JPH0698530A - Dc capacitor circuit - Google Patents

Abstract

PURPOSE:To detect a failure before a capacitor case is damaged even if the breakdown of a capacitor element occurs by providing a detector between the voltage-dividing point and a leading terminal of a voltage divider. CONSTITUTION:When a capacitor element 3a-1 in a DC capacitor 1-1 is short- circuited due to breakdown, the energy of a capacitor 3b-1 connected in parallel in a same capacitor case 5-1 flows to the capacitor element 3a-1 and at the same time the energy of capacitors 1-2-1-n connected in parallel externally flows to the capacitor 1-1. However, the flowing energy is suppressed by sound capacitors 4a-1 and 4b-1 connected in series, the capacitor case 5-1 does not breakdown quickly. On the other hand, a terminal 7-1 which is a connection point of capacitor elements connected in series is the potential of a bus P, thus generating a potential difference at the point between voltage-divider resistors 8a-1 and 8b-1 and activating a capacitor shortcircuit detector 901 and breaking a power supply.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC capacitor circuit capable of detecting an abnormality in a DC capacitor used in a DC filter of a power converter.

[0002]

2. Description of the Related Art A DC capacitor circuit used in a DC filter of a conventional power converter will be described with reference to FIG.

The DC capacitors 1-1 to 1-n are the power converter 2
It is used by inserting it between the DC busbars P and N in parallel with the power converter 2 for the purpose of absorbing the switching ripple of, or suppressing the DC voltage fluctuation due to the active power fluctuation. Power converter 2
When the DC voltage of DC exceeds 2000 V DC, an aluminum foil capacitor is often used as the DC capacitor for the DC filter. In that case, the structure of the DC capacitor 1-1 is the capacitor elements 3a-1, 3b-1 and 4a-1, 4 connected in parallel.
b-1 is connected in series and is housed in a capacitor case 5-1 and one terminal of the capacitor elements 3a-1 and 3b-1 connected in parallel is connected to the capacitor case 5-1 and a terminal 6a-1 is insulated. Connect to
The opposite terminals of the parallel-connected capacitor elements 4a-1 and 4b-1 are connected to the terminal 6b-1 insulated from the capacitor case 5-1. (For the structure of the DC capacitor 1-1, the capacitor elements are not connected in parallel, that is, one parallel structure is also included.) The terminals 6a-1 and 6b-1 insulated from the capacitor case 5-1 are the DC buses P and N. Is connected in between.
A DC capacitor 1n is connected in parallel with the DC capacitor 1-1.

[0004]

When a capacitor element is dielectrically broken down, if the capacitor elements are not connected in series (when there is no capacitor element 4a-1 or 4b-1), they are connected in parallel in the same capacitor case. The energy of the capacitor element flows into the capacitor element whose insulation has been destroyed, and the energy of capacitors 1-2 to 1-n connected in parallel externally flows into the capacitor 1-1 that has insulation breakdown, and the capacitor case 5 -1 is more likely to be destroyed. Even when the capacitor elements are connected in series, if the capacitor element 3a-1 has a dielectric breakdown, the same capacitor case
The energy of the capacitor element 3b-1 connected in parallel inside the capacitor flows into the capacitor element 3a-1 that has a dielectric breakdown, and the energy of the capacitors 1-2 and 1-n connected in parallel outside has a dielectric breakdown. -1 flows into. In this case, the healthy capacitors 4a-1 and 4b-1 connected in parallel in the capacitor case 5-1 suppress the inflow energy, and the capacitor case is not destroyed in a short time (several hours to several weeks). . However, if left as it is, the capacitor element 4a-1
Or when the insulation of 4b-1 is caused, the capacitor case 5-1 is destroyed with an impulsive sound, and the contents of the capacitor are scattered.

Therefore, an object of the present invention is to provide a DC capacitor circuit capable of detecting a failure so that the capacitor case is not destroyed even when the dielectric breakdown of the capacitor element occurs.

[0006]

The above object is to provide a series of capacitor elements 3a-1 and 4a-1 and series-connected capacitor elements 3a-1 and 4a- in a DC capacitor circuit used for a DC filter of a power converter. Condenser case for storing 1
5-1, and capacitor elements 3a-1 and 4a-1 connected in series
Connect one terminal and one terminal to the capacitor case 5 respectively.
-1 to the outside of the capacitor case 5-1 and terminals 6a-1 and 6b-1 insulated from the capacitor case 5-1 and capacitor elements 3a-1 and 4a-
DC capacitor 1-1 and DC capacitor 1 provided with terminal 7-1 leading from the series connection part of 1 to capacitor case 5-1
This can be achieved by attaching the detector 9-1 to the terminal 7-1 of -1.

[0007]

When any one of the capacitor elements 3a-1 and 4a-1 connected in series breaks down, a short-circuit current flows and a difference occurs between the voltage across the capacitor element 3a-1 and the voltage across the capacitor element 4a-1. The current or voltage is detected by the detector. Even when one of the capacitor elements connected in series is short-circuited due to dielectric breakdown, the capacitor can operate without dielectric breakdown for a short time (several hours to several weeks), so that protection is possible during that time.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the block diagram of FIG. The DC capacitor 1-1 is used by inserting it between the DC buses P and N in parallel with the power converter 2 for the purpose of absorbing switching ripple of the power converter 2 or suppressing active power fluctuation. The structure of the DC capacitor 1-1 is the capacitor elements 3a-1, 3b-1 and 4a-1, 4b-1 connected in series.
Are connected in series and are housed in the capacitor case 5-1 and one side terminals of the capacitor elements 3a-1 and 3b-1 connected in parallel are connected to the terminal 6a-1 which is insulated from the capacitor case 5-1. Connect the opposite terminals of the parallel-connected capacitor elements 3a-1 and 3b-1 to one terminal of the parallel-connected capacitor elements 4a-1 and 4b-1 to the terminal 7-1 that has the same potential as the capacitor case, and connect them in parallel. The opposite terminals of the connected capacitor elements 4a-1 and 4b-1 are connected to the terminal 6b-1 insulated from the capacitor case 5-1.

