Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K3/00—Details of windings
  • H02K3/04—Windings characterised by the conductor shape, form or construction, e.g. with bar conductors
  • H02K3/12—Windings characterised by the conductor shape, form or construction, e.g. with bar conductors arranged in slots
  • H02K3/16—Windings characterised by the conductor shape, form or construction, e.g. with bar conductors arranged in slots for auxiliary purposes, e.g. damping or commutating
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K17/00—Asynchronous induction motors; Asynchronous induction generators
  • H02K17/02—Asynchronous induction motors
  • H02K17/28—Asynchronous induction motors having compensating winding for improving phase angle

Definitions

• the present invention relates to single and polyphase electromagnetic induction machines having regulated polar magnetic symmetry.
• the single-phase, dynamoelectric machine which can be a motor or a generator, includes a rotatable rotor usually in the interior space defined by a hollow cylindrical stationary stator. Both the rotor and stator have slots therein facing each other within which are disposed windings. The rotor windings may be connected at each end to form a squirrel cage or brought out via slip rings.
• two windings are electrically connected in series and are circumferentially placed around the interior surface of the hollow stator core to form magnetic poles.
• a capacitor is coupled in parallel with one winding and this combination is connected in series with the second winding.
• the size of the capacitor is such that a quasi-series resonant circuit is formed with the second winding and a quasi-parallel resonant circuit is formed with the first winding.
• the serially connected stator windings are connected across the single-phase or polyphase power input terminals.
• a balanced rotating magnetic field is generated wherein the Q factor of the circuit is continually adjusted by the admittance of the rotor windings. Because of the interaction between the quasi-series resonant circuit and the quasi-parallel resonant circuit, unused energy delivered to the rotor in the form of magnetic flux is returned via one of the stator windings and, upon collapse of the magnetic field, the resulting voltage is stored in the capacitor.
• the capacitor delivers stored energy to the appropriate winding to compensate for the additional power requirements and maintain a balanced distribution of magnetic flux circumferentially rotating around the rotor.
• the method of generating torque from an a.c. power source includes the step of forming a quasi-double-resonant circuit, including a capacitive element which is connected in parallel to one of the inductive elements and this combination connected in series with the other inductive element, providing a rotatable inductive element adapted to deliver torque; applying power across the two serially connected, stationary inductive elements, magnetically coupling all the inductive elements and producing a balanced rotating magnetic flux wave via the mechanism described above with respect to the quasi-serial and quasi-parallel resonant circuits.
• the polyphase induction motor includes three pairs of serially connected stator windings wherein a capacitor is coupled in parallel to one of the windings in each pair and the combination coupled in series with other winding in the pair to form a quasi-doubleresonant circuit.
• a further embodiment of the polyphase motor includes three primary stator windings which receive, via one of the power input terminals, a different phase of the three-phase power applied to the motor.
• Three secondary stator windings are circumferentially interleaved in the stator between the three primary stator windings and are magnetically coupled to the primary windings but are not directly connected to the power input terminals of the motor.
• a capacitor is provided for each pair of secondary stator windings and the respective capacitor is in parallel with at least one secondary stator winding. Each capacitor is sized to form a quasi-parallel floating resonant circuit with the parallel connected secondary stator winding.
• Figure 1 is a diagrammatical representation of a single-phase motor with regulated magnetic polar symmetry.
• Figure 2 is an electrical schematic diagram of the single-phase motor of Figure 1, but the circuit does not include representations of the stator core material or the rotor material.
• Figure 3A is an oscilloscope trace of the voltage waveforms associated with each of the stator windings (and the capacitor) when the oscilloscope is set to trigger on the positive going slope of the supply line voltage.
• Figure 3B is an oscilloscope trace of the current waveforms associated with each of the stator windings and the capacitor when the scope is also set to trigger on the positive going slope of the supply line voltage.
• Figure 4A is an oscilloscope trace of the line supply voltage V L and the line current II at approximately full load for a 1/4 horsepower motor supplied with 120 volts a.c.
