Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K35/00—Generators with reciprocating, oscillating or vibrating coil system, magnet, armature or other part of the magnetic circuit
  • H02K35/02—Generators with reciprocating, oscillating or vibrating coil system, magnet, armature or other part of the magnetic circuit with moving magnets and stationary coil systems
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K41/00—Propulsion systems in which a rigid body is moved along a path due to dynamo-electric interaction between the body and a magnetic field travelling along the path
  • H02K41/02—Linear motors; Sectional motors
  • H02K41/03—Synchronous motors; Motors moving step by step; Reluctance motors
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
  • H02K7/18—Structural association of electric generators with mechanical driving motors, e.g. with turbines
  • H02K7/1869—Linear generators; sectional generators
  • H02K7/1876—Linear generators; sectional generators with reciprocating, linearly oscillating or vibrating parts
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
  • H02P25/00—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details
  • H02P25/02—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details characterised by the kind of motor
  • H02P25/06—Linear motors
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
  • H02P9/00—Arrangements for controlling electric generators for the purpose of obtaining a desired output

Definitions

• LEGs linear electric generators
• a LEG may be constructed, as shown in Figs. 1 and 2, so as to have a long stator (e.g., an induction coil assembly 24 of length d1) and a relatively short permanent magnet assembly 22, of length d2.
• Still another advantage of having a relatively short permanent magnet is that big and long magnets present a hazard in that they tend to attract a large amount of debris.
• a problem with known linear electric generators having a long induction coil assembly and a relatively short permanent magnet assembly is that the electric current generated in the coils has to pass (flow) through the entire coil assembly (i.e., all the coils) in the stator, as illustrated in Fig. 1.
• the useful voltage derived from the coils is obtained from those coils and coil sections directly opposite and very close to the permanent magnet assembly. This useful voltage induces a current which flows through the coils.
• stator coils that are not adjacent (or directly opposite) to the permanent magnet assembly (PMA) and those that do not interact with the magnet assembly cause a voltage drop in the coil (i.e., due to the resistance and inductance of the coil) without enhancing the generation of additional current.
• a proposed solution to the problem is shown and discussed in a co- pending application titled Coil Switching Circuit for Linear Electric Generator by David B. Stewart et al filed concurrently herewith and bearing serial number and assigned to the same assignee as the instant application and whose teachings are incorporated herein by reference.
• the Coil Switching application teaches the use of a switching arrangement for coupling only selected sections of coils of the induction coil assembly (ICA) of a LEG across output lines of the LEG.
• the selected sections include those sections of coils of the ICA closest to the passing PMA.
• a disadvantage of the proposed solution is that it requires the use of switches to couple the active coils to the output lines of the LEG and switches to decouple or bypass the inactive coils.
• position sensors, and/or other appropriate means are needed to sense the position of the PMA relative to the ICA to constantly turn switches on and off in order to ensure that only desired coils are in fact-connected in circuit. This disadvantage is overcome in circuits and systems embodying the invention.
• a linear electric generator (LEG) system embodying the invention includes: (a) an induction coil assembly (ICA), which may be either of the type known as a "tapped” configuration or as a “segmented” configuration, having N sections of induction coils disposed linearly along a length d1 with the coils exhibiting inductance and resistance along their length; (b) apparatus for passing a permanent magnetic assembly (PMA) of length d2, where d2 is smaller than d-1 , along and over the ICA for generating voltages across the coils in close proximity to the PMA; and (c) unidirectional conducting means coupled between the sections of induction coils and first and second output points of the LEG for automatically coupling those coil sections rendered active by the passing PMA to the first and second output points while isolating or decoupling the non-active coil sections from being coupled to the first and second output points.
• ICA induction coil assembly
• PMA permanent magnetic assembly
• each coil has first and second terminals with each coil terminal being coupled via a first diode to a first output line and via a second diode to a second output line.
• a central energy storage element is coupled to the first and second output lines for gathering the energy produced by the coils due to the passing PMA.
• the energy storage elements of all the coil sections are selectively coupled via sampling circuits to a central energy storage element.
• LEGs embodying the invention are highly suited for use with WECs.
• FIG. 1 is a schematic diagram illustration of a prior art Linear Electric Generator (LEG) permanent magnet and coil assembly
• Figure 2 is a schematic diagram illustrating a prior art permanent magnet and induction coil assembly of a LEG
• Figures 3A is a schematic representation of a "tapped” induction coil assembly for use in practicing the invention
• Figure 3B is a schematic representation of a "segmented” induction coil assembly for use in practicing the invention
• Figures 4A and 4B illustrate the mounting of LEGs embodying the invention in a WEC
• Figures 5A and 5B are schematic diagrams of one embodiment of the invention using a segmented ICA
• Figure 6 is a schematic diagram of another embodiment of the invention using a segmented ICA
• Figure 7 is a schematic diagram of a power summing system embodying the invention for use with the embodiment of Fig. 6;
• Figure 8 is a schematic diagram of one embodiment of the invention using a tapped ICA configuration
• Figure 9 is a schematic diagram of another embodiment of the invention using a tapped coil configuration.
