# US 11,114,966 B2 · Device and method for determining rotation of an induction machine > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,114,966 B2 - Document ID: US11114966B2 - Status: Granted - Kind: B2 - Application number: 16/861,391 - Filed: 2020-04-29 - Published: 2020-11-05 - Granted: 2021-09-07 - Earliest claimed: 2019-04-30 - Assignees: Danfoss Editron Oy - Applicants: Danfoss Editron Oy - Inventors: Anssi Sakari Sinervo - Web page: https://patentgrep.com/patent/US11114966B2 ## CPC - H02P 1/029: {Restarting, e.g. after power failure} - H02P 21/24: Vector control not involving the use of rotor position or rotor speed sensors - H02P 21/18: Estimation of position or speed - H02P 21/30: Direct torque control [DTC] or field acceleration method [FAM] - H02P 21/34: Arrangements for starting - H02P 23/24: Controlling the direction, e.g. clockwise or counterclockwise - H02P 25/02: characterised by the kind of motor - H02P 27/08: with pulse width modulation - H02P 2207/01: Asynchronous machines - H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS ## Abstract A device for estimating a rotation speed and/or a direction of rotation of an induction machine is presented. The device controls stator voltages (uu, uv, uw) of the induction machine so that a voltage space-vector constituted by the stator voltages has a fixed direction and a current space-vector constituted by stator currents (iu, iv, iw) of the induction machine has a pre-determined length or a predetermined d-component. The rotation speed and/or the direction of rotation is/are estimated based on a waveform of a q-component of the current space-vector, where the d-component of the current space-vector is parallel with the voltage space-vector and the q-component of the current space-vector is perpendicular to the voltage space-vector. The device is usable when the induction machine does not have enough magnetic flux for flux-based determination of the rotation speed and/or the direction of rotation. ## Claims ### Claim 1 A device, wherein the device comprises a processing system implemented with one or more processor circuits configured to: control stator voltages of an induction machine to constitute a voltage space-vector having a fixed direction with respect to a stator of the induction machine, control a length of the voltage space-vector to regulate stator currents of the induction machine to fulfill a condition that a current space-vector constituted by the stator currents has a pre-determined length, and estimate at least one of the following based on a waveform of a q-component of the current space-vector: rotation speed of a rotor of the induction machine, a direction of rotation of the rotor, wherein a d-component of the current space-vector is parallel with the voltage space-vector and the q-component of the current space-vector is perpendicular to the voltage space-vector. ### Claim 2 (depends on 1) The device according to claim 1, wherein the processing system is configured to detect a direction of change of the q-component of the current space-vector at a beginning of fulfillment of the condition related to the stator currents, and to determine the direction of rotation based on the detected direction of change. ### Claim 3 (depends on 1) The device according to claim 1, wherein the processing system is configured to detect a polarity of a first local extreme of the waveform of the q-component of the current space-vector occurring after a beginning of fulfillment of the condition related to the stator currents, and to determine the direction of rotation based on the detected polarity. ### Claim 4 (depends on 1) The device according to claim 1, wherein the processing system is configured to measure a first time-value indicative of time elapsed from a beginning of fulfillment of the condition related to the stator currents to a moment when the waveform of the q-component of the current space-vector reaches a first local extreme value after the beginning of fulfillment of the condition related to the stator currents, and to estimate the rotation speed based on the measured first time-value. ### Claim 5 (depends on 1) The device according to claim 1, wherein the processing system is configured to measure at least one second time-value indicative of time elapsed between two local maximum values or between two local minimum values of the waveform of the q-component of the current space-vector, and to estimate the rotation speed based on the measured at least one second time-value. ### Claim 6 (depends on 1) The device according to claim 1, wherein the processing system is configured to estimate the rotation speed based on the waveform of the q-component of the current space-vector, and subsequently to control the stator voltages to rotate the current space-vector at the estimated rotation speed. ### Claim 7 (depends on 6) The device according to claim 6, wherein the processing system is configured to estimate a flowing direction of air-gap power of the induction machine based on the stator voltages, the stator currents, and stator resistance when the current space-vector is rotated, to decrease the rotation speed of the current space-vector when the estimated flowing direction is towards the rotor of the induction machine, and to increase the rotation speed of the current space-vector when the estimated flowing direction is out from the rotor of the induction machine. ### Claim 8 (depends on 1) The device according to claim 1, wherein the processing system is configured to: monitor whether the waveform of the q-component of the current space-vector reaches a local extreme value within a predetermined time period after a beginning of fulfillment of the condition related to the stator currents, and estimate, in response to a situation in which the q-component of the current space-vector reaches no local extreme value within the predetermined time period, at least one of the following based on behavior of the induction machine having a magnetic flux generated during the predetermined time period: the rotation speed, the direction of rotation. ### Claim 9 (depends on 1) The device according to claim 1, wherein the condition related to the stator currents is that the current space-vector has the pre-determined length, and the pre-determined length is within a range from 30% to 100% of a peak-value of a nominal current of the induction machine. ### Claim 10 (depends on 1) The device according to claim 1, wherein the condition related to the stator currents is that the current space-vector has the predetermined d-component, and the pre-determined d-component is within a range from 20% to 70% of a peak-value of a nominal current of the induction machine. ### Claim 11 (depends on 1) A power electronic converter comprising: a converter stage for forming stator voltages for an induction machine, a controller for controlling the stator voltages at least partly based on stator currents of the induction machine, and a device according to claim 1 for estimating at least one of the following: a rotation speed of a rotor of the induction machine, a direction of rotation of the rotor. ### Claim 12 A method, wherein the method comprises: controlling stator voltages of an induction machine to constitute a voltage space-vector having a fixed direction with respect to a stator of the induction machine, controlling a length of the voltage space-vector to regulate stator currents of the induction machine to fulfill a condition that a current space-vector constituted by the stator currents has a pre-determined length, and estimating at least one of the following based on a waveform of a q-component of the current space-vector: rotation speed of a rotor of the induction machine, a direction of rotation of the rotor, wherein a d-component of the current space-vector is parallel with the voltage space-vector and the q-component of the current space-vector is perpendicular to the voltage space-vector. ### Claim 13 A computer program, wherein the computer program comprises computer executable instructions for controlling a programmable processor to: control stator voltages of an induction machine to constitute a voltage space-vector having a fixed direction with respect to a stator of the induction machine, control a length of the voltage space-vector to regulate stator currents of the induction machine to fulfill a condition that a current space-vector constituted by the stator currents has a pre-determined length, and estimate at least one of the following based on a waveform of a q-component of the current space-vector: rotation speed of a rotor of the induction machine, a direction of rotation of the rotor, wherein a d-component of the current space-vector is parallel with the voltage space-vector and the q-component of the current space-vector is perpendicular to the voltage space-vector. ### Claim 14 (depends on 13) A non-volatile computer readable medium encoded with a computer program according to claim 13.