Terminal 6 insulated from the capacitor case 5-1
a-1 and 6b-1 are connected between the DC buses P and N. One end of the voltage dividing resistor 8a-1 is connected to the DC bus P, and one end of the voltage dividing resistor 8b-1 is connected to the other end of the voltage dividing resistor 8a-1. The other end of the voltage dividing resistor 8b-1 is connected to the DC bus N. The capacitor short-circuit detector 9-1 includes a connecting portion of the voltage dividing resistors 8a-1 and 8b-1 and the capacitor elements 3a-1 and 3b-1.
And the capacitor elements 4a-1 and 4b-1 are connected to the terminal 7-1 having the same potential as the capacitor case 5-1. Similarly, the capacitor short-circuit detector 9-n includes a connecting portion of the voltage dividing resistors 8a-n and 8b-n and the capacitor elements 3a-n, 3b-n.
And the capacitor elements 4a-n and 4b-n are connected to the terminal 7-n having the same potential as the capacitor case 5-n.

In FIG. 1, when the DC capacitor 1-1 is normal, capacitor elements 3a-1 and 3b-1 connected in series are connected.
Since the terminal 7-1, which is the connection point of 4a-1 and 4a-1 and 4b-1, and the point between the voltage dividing resistors 8a-1 and 8b-1 have the same potential, the capacitor short-circuit detector 9-1 does not operate. . If the capacitor element 3a-1 in the DC capacitor 1-1 is short-circuited due to dielectric breakdown, the energy of the capacitor element 3b-1 connected in parallel in the same capacitor case 5-1 will cause dielectric breakdown.
Capacitor 1 in which the energy of capacitors 1-2 to 1-n that have flowed into a-1 and are connected in parallel externally have a dielectric breakdown
-1 flows into. The healthy capacitors 4a-1 and 4b-1 connected in series in the capacitor case 5-1 suppress the inflow energy, and the capacitor case 5-1 is not destroyed in a short time. On the other hand, due to the short circuit of the capacitor element 3a-1, the series connected capacitor elements 3a-1, 3b-1 and 4a-1, 4b-
Since the terminal 7-1, which is the connection point of 1, has the potential of the bus bar P,
A potential difference is generated between the terminal 7-1 and the voltage dividing resistors 8a-1 and 8b-1.

Due to this potential difference, the capacitor short-circuit detector 9-1 operates. It is possible to prevent the capacitor case 5-1 from being broken by stopping the power converter 2 and shutting off the power according to the detection signal of the capacitor short-circuit detector 9-1.

In this embodiment, the DC capacitors 1-1 to 1-n are used.
Up to this example, the parallel connection is shown, but the parallel connection is not necessary. Further, the capacitor elements in the DC capacitor do not have to be connected in parallel. Furthermore, the number of series capacitor elements in the DC capacitor may be two or more series.

[0013]

As described above, according to the present invention, since it is possible to detect the dielectric breakdown of the capacitor element in the DC capacitor, it is possible to provide a safe DC capacitor circuit.

Further, as compared with the case where the capacitor element is rated so that even if the capacitor element is short-circuited, the remaining healthy elements can withstand the voltage, the capacitor element can withstand only a short time, so an inexpensive DC capacitor A circuit can be provided.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a DC capacitor circuit showing an embodiment of the present invention.

FIG. 2 is a configuration diagram of a conventional DC capacitor circuit.

[Explanation of symbols]

1-1 to 1-n ...... DC capacitor, 2 ...... Power conversion circuit 3a-1 to 3a-n ...... Capacitor element, 3b-1 to 3b-n ...... Capacitor element 4a-1 to 4a-n ...... Capacitor element, 4b-1 to 4b-14 ... Capacitor element 5-1 to 5-n ... Capacitor case, 6a-1 to 6a-n ... Terminal insulated from the capacitor, 6b-1 to 6b- n: Terminal insulated from the capacitor, 7-1 to 7-n ... Terminal of the same potential as the capacitor case, 8a-1 to 8a-n ... Voltage dividing resistor, 8b-1 to 8b-n ... … Voltage resistance, 9-1 to 9-n …… Capacitor short-circuit detector

Claims (1)

[Claims] 1. A DC capacitor circuit used for a DC filter of a power converter, wherein at least two DC capacitors are connected in series.
A series circuit composed of individual capacitor elements, a capacitor case for housing the series circuit, and one terminal and the other terminal of the series circuit for respectively pulling the capacitor case to the outside of the capacitor case. Between a pair of terminals that are provided insulated from each other, a lead-out terminal that is provided in the capacitor case and has the same potential as the series connection point of the capacitor elements, and the positive and negative bus lines to which the pair of terminals are connected. It comprises a voltage divider connected, and a detector connected between the voltage dividing point of the voltage divider and the lead-out terminal, and by the detector,
A DC capacitor circuit, which detects dielectric breakdown of the capacitor element.