IPC분류정보
국가/구분 |
United States(US) Patent
등록
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국제특허분류(IPC7판) |
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출원번호 |
US-0711625
(2010-02-24)
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등록번호 |
US-8400085
(2013-03-19)
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발명자
/ 주소 |
- Rineh, Ghodratollah Esmaeili
- Nam, Sang Woo
- Pande, Manish
- Cheng, Zhongyuan
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출원인 / 주소 |
- Rockwell Automation Technologies, Inc.
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대리인 / 주소 |
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인용정보 |
피인용 횟수 :
2 인용 특허 :
6 |
초록
▼
Current source converter (CSC) based motor drives and control techniques are presented in which DC link current is regulated to a level set by the output inverter during dynamic braking operation by pulse width modulation of a braking resistance connection signal to maintain control of motor torque
Current source converter (CSC) based motor drives and control techniques are presented in which DC link current is regulated to a level set by the output inverter during dynamic braking operation by pulse width modulation of a braking resistance connection signal to maintain control of motor torque and speed while mitigating or preventing line side regenerative currents.
대표청구항
▼
1. A current source converter motor drive, comprising: an active rectifier comprising an AC input having a plurality of AC input nodes to receive AC electrical input power, a DC output having first and second DC output nodes, and a rectifier switching network comprising a plurality of rectifier swit
1. A current source converter motor drive, comprising: an active rectifier comprising an AC input having a plurality of AC input nodes to receive AC electrical input power, a DC output having first and second DC output nodes, and a rectifier switching network comprising a plurality of rectifier switching devices individually coupled between one of the AC input nodes and one of the first and second DC output nodes, the rectifier switching devices individually operable to selectively couple the AC input node with the corresponding DC output node according to a corresponding rectifier switching control signal;a DC circuit comprising a DC link inductor with first and second windings coupled in corresponding first and second DC current paths;a dynamic braking circuit operatively coupled between the DC output nodes and the first and second DC current paths, the dynamic braking circuit comprising at least one resistance and at least one switching device, operable to selectively connect the resistance into a circuit formed with the DC circuit according to a corresponding dynamic braking switching control signal;an inverter comprising an AC output having a plurality of AC output nodes for supplying AC electrical power to a motor load, and an inverter switching network comprising a plurality of inverter switching devices individually coupled between one of the DC current paths and one of the AC output nodes, the inverter switching devices individually operable to selectively electrically couple the corresponding DC current path with the corresponding AC output node according to a corresponding inverter switching control signal;a switch control system selectively operable in a first mode for normal motor drive operation and in a second mode for dynamic braking operation, the switch control system comprising: an inverter control component operative to provide the inverter switching control signals in the first and second modes to cause the inverter to selectively convert DC current from the DC circuit to provide AC electrical power to the AC output according to at least one setpoint,a rectifier control component operative to provide the rectifier switching control signals in the first mode to convert AC electrical input power to provide a regulated DC current to the DC circuit according to a desired DC current value representing the requirements of the inverter and in the second mode to disconnect the AC input from the DC output to prevent regenerative current from flowing to the AC input, anda dynamic braking control component operative to provide at least one dynamic braking switching control signal in the first mode to prevent current from flowing in the at least one resistance and in the second mode to selectively connect the at least one resistance into a circuit formed with the DC circuit to regulate the DC current provided to the inverter according to the desired DC current value; anda feedback circuit providing at least one feedback signal or value based on a sensed condition of at least one of the rectifier, the DC circuit, and the inverter, wherein the switch control system further comprises a mode control component operative to set the switch control system to either the first or second mode according to at least one feedback signal or value from the feedback circuit. 2. The motor drive of claim 1, wherein the mode control component is operative to set the switch control system to the second mode when a detected or sensed motor speed and a desired motor torque are of opposite polarities. 