• Figure 4B is an oscilloscope trace of the line supply voltage a"nd the line current at approximately half-load.
• Figure 4C is an oscilloscope trace of the line supply voltage and the line current at no-load.
• Figure 5 is a time-lapse illustration of an oscilloscope trace of the line supply voltage and line current over the entire load range of the motor.
• Figure 6 is a graphic representation of the rotor current versus slip speed in the induction motor of Figure 1.
• Figure 7A shows the effect of resistance on the shape of a series resonance curve .
• Figure 7B shows the effect of L/C ratio on the shape of a series resonance curve.
• Figure 7C shows the parallel resonance curve.
• Figure 8 is a diagrammatical representation of a polyphase induction motor with regulated polar magnetic symmetry including a quasi-double-resonant equalizer circuit.
• Figure 9 is an electrical schematic diagram of the polyphase, quasi-double-resonant induction motor of Figure 8 wherein the stator resonant windings are connected in a ⁇ configuration with respect to the source.
• Figure 10 is an electrical schematic diagram of the polyphase, quasi-double-resonant induction motor of Figure 8 wherein the stator resonant windings are connected in wye configuration with respect to the source.
• Figures 11A through 11L are diagrams showing the electric current and magnetic conditions in a two-pole, three-phase induction motor for each 30° of a complete cycle.
• Figure 12A is an oscilloscope trace of the line supply voltage V L and the line current II of one phase at full load in a 40 horsepower, three-phase, quasi-double-resonant induction motor.
• Figure 12B is an oscilloscope trace of the line supply voltage and the line current of one phase at 75% load for the motor of Figure 12A.
• Figure 13 is a switching network for changing rotation of the double-resonant polyphase motor of Figure 8.
• Figure 14A is a diagrammatical representation of a polyphase induction motor with regulated magnetic symmetry with a parallel floating quasi-resonant circuit.
• the primary stator windings are connected in a wye configuration to the source, its parallel floating windings are connected in a wye configuration, and the capacitors in the floating circuit are connected in a ⁇ configuration.
• Figure 14B is an electrical representation of a polyphase induction motor with regulated polar magnetic symmetry including a parallel floating quasi-resonant circuit with its primary stator windings connected in a wye configuration to the source, its parallel floating winding are in a wye configuration and the capacitors in the floating circuits are in a ⁇ configuration.
• Figure 15 is an electrical diagram of the polyphase, parallel floating quasi-resonant induction motor wherein the primary stator windings are in a wye configuration with respect to the inputs and the parallel floating stator windings and capacitors are in a ⁇ configuration.
• Figure 16 is an electrical schematic diagram of a polyphase induction motor with regulated polar magnetic symmetry having a floating quasi-parallel resonant design with its primary phase, stator windings connected in a ⁇ configuration with the source, its parallel floating resonant stator windings connected in a wye configuration and the capacitors in the floating circuits are in a ⁇ configuration.
• Figure 17 is an electrical schematic diagram of a polyphase, parallel floating induction motor wherein the primary stator windings are in a ⁇ configuration, the secondary stator or parallel floating windings are in a ⁇ configuration and the capacitors in the floating circuits are in a wye configuration.
• Figure 18A is an oscilloscope trace of the line supply voltage and the line current of one phase at full load in a
• Figure 18B is an oscilloscope trace of the line supply voltage and the line current of one-phase at 75% load in the quasi-parallel floating resonant induction motor.
• Figure 19 is a phaser diagram of an ideal doubleresonant motor with quasi-series resonance at full-load.
• Figure 20 is the phaser diagram of a 1/3 HP motor after conversion to a quasi-double-resonant motor with quasiseries resonance at full-load.
• Figure 21 is a phaser diagram of an ideal doubleresonant motor with parallel resonance at no-load.
• Figure 22 is the phaser diagram of a 1/3 HP motor after conversion to a quasi-double-resonant motor with quasiparallel resonance at no-load.
• Figure 23 is an electrical schematic diagram of a double-resonant motor incorporating the teachings of the present invention and used in conjunction with explaining Figure 19 through 22.