• Figure 10 is a waveform diagram illustrating the operation of a LEG embodying the invention.
• linear electric generators embodying the invention are shown in Figures 3 - 10. In these figures, for ease of description, only one of three possible electrical phases is shown. However, it should be understood that the apparatus may, and typically will, include one or more (e.g. 3) phases.
• One application of linear electric generators (LEGs) embodying the invention is as a power take off (PTO) device in wave energy converters (WECs) which are placed in a body of water and which include elements (e.g., shaft ,3 and shell, 5) responsive to the motion of the waves in the body of water to produce electric energy.
• PTO power take off
• WECs wave energy converters
• LEGs embodying the invention may be used in any other suitable application.
• LEGs embodying the invention include a permanent magnetic assembly (PMA) 30 and an induction coil assembly (ICA) 20 separated by a small air gap.
• PMA permanent magnetic assembly
• ICA induction coil assembly
• the length (d2) of the PMA 30 is smaller than the length (d1) of the ICA 20.
• the PMA 30 may be attached to (or mounted on) one of a shaft 3 and shell 5
• the ICA 20 may be attached to (or mounted on) and disposed along the other one of the shaft 3 and shell 5 as shown in Figs. 4A and 4D.
• the shaft or the shell may move relative to the other, or both may move relative to each other.
• the PMA 30 is typically constructed of multiple pairs of "north" and “south” polarized magnets mounted on the surface of a ferromagnetic material structure (e.g. steel) with the poles oriented perpendicular to the line of the air gap . These magnets comprise a magnetic "pole pair".
• the magnetic circuit may be comprised of a pair of magnets, "air” gaps, a stator yoke, and a magnet backing plate, the latter two items being constructed of ferromagnetic material.
• the PMA 30 may also be constructed of multiple pairs of north and south polarized magnets "buried" in a ferromagnetic yoke.
• An induction coil assembly (ICA) 20 used to practice the invention may include either a "tapped" coil configuration 20a as shown in Fig. 3A, or a "segmented" coil configuration 20b, as shown in Fig. 3B.
• Figures 3A and 3B are simplified schematic representations illustrating the use of a "tapped" coil configuration 20a (Fig. 3A) and a “segmented” coil configuration 20b (Fig. 3B).
• each coil (Li) has first and second ends and, except for the first and last coil, one end of each coil is fixedly connected to one end of the previous coil and the other end of each coil is fixedly connected to one end of the next, succeeding, coil.
• each coil (Li) has two terminals (Xi1 , Xi2) which may be freely connected.
• the ICA (generically identified as ICA 20) may be linearly disposed along the length of a supporting member (e.g., a shell or shaft).
• Flux from a pair of "north" and “south” polarized magnets is coupled to the coil segment via an air gap.
• the length of each coil segment may be equal to the length of one of these magnet pole pairs.
• a PMA may consist of several pole pairs and extend over less than one, one, or more than one, coil segment.
• a permanent magnetic assembly (PMA) 20 passes over and along the ICA separated from it by a gap to generate a voltage in the ICA.
• the basic operation of the voltage generating system may be described as follows. Assume that the PMA 30 is impelled to move relative to, and along the, ICA 20 in response to naturally occurring forces (e.g., ocean waves).
• FIG. 4A is semi-schematic semi-block simplified diagram showing a permanent magnetic assembly (PMA) 30 attached to the shaft 3 of a WEC and eight coil sections (L1-L8) of a tapped coil assembly, ICA 20a, are laid out linearly along the length of one side of a shell 5 and eight coil sections (L1-L8) of a segmented induction coil assembly (ICA) 20b laid out linearly along the length of another side of shell 5.
• PMA permanent magnetic assembly
• ICA 20a a tapped coil assembly
• ICA 20b segmented induction coil assembly
• FIG. 4A also shows eight coil sections (L1-L8) of a tapped induction coil assembly (ICA) 20a laid out linearly along the length of a shell 5. In this ICA 20a configuration the coils are connected end to end.
• ICA tapped induction coil assembly
• the voltages produced at the outputs of the coil sections are coupled via a rectifying network 111 to output lines 310, 312 across which is connected a power converter 520.
• the rectifying network 111 may be comprised of unidirectional conducting elements (e.g., rectifiers or diodes) which provide conduction paths to the output lines (e.g., 310, 312) to which may be connected one or more loads.