3. The motor drive of claim 1, wherein the dynamic braking circuit comprises a first series circuit path coupling the first rectifier DC output node to the first DC current path of the DC circuit, a second series circuit path coupling the second rectifier DC output node to the second DC current path of the DC circuit, a first shunt circuit branch including a first switching device coupled between the first and second series circuit paths, and a second shunt circuit branch including a second switching device and the resistance coupled in series with one another between the between the first and second series circuit paths; and wherein the dynamic braking control component is operative in the first mode to provide dynamic braking switching control signals to turn the first and second switching devices, off, and in the second mode to provide a dynamic braking switching control signal to turn the second switching device on and to provide a pulse width modulated dynamic braking switching control signal to alternately turn the first switching device on and off to control the DC current provided to the inverter according to the desired DC current value requested by the inverter control component. 4. The motor drive of claim 1, wherein the dynamic braking circuit comprises a first series circuit path coupling the first rectifier DC output node to the first DC current path of the DC circuit, a second series circuit path coupling the second rectifier DC output node to the second DC current path of the DC circuit, a shunt circuit branch between the first and second series circuit paths, the shunt circuit branch including a first switching device coupled in parallel with the resistance and a second switching device coupled in series with the parallel combination of the first switching device and the resistance; and wherein the dynamic braking control component is operative in the first mode to provide dynamic braking switching control signals to turn the first and second switching devices, off, and in the second mode to provide a dynamic braking switching control signal to turn the second switching device on and to provide a pulse width modulated dynamic braking switching control signal to alternately turn the first switching device on and off to control the DC current provided to the inverter according to the desired DC current value representing the requirements of the inverter. 5. The motor drive of claim 1, wherein the dynamic braking circuit comprises a first series circuit path coupling the first rectifier DC output node to the first DC current path of the DC circuit, a second series circuit path coupling the second rectifier DC output node to the second DC current path of the DC circuit, first and second resistances, and first and second switching devices, the first switching device being coupled in parallel with the first resistance in the first series circuit path, and the second switching device being coupled in parallel with the second resistance in the second series circuit path; and wherein the dynamic braking control component is operative in the first mode to provide a dynamic braking switching control signal to turn the first and second switching devices on, and in the second mode to provide pulse width modulated dynamic braking switching control signals to turn the first and second switching devices on and off to control the DC current provided to the inverter according to the desired DC current value representing the requirements of the inverter. 6. The motor drive of claim 5, wherein the dynamic braking circuit further comprises a shunt circuit branch including a third switching device coupled between the first and second series circuit paths; and wherein the dynamic braking control component is operative in the first mode to provide a dynamic braking switching control signal to turn the third switching device off, and in the second mode to provide a dynamic braking switching control signal to turn the third switching device on. 7. The motor drive of claim 1, wherein the dynamic braking circuit comprises a first series circuit path coupling the first rectifier DC output node to the first DC current path of the DC circuit, a second series circuit path coupling the second rectifier DC output node to the second DC current path of the DC circuit, a first resistance and a first switching device coupled in parallel with the resistance in one of the first and second series circuit paths; and wherein the dynamic braking control component is operative in the first mode to provide a dynamic braking switching control signal to turn the first switching device on, and in the second mode to provide a pulse width modulated dynamic braking switching control signal to alternately turn the first switching device on and off to control the DC current provided to the inverter according to the desired DC current value representing the requirements of the inverter. 8. The motor drive of claim 7, wherein the dynamic braking circuit further comprises a shunt circuit branch including a third switching device coupled between the first and second series circuit paths; and wherein the dynamic braking control component is operative in the first mode to provide a dynamic braking switching control signal to turn the third switching device off, and in the second mode to provide a dynamic braking switching control signal to turn the third switching device on. 9. A current source converter motor drive, comprising: an active rectifier comprising an AC input having a plurality of AC input nodes to receive AC electrical input power, a DC output having first and second DC output nodes, and a rectifier switching network comprising a plurality of rectifier switching devices individually coupled between one of the AC input nodes and one of the first and second DC output nodes, the rectifier switching devices individually operable to selectively couple the AC input node with the corresponding DC output node according to a corresponding rectifier switching control signal;a DC circuit comprising a DC link inductor with first and second windings coupled in corresponding first and second DC