JP2733334B2 - Electrolytic capacitor short circuit detection device - Google Patents

Description

The present invention relates to an electrolytic capacitor short circuit for detecting a short circuit of a plurality of electrolytic capacitors arranged in parallel or a plurality of columns of electrolytic capacitors connected in series. The present invention relates to a detection device.

[Prior Art] FIG. 4 is a circuit diagram showing a general transistor inverter, in which (16) is a diode converter, and (17) is a plurality of electrolytic capacitors (18) arranged in parallel. The configured capacitor bank, (19) is an inverter.

As shown in FIG. 5, the capacitor bank (17) may be constituted by five columns of electrolytic capacitors connected in series by four.

 Next, the operation will be described.

The input / output of the inverter shown in FIG. 4, that is, the current of the diode converter (16) and the inverter (19) contains a large amount of ripple current, and this ripple current is absorbed by the large-capacity capacitor bank (17).

Since the ripple current increases in proportion to the capacity of the inverter, the number of electrolytic capacitors (18) constituting the capacitor bank (17) also increases in proportion to the capacity of the inverter.

For example, 450WV, 5600μ for an inverter of about 1000KVA
About 80 large-capacity electrolytic capacitors (18) of F are used.

[Problems to be Solved by the Invention] Since the conventional inverter is configured as described above, the reliability of the inverter is reduced by using a large number of electrolytic capacitors having a higher failure rate than other components. There were challenges. Therefore, effective means for detecting an internal short circuit of the electrolytic capacitor has been desired.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and has as its object to provide a device capable of reliably and easily detecting an internal short circuit of an electrolytic capacitor.

[Means for Solving the Problems] An electrolytic capacitor short-circuit detecting device according to the present invention provides a current path for each of a plurality of electrolytic capacitors connected in parallel or a plurality of rows of electrolytic capacitors connected in series. A first current detecting means provided in each current path and having its polarity alternately connected to a positive polarity and a reverse polarity; and a second current calculating means for obtaining a sum of output currents of the first current detecting means. It is provided with a current detection means and a detection circuit for inputting an output current of the second current detection means, wherein the detection circuit detects a short circuit of the electrolytic capacitor based on an output current of the second current detection means.

[Action] The electrolytic capacitor short-circuit detecting device according to the present invention includes a plurality of first electrolytic capacitors provided for each of a plurality of electrolytic capacitors arranged in parallel or a plurality of electrolytic capacitors connected in series. The stationary current is canceled by alternately connecting the polarities of the current detecting means to positive and reverse polarities, only the internal short-circuit current is detected by the first current detecting means, and the internal short-circuit current is detected by the second current detecting means. The short circuit of the electrolytic capacitor is detected by a detection circuit which receives the output current of the second current detection means.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, (1), (2), (3), (4),
(5) is a current detecting means (hereinafter referred to as an alternately connected reverse polarity)
CT1 to CT5), (6), (7), (8), (9),
(10) is an electrolytic capacitor or an electrolytic capacitor row connected in series.

Further, (11) is a second CT for detecting the sum of the secondary currents of CT1 (1) to CT5 (5), and (12) is an electrolytic capacitor (6) to (5) based on the output of the second CT (11). This is a short-circuit detection circuit that performs short-circuit detection of 10).

Further, as shown in detail in FIG. 3, CT1 (1) to CT5 (5) fix a cable (