• unidirectional conducting elements e.g., rectifiers or diodes
• each coil Li of the segmented configuration has two output nodes (ends or terminals) Xi1 and Xi2.
• the unexcited or inactivated coils function either as low impedance paths which shunt and dissipate the energy produced by the activated and excited coils or act as series impedances which cause much of the generated energy to be dissipated.
• Fig. 4A the two ends of each coil section of ICA 20b are free to be connected to any selected circuit.
• Fig. 5A shows the components of a rectifying circuit 111 for interconnecting the coils of the ICA 20b of Fig. 4A to output lines 310 and 312 so the sinusoidal voltages produced across each coil, as the PMA 30 moves across the coil, are fully captured; and such that the unexcited coils do not load down the excited coils.
• the ICA 20b and the rectifying network of Fig. 5A may be redrawn as shown, schematically, in Fig.
• each coil (Li) is effectively connected across the mid-point of a four (4) diode bridge for providing full wave rectification for the AC voltages induced in the coil due the passing of the PMA 30 over the coil.
• each coil (Li) there is: (a) a diode Di1 connected at its anode to terminal Xi1 and at its cathode to line 310; (b) a diode Di2 is connected at its anode to line 312 and at its cathode to node Xi1 ; (c) a diode Di3 connected at its anode to node Xi2 and at its cathode to line 310; and (d) a diode Di4 connected at its anode to line 312 and at its cathode to terminal Xi2.
• Figs. 5A and 5B there are 4 diodes per coil which are poled to ensure that, regardless of the direction of the voltage induced across the coil, conventional current will flow such that the voltage on line 310 will be positive relative to the voltage on line 312.
• a current 11 flows from line 312 via diode D14, coil L1 , and diode D11 into line 310 and then into RL and through RL back to line 312. This voltage/current causes the voltage on line 310 to be more positive than the voltage on line 312.
• the diode networks interconnecting the other coils between lines 310 and 312 are back-biased and prevent the flow of currents (except for leakage currents which are negligible) through the unexcited coils.
• PMA 30 induces a voltage across the coil such that the voltage at X12 is greater than the voltage at X11 , a current 12 flows from line 312 via diode D12 through the coil L1 and then through diode D13 into line 310 and then to the load RL.
• each coil section (Li) is connected via its own full wave rectifying network (Di1 , Di2, Di3, Di4) to its own local load (Ci), which in this figure is shown to be a capacitive storage element.
• Each coil section (Li) has its own outputs (Oil , Oi2).
• each coil section may be treated as being physically and electrically separated and independent of any other coil section.
• Each coil section can then function has an independent power generator, whose power generating capability is unaffected by the action and output of any other coil section.
• the configuration of Fig. 6 in which each coil has its own output is intended to avoid a problem which may occur with the circuit of Figs 5A and 5B.
• each coil section is coupled to its own load or storage element (e.g., Ci) which can store the energy produced by its corresponding coil section. Due to the connection of a rectifying circuit to each coil (Li), the output voltages (VOi) produced across each local storage element (Ci) will be direct current (d.c.) type voltages.
• Ci load or storage element
• FIG. 7 illustrates that the output voltages (VOi1 , VOi2) of the separate storage elements of the coils of Fig. 6 can be sampled and supplied to a central storage and load element 520 which may include resistance (RL) and capacitance CT.
• a central storage and load element 520 which may include resistance (RL) and capacitance CT.
• the more negative output terminals (Oi2) of the separate coil sections (see also Fig. 6) are connected in common to an output power line 312.
• Each more positive output terminal (Oil) of each coil section is connected to one side of a switch (Fi) which may be an insulated gate field effect transistor (IGFET) (or any suitable switch which may include any of the type of switches discussed in co-pending application).
• the other side of each switch Fi is shown connected via a network Ki to an output power line 310.
• the switches Fi may be sampled (turned on and off) by a load switch control circuit 161 to effectuate a transfer of the power developed across the individual storage elements Ci to a central storage element CT in power device 520. That is, the main (source to drain) conduction path of each transistor switch Fi is connected between a coil output (Oi) and a network (Ki) and the gate of each Fi is coupled to switch control network 161 which selectively turns the switches Fi on and off to effectuate the transfer of power from each coil section to the central load.
• a load switch control circuit 161 to effectuate a transfer of the power developed across the individual storage elements Ci to a central storage element CT in power device 520. That is, the main (source to drain) conduction path of each transistor switch Fi is connected between a coil output (Oi) and a network (Ki) and the gate of each Fi is coupled to switch control network 161 which selectively turns the switches Fi on and off to effectuate the transfer of power from each coil section to the central load.
