Patents by Inventor Krishnan Ramu

Krishnan Ramu has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 8319456
    Abstract: A method for controlling a multi-phase motor includes withholding energization of a first phase of the motor for a non-zero period when the first phase's dwell time begins. Energization of the first phase is activated upon the expiration of the non-zero period. Energization of the first phase is deactivated for the remainder of the dwell time at a deactivation time occurring before or at the expiration of the dwell time.
    Type: Grant
    Filed: August 13, 2008
    Date of Patent: November 27, 2012
    Assignee: Ramu, Inc.
    Inventor: Krishnan Ramu
  • Patent number: 8264182
    Abstract: A power factor correction system includes a rectifier that rectifies the voltage of an alternating current (ac) power source to produce a voltage waveform that transitions, in a half sinusoid, from a minimum amplitude to a maximum amplitude and back to the minimum amplitude twice in the period of the ac power source. A phase winding of a motor conveys current induced by the voltage waveform, and a regulator regulates the flow of the current conveyed by the phase winding for storage as energy in a storage component.
    Type: Grant
    Filed: August 13, 2008
    Date of Patent: September 11, 2012
    Assignee: Ramu, Inc.
    Inventor: Krishnan Ramu
  • Patent number: 8203302
    Abstract: A single controllable switch (509) drive system for regulating the speed of a two-phase switched reluctance machine (TPSRM) (700) rotor may include a speed control feedback loop (970) component that uses an established speed control signal and a signal indicative of the rotor's speed to dynamically adjust a first parameter. And a current control feedback loop (976) component that uses an established current control signal and a signal indicative of the current flowing through a stator winding (505,508) of the TPSRM to dynamically adjust a second parameter.
    Type: Grant
    Filed: October 3, 2005
    Date of Patent: June 19, 2012
    Assignee: Virginia Tech Intellectual Properties, Inc.
    Inventors: Krishnan Ramu, Keunsoo Ha, Sung-Yeul Park
  • Publication number: 20120104980
    Abstract: A method of operating an electrical machine having first and second phase windings. The method includes: (1) applying positive first current to the first phase winding while the first phase winding's back electromotive force (emf) is positive; (2) applying negative second current to the first phase winding while the first phase winding's back emf is negative; and (3) applying positive third current to the second phase winding while the second phase winding's back emf is positive. The first current is conducted through a circuit composed of a battery, the first phase winding, and a first switch. The second current is conducted through a circuit composed of a first capacitive storage element, the battery, the first phase winding, and a second switch, and the third current is conducted through a circuit composed of the battery, the second phase winding, and a third switch.
    Type: Application
    Filed: November 2, 2011
    Publication date: May 3, 2012
    Inventor: Krishnan RAMU
  • Publication number: 20120104982
    Abstract: An electrical machine rotor includes a flux-conducting portion and a flux-inhibiting portion. The flux-conducting portion is conducive to conveying an electromagnetic flux and has a plurality of salient rotor poles and a portion of back material. The flux-inhibiting portion is less conducive to conveying an electromagnetic flux than the flux-conducting portion and is disposed entirely outside the boundaries of the rotor poles.
    Type: Application
    Filed: October 31, 2011
    Publication date: May 3, 2012
    Inventor: Krishnan RAMU
  • Publication number: 20120104895
    Abstract: An electromagnetic machine stator has a common pole and a plurality of excitation poles. Each excitation pole has a coil wound around it for inducing a magnetic flux through the excitation pole. The common pole that does not have a coil wound around it for inducing a magnetic flux. A flux barrier, disposed within the common pole, inhibits the flow of flux from one part of the common pole across the flux barrier to another part of the common pole. The flux barrier is less conducive to the flow of flux than is the common pole.
    Type: Application
    Filed: October 31, 2011
    Publication date: May 3, 2012
    Inventor: Krishnan RAMU
  • Publication number: 20120104984
    Abstract: An electrical device has a capacitive storage element and first and second switches. The capacitive storage element and first and second switches are interconnected such that when interconnected with a direct current (dc) voltage supply and first and second windings of an electrical machine: (1) a first operational state exists in which conductive states of the first and second switches cause the dc voltage supply to conduct current through the first winding and the first switch and conduct current through the first and second switches and the second winding, respectively, thereby storing energy within the first and second windings, and (2) a second operational state exists in which non-conductive states of the first and second switches cause each of the first and second windings to discharge stored energy by conducting current through the capacitive storage element, thereby storing energy in the capacitive storage element.
