# US 10,770,987 B2 · Motor drive architecture for variable frequency alternating current loads > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,770,987 B2 - Document ID: US10770987B2 - Status: Granted - Kind: B2 - Application number: 16/028,652 - Filed: 2018-07-06 - Published: 2019-11-14 - Granted: 2020-09-08 - Earliest claimed: 2018-05-11 - Assignees: Hamilton Sunstrand Corporation - Applicants: Hamilton Sundstrand Corporation - Inventors: Dhananjay Kumar; Vaibhav Kumar Somani - Web page: https://patentgrep.com/patent/US10770987B2 ## CPC - H02M 7/487: Neutral point clamped inverters - H02P 6/08: Arrangements for controlling the speed or torque of a single motor (H02P6/10, H02P6/28 take precedence) - H02H 1/043: {to inrush currents (H02H1/046 takes precedence; differential protection of transformers H02H7/045)} - H02H 9/002: {limiting inrush current on switching on of inductive loads subjected to remanence, e.g. transformers} - H02M 5/4505: {having a rectifier with controlled elements} - H02M 7/49: Combination of the output voltage waveforms of a plurality of converters - H02P 1/16: for starting dynamo-electric motors or dynamo-electric converters - H02P 27/14: with three or more levels of voltage - H02H 3/025: {Disconnection after limiting, e.g. when limiting is not sufficient or for facilitating disconnection} - H02M 7/5395: by pulse-width modulation - H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P) - H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS - H02H: EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS (indicating or signalling undesired working conditions G01R, e.g. G01R31/00, G08B; locating faults along lines G01R31/08; emergency protective devices H01H) ## Abstract A method and system for controlling a three-phase drive connected to a three phase power source. The method includes connecting a converter to transfer power from the power source to a first direct current (DC) bus, where the converter and the first DC bus each have a neutral common point (NCP). Connecting a second DC bus to the first DC bus and configuring an inverter connected to the second DC bus to draw power from the second DC bus to provide a plurality of motor signals, the inverter having an inverter NCP. The method also includes connecting a neutral point selection device to the first DC bus NCP and selectively connecting to the converter NCP or the inverter NCP, the bus selection device configured to disconnect the converter NCP or the inverter NCP from the first DC bus NCP under selected conditions. ## Claims ### Claim 1 A three-phase active front-end motor drive system with short circuit protection, the drive system comprising: a multi-level converter having a converter neutral common point configured to transfer power from a three-phase alternating current (AC) power source to a first direct current (DC) bus, the first direct current bus having a positive terminal, a negative terminal, and a neutral common point; a second DC bus having a positive terminal and a negative terminal, the second DC bus operably connected to the first DC bus, with the positive terminal of the second DC bus operably connected to the positive terminal of the first DC bus, and the negative terminal of the second DC bus operably connected to the negative terminal of the first DC bus; an inverter operably connected to the second DC bus, the inverter configured to draw power from the positive terminal of the second DC bus and negative terminal of the second DC bus to provide a plurality of motor excitation signals, the inverter having an inverter neutral common point; a neutral point selection device operably connected to the first DC bus neutral common point of the first DC bus and selectively connectable to at least one of the converter neutral common point and the inverter neutral common point, the bus selection device configured to disconnect the at least one of the converter neutral common point and the inverter neutral common point from the first DC bus neutral common point under selected conditions; and an inrush current limiter, wherein the converter is a multilevel converter including the inrush current limiter, the inrush current limiter comprises a bypass diode and a series positive temperature coefficient thermistor selectively shunted by an active switching device. ### Claim 2 (depends on 1) The three-phase active front-end motor drive of claim 1, further comprising a controller operably connected to the multi-level converter and the inverter, the controller configured to: generate control signals to cause the multi-level converter to transfer power to the first DC bus; and generate control signals to cause the inverter to transfer power from the second DC bus to generate a plurality of motor excitation signals. ### Claim 3 (depends on 2) The three-phase active front-end motor drive of claim 2, wherein the controller generates a pulse width modulation (PWM) signal with a selected duty cycle for the converter control signals based on at least a current loading of the DC bus. ### Claim 4 (depends on 2) The three-phase active front-end motor drive of claim 2, wherein the controller generates a pulse width modulation (PWM) signal with a selected duty cycle for the inverter control signals based on at least one of a position of the motor, a speed of the motor, and a load of the motor. ### Claim 5 (depends on 1) The three-phase active front-end motor drive of claim 1, further including a first bus selection device operably connected to the positive terminal of first DC bus and selectively connectable to the positive terminal of second DC bus, and a second bus selection device operably connected to the negative terminal of first DC bus and selectively connectable to the negative terminal of second DC bus, the first and second bus selection devices configured to disconnect the second DC bus from the first DC bus under selected conditions. ### Claim 6 (depends on 5) The three-phase active front-end motor drive of claim 5, wherein at least one of the first bus selection device and the second bus selection device is at least one of a fuse, a circuit breaker, a contactor, a passive current interruption device, and an active switching device. ### Claim 7 (depends on 6) The three-phase active front-end motor drive of claim 6, wherein at least one of the first bus selection