• Figure 24 is a representation of the magnetomotive force in the air gap surrounding the circumference of the rotor in a quasi-double-resonant motor. Each wave represents the force (flux) in the air gap over the circumference of the rotor at a given time in one cycle of the input power.
• FIG. 1 is a diagrammatical representation of a single- phase a.c. induction motor in a squirrel cage rotor configuration.
• Stator ST 1 is a generally hollow, cylindrically shaped, slotted structure of laminated sheet steel.
• a rotor RO 1 is rotatably disposed in the interior space of the stator and is of like material.
• the stator is shown as having four polar areas or teeth TA 1 , TB 1 , TC 1 , TD 1 , protruding from a return magnetic path or back iron BI 1 of stator ST 1 .
• the actual number of poles or teeth is dependent upon physical size, horsepower and rotational speed.
• the physical dimensions of the motor and its integral parts are only graphically represented and the illustration does not necessarily indicate an optimum physical construction.
• the stator or primary is shown as having two windings WA and WB commonly referred to as "wound on" teeth TA 1 TB 1 , TC 1 , and TD 1 .
• the stator windings are disposed in axially extending slots on the interior of the stator.
• rotor windings WC are disposed in axially extending slots on the periphery of rotor RO 1 .
• Stator windings WA and WB are connected in series at midpoint MP and the serial circuit is connected across power input terminals L 1 and L 2 .
• Midpoint connection MP is passively coupled to input terminal L 1 by means of two capacitors CA and CB.
• Capacitor CB is permanently coupled while capacitor CA is removed from the circuit by means of centrifugal switch CS when the motor reaches a predetermined speed during a start-up operation.
• capacitor CA and centrifugal switch CS are omitted from the circuit.
• Rotor winding WC is closely magnetically coupled to stator windings WA and WB by means of the four polar areas or teeth TA 1 , TB 1 , TC 1 , TD 1 , air gap AG, the magnetic material of rotor RO 1 , and the return magnetic path or back iron BI 1 .
• the present invention provides a regulatory circuit that equalizes the polar magnetic regions about the rotor regardless of the magnitude of the electromotive force or its wave form.
• This axisymmetrical alignment of the magnetic flux reduces space harmonics in the air gap between stator and rotor allowing a greater net-usable flux to link the rotor windings.
• This symmetry reduces the possibility of negative sequential currents being established in the rotor and results in a higher torque rating for the motor without increasing hysteresis loss due to magnetic saturation.
• Increased efficiency is also achieved through intermediate transfer and storage of energy and a shorter current rise time in the resonant circuit as opposed to the induction/resistance ratio in prior art induction motors.
• the amount of force or mechanical torque exerted on the rotor is based on the equation:
• F B1I (1)
• B the magnetic flux density linking the rotor windings
• 1 the physical length of the windings
• I the current flowing in the windings.
• the greatest energy loss in a squirrel-cag, induction motor is heat produced as current flows through the windings due to the resistance of the windings. The amount of loss is based on the formula:
• I is the Current in amperes, and R the resistance in ohms; therefore, by increasing the net-usable flux linking the rotor (e.g., increasing B and maintaining F and 1 constant in (1)), the current component I is reduced in the rotor resulting in less heat, longer bearing life and increased efficiency.
• the reduction of space harmonics also reduces the eddy current effect present in all induction motors and generators. Since the resonant circuit does not return unused energy to the source but rather saves it primarily in the capacitor, it has an energy efficient topology due to its transfer of energy in phase to the rotor and transfer between bifilar phase pairs.
• Conductance G of a resonant circuit is governed by the equation:
• Y is the admittance (the reciprocal of impedance) or overall ability to pass an alternating current
• G equals the circuit conductance in seimons (the reciprocal of resistance) or the ability of a pure resistance to pass electric current
• B equals susceptance in seimons (the reciprocal of reactance) or the ability of inductance or capacitance to pass alternating current.
• B eq - B c - B L is the net equivalent susceptance in (3).