current paths;a dynamic braking circuit operatively coupled between the DC output nodes and the first and second DC current paths, the dynamic braking circuit comprising at least one resistance and at least one switching device, operable to selectively connect the resistance into a circuit formed with the DC circuit according to a corresponding dynamic braking switching control signal;an inverter comprising an AC output having a plurality of AC output nodes for supplying AC electrical power to a motor load, and an inverter switching network comprising a plurality of inverter switching devices individually coupled between one of the DC current paths and one of the AC output nodes, the inverter switching devices individually operable to selectively electrically couple the corresponding DC current path with the corresponding AC output node according to a corresponding inverter switching control signal; anda switch control system selectively operable in a first mode for normal motor drive operation and in a second mode for dynamic braking operation, the switch control system comprising: an inverter control component operative to provide the inverter switching control signals in the first and second modes to cause the inverter to selectively convert DC current from the DC circuit to provide AC electrical power to the AC output according to at least one setpoint,a rectifier control component operative to provide the rectifier switching control signals in the first mode to convert AC electrical input power to provide a regulated DC current to the DC circuit according to a desired DC current value representing the requirements of the inverter and in the second mode to disconnect the AC input from the DC output to prevent regenerative current from flowing to the AC input, anda dynamic braking control component operative to provide at least one dynamic braking switching control signal in the first mode to prevent current from flowing in the at least one resistance and in the second mode to selectively connect the at least one resistance into a circuit formed with the DC circuit to regulate the DC current provided to the inverter according to the desired DC current value;wherein the dynamic braking circuit comprises a first series circuit path coupling the first rectifier DC output node to the first DC current path of the DC circuit, a second series circuit path coupling the second rectifier DC output node to the second DC current path of the DC circuit, a first shunt circuit branch including a first switching device coupled between the first and second series circuit paths, and a second shunt circuit branch including a second switching device and the resistance coupled in series with one another between the between the first and second series circuit paths; andwherein the dynamic braking control component is operative in the first mode to provide dynamic braking switching control signals to turn the first and second switching devices, off, and in the second mode to provide a dynamic braking switching control signal to turn the second switching device on and to provide a pulse width modulated dynamic braking switching control signal to alternately turn the first switching device on and off to control the DC current provided to the inverter according to the desired DC current value representing the requirements of the inverter. 10. A current source converter motor drive, comprising: an active rectifier comprising an AC input having a plurality of AC input nodes to receive AC electrical input power, a DC output having first and second DC output nodes, and a rectifier switching network comprising a plurality of rectifier switching devices individually coupled between one of the AC input nodes and one of the first and second DC output nodes, the rectifier switching devices individually operable to selectively couple the AC input node with the corresponding DC output node according to a corresponding rectifier switching control signal;a DC circuit comprising a DC link inductor with first and second windings coupled in corresponding first and second DC current paths;a dynamic braking circuit operatively coupled between the DC output nodes and the first and second DC current paths, the dynamic braking circuit comprising at least one resistance and at least one switching device, operable to selectively connect the resistance into a circuit formed with the DC circuit according to a corresponding dynamic braking switching control signal;an inverter comprising an AC output having a plurality of AC output nodes for supplying AC electrical power to a motor load, and an inverter switching network comprising a plurality of inverter switching devices individually coupled between one of the DC current paths and one of the AC output nodes, the inverter switching devices individually operable to selectively electrically couple the corresponding DC current path with the corresponding AC output node according to a corresponding inverter switching control signal; anda switch control system selectively operable in a first mode for normal motor drive operation and in a second mode for dynamic braking operation, the switch control system comprising: an inverter control component operative to provide the inverter switching control signals in the first and second modes to cause the inverter to selectively convert DC current from the DC circuit to provide AC electrical power to the AC output according to at least one setpoint,a rectifier control component operative to provide the rectifier switching control signals in the first mode to convert AC electrical input power to provide a regulated DC current to the DC circuit