device and the second bus selection device is operably connected to a controller, and responsive to a control signal from the controller based on at least a current load of the inverter. ### Claim 8 (depends on 1) The three-phase active front-end motor drive of claim 1, wherein the neutral point selection device is at least one of a fuse, a circuit breaker, a contactor, a passive current interruption device, and an active switching device. ### Claim 9 (depends on 8) The three-phase active front-end motor drive of claim 8, wherein the neutral point selection device is operably connected to a controller and responsive to a control signal from a controller based on at least one of a current load of the inverter and input current level. ### Claim 10 (depends on 1) The three-phase active front-end motor drive of claim 1, wherein the converter is a three level, three phase converter, and the inverter is a two level, three phase inverter. ### Claim 11 (depends on 1) The three-phase active front-end motor drive of claim 1, wherein at least one of the converter and the inverter, is a three level converter or inverter respectively. ### Claim 12 (depends on 1) The three-phase active front-end motor drive of claim 1, wherein at least one of the converter and the inverter comprise at least six switching devices. ### Claim 13 (depends on 1) The three-phase active front-end motor drive of claim 1, wherein the active switching device incudes a thyristor operatively connected to a controller and responsive to a control signal from the controller based on a current in the converter. ### Claim 14 (depends on 1) The three-phase active front-end motor drive of claim 1, wherein the converter neutral point is not electrically connected to the inverter neutral point. ### Claim 15 A motor control system with a three-phase active front-end drive including short circuit protection, comprising: a multi-level converter having a converter neutral common point configured to transfer power from a three-phase alternating current (AC) power source to a first direct current (DC) bus, the first direct current bus having a positive terminal, a negative terminal, and neutral common point; a second DC bus having a positive terminal and a negative terminal, the second DC bus operably connected to the first DC bus, with the positive terminal of the second DC bus operably connected to the positive terminal of the first DC bus, and the negative terminal of the second DC bus operably connected to the negative terminal of the first DC bus; an inverter operably connected to a second DC bus; the inverter configured to draw power from the positive terminal of the second DC bus and negative terminal of the second DC bus to provide a plurality of motor excitation signals, the inverter having an inverter neutral common point; a neutral point selection device operably connected to the first DC bus neutral common point of the first DC bus and selectively connectable to at least one of the converter neutral common point and the inverter neutral common point, the bus selection device configured to disconnect the at least one of the converter neutral common point and the inverter neutral common point from the first DC bus neutral common point under selected conditions; a motor operably connected to the inverter, the motor configured to receive the plurality of motor excitation signals; and an inrush current limiter, wherein the multilevel converter includes the inrush current limiter, the inrush current limiter comprises a bypass diode and a series positive temperature coefficient thermistor selectively shunted by an active switching device. ### Claim 16 (depends on 15) The motor control system of claim 15, further comprising: a controller operably connected to the multi-level converter as well as the inverter, the controller configured to: generate control signals to cause the multi-level converter to transfer power to the first DC bus; and generate control signals to cause the inverter to transfer power from the second DC bus to generate a plurality of motor excitation signals respectively. ### Claim 17 (depends on 15) The motor control system of claim 15, further including a first bus selection device operably connected to the positive terminal of first DC bus and selectively connectable to the positive terminal of second DC bus, and a second bus selection device operably connected to the negative terminal of first DC bus and selectively connectable to the negative terminal of second DC bus, the first and second bus selection devices configured to disconnect the second DC bus from the first DC bus under selected conditions. ### Claim 18 A method of controlling a three-phase active front- end drive configured for connection to a three phase alternating current power source; the method comprising: operably connecting a multi-level converter having a converter neutral common point to transfer power from the three phase alternating current (AC) power source to a first direct current (DC) bus, the first DC bus having a positive terminal, a negative terminal, and a neutral common point; operably connecting a second DC bus to the first DC bus, the second DC bus with a positive terminal of the second DC bus operably connected to the positive terminal of the first DC bus , and a negative terminal of the second DC bus operably connected to the negative terminal of the first DC bus; configuring an inverter operably connected to the second DC bus to draw power from the positive terminal of the second DC bus and negative terminal of the second DC bus to provide a plurality of motor excitation signals, the inverter having an inverter neutral common point; and operably connecting a neutral point selection device to the first DC bus neutral common point of the first DC bus and selectively connecting to at least one of the converter neutral common point and the inverter neutral common point, the bus selection device configured to disconnect the at least one of the converter neutral common point and the inverter neutral common point from the first DC bus neutral common point under selected conditions, wherein the multilevel converter comprises an inrush current limiter, the inrush current limiter comprises a bypass diode and a series positive temperature coefficient thermistor selectively shunted by an active switching device.