• the admittance of a circuit is equal to the conductance (the real component) plus the susceptance (the imaginary component):
• FIGS 19 through 22 contain vector diagrams for the quasi-double-resonant motor discussed in Tables 1, 2 and 3.
• Figure 23 is an equivalent circuit for that motor for use in considering the vector diagrams of Figures 19 through 22. It will be apparent to those skilled in the art that at no-load the conditions exist wherein the currents in WB and CB are near equal and 180° apart, a condition referred to as parallel resonance.
• Equation (6) shows that an RLC circuit can be brought into resonance at a certain frequency by varying either the inductance or capacitance. It should be noted that the resistance of the series resonant circuit has no bearing on the resonant frequency f r .
• the instantaneous energy (1/2 CV 2 ) is stored in the capacitor as a voltage increase, while the energy in the inductance (1/2 LI 2 ) is stored as a current increase, alternately, twice each cycle. Therefore, an exchange of reactive energy takes place between the inductance and capacitance.
• the source of emf (the energy supplied to the motor) is required to supply only the difference between the reactive energy of the inductance and the reactive energy of the capacitance. This accounts for the net reactance of a series circuit being the difference between the inductive and capacitive reactance:
• the Q factor of a resonant circuit is the ratio of reactive power to power displaced in the resistance.
• the resistance is a representation of the mechanical load on the motor.
• the resonance curve of the parallel branch or quasiparallel resonant circuit (CB and WB) is shown in Figure 7C and is generally the inverse function of the series resonant curve. Since the Q of the parallel winding has the inverse effect on the circuit as compared with the Q of the series winding, the quasi-parallel resonant circuit is balanced with the quasi-series resonant circuit and any instantaneous energy imbalance in one of those circuits is very quickly compensated for by the other circuit. This produces the balanced rotating magnetic flux wave around the rotor, as illustrated in Figure 24.
• the sensitivity of a resonant circuit can be increased by an increase in the Q of the circuit or decreased by a decrease in its Q.
• critical damping is the damping of the movement of a pointer in a meter to keep the pointer from oscillating. It is possible then to capitalize on this characteristic of resonance in the quasi-double-resonant induction motor.
• energy transfer to the rotor can be controlled, as well as energy supplied from the source. In-rush current can be reduced since Q is the admittance magnification factor, and an even distribution of power from all associated motor windings can be maintained.
• Figures 3A and 3B show certain phase relationships for a single-phase motor with regulated magnetic polar symmetry.
• the motor is a double-resonant 1/4 horsepower motor with 120 volts a.c. input.
• Figure 3A is a representation of the voltages across WA and WB, respectively. The representation clearly shows the phase relationships between V WA , V WB and V CB and this phase relationship creates a balanced rotating magnetic field.
• the traces in both Figures 3A and 3B begin at the positive going slope of the voltage supplied to the motor. These have shown that V WA lags the supply voltage V L by approximately 45o.
• This wave rotates from the horizontal polar axis already established in the motor magnetic material, to a vertical position centered through stator teeth TC 1 and TD 1 , their respective air gaps, the rotor magnetic material, and the return magnetic path or back iron BI 1 .
• This rotating flux wave cuts the rotor windings WC in rotor RO 1 which causes current to flow and consequently establishes a magnetic field in the rotor which tries to align itself with the rotating magnetic flux wave established in the stator ST 1 magnetic material.
• Figure 3B is a representation of the current wave forms I CB , I WA and I WB which flow in capacitor CB and stator windings WA and WB, respectively.
• I WA and I WB display a full 90° phase shift with respect to each other and I CB is 180° out of phase with respect to I WB .
• Representations in Figures 3A and 3B have the same time base; therefore, a direct comparison between the voltages and currents can be made.
• the ability of the quasi-series resonant circuit to produce a voltage higher than the applied voltage is one of the most important characteristics of the circuit. This is possible due to its ability to store unused energy in WA and QB.
• Q is the magnification (admittance) factor which determines how much the voltage across WA and CB can increase above the applied voltage.