according to a desired DC current value representing the requirements of the inverter and in the second mode to disconnect the AC input from the DC output to prevent regenerative current from flowing to the AC input, anda dynamic braking control component operative to provide at least one dynamic braking switching control signal in the first mode to prevent current from flowing in the at least one resistance and in the second mode to selectively connect the at least one resistance into a circuit formed with the DC circuit to regulate the DC current provided to the inverter according to the desired DC current value;wherein the dynamic braking circuit comprises a first series circuit path coupling the first rectifier DC output node to the first DC current path of the DC circuit, a second series circuit path coupling the second rectifier DC output node to the second DC current path of the DC circuit, a shunt circuit branch between the first and second series circuit paths, the shunt circuit branch including a first switching device coupled in parallel with the resistance and a second switching device coupled in series with the parallel combination of the first switching device and the resistance; andwherein the dynamic braking control component is operative in the first mode to provide dynamic braking switching control signals to turn the first and second switching devices, off, and in the second mode to provide a dynamic braking switching control signal to turn the second switching device on and to provide a pulse width modulated dynamic braking switching control signal to alternately turn the first switching device on and off to control the DC current provided to the inverter according to the desired DC current value representing the requirements of the inverter. 11. A current source converter motor drive, comprising: an active rectifier comprising an AC input having a plurality of AC input nodes to receive AC electrical input power, a DC output having first and second DC output nodes, and a rectifier switching network comprising a plurality of rectifier switching devices individually coupled between one of the AC input nodes and one of the first and second DC output nodes, the rectifier switching devices individually operable to selectively couple the AC input node with the corresponding DC output node according to a corresponding rectifier switching control signal;a DC circuit comprising a DC link inductor with first and second windings coupled in corresponding first and second DC current paths;a dynamic braking circuit operatively coupled between the DC output nodes and the first and second DC current paths, the dynamic braking circuit comprising at least one resistance and at least one switching device, operable to selectively connect the resistance into a circuit formed with the DC circuit according to a corresponding dynamic braking switching control signal;an inverter comprising an AC output having a plurality of AC output nodes for supplying AC electrical power to a motor load, and an inverter switching network comprising a plurality of inverter switching devices individually coupled between one of the DC current paths and one of the AC output nodes, the inverter switching devices individually operable to selectively electrically couple the corresponding DC current path with the corresponding AC output node according to a corresponding inverter switching control signal; anda switch control system selectively operable in a first mode for normal motor drive operation and in a second mode for dynamic braking operation, the switch control system comprising: an inverter control component operative to provide the inverter switching control signals in the first and second modes to cause the inverter to selectively convert DC current from the DC circuit to provide AC electrical power to the AC output according to at least one setpoint,a rectifier control component operative to provide the rectifier switching control signals in the first mode to convert AC electrical input power to provide a regulated DC current to the DC circuit according to a desired DC current value representing the requirements of the inverter and in the second mode to disconnect the AC input from the DC output to prevent regenerative current from flowing to the AC input, anda dynamic braking control component operative to provide at least one dynamic braking switching control signal in the first mode to prevent current from flowing in the at least one resistance and in the second mode to selectively connect the at least one resistance into a circuit formed with the DC circuit to regulate the DC current provided to the inverter according to the desired DC current value;wherein the dynamic braking circuit comprises a first series circuit path coupling the first rectifier DC output node to the first DC current path of the DC circuit, a second series circuit path coupling the second rectifier DC output node to the second DC current path of the DC circuit, first and second resistances, and first and second switching devices, the first switching device being coupled in parallel with the first resistance in the first series circuit path, and the second switching device being coupled in parallel with the second resistance in the second series circuit path; andwherein the dynamic braking control component is operative in the first mode to provide dynamic braking switching control signals to turn the first and second switching devices on, and in the second mode to provide pulse width modulated dynamic braking switching control signals to turn the first send second switching devices on and off to control the DC current provided to the inverter according to the desired DC current value representing the requirements of the inverter. 