Over-voltage prevention device and current rectifying circuit

Patent metadata

Field	Value
Publication number	US-9548685-B2
Application number	US-201514605424-A
Country	US
Kind code	B2
Filing date	Jan 26, 2015
Priority date	Jan 27, 2014
Publication date	Jan 17, 2017
Grant date	Jan 17, 2017

Abstract

According to one embodiment, an over-voltage prevention device includes a first short-circuit device provided between a secondary side of a wound-rotor induction machine and a frequency converter configured to excite the secondary side by a three-phase AC current and having a function of short-circuiting between phases of the three-phase AC current, resistors each connected between the first short-circuit device and the frequency converter for each phase, and second short-circuit devices connected respectively to the resistors in parallel and having a function of short-circuiting between the frequency converter and the secondary side of the wound-rotor induction machine.

First claim

The invention claimed is:

1. An over-voltage prevention device comprising:
a first short-circuit device provided between a secondary side of a wound-rotor induction machine and a frequency converter configured to excite the secondary side by a three-phase AC current and having a function of short-circuiting between phases of the three-phase AC current;
resistors each connected between the first short-circuit device and the frequency converter for each phase; and
second short-circuit devices connected respectively to the resistors in parallel and having a function of short-circuiting between the frequency converter and the secondary side of the wound-rotor induction machine
a controller i) configured to, in response to a detection of an over-voltage at the secondary side of the wound-rotor induction machine, activate the first short-circuit device to perform short-circuiting, deactivate the frequency converter, and cancel short-circuiting of the second short-circuit devices, at a first time point ii) configured to restart the frequency converter to set the current flowing through the first short-circuit device to be zero, and cancel short-circuiting of the first short-circuit device, at a second time point after a predetermined time period has elapsed from the first time point and iii) configured to control the second short-circuit devices to perform short-circuiting, at a third time point after a predetermined time has elapsed from the first time point, wherein the third time point comes after the second time point comes,
the over-voltage prevention device being controllable such that a short-circuit current flows from the first short-circuit device through the resistors into the frequency converter when short-circuiting of the first short-circuit device is canceled.

2. The over-voltage prevention device according to claim 1 , wherein a resistance of the resistor is smaller than a value obtained by dividing a maximum output voltage of the frequency converter by a maximum current when flowing from the first short-circuit device through the resistor into the frequency converter.

3. The over-voltage prevention device according to claim 1 , wherein a resistance of the resistor is a value ensuring that a voltage of a DC link capacitor provided in the frequency converter at a time when a short-circuit current flows into the frequency converter from the first short-circuit device due to restart of the frequency converter is below an operational threshold of the first short-circuit device.

4. The over-voltage prevention device according to claim 1 , wherein the second short-circuit device is formed of a mechanical breaker.

5. The over-voltage prevention device according to claim 1 , wherein the second short-circuit device is formed of a plurality of mechanic breakers connected in parallel.

6. The over-voltage prevention device according to claim 1 , wherein the second short-circuit device is formed of a semiconductor breaker.

7. The over-voltage prevention device according to claim 1 , wherein the second short-circuit device is formed of a plurality of semiconductor breakers connected in parallel.

8. The over-voltage prevention device according to claim 1 , wherein a resistance of the resistor is smaller than a value obtained by dividing a maximum output voltage of the frequency converter by a maximum current when flowing from the first short-circuit device through the resistor into the frequency converter.

9. A current rectifying circuit applied to a device which includes a frequency converter configured to excite a secondary side of a wound-rotor induction machine by a three-phase AC current, and a first short-circuit device provided between the secondary side of the wound-rotor induction machine and the frequency converter and having a function of short-circuiting between phases of the three-phase AC current, the current rectifying circuit comprising:
resistors each connected between the first short-circuit device and the frequency converter for each phase; and
second short-circuit devices connected respectively to the resistors in parallel and having a function of short-circuiting between the frequency converter and the secondary side of the wound-rotor induction machine,
a controller i) configured to, in response to a detection of an over-voltage at the secondary side of the wound-rotor induction machine, activate the first short-circuit device to perform short-circuiting, deactivate the frequency converter, and cancel short-circuiting of the second short-circuit devices, at a first time point ii) configured to restart the frequency converter to set the current flowing through the first short-circuit device to be zero, and cancel short-circuiting of the first short-circuit device, at a second time point after a predetermined time period has elapsed from the first time point and iii) configured to control the second short-circuit devices to perform short-circuiting, at a third time point after a predetermined time has elapsed from the first time point, wherein the third time point comes after the second time point comes,
the over-voltage prevention device being controllable such that a short-circuit current flows from the first short-circuit device through the resistors into the frequency converter when short-circuiting of the first short-circuit device is canceled.

10. The current rectifying circuit according to claim 9 , wherein a resistance of the resistor is smaller than a value obtained by dividing a maximum output voltage of the frequency converter by a maximum current when flowing from the first short-circuit device through the resistor into the frequency converter.

11. The over-voltage prevention device according to claim 9 , wherein a resistance of the resistor is a value ensuring that a voltage of a DC link capacitor provided in the frequency converter at a time when a short-circuit current flows into the frequency converter from the first short-circuit device due to restart of the frequency converter is below an operational threshold of the first short-circuit device.

12. The current rectifying circuit according to claim 9 , wherein the second short-circuit device is formed of a mechanical breaker.

13. The current rectifying circuit according to claim 9 , wherein the second short-circuit device is formed of a plurality of mechanic breakers connected in parallel.

14. The current rectifying circuit according to claim 9 , wherein the second short-circuit device is formed of a semiconductor breaker.

15. The current rectifying circuit according to claim 9 , wherein the second short-circuit device is formed of a plurality of semiconductor breakers connected in parallel.

Assignees

• Toshiba Kk

Inventors

• Hasegawa Ryuta
• Ishizuki Teruyuki
• Fujita Takashi
• Kageyama Takahisa
• Kitamori Yutaro
• Sato Sho

Classifications

• H02P29/0241

  the fault being an overvoltage · CPC title

• H02H7/12

  for static converters or rectifiers {(for discharge lamp power supplies using static converters H05B41/2851, H05B41/2921, H05B41/2981)} · CPC title

• H02P9/007

  Control circuits for doubly fed generators · CPC title

• H02H7/06 Primary

  for dynamo-electric generators; for synchronous capacitors · CPC title

• H02H9/002

  limiting inrush current on switching on of inductive loads subjected to remanence, e.g. transformers · CPC title