• Figures 4A, 4B and 4C are representations of the current (line current I L ) relationship with respect to the applied electromotive force (line voltage V L ) in a single- phase motor with regulated magnetic polar symmetry of the same type as referred to with reference to Figures 3A and 3B.
• Figure 4A is at approximately full load.
• Figure 4B is at approximately half load and Figure 4C at no-load.
• line current I L remains closely in phase with the line voltage V L . Consequently, the power factor of the circuit is near unity over the entire load range.
• Figure 5 is a time exposure representation of the entire load range for the single-phase motor of Figures 3A and 3B.
• Figure 5 shows the phase relationship of line voltage and current throughout the entire load range.
• I L is non-sinusoidal, its RMS or effective value is considerably higher than that of a sine wave with the same peak value and results in a magnetic field that remains high for a long time without saturating the iron. This maintains high torque and reduces the hysteresis losses in the magnetic core material.
• the motor operates in the linear portion of the BH curve.
• the present invention virtually eliminates the preponderance of current problems associated with conventional induction motors and generators. It is to be noted that, although the description of the invention is made in reference to a motor, the device can operate as a generator if torque is applied to the rotor and the device is driven above synchronous speed.
• the generator need not be supplied with reactive power since the power factor of the device is unity.
• the claims are meant to encompass this usage of the device.
• the conventional polyphase motor has by design a rotating magnetic flux wave which is unregulated and under certain operating conditions it can become distorted non- symmetrized.
• the present invention provides a regulatory circuit to equalize the polar magnetic regions regardless of the magnitude of electromotive force or its wave form. This axisymmetrical alignment of the magnetic flux reduces undesired space harmonics in the air gap between stator and rotor allowing a greater net-usable flux to link the rotor windings as illustrated in Figure 24.
• Magnetic symmetry reduces the hazards of negative sequence currents being established in the rotor and results in a higher torque value without increasing hysteresis loss due to magnetic saturation. Increased efficiency is also achieved through intermediate transfer and storage of energy and a shorter current rise time in the resonant circuit as opposed to that in a standard motor.
• the polyphase motors are discussed below.
• Some important characteristics of the quasi-double-resonant circuit are its check and balance network, its ability to produce a rotating magnetic vector, and the ability of the circuit to act as a phase doubler. Therefore, coil placement should be so as to enhance the rotating sinusoidal magnetic wave.
• One example of proper coil placement is shown in Figure 8, but it should be understood that coil arrangement and number of poles can be varied so as to produce a motor having different operating characteristics.
• the invention is not limited to the illustrated embodiment in Figure 8.
• the vector sum of the voltage drops across the capacitor and inductor of the quasi-series branch equate to line voltage ( Figure 19) and further the vector sum of the currents of the quasi-parallel branch equate to line current ( Figure 19).
• FIGs 9 and 10 Two electrical schematics of the quasi-double-resonance polyphase motor are illustrated in Figures 9 and 10.
• the configuration shown in Figure 9 is diagrammatically illustrated in Figure 8.
• Figure 8 the windings of each quasi-resonant circuit are separated by 90° electrical. It needs to be understood that this angle can be adjusted to produce different torque and operating characteristics for the motor.
• Figure 8 is a diagrammatical representation of a quasidouble-resonant polyphase a.c. induction motor of the squirrel cage design. It has a sheet-steel laminated stator ST 2 and a rotor RO 2 of like material.
• stator is shown as having 12 poles or teeth TA, TB, TC, etc., through and including TL protruding from a return magnetic path or back iron BI 2 ; the actual number of teeth being dependent upon physical size, horsepower, and rotational speed.
• the physical dimensions of the motor and its integral parts are for graphical representation only and do not indicate its optimum physical construction.
• the stator is shown as having three sets of quasidouble-resonant circuits or one set per input phase.
• the first quasi-double-resonant circuit consists of serially connected windings WBa and WAa are wound on teeth TA, TB, TC, and TD with the windings being connected in series atmidpoint MPa across inputs A and B.
• the midpoint is then passively coupled to input terminal A by means of capacitor CBa, i.e., in parallel to winding WBa and in series with WAa.