12. The motor drive of claim 11, wherein the dynamic braking circuit further comprises a shunt circuit branch including a third switching device coupled between the first and second series circuit paths; and wherein the dynamic braking control component is operative in the first mode to provide a dynamic braking switching control signal to turn the third switching device off, and in the second mode to provide a dynamic braking switching control signal to turn the third switching device on. 13. A current source converter motor drive, comprising: an active rectifier comprising an AC input having a plurality of AC input nodes to receive AC electrical input power, a DC output having first and second DC output nodes, and a rectifier switching network comprising a plurality of rectifier switching devices individually coupled between one of the AC input nodes and one of the first and second DC output nodes, the rectifier switching devices individually operable to selectively couple the AC input node with the corresponding DC output node according to a corresponding rectifier switching control signal;a DC circuit comprising a DC link inductor with first and second windings coupled in corresponding first and second DC current paths;a dynamic braking circuit operatively coupled between the DC output nodes and the first and second DC current paths, the dynamic braking circuit comprising at least one resistance and at least one switching device, operable to selectively connect the resistance into a circuit formed with the DC circuit according to a corresponding dynamic braking switching control signal;an inverter comprising an AC output having a plurality of AC output nodes for supplying AC electrical power to a motor load, and an inverter switching network comprising a plurality of inverter switching devices individually coupled between one of the DC current paths and one of the AC output nodes, the inverter switching devices individually operable to selectively electrically couple the corresponding DC current path with the corresponding AC output node according to a corresponding inverter switching control signal; anda switch control system selectively operable in a first mode for normal motor drive operation and in a second mode for dynamic braking operation, the switch control system comprising: an inverter control component operative to provide the inverter switching control signals in the first and second modes to cause the inverter to selectively convert DC current from the DC circuit to provide AC electrical power to the AC output according to at least one setpoint,a rectifier control component operative to provide the rectifier switching control signals in the first mode to convert AC electrical input power to provide a regulated DC current to the DC circuit according to a desired DC current value representing the requirements of the inverter and in the second mode to disconnect the AC input from the DC output to prevent regenerative current from flowing to the AC input, anda dynamic braking control component operative to provide at least one dynamic braking switching control signal in the first mode to prevent current from flowing in the at least one resistance and in the second mode to selectively connect the at least one resistance into a circuit formed with the DC circuit to regulate the DC current provided to the inverter according to the desired DC current value;wherein the dynamic braking circuit comprises a first series circuit path coupling the first rectifier DC output node to the first DC current path of the DC circuit, a second series circuit path coupling the second rectifier DC output node to the second DC current path of the DC circuit, a first resistance and a first switching device coupled in parallel with the resistance in one of the first and second series circuit paths; andwherein the dynamic braking control component is operative in the first mode to provide a dynamic braking switching control signal to turn the first switching device on, and in the second mode to provide a pulse width modulated dynamic braking switching control signal to alternately turn the first switching device on and off to control the DC current provided to the inverter according to the desired DC current value representing the requirements of the inverter. 14. The motor drive of claim 13, wherein the dynamic braking circuit further comprises a shunt circuit branch including a third switching device coupled between the first and second series circuit paths; and wherein the dynamic braking control component is operative in the first mode to provide a dynamic braking switching control signal to turn the third switching device off, and in the second mode to provide a dynamic braking switching control signal to turn the third switching device on. 15. A method for operating a current source converter motor drive, the method comprising: in a first operational mode of the motor drive: providing rectifier switching control signals to an active rectifier to convert AC electrical input power to provide a DC current to an intermediate DC circuit having a DC link inductor;regulating the DC current provided to the intermediate DC circuit according to a desired DC current value representing the requirements of the inverter; andproviding inverter switching control signals to the inverter to convert DC current from the intermediate DC circuit to provide AC electrical power to the AC output according to at least one setpoint; andin a second operational mode of the motor drive: connecting the intermediate DC circuit