    Type: Application
    Filed: November 2, 2011
    Publication date: May 3, 2012
    Inventor: Krishnan RAMU
  • Publication number: 20120104988
    Abstract: A power converter having a first switch and a first unidirectional current device that conducts current unidirectionally. The first switch and first unidirectional current device are interconnected such that when interconnected with a dc voltage supply, battery, and first phase winding of an electrical machine: (1) a first operational state exists in which a conductive state of the first switch causes the dc voltage supply to conduct current through the first switch and first phase winding, so as to store energy within the first phase winding and (2) a second operational state exists in which a non-conductive state of the first switch causes the first phase winding to discharge its stored energy by conducting current through the first unidirectional current device and battery, so as to store energy in the battery.
    Type: Application
    Filed: November 2, 2011
    Publication date: May 3, 2012
    Inventor: Krishnan RAMU
  • Publication number: 20120104879
    Abstract: An electrical machine rotor or stator having a plurality of salient poles and a barrier that inhibits the flow of air along an axial path between the environment outside the rotor or stator and the space between adjacent pairs of the poles. The barrier serves to reduce acoustic noise.
    Type: Application
    Filed: October 31, 2011
    Publication date: May 3, 2012
    Inventor: Krishnan RAMU
  • Publication number: 20120056570
    Abstract: A method for collecting operational parameters of a motor may include controlling the energization of a phase winding of the motor to establish an operating point, monitoring operational parameters of the motor that characterize a relationship between the energization control applied to the motor's phase winding and the motor's response to this control, and collecting information of the operational parameters for the operating point that characterizes the relationship between the applied energization control and the motor's response. The collected information characterizing the relationship between the applied energization control and the motor's response may be employed by a neural network to estimate the regions of operation of the motor. And a system for controlling the operation of motor may employ this information, the neural network, or both to regulate the energization of a motor's phase winding during a phase cycle.
    Type: Application
    Filed: November 15, 2011
    Publication date: March 8, 2012
    Applicant: Virginia Tech Intellectual Properties, Inc.
    Inventors: Christopher Allen Hudson, Nimal Lobo, Krishnan Ramu
  • Patent number: 8080964
    Abstract: A method for collecting operational parameters of a motor may include controlling the energization of a phase winding of the motor to establish an operating point, monitoring operational parameters of the motor that characterize a relationship between the energization control applied to the motor's phase winding and the motor's response to this control, and collecting information of the operational parameters for the operating point that characterizes the relationship between the applied energization control and the motor's response. The collected information characterizing the relationship between the applied energization control and the motor's response may be employed by a neural network to estimate the regions of operation of the motor. And a system for controlling the operation of motor may employ this information, the neural network, or both to regulate the energization of a motor's phase winding during a phase cycle.
    Type: Grant
    Filed: October 31, 2005
    Date of Patent: December 20, 2011
    Assignee: Virginia Tech Intellectual Properties, Inc.
    Inventors: Christopher Allen Hudson, Nimal Lobo, Krishnan Ramu
  • Publication number: 20110260672
    Abstract: A switched reluctance machine having salient stator and rotor poles. Alternating ones of the stator poles having windings and the others having permanent magnets attached on their pole faces. The alternate stator pole windings are provided with polarities that are suitable for unidirectional and bidirectional current operation of the switched reluctance machine. The alternate poles with permanent magnets in the switched reluctance machines can have also concentric windings placed on them and excited with currents to further augment the flux linkages in the stator poles. The windings on the poles with permanent magnets can be excited from the same source as the windings on the poles without permanent magnets to enhance power output or provide power factor correction.
    Type: Application
    Filed: April 25, 2011
    Publication date: October 27, 2011
    Inventor: Krishnan RAMU
  • Publication number: 20110234027
    Abstract: A switched reluctance motor includes at least four stator poles and an electrically conductive material around each of the stator poles. The geometric outline, on one side of the stator pole, of at least one of the conductive materials is not rectangular, as viewed from a cross-section of the switched reluctance motor showing each of the stator poles.
    Type: Application
    Filed: March 29, 2011
    Publication date: September 29, 2011
    Inventor: Krishnan RAMU
  • Publication number: 20110234134
    Abstract: An inverter for a permanent magnet brushless do machine, having a permanent magnet rotor and a set of stator windings, applies the full dc voltage provided to the inverter to each phase of the machine.