• the rotor winding WC is magnetically coupled to the stator windings WBa and WAa by means of the four polar areas or teeth TA, TB, TC, TD, their respective air gaps AG, the rotor magnetic material RO 2 and the return magnetic path or back iron BI 2 .
• the second set of quasi-resonant windings WBb and WAb are connected to input terminals A and C. They are wound on teeth TE, TF, TG and TH and are likewise connected in series at midpoint MPb, the connection of which is passively coupled to input terminal B by means of capacitor CBb.
• the rotor winding WC is also' closely coupled to the stator windings WBb and WAb by means of the four polar areas or teeth TE, TF, TG, TH, their respective air gaps AG, the rotor magnetic material RO 2 and the return magnetic path or back iron BI 2 .
• the third set of quasi-resonant windings WBc and WAc are connected to input terminals A and C.
• the midpoint connection MPc is passively coupled to input terminal C by means of capacitor CBc.
• the secondary winding WC is closely coupled to the primary windings WBc and WAc by means of the four polar areas or teeth TI, TJ, TK, TL, the irrespective air gaps AG, the rotor magnetic material RO 2 and the return magnetic path or back iron BI 2 .
• FIGS 11A through 11L illustrate current and flux paths through a standard induction motor for a full revolution in increments of 30°. These figures are presented to help explain the very complex conditions that exist in the motor and particularly in the quasi-double- resonant induction motor. Although both prior art induction motors and the present invention develop a rotating magnetic flux wave, the flux wave in the conventional motor is not necessarily symmetrical or balanced under all operating conditions as is the wave in the present quasi-double- resonant motor.
• solid lines and dashed lines represent current flow through the stator windings and the dash-dot-dash lines represent the magnetic flux paths through the stator and the rotor.
• the quasi-double-resonant induction motor for example, has a winding circumferentially interleaved between the stator windings coupled to power input terminals A and B.
• windings which are serially connected with respect to the capacitor are identified by “A” in the term “WAa” whereas the lower case letter refers to the phase of the winding.
• stator windings WAa and WBa both these stator windings are serially connected together with respect to one another because of the term "a,” winding WAa is serially connected to capacitor CBa and stator winding WBa is parallelly connected to capacitor CBa.
• one of the physical differences between the conventional motor and the motor of the present invention is that the present invention includes an additional winding interposed between the two primary stator windings.
• the circumferential disposition of teeth TA, TK and TE is shown in the figure. Referring jointly to that figure and Figure
• power input phase A is applied to winding WBa wound on tooth TA at the same time that current flows through winding
• winding WAc is wound on tooth TK, as well as tooth TL, and that winding is circumferentially interleaved between windings WBa and WBb.
• FIG 11B illustrates that the rotor has turned 30o clockwise due to the rotating magnetic flux wave.
• flux waves cut stator winding WAc wound on tooth TK as well as tooth TL.
• the energy stored in capacitor CBa begins to discharge into winding WBa.
• This energy together with that stored in the magnetic field of WAa is transferred to winding WBa setting up a magnetic flux pattern through teeth TA and TB, their respective air gaps, the rotor return magnetic material and the return magnetic path or back iron BI.
• This flux path would be similar to that shown in Figure 11L that illustrates in general sense the motor at 330°.
• a potential is also building in a positive direction with respect to terminal C, thus causing current to flow in stator winding WAc in an attempt to charge capacitor CBc.
• the magnetic field in WBc begins to collapse and the energy stored in WBc together with the energy now flowing in winding WAc is stored in capacitor CBc and in the new magnetic field in WAc.
• This moves the position of the magnetic flux wave 30° clockwise to that shown in Figure 11A at 0°.
• This process continues as long as the polyphase source is applied to the motor terminals A, B and C . Consequently with each new cycle of alternating current, the windings in the motor marked with the prefix WA, i. e .
• WAx where x is a, b or c (the windings serially connected to the capacitors), pass an electric current in an attempt to charge their respective capacitors. Therefore, a magnetic field is established in these windings and an electric field or potential is developed across the associated capacitors.