• each coil capacitor can be selectively sampled and its contents transferred to a central storage element .
• the capacitive storage elements can be directly connected in parallel to form a common load as shown in Fig. 8 (and Figs. 5A and 5B).
• the coil sections (L1-L8) of an ICA 20 are shown connected end to end. with adjacent coils having their end terminals connected in common. This configuration may be achieved by connecting the coils of a segmented configuration end to end or starting off with a tapped configuration.
• the coil configuration is equivalent to, and may be termed, a "tapped" coil configuration, as discussed above. That is, the second terminal X12 of L1 is connected to the first terminal X21 of L2 and the second terminal X22 of L2 is connected to the first terminal X31 of L3, and so forth.
• Each coil section Li is shown connected via a fully rectifying network of 4 diodes between output power terminals 310 and 312. For this configuration, adjacent coil sections share two diode ' s (e.g.7 ' 171 and 172). For this configuration, the number of diodes may be reduced and the total number of diodes could be equal to two plus two times the number of coil sections.
• This circuit configuration when compared to that of Figures 5A and 5B, has the advantage that all "excited,” or “active,” coil sections contribute voltage and power to the output lines 310 and 312, regardless of their individual coil voltage, provided the voltages of the individual coils are "in phase” or nearly in phase (i.e. the voltage of each excited circuit rises at the same time and falls at the same time).
• diodes D12, D13, D21 , D14, D22, D23 and D31 are all back-biased due to the polarity of voltage on these active coils, and therefore, prevent the flow of any appreciable current through these back-biased diodes.
• diode networks interconnecting the other coils between lines 310 and 312 are back- biased and prevent the flow of current (except for leakage currents which are n ⁇ g ⁇ Tgi ⁇ le) o ⁇ gfi he " unexcited coils. Thus, there is no low impedance path shunting the active coils and the PMA30.
• Figure 9 illustrates that an ICA whose coils are configured in a "tapped” coil configuration can be operated so that each coil section is electrically independent of the other and can function similarly to the configuration of the circuit of Fig. 5 (and Fig. 7).
• adjacent coils e.g., Li and L(i+1)] share a common node [e.g., Xi2 and X(i+1)1].
• Each coil may have its own independent output (Oil) and each coil terminal (Xi1 , Xi2) may be connected via its own diodes (DM , Di3) to the output Oil .
• Fig. 10 shows typical waveforms which help explain the operation of a LEG embodying the invention.
• Waveform A suggests a sinusoidal motion for the PMA 30 which may well be encountered in WECs.
• Waveforms B, C, D, E, E, F and G illustrate the voltages produced across the individual coils when the PMA passes over or in close proximity to the coils.
• Waveform H of Fig 10 represents the composite or total voltage seen across the power terminals (310, 312) when the unidirectional coil coupling embodying the invention is employed. That is, the "active" coils are connected across the output lines 310 and 312 via two forward biased diodes while the “inactive” coils are de-coupled from the output lines by at least one reverse biased diode.
• Waveform I of Fig 10 represents the prior art composite voltage seen across the power terminals for a configuration of the type shown in Fig.1.
• the voltage (e.g., waveform H) generated across the power terminals (310, 312), when only the excited coils are coupled via two diodes across the output power lines, is of larger amplitude than that shown in waveform I, when all the coils are connected in series across the power lines.
• waveform H The voltage (e.g., waveform H) generated across the power terminals (310, 312), when only the excited coils are coupled via two diodes across the output power lines, is of larger amplitude than that shown in waveform I, when all the coils are connected in series across the power lines.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Physics & Mathematics (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Electromagnetism (AREA)
• Rectifiers (AREA)
• Control Of Eletrric Generators (AREA)
• Linear Motors (AREA)
• Coils Of Transformers For General Uses (AREA)
• Ac-Ac Conversion (AREA)

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• 2005
  • 2005-01-07 US US11/030,933 patent/US7397152B2/en not_active Expired - Fee Related
  • 2005-03-15 AU AU2005222959A patent/AU2005222959B2/en not_active Ceased
  • 2005-03-15 EP EP05725553.1A patent/EP1741177B1/en not_active Expired - Lifetime
  • 2005-03-15 ES ES05725553T patent/ES2769243T3/es not_active Expired - Lifetime
  • 2005-03-15 CA CA2537107A patent/CA2537107C/en not_active Expired - Fee Related
  • 2005-03-15 JP JP2007504004A patent/JP4829214B2/ja not_active Expired - Fee Related
  • 2005-03-15 WO PCT/US2005/008463 patent/WO2005089281A2/en not_active Ceased
• 2006
  • 2006-05-03 NO NO20061963A patent/NO20061963L/no not_active Application Discontinuation

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