and the inverter into a series circuit;providing rectifier switching control signals to disconnect the AC input from the DC circuit to prevent regenerative current from flowing to the AC input; providing the inverter switching control signals to the inverter to convert DC current from the intermediate DC circuit to provide AC electrical power to the AC output according to the at least one setpoint; andproviding dynamic braking switching control signals to selectively connect at least one resistance in the series circuit to regulate the DC current provided to the inverter according to the desired DC current value representing the requirements of the inverter;wherein providing dynamic braking switching control signals in the second operational mode comprises providing a pulse width modulated dynamic braking switching control signal to a switching device of the series circuit to selectively couple at least one resistance into the series circuit to regulate the DC current provided to the inverter according to the desired DC current value. 16. The method of claim 15, further comprising: sensing a condition of at least one of the rectifier, the intermediate DC circuit, and the inverter; andsetting the operational mode of the motor drive to either the first or second mode according the sensed condition. 17. A method for operating a current source converter motor drive, the method comprising: in a first operational mode of the motor drive: providing rectifier switching control signals to an active rectifier to convert AC electrical input power to provide a DC current to an intermediate DC circuit having a DC link inductor,regulating the DC current provided to the intermediate DC circuit according to a desired DC current value representing the requirements of the inverter, andproviding inverter switching control signals to the inverter to convert DC current from the intermediate DC circuit to provide AC electrical power to the AC output according to at least one setpoint; andin a second operational mode of the motor drive: connecting the intermediate DC circuit and the inverter into a series circuit;providing rectifier switching control signals to disconnect the AC input from the DC circuit to prevent regenerative current from flowing to the AC input, providing the inverter switching control signals to the inverter to convert DC current from the intermediate DC circuit to provide AC electrical power to the AC output according to the at least one setpoint, andproviding dynamic braking switching control signals to selectively connect at least one resistance in the series circuit to regulate the DC current provided to the inverter according to the desired DC current value representing the requirements of the inverter;sensing a condition of at least one of the rectifier, the intermediate DC circuit, and the inverter; andsetting the operational mode of the motor drive to either the first or second mode according the sensed condition. 18. The method of claim 17, comprising setting the operational mode of the motor drive to the second mode when a detected or sensed motor speed and a desired motor torque are of opposite polarities. 19. A current source converter motor drive, comprising: an active rectifier comprising an AC input having a plurality of AC input nodes to receive AC electrical input power, a DC output having first and second DC output nodes, and a rectifier switching network comprising a plurality of rectifier switching devices individually coupled between one of the AC input nodes and one of the first and second DC output nodes, the rectifier switching devices individually operable to selectively couple the AC input node with the corresponding DC output node according to a corresponding rectifier switching control signal;a DC circuit comprising a DC link inductor with first and second windings coupled in corresponding first and second DC current paths;a dynamic braking circuit operatively coupled between the DC output nodes and the first and second DC current paths, the dynamic braking circuit comprising at least one resistance and at least one switching device, operable to selectively connect the resistance into a circuit formed with the DC circuit according to a corresponding dynamic braking switching control signal;an inverter comprising an AC output having a plurality of AC output nodes for supplying AC electrical power to a motor load, and an inverter switching network comprising a plurality of inverter switching devices individually coupled between one of the DC current paths and one of the AC output nodes, the inverter switching devices individually operable to selectively electrically couple the corresponding DC current path with the corresponding AC output node according to a corresponding inverter switching control signal; anda switch control system selectively operable in a first mode for normal motor drive operation and in a second mode for dynamic braking operation, the switch control system comprising: an inverter control component operative to provide the inverter switching control signals in the first and second modes to cause the inverter to selectively convert DC current from the DC circuit to provide AC electrical power to the AC output according to at least one setpoint,a rectifier control component operative to provide the rectifier switching control signals in the first and second modes to convert AC electrical input power to provide a regulated DC current to the DC circuit according to a desired DC current value representing the requirements of the inverter, anda dynamic braking control component operative to provide at least one dynamic braking switching control signal in the first mode to prevent current from flowing in the at least one resistance and in the second mode to connect the at least one resistance into a circuit formed with the DC circuit;wherein the first winding of the DC link inductor is coupled in the first DC current path between the first DC output node of the active rectifier and the inverter, and wherein the second winding of the DC link inductor is coupled in the second DC current path between the second DC output node of the active rectifier and the inverter. 