JP3036824B2 - DC capacitor with built-in internal failure detection device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC capacitor having a built-in internal failure detection device used as a DC power supply for a charge / discharge device or an inverter.

2. Description of the Related Art Large-capacity high-voltage DC capacitors are used in DC power supplies such as charge / discharge devices and inverters.

Should the capacitor become short-circuited due to an internal failure, the charged energy is discharged internally, and this energy may explode and explode the capacitor, causing serious damage.

In order to prevent this, a capacitor is divided into small capacitors, and a current limiting resistor or a current limiting coil is DC-connected to each capacitor so that a large discharge energy is not generated in the failed capacitor.

However, dividing a capacitor into small capacitors as described above has many disadvantages, such as high cost and large installation space, and insertion of a current-limiting resistor and a current-limiting coil requires a circuit. The fact is that in many cases, the performance of the device is lowered due to the increase in the impedance, and the loss is increased, which is not preferable.

Means to solve the problem If the internal failure of the capacitor is detected early and opened from the power supply before short-circuiting, the damage of the failed capacitor due to the explosion oil can be prevented. It is.

That is, the internal current elements are divided into two groups so as to have substantially the same capacity, these are connected in parallel, and in the capacitor having a built-in current transformer for detecting the current of the element groups of the two groups, the upstream current transformer is An internal fault detection device consisting of a secondary winding and two sets of primary windings is configured. The current of each element group flows differentially through the primary winding and detects the current generated in the secondary winding. This is a DC capacitor with a built-in internal failure detection device.

Function Although it is a DC capacitor, it is charged and discharged during use, so a ripple current or pulse current always flows.This current is compared with other healthy element groups to detect a difference current. Detects capacitor failure.

Embodiment An embodiment of the present invention is shown in FIG.

Reference numerals 1 and 2 denote element groups inside the capacitor. Numeral 3 denotes a current transformer having two sets of primary windings.
2 are connected so as to flow differentially. The terminals 4 and 5 of the secondary winding are drawn out of the capacitor case 6.

The capacitor 7 is a DC capacitor charged by an AC power supply 8 through a diode 9 as shown in FIG. 2, and the load 10 is a discharge device or an inverter device. The secondary terminal of the current transformer 3 built in the capacitor is drawn out of the case and connected to a relay 11 which operates by detecting current or voltage.

Since the element groups 1 and 2 in the capacitor are composed of a plurality of elements connected in series as shown in the figure in a high-voltage capacitor, if a short circuit occurs due to dielectric breakdown of some elements, the capacitance of this element group becomes As a result, the ripple current or the pulse current generated by charging and discharging the capacitor changes. Since two sets of primary windings of the built-in current transformer 3 are connected so that the currents of the element groups 1 and 2 flow differentially, the element groups 1 and 2 have substantially the same capacity. When sound, the current of each element group is negated, and no current or voltage is generated in the secondary winding. However, if a part of the elements of element group 1 is broken and short-circuited, the current of element group 1 is reduced. Element group 2
, And is not canceled inside the current transformer 3, so that current and voltage are generated in the secondary winding.

If this is detected by the relay 11 and a contact signal is obtained and the power supply is opened by this, the failure of the capacitor will not progress further and the occurrence of damage due to the explosion oil can be prevented beforehand.

As a method for detecting the current of the element group, there is a method of separately installing a current transformer in each element group and detecting the difference current on the secondary side.However, in the case of a DC capacitor, the current transformer is determined by the DC component of the current. Since the iron core is demagnetized and the characteristics deteriorate, the detection accuracy is lowered, which is not preferable. The method of the present invention is very advantageous in this respect.

It is a matter of course that the current transformer may be of a general penetration type and the lead wires of each element group may be penetrated so as to be opposite to each other.

Effect of the Invention As described above, by using the method of the present invention, a capacitor failure is detected at the early stage of destruction of some elements. This has the effect of preventing the occurrence of such a problem and significantly improving the safety, and is of great industrial and practical value.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a DC capacitor according to one embodiment of the present invention,
FIG. 2 is an example of a connection circuit of a DC capacitor according to the present invention. 1, 2: element group inside capacitor 3: current transformer 7: DC capacitor

Continuation of the front page (56) References JP-A-1-255433 (JP, A) JP-A-61-106070 (JP, A) JP-A-64-39228 (JP, A) JP-A-58-196540 (JP) , U) Shokai Sho 56-44536 (JP, U) Shokai Sho 52-1220928 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02H 3/08-3/28 H02H 7/00-7/122 H02M 7/48

Claims (1)

(57) [Claims] An internal element is divided into two groups so as to have substantially the same capacity, these are connected in parallel, and a capacitor having a built-in current transformer for detecting the current of the element group of each of the two groups is provided. The current transformer constitutes an internal failure detection device including a secondary winding and two sets of primary windings, and the current of each of the above-described element groups flows differentially through the primary winding and is generated in the secondary winding. A DC capacitor having a built-in internal failure detection device, comprising an internal failure detection device for detecting a current.