    Type: Application
    Filed: March 29, 2011
    Publication date: September 29, 2011
    Inventor: Krishnan RAMU
  • Publication number: 20110234136
    Abstract: Drive circuits that provide power factor correction and input current waveform shaping for controlling the speed and torque in a switched reluctance machine (SRM). The machine's phase windings are split into two segments, one of which is used for active power factor correction, input ac current waveform shaping and partial torque generation and the other of which is used for torque generation.
    Type: Application
    Filed: March 29, 2011
    Publication date: September 29, 2011
    Inventor: Krishnan RAMU
  • Publication number: 20110193507
    Abstract: A method for controlling a multi-phase motor includes withholding energization of a first phase of the motor for a non-zero period when the first phase's dwell time begins. Energization of the first phase is activated upon the expiration of the non-zero period. Energization of the first phase is deactivated for the remainder of the dwell time at a deactivation time occurring before or at the expiration of the dwell time.
    Type: Application
    Filed: August 13, 2008
    Publication date: August 11, 2011
    Inventor: Krishnan Ramu
  • Publication number: 20110187300
    Abstract: A power factor correction system includes a rectifier that rectifies the voltage of an alternating current (ac) power source to produce a voltage waveform that transitions, in a half sinusoid, from a minimum amplitude to a maximum amplitude and back to the minimum amplitude twice in the period of the ac power source. A phase winding of a motor conveys current induced by the voltage waveform, and a regulator regulates the flow of the current conveyed by the phase winding for storage as energy in a storage component.
    Type: Application
    Filed: August 13, 2008
    Publication date: August 4, 2011
    Inventor: Krishnan Ramu
  • Publication number: 20110025253
    Abstract: An improved single-switch control circuit for use in a multi-phase switched reluctance machine is provided. The control circuit includes at least first and second phase windings, a switch, a capacitor, and a diode. The capacitor may have a polarity opposite that of a power source in the control circuit. The first winding may be connected in series with the switch and connected in parallel with a circuit block comprising the second winding. The second winding may be connected in parallel with the capacitor and in series with the diode. In operation, the switch may be used to redirect current from the first winding to the second winding. The capacitor can become charged by the redirected current until it eventually stores enough energy to essentially discontinue current flow in the first winding. Then, the capacitor can discharge its stored energy as a current through the second winding. In this manner, substantially all of the energy from the first winding can be transferred to the second winding.
    Type: Application
    Filed: August 12, 2008
    Publication date: February 3, 2011
    Inventor: Krishnan Ramu
  • Patent number: 7852038
    Abstract: An improved single-switch control circuit for use in a multi-phase switched reluctance machine is provided. The control circuit includes at least first and second phase windings, a switch, a capacitor, and a diode. The capacitor may have a polarity opposite that of a power source in the control circuit. The first winding may be connected in series with the switch and connected in parallel with a circuit block comprising the second winding. The second winding may be connected in parallel with the capacitor and in series with the diode. In operation, the switch may be used to redirect current from the first winding to the second winding. The capacitor can become charged by the redirected current until it eventually stores enough energy to essentially discontinue current flow in the first winding. Then, the capacitor can discharge its stored energy as a current through the second winding. In this manner, substantially all of the energy from the first winding can be transferred to the second winding.
    Type: Grant
    Filed: December 5, 2007
    Date of Patent: December 14, 2010
    Assignee: Ramu Inc.
    Inventor: Krishnan Ramu
  • Publication number: 20100141061
    Abstract: A two-phase switched reluctance machine is provided using discontinuous core structures as the stator for low-cost, high-performance drives. This discontinuous stator core structure contains short flux paths and maximum overlap between the rotor poles and stator poles in the stator discontinuous core structures, regardless of the rotor position. Example configurations of such core structure include E-core, L-core and I-core configurations. Using less steel and magnet wire than in conventional SRM designs results in cost savings of stator material and winding material. Efficiency of this novel SRM is improved because of shorter flux paths resulting in reduction of core losses and decreased phase resistance resulting in reduction of copper losses. Two-phase simultaneous excitation of the novel SRM can reduce torque ripple during commutation as compared with existing two-phase SRMs.
    Type: Application
    Filed: May 30, 2008
    Publication date: June 10, 2010
    Inventors: Krishnan Ramu, Nimai Lobo, Cheewoo Lee