# US 10,770,999 B2 · Brushless, self-excited synchronous field-winding machine > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,770,999 B2 - Document ID: US10770999B2 - Status: Granted - Kind: B2 - Application number: 16/385,556 - Filed: 2019-04-16 - Published: 2019-10-17 - Granted: 2020-09-08 - Earliest claimed: 2018-04-17 - Assignees: The Regents of the University of Michigan - Applicants: The Regents of the University of Michigan - Inventors: Heath F. Hofmann - Web page: https://patentgrep.com/patent/US10770999B2 ## CPC - H02P 21/24: Vector control not involving the use of rotor position or rotor speed sensors - H02P 21/30: Direct torque control [DTC] or field acceleration method [FAM] - H02P 21/22: Current control, e.g. using a current control loop - H02P 25/03: with brushless excitation - H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS ## Abstract A brushless, self-excited synchronous field winding machine is presented. The AC stator is configured with four or more phases to produce independent magnetic fields at different spatial harmonics. Windings in the rotor are configured to magnetically couple to the different spatial harmonics produced by the AC stator. More specifically, an oscillating field generated by the stator magnetically couples to the excitation winding on the rotor. This induces an AC voltage which results in current flowing through the field winding of the rotor. The magnitude of the field current is therefore controlled by the magnitude of the oscillating field. The AC stator also produces a magnetic field at a different spatial harmonic which magnetically couples to field winding of the rotor. This component will interact with the field current to produce torque. With this approach, the power density of the electric machine is significantly increased as compared to conventional field winding designs. ## Claims ### Claim 1 An electric machine, comprising: a rotor; an AC stator configured to receive an AC drive signal and arranged adjacent to and interoperable with the rotor, wherein the AC stator is configured with four or more phases to independently produce magnetic fields at two or more spatial harmonics; wherein the rotor includes an excitation winding and a field winding and the field winding is electrically coupled to the excitation winding, wherein the excitation winding and the field winding are configured to magnetically couple to the two or more spatial harmonics of the AC drive signal, such that the excitation winding is independently excitable from the field winding by different spatial harmonics of the AC drive signal; and a controller electrically coupled to windings of the AC stator and independently controls the magnetic fields at the two or more spatial harmonics. ### Claim 2 (depends on 1) The electric machine of claim 1 wherein torque of the electric machine is determined as a function of current in the field winding and current in the AC stator that produces a spatial harmonic which magnetically couples to the field winding. ### Claim 3 (depends on 1) The electric machine of claim 1 wherein the excitation winding is configured to magnetically couple to a given harmonic of the magnetic fields produced by the AC stator and the field winding is configured to magnetically couple to another harmonic which is three times the given harmonic. ### Claim 4 (depends on 1) The electric machine of claim 1 wherein the AC stator includes windings arranged to generate an AC drive signal. ### Claim 5 (depends on 1) The electric machine of claim 1 wherein the AC stator is configured with five windings and the excitation winding is further defined as a three phase winding. ### Claim 6 (depends on 1) The electric machine of claim 1 wherein the field winding is electrically coupled by a rectifier circuit to the excitation winding. ### Claim 7 (depends on 1) The electric machine of claim 1 wherein the controller is electrically coupled via an inverter circuit to windings of the AC stator. ### Claim 8 (depends on 1) The electric machine of claim 1 wherein the controller is configured to receive measurements of current in the windings of the stator and convert the measurements to d-q currents using a direct-quadrature-zero transformation. ### Claim 9 (depends on 8) The electric machine of claim 8 where the controller calculate differences between the d-q currents and a set of reference currents, converts the differences to voltages and generate command voltages for the AC stator using an inverse direct-quadrature-zero transformation. ### Claim 10 An electric machine, comprising: a rotor; an AC stator configured to receive an AC drive signal and arranged adjacent to and interoperable with the rotor, wherein the AC stator having windings arranged to independently produce magnetic fields at two or more spatial harmonics; wherein the rotor includes an excitation winding and a field winding and the field winding is electrically coupled by a rectifier circuit to the excitation winding, such that the excitation winding is configured to magnetically couple to a given spatial harmonic of the two or more spatial harmonics of the AC drive signal and the field winding is configured to magnetically couple to another harmonic of the two or more spatial harmonics of the AC drive signal, where the given spatial harmonic differs from the another harmonic; and a controller electrically coupled via an inverter circuit to windings of the AC stator and independently controls the magnetic fields at the two or more spatial harmonics. ### Claim 11 (depends on 10) The electric machine of claim 10 wherein torque of the electric machine is determined as a function of current in the field winding and current in the AC stator that produces the spatial harmonic which magnetically couples to the field winding. ### Claim 12 (depends on 10) The electric machine of claim 10 wherein the excitation winding is configured to magnetically couple to a given harmonic of the magnetic fields produced by the AC stator and the field winding is configured to magnetically couple to another harmonic which is three times the given harmonic. ### Claim 13 (depends on 10) The electric machine of claim 10 wherein the excitation winding has a 2-pole winding arrangement and the field winding has a 6-pole winding arrangement. ### Claim 14 (depends on 10) The electric machine of claim 10 wherein the excitation winding has a 4-pole winding arrangement and the field winding has a 12-pole winding arrangement. ### Claim 15 (depends on 10) The electric machine of claim 10 wherein the AC stator has 4-pole winding arrangement. ### Claim 16 (depends on 10) The electric machine of claim 10 wherein the controller is configured to receive measurements of current in the windings of the AC stator and convert the current measurements to d-q currents using a direct-quadrature-zero transformation. ### Claim 17 (depends on 16) The electric machine of claim 16 where the controller calculate differences between the d-q currents and a set of reference currents, converts the differences to voltages and generate command voltages for the AC stator using an inverse direct-quadrature-zero transformation.