JP2012231627A - Arc prevention method for breaker for power conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that a power conversion device which includes no input current detector cannot confirm that there is no input current, and the problem that when a breaker of the power conversion device which includes no input current detector is opened, an arc is generated with a fine current and continues with a discharge switch closed.SOLUTION: An input current increase is cut off by short-circuiting a charging resistance, and the discharge switch is closed after an input voltage detector and a capacitor voltage detector determine that there is no input current. When an arc generated between contacts of the breaker with a fine current flowing at the time of opening operation of the breaker is cut off, the ark prevention method performs control so that the voltage detectors confirm an input voltage and a capacitor voltage after a charge voltage short-circuiting switch is closed to determine that there is no input current, and then the discharge switch is closed. Even when the breaker is opened halfway during capacitor charging in the power conversion device which includes no input current detector, it is securely determined that there is no input current, and then the discharge switch is closed, thereby achieving arc prevention.

Description

  The present invention relates to a method for preventing an arc generated in a circuit breaker for a power converter.

The circuit breaker for a power converter has a role of opening and closing a circuit when the power converter is started and stopped. When the power converter is activated, when the contact of the circuit breaker is closed, the DC filter capacitor is charged through the charging resistor, and when the capacitor voltage is charged to a certain value, the charging resistor is short-circuited by the switch. When the capacitor voltage becomes equal to the power supply voltage, the power converter starts operating and supplies power to the load.
When stopping, the power supply to the load is stopped, and the power supply voltage and the capacitor voltage are equal, so that the current flowing through the circuit breaker becomes zero and the circuit breaker can open the circuit without generating an arc. Thereafter, when the discharge switch is closed, the capacitor voltage is discharged by the discharge resistor.

  If the circuit breaker is opened during the charging of the DC filter capacitor during startup, an arc may occur between the contacts of the circuit breaker. At this time, the capacitor is charged through the charging resistor by the arc, but when the discharge switch is turned on at this stage, a discharge circuit is formed, the capacitor cannot be charged, and a small charging current generated from the potential difference between the power supply voltage and the capacitor voltage The arc may continue and burn out the circuit breaker.

  As an improvement measure, there is an arc prevention method in which when the circuit breaker is opened during the charging of the DC filter capacitor, the charging resistor is short-circuited by the switch, the input current detector detects zero input current, and then the discharge switch is closed.

JP 2001-157359 A

  In the background art, there is a problem that the input current zero cannot be confirmed in the power conversion device having no input current detector.

According to the invention of claim 1,
Power supply circuit breaker, DC filter reactor, charging circuit and charging resistor short-circuit switch connected in parallel, DC filter capacitor provided on the output side of the charging circuit, discharge provided in parallel with the DC filter capacitor In the arc prevention method for the circuit breaker of a power converter comprising a discharge circuit in which a resistor and a discharge switch are connected in series, and a load that receives a DC voltage stored in the DC filter capacitor, the circuit breaker is opened. When the arc generated between the contact points of the circuit breaker is interrupted by a minute input current that flows, the input voltage and the capacitor voltage are confirmed by a voltage detector after closing the charging resistance short-circuit switch. Control is performed so as to close the discharge switch by judging that the current is zero.

  According to a second aspect of the present invention, in the arc prevention method according to the first aspect, when determining that the input current is zero, the input current is set to a difference voltage value between the input voltage and the capacitor voltage. The calculation is performed by dividing the charging resistor by the charging resistance value of the charging resistor, and it is determined that the input current is zero and the discharge switch is controlled to be closed.

  That is, it is characterized in that the potential difference is confirmed using the input voltage and the capacitor voltage, the input current is determined to be zero, and the discharge switch is closed so that a power conversion device without an input current detector can detect zero input current.

  Even if the circuit breaker is opened in the middle of charging the capacitor with a power conversion device that does not have an input current detector, the discharge switch is closed after reliably determining the input current to zero, thereby preventing arcing.

It is the circuit diagram which showed this invention technique. (Example 1) It is a timing chart of FIG. It is the circuit diagram which showed background art.

  The input voltage detector 14 and the capacitor voltage detector 15 are used in the power converter 1 to determine zero input current.

FIG. 1 is a circuit diagram showing the technique of the present invention. FIG. 2 is a timing chart of FIGS. This will be described below with reference to FIG.
There is a power supply voltage at point a in FIG. 2, and the DC filter capacitor voltage is 0V. The switch 2 of the discharge circuit 7 is opened, the circuit breaker 8 is turned on at point b, and the input current starts charging through the charging resistor 6. When the circuit breaker 8 is opened at the point c, an arc is generated between the contacts of the circuit breaker 8. By short-circuiting the charging resistor 6 by the switch 1 in FIG. 1 at point d and increasing the input current, the circuit breaker 8 can interrupt the input current and extinguish the arc. Further, the input voltage = capacitor voltage is detected by the capacitor voltage detector 15, and after judging that the input current is zero, the switch 2 of the discharge circuit 7 is closed at the point e to discharge the capacitor voltage. At the point f, the capacitor voltage ends discharging.

  Even in a power converter breaker that does not have an input current detector, arcing can be prevented, which is very useful.

DESCRIPTION OF SYMBOLS 1 Switch 2 Switch 3 DC filter reactor 4 Input circuit 5 DC power supply 6 Charge resistor 7 Discharge circuit 8 Breaker 9 Discharge resistor 10 DC filter capacitor 11 Power converter 12 Controller 13 Input current detector 14 Input voltage detector 15 Capacitor voltage detector

Claims (2)

  Power supply circuit breaker, DC filter reactor, charging circuit and charging resistor short-circuit switch connected in parallel, DC filter capacitor provided on the output side of the charging circuit, discharge provided in parallel with the DC filter capacitor In the arc prevention method for the circuit breaker of a power converter comprising a discharge circuit in which a resistor and a discharge switch are connected in series, and a load that receives a DC voltage stored in the DC filter capacitor, the circuit breaker is opened. When the arc generated between the contact points of the circuit breaker is interrupted by a minute input current that flows, the input voltage and the capacitor voltage are confirmed by a voltage detector after closing the charging resistance short-circuit switch. A circuit breaker for a power converter, wherein the discharge switch is controlled to be closed by judging that the current is zero Arc prevention method.   2. The arc prevention method for a circuit breaker for a power converter according to claim 1, wherein when the input current is determined to be zero, the input current is set to a difference voltage value between the input voltage and the capacitor voltage. An arc prevention method for a circuit breaker for a power converter, comprising: calculating by dividing by a charging resistance value of a resistor; determining that the input current is zero; and controlling to close the discharge switch .

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