Rectifier for reducing current harmonics from unbalanced source

• US 20060227582A1
• Filed: 03/31/2005
• Published: 10/12/2006
• Est. Priority Date: 03/31/2005
• Status: Active Grant

• Current Assignee: Rockwell Automation Technologies Incorporated (Allen-Bradley Co., Inc.)
• Original Assignee: Rockwell Automation Technologies Incorporated (Allen-Bradley Co., Inc.)
• Inventors: Skibinski, Gary L., Lukaszewski, Richard A., Wei, Lixiang
• Granted Patent: US 7,502,238 B2
• Time in Patent Office: Days
• US Class Current: 363/126
• CPC Class Codes: H02M 1/126 using passive filters
• CPC Class Codes: H02M 7/06 using discharge tubes without control electrode or semiconductor devices without control electrode

Abstract

A rectifier includes a transformer, a rectifying bridge, a link capacitor, and at least a first resonance loop. The transformer is operable to receive three phase input signals having a source frequency and generate a plurality of transformer phase signals. The rectifying bridge has a number of stages corresponding to the number of transformer phase signals and is operable to generate a rectified output signal based on the transformer phase signals. The link capacitor is coupled across the rectifying bridge. The first resonance loop is coupled between the rectifying bridge and the link capacitor. The first resonance loop has a first resonance frequency corresponding to a harmonic frequency of the source frequency.

Claims

1. A rectifier, comprising:

a transformer operable to receive three phase input signals having a source frequency and generate a plurality of transformer phase signals;

a rectifying bridge having a number of stages corresponding to the number of transformer phase signals and operable to generate a rectified output signal based on the transformer phase signals;

a link capacitor coupled across the rectifying bridge; and

at least a first resonance loop coupled between the rectifying bridge and the link capacitor, the first resonance loop having a first resonance frequency corresponding to a harmonic frequency of the source frequency.

2. The rectifier of claim 1, wherein the first resonant loop is operable to block signals having frequencies corresponding to the first resonance frequency.

3. The rectifier of claim 1, further comprising a second resonance loop coupled between the rectifying bridge and the link capacitor, the second resonance loop having a second resonance frequency corresponding to a harmonic frequency of the source frequency.

4. The rectifier of claim 3, wherein the first resonance frequency corresponds to a second harmonic frequency of the source frequency, and the second resonance frequency corresponds to a sixth harmonic frequency of the source frequency.

5. The rectifier of claim 3, further comprising a third resonance loop coupled between the rectifying bridge and the link capacitor, the third resonance loop having a third resonance frequency corresponding to a harmonic frequency of the source frequency.

6. The rectifier of claim 5, wherein the first resonance frequency corresponds to a second harmonic frequency of the source frequency, the second resonance frequency corresponds to a sixth harmonic frequency of the source frequency, and the third resonance frequency corresponds to a twelfth harmonic frequency of the source frequency.

7. The rectifier of claim 1, wherein the first resonance loop comprises an inductor, a capacitor, and a resister coupled in parallel.

8. The rectifier of claim 7, wherein ω

represents the source frequency, k represents an integer corresponding to the order of the harmonic, L_k represents an inductance of the inductor, C_k represents a capacitance of the capacitor, and the first resonance loop is tuned in accordance with the equation;

$k<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\omega <br><br>}·<br><br>L_k=\frac{1}{k<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\omega <br><br>}·<br><br>C_k}.$

9. The rectifier of claim 1, wherein the transformer comprises at least one of a 6 phase transformer, a 9 phase transformer, and a 12 phase transformer.

10. A motor control system, comprising:

a power supply operable to provide three phase input signals having a source frequency;

a rectifier operable to receive the three phase input signals and generate a direct current output signal over positive and negative buses, the rectifier comprising at least a first direct current resonance loop having a first resonance frequency corresponding to a harmonic frequency of the source frequency;

an inverter operable to switch between the positive and negative buses to generate a plurality of motor drive signals; and

a motor operable to rotate responsive to the plurality of motor drive signals.

11. The motor control system of claim 10, wherein the first direct current resonant loop is operable to block signals having frequencies corresponding to the first resonance frequency.

12. The motor control system of claim 10, wherein the rectifier further comprises:

a transformer operable to receive the three phase input signals and generate a plurality of transformer phase signals;

a rectifying bridge having a number of stages corresponding to the number of transformer phase signals and operable to generate a rectified output signal based on the transformer phase signals; and

a link capacitor coupled across the rectifying bridge, wherein the first resonance loop is coupled between the rectifying bridge and the link capacitor.

13. The motor control system of claim 12, further comprising a second resonance loop coupled between the rectifying bridge and the link capacitor, the second resonance loop having a second resonance frequency corresponding to a harmonic frequency of the source frequency.

14. The motor control system of claim 13, wherein the first resonance frequency corresponds to a second harmonic frequency of the source frequency, and the second resonance frequency corresponds to a sixth harmonic frequency of the source frequency.

15. The motor control system of claim 13, further comprising a third resonance loop coupled between the rectifying bridge and the link capacitor, the third resonance loop having a third resonance frequency corresponding to a harmonic frequency of the source frequency.

16. The motor control system of claim 15, wherein the first resonance frequency corresponds to a second harmonic frequency of the source frequency, the second resonance frequency corresponds to a sixth harmonic frequency of the source frequency, and the third resonance frequency corresponds to a twelfth harmonic frequency of the source frequency.

17. The motor control system of claim 12, wherein the first resonance loop comprises an inductor, a capacitor, and a resister coupled in parallel.

18. The motor control system of claim 17, wherein ω

represents the source frequency, k represents an integer corresponding to the order of the harmonic, L_k represents an inductance of the inductor, C_k represents a capacitance of the capacitor, and the first resonance loop is tuned in accordance with the equation;

$k<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\omega <br><br>}·<br><br>L_k=\frac{1}{k<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\omega <br><br>}·<br><br>C_k}.$

19. The motor control system of claim 12, wherein the transformer comprises at least one of a 6 phase transformer, a 9 phase transformer, and a 12 phase transformer.