inwardly spaced from the exciter field device, main stator device, and the
rotor field device.
15
2. The apparatus of claim 1, wherein the exciter armature device and the
rotor field device lie on the common plane normal to the axis of rotation.
3. The apparatus of claim 1, wherein the exciter armature device and the
20 rotor field device lie on an axially spaced plane different than the common
plane.
29
4. The apparatus of claim 1, wherein the exciter armature device and the
rotor field device are rigidly mounted to each other.
5. The apparatus of claim 1, wherein the rotor field device is radially and
outwardly spaced from the exciter armature device, the exciter 5 field device,
the main stator device.
6. The apparatus of claim 1, wherein the first gap and the second gaps
are concentric.
10
7. The apparatus of claim 1, wherein the exciter armature device, the
exciter field device, the main stator device, and the rotor field device are
integrated in a flywheel of an engine.
15 8. The apparatus of claim 1, further comprising:
a coolant system configured to cool the main stator device, the exciter
field device, or both.
9. The apparatus of claim 8, wherein the coolant system includes a
20 common coolant passage with an engine.
30
10. The apparatus of claim 8, wherein the coolant system is coupled to an
external coolant source.
11. The apparatus of claim 8, wherein the coolant system includes a heat
5 exchanger.
12. The apparatus of claim 8, wherein the coolant system includes a
coolant passage through at least one of the main stator device and the
exciter armature device.
10
13. The apparatus of claim 1, further comprising:
a rectifying device configured to convert the first current in the first
set of coils into a rectified signal supplied to the rotor field device.
15 14. The apparatus of claim 13, wherein the rectifying device is an analog
circuit.
15. The apparatus of claim 13, wherein the rectifying device is a controlled
rectifier.
20
31
16. The apparatus of claim 15, wherein the controlled rectifier controls an
output voltage of the stator device.
17 The apparatus of claim 15, wherein the rotor field device is axially
outward of the exciter armature device, the exciter field device, 5 and the main
stator device.
18. The apparatus of claim 17, wherein the rectifying device is mounted to
the rotor field device.
10
19. The apparatus of claim 1, further comprising:
a generator controller configured to operate in a plurality of power
modes.
15 20. The apparatus of claim 19, wherein at least one of the plurality of
power modes includes a power quality mode having a first droop setting, a
fuel efficiency model having a second droop setting, or a constant mode
having a third droop setting.
20 21. The apparatus of claim 19, where the plurality of power modes
includes a sound mode having a sound to speed profile.
32
22. A method including:
rotating an exciter field device configured to generate an exciter
magnetic field in a first air gap;
imparting a first voltage at a first set of coils via the exciter magnetic
field and the 5 first air gap;
rotating a main stator device including a second set of coils; and
generating a main magnetic field that imparts a second voltage on the
main stator device via a second air gap.
wherein the main stator device and the exciter field device lie in on a
10 common plane normal to an axis of rotation, and the exciter armature device
is inwardly spaced from the exciter field device, main stator device, and the
rotor field device.
23. An engine comprising:
15 at least one piston configured to drive a crankshaft;
a flywheel driven by the crankshaft; and
an alternator integrated with the flywheel, wherein the alternator
includes:
an exciter field device generating an exciter magnetic field in a first air
20 gap;
33
an exciter armature device configured to rotate with respect to the
exciter magnetic field and impart a first voltage in a first set of coils at the
first air gap;
a main stator device including a second set of coils; and
a rotor field device configured to be energized by the 5 first current in
the first set of coils and generate a main magnetic field that imparts a second
voltage on the main stator device at a second air gap,
wherein the main stator device and the exciter field device lie in on a
common plane normal to an axis of rotation and the exciter armature device
10 is inwardly spaced from the exciter field device, main stator device, and the
rotor field device.