• Figures 12A and 12B are representations of the relationship between the line current (I ⁇ J and the applied electromotive force (line voltage VjJ for one phase of the three phase power line connected to the quasi-double- resonant, polyphase motor, which is a double-resonant 40 horsepower motor.
• the power input was 460 volts three- phase.
• Figure 12A is the relationship of line voltage with respect to line current at approximately full load.
• Figure 12B is the relationship of line voltage with respect to line current at approximately 75% load. It should be noted that the line potential V L is in phase with the line current I L and that the power factor of the circuit is near unity over the entire load range as illustrated in Figure 5.
• I L is non-sinusoidal, its RMS or effective value is considerably higher and results in a magnetic energy transfer that is consequently more intense than that produced by a standard sine wave of current. This reduces the hysteresis loss in the magnetic core material due to the fact that the current does not drive the core into saturation to accomplish the same work as some conventional motors, thereby reducing the coercive force or energy needed to return the magnetic material to 0. The reduction of harmonics also tends to reduce eddy current losses in the magnetic core material.
• Switching of rotation of the motor is accomplished by two reversing contactors (C1, C2) and (C3, C4). C1 and C3 are closed while C2 and C4 remain open for one direction of rotation. The reverse switching situation exists for rotation in the opposite direction.
• the network basically consists of two reversing motor contactors connected such that the top two reverse the phase sequence and bottom two reverse the windings with respect to the phase change.
• a balanced rotating magnetic flux wave is by connecting the primary stator windings directly to the input polyphase source, e.g., winding, WAa to terminal A and the neutral point fdrming a wye configuration as in Figure 14B; a secondary stator winding, being connected in a ⁇ ( Figure 15) or wye ( Figure 14B) configuration and left floating or closely magnetically coupled to the primary stator winding, e.g., WBa'.
• the angular displacement of each winding can be modified to give the motor different operatiing characteristics.
• the invention is not limited to any set angular displacement of the windings.
• the parallel floating concept is shown in the electrical schematic of Figures 14A, 14B, 15, 16 and 17. Since the floating stator windings (secondary) are only inductively coupled to the power source, turns of the secondary can be chosen so as to allow the most economical amount of capacitive reactance to be used.
• the capacitor CBx, x being a, b or c, is connected in parallel with WBx so as to form a parallel resonant circuit, the Q factor of which is determined similar to that of the quasi-double- resonant circuit.
• the combination of the floating quasi-parallel resonant circuit and phase winding operate in similitude to that of the quasi-double-resonant circuit. Energy is transferred magnetically between bifilar pairs and the rotor winding.
• the source sees the primary winding as one having 0 reactance or unity power factor and therefore has to supply only the power required by the mechanical torque of the rotor and the resistance of the circuit.
• the circuit allows for change in rotor rotation by simple reversal of the incoming phase sequence.
• a dual voltage primary can also be used without changing the capacitive reactance of the resonant circuit.
• the quasi-double-resonant polyphase motor can be used in applications which require greatly reduced inrush current control but do not need to be reversible in their operation.
• the floating parallel resonant motor is more suitable.
• the secondary stator windings WBx can also be connected as though they were individual single-phase circuits. Each of these connections gives the motor different operating characteristics, such as that achieved with wye- ⁇ starting etc.
• Figure 14A is a diagrammatical representation of a parallel-resonant or parallel floating polyphase, a.c. induction motor having a squirrel cage rotor design.
• the motor includes a sheet-steel laminated stator ST 2 and a rotor RO of like material.
• the stator is shown as having twelve poles or teeth TA, TB, TC, etc., through and including TL protruding from a return magnetic path or back iron BI 2 ; the actual number of teeth being dependant upon physical size, horsepower and rotational speed for the motor.
• the physical dimensions of the motor and its integral parts are only graphically represented herein and hence the illustrations do not indicate the motor's optimum physical construction.
• the stator includes three primary phase windings which can be connected to the source in a ⁇ or wye configuration and three sets of floating parallel resonant circuits, one set per input phase.
