Methods and systems for reducing conducted electromagnetic interference

• US 10,193,488 B2
• Filed: 01/14/2016
• Issued: 01/29/2019
• Est. Priority Date: 01/14/2016
• Status: Active Grant

• Current Assignee: Regal Beloit America, Inc.
• Original Assignee: Regal Beloit America, Inc.
• Inventors: Li, Ming, Carnes, Joseph, Becerra, Roger Carlos
• Primary Examiner(s): Chan, Kawing
• Application Number:
  US14/995,418
• Publication Number:
  US 20170207763A1
• Time in Patent Office: 1,111 Days
• Field of Search: 318 53
• CPC Class Codes: H02M 1/44 Circuits or arrangements for compensating for electromagnetic interference in converters or inverters
• CPC Class Codes: H02P 27/06 using dc to ac converters or inverters H02P27/05 takes precedence
• CPC Class Codes: H02P 29/50 Reduction of harmonics

Abstract

An EMI filter is described that includes an input having first and second input terminals, and an output having first and second output terminals. A first conductive path is defined between the first input and output terminals, and a second conductive path is defined between the second input and output terminals. The EMI filter also includes a first choke device coupled across the first and second conductive paths, and a first Y capacitor including a first end and a second end opposite the first end, the first end coupled to the first conductive path downstream from the first choke device. The EMI filter further includes a second Y capacitor including a first end and a second end opposite the first end, the first end coupled to the second conductive path downstream from the first choke device, and a second choke device coupled to an inverter output.

Claims

1. An electromagnetic interference (EMI) filter system for a twin motor system that includes a first drive circuit having a first direct current (DC) link with a capacitor having a capacitance less than 10 μ

F and a first inverter for driving a first motor, and a second drive circuit having a second DC link coupled to the first DC link and including a capacitor having a capacitance between about 200 μ

F and 1000 μ

F and a second inverter for driving a second motor;

said EMI filter system comprising;

a line-side filter configured to filter input power for transmission to the first DC link and the second DC link, said line-side filter comprising;

an input comprising a first input terminal and a second input terminal;

an output comprising a first output terminal and a second output terminal, wherein a first conductive path is defined between the first input terminal and the first output terminal, and a second conductive path is defined between the second input terminal and the second output terminal;

a first choke device coupled across the first and second conductive paths;

a first Y capacitor including a first end and a second end opposite the first end, the first end coupled to the first conductive path downstream from said first choke device; and

a second Y capacitor including a first end and a second end opposite the first end, the first end coupled to the second conductive path downstream from said first choke device; and

a load-side filter comprising a second choke device coupled between the second inverter and the second motor.

2. The EMI filter system according to claim 1, wherein said input further comprises a ground terminal, the second ends of said first and said second Y capacitors are operatively coupled to the ground terminal.

3. The EMI filter system according to claim 1, further comprising:

a first X capacitor coupled from the first conductive path to the second conductive path between said input and said first choke device; and

a second X capacitor coupled from the first conductive path to the second conductive path between said first choke device and said output.

4. The EMI filter system according to claim 3, wherein said first X capacitor, said second X capacitor, and said first choke device form a differential mode EMI filter.

5. The EMI filter system according to claim 1, wherein said second choke device comprises a three-phase common mode choke.

6. The EMI filter system according to claim 1, wherein said second choke device comprises:

a first choke inductor coupled to a first phase inverter output;

a second choke inductor coupled to a second phase inverter output; and

a third choke inductor coupled to a third phase inverter output.

7. The EMI filter system according to claim 1, further comprising a third choke device coupled across the first and second conductive paths between said first choke device and said output.

8. The EMI filter system according to claim 7, further comprising:

a third Y capacitor coupled to the first conductive path and a ground terminal between said third choke device and said output; and

a fourth Y capacitor coupled to the second conductive path and the ground terminal between said third choke device and said output.

9. The EMI filter system according to claim 7, wherein said third choke device comprises one of a ferrite core or a radio frequency (RF) core having lower common mode inductance relative to said first choke device.