20. The motor drive of claim 19, a feedback circuit providing at least one feedback signal or value based on a sensed condition of at least one of the rectifier, the DC circuit, and the inverter, wherein the switch control system further comprises a mode control component operative to set the switch control system to either the first or second mode according to at least one feedback signal or value from the feedback circuit. 21. The motor drive of claim 20, wherein the mode control component is operative to set the switch control system to the second mode when a detected or sensed motor speed and a desired motor torque are of opposite polarities. 22. The motor drive of claim 19, wherein the dynamic braking circuit comprises a first series circuit path coupling the first rectifier DC output node to the first DC current path of the DC circuit, a second series circuit path coupling the second rectifier DC output node to the second DC current path of the DC circuit, a first shunt circuit branch including a first switching device coupled between the first and second series circuit paths, and a second shunt circuit branch including a second switching device and the resistance coupled in series with one another between the between the first and second series circuit paths; and wherein the dynamic braking control component is operative in the first mode to provide dynamic braking switching control signals to turn the first and second switching devices, off, and in the second mode to provide a dynamic braking switching control signal to turn the second switching device on and to provide a pulse width modulated dynamic braking switching control signal to alternately turn the first switching device on and off to control the DC current provided to the inverter according to the desired DC current value requested by the inverter control component. 23. The motor drive of claim 19, wherein the dynamic braking circuit comprises a first series circuit path coupling the first rectifier DC output node to the first DC current path of the DC circuit, a second series circuit path coupling the second rectifier DC output node to the second DC current path of the DC circuit, a shunt circuit branch between the first and second series circuit paths, the shunt circuit branch including a first switching device coupled in parallel with the resistance and a second switching device coupled in series with the parallel combination of the first switching device and the resistance; and wherein the dynamic braking control component is operative in the first mode to provide dynamic braking switching control signals to turn the first and second switching devices, off, and in the second mode to provide a dynamic braking switching control signal to turn the second switching device on and to provide a pulse width modulated dynamic braking switching control signal to alternately turn the first switching device on and off to control the DC current provided to the inverter according to the desired DC current value representing the requirements of the inverter. 24. The motor drive of claim 19, wherein the dynamic braking circuit comprises a first series circuit path coupling the first rectifier DC output node to the first DC current path of the DC circuit, a second series circuit path coupling the second rectifier DC output node to the second DC current path of the DC circuit, first and second resistances, and first and second switching devices, the first switching device being coupled in parallel with the first resistance in the first series circuit path, and the second switching device being coupled in parallel with the second resistance in the second series circuit path; and wherein the dynamic braking control component is operative in the first mode to provide a dynamic braking switching control signal to turn the first and second switching devices on, and in the second mode to provide pulse width modulated dynamic braking switching control signals to turn the first and second switching devices on and off to control the DC current provided to the inverter according to the desired DC current value representing the requirements of the inverter. 25. The motor drive of claim 19, wherein the dynamic braking circuit comprises a first series circuit path coupling the first rectifier DC output node to the first DC current path of the DC circuit, a second series circuit path coupling the second rectifier DC output node to the second DC current path of the DC circuit, a first resistance and a first switching device coupled in parallel with the resistance in one of the first and second series circuit paths; and wherein the dynamic braking control component is operative in the first mode to provide a dynamic braking switching control signal to turn the first switching device on, and in the second mode to provide a pulse width modulated dynamic braking switching control signal to alternately turn the first switching device on and off to control the DC current provided to the inverter according to the desired DC current value representing the requirements of the inverter.
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