• the three primary phase windings WAa', WAb' and WAc' are connected to input terminals A, B and C in the wye configuration.
• Three secondary stator windings WBa', WBb' and WBc' are part of the floating parallel resonant circuits and are connected in Figure 14 in a wye configuration and in parallel with three capacitors CBa', CBb' and CBc' that are connected in a ⁇ configuration with respect to each other.
• capacitor CBb' is parallel to secondary stator windings WBb' and WBc'; however, as shown in Figure 15, the parallel floating capacitor need only be parallel to one secondary stator winding to form the floating parallel resonant circuit.
• the floating parallel circuitry consists of secondary windings WBa', WBb' and WBc' and capacitors CBa', CBb' and CBc'.
• the secondary stator windings are wound on teeth TC, TD, TG, TH, TK and TL, respectively.
• the primary stator phase windings WAa', WAb' and WAc' are wound on teeth TA, TB, TE,TF, TI and TJ, respectively.
• the secondary windings are circumferentially interleaved between the primary windings, e.g., WBa', is between WAa' and WAb'.
• the floating circuit is magnetically coupled to the primary phase windings and rotor RO.
• This current waveform is very desirable since the RMS energy level is higher than that of a sinusoidal wave resulting in more energy transfer within the same time frame. Thus a lower current component is needed resulting in less copper losses in the associated motor winding .
• Another important characteristic is the symmetry of the magnetic flux wave cutting the winding WC in the rotor RO. This symmetry or physiomagnetic regulation created by intermediate exchange of energy between bifilar windings results in a higher net magnetic coupling of the rotor and therefore reduced losses.
• This particular topology also allows for direct motor reversal without reconfiguration of the motor windings or elaborate switching mechanisms. Since the parallel branch windings are floating they are similar to that of the secondary of a transformer. This allows for a selection in both turns and connection which will reduce the cost and physical size of the capacitors needed for the appropriate Q factor.
• Table 1 compares the performance of an original 1/3 HP Marathon single-phase induction motor and the same motor rewound incorporating the quasi-double resonant technology:
• Table 2 gives a comparison of the wind specifications of the original Marathon motor with those the quasi-double resonant motor.
• Table 3 gives test data on the Marathon motor after conversion of the motor to quasi-double-resonant circuitry.
• Table 3 shows that the power factor stays near unity throughout the entire load range (97.27 at no-load to 99.9 at full-load). Because of the accuracy of the test equipment, it is easily seen that the total of the watt measurements for each component equals the amount of wattage taken from the power supply. The energy (watts) in the two windings is nearly equal, at both no-load and full-load, even though the voltage, current and power factor are not equal.
• Table 1 shows that, after the conversion to quasi-double-resonant circuitry, the motor has less slip, higher efficiency, higher power factor, reduced temperature, lower sound level, reduced in-rush current and increased starting torque.

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• Synchronous Machinery (AREA)
• Magnetic Treatment Devices (AREA)
• Control Of Ac Motors In General (AREA)

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Publications (1)

Family

ID=25412953

Family Applications (1)

Country Status (8)

Cited By (2)

Families Citing this family (1)

Citations (10)

• 1987
  • 1987-08-12 AU AU78765/87A patent/AU7876587A/en not_active Abandoned
  • 1987-08-12 EP EP87905824A patent/EP0279842A1/en not_active Withdrawn
  • 1987-08-12 JP JP62505433A patent/JPH01501356A/ja active Pending
  • 1987-08-12 BR BR8707441A patent/BR8707441A/pt unknown
  • 1987-08-12 WO PCT/US1987/001929 patent/WO1988001803A1/en not_active Application Discontinuation
  • 1987-08-25 ZA ZA876298A patent/ZA876298B/xx unknown
  • 1987-08-27 IL IL83667A patent/IL83667A0/xx unknown
• 1988
  • 1988-04-27 KR KR1019880700450A patent/KR880701993A/ko not_active Application Discontinuation

Patent Citations (10)

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