10. An electric motor drive circuit configured to drive a first electric motor and a second electric motor, said electric motor drive circuit comprising:

a rectifier configured to convert an AC input voltage to a pulsed DC voltage;

a first DC link electrically coupled to said rectifier, said first DC-link comprising a low-capacitance capacitor having a capacitance less than 10 μ

F;

a first inverter coupled to said first DC-link, said first inverter configured to generate a conditioned output voltage to drive the first electric motor;

a second DC-link electrically coupled to said first DC-link;

a second inverter coupled to said second DC-link, said second inverter configured to generate a conditioned output voltage to drive the second electric motor; and

an electromagnetic interference (EMI) filter system comprising;

a line-side filter configured to filter input power for transmission to said rectifier, said line-side filter comprising;

an input comprising a first input terminal and a second input terminal;

an output coupled to an input of said rectifier, said output comprising a first output terminal and a second output terminal, wherein a first conductive path is defined between the first input terminal and the first output terminal, and a second conductive path is defined between the second input terminal and the second output terminal;

a first choke device coupled across the first and second conductive paths;

a first Y capacitor including a first end and a second end opposite the first end, the first end coupled to the first conductive path downstream from said first choke device; and

a second Y capacitor including a first end and a second end opposite the first end, the first end coupled to the second conductive path downstream from said first choke device; and

a load-side filter comprising a second choke device coupled between said second inverter and the second electric motor.

11. The electric motor drive circuit according to claim 10, wherein said second DC-link comprises a high-capacitance capacitor having a capacitance between about 200 μ

F and 1000 μ

F.

12. The electric motor drive circuit according to claim 10, wherein said input further comprises a ground terminal, the second ends of said first and said second Y capacitors are operatively coupled to the ground terminal.

13. The electric motor drive circuit according to claim 10, further comprising:

a first X capacitor coupled from the first conductive path to the second conductive path between said input and said first choke device; and

a second X capacitor coupled from the first conductive path to the second conductive path between said first choke device and said output.

14. The electric motor drive circuit according to claim 13, wherein said first X capacitor, said second X capacitor, and said first choke device form a differential mode EMI filter.

15. The electric motor drive circuit according to claim 10, wherein said second choke device comprises a three-phase common mode choke.

16. The electric motor drive circuit according to claim 10, wherein said second choke device comprises:

a first choke inductor coupled to a first phase inverter output;

a second choke inductor coupled to a second phase inverter output; and

a third choke inductor coupled to a third phase inverter output.

17. The electric motor drive circuit according to claim 10, further comprising a third choke device coupled across the first and second conductive paths between said first choke device and said output.

18. The electric motor drive circuit according to claim 17, further comprising:

a third Y capacitor coupled to the first conductive path and a ground terminal between said third choke device and said output; and

a fourth Y capacitor coupled to the second conductive path and the ground terminal between said third choke device and said output.

19. An electric motor system comprising:

a first electric motor including a first electric motor drive circuit having a first direct current (DC) link with a capacitor having a capacitance less than 10 μ

F and a first inverter configured to drive said first electric motor;

a second electric motor including a second electric motor drive circuit having a second DC link coupled to the first DC link and including a capacitor having a capacitance between about 200 μ

F and 1000 μ

F and a second inverter configured to drive said second electric motor; and

a common electric motor drive circuit configured to condition power provided to the first and second electric motor drive circuits, said common electric motor drive circuit comprising;

an electromagnetic interference (EMI) filter system comprising;

a line-side filter configured to filter input power for transmission to said common electric motor drive circuit, said line-side filter comprising;

an input comprising a first input terminal and a second input terminal;

an output comprising a first output terminal and a second output terminal, wherein a first conductive path is defined between the first input terminal and the first output terminal, and a second conductive path is defined between the second input terminal and the second output terminal;

a first choke device coupled across the first and second conductive paths;

a first Y capacitor including a first end and a second end opposite the first end, the first end coupled to the first conductive path downstream from said first choke device; and

a second Y capacitor including a first end and a second end opposite the first end, the first end coupled to the second conductive path downstream from said first choke device; and

a load-side filter comprising a second choke device coupled between the second electric motor drive circuit and the second electric motor.

20. The electric motor system according to claim 19, wherein said electric motor system is configured for use in a heating, ventilation, and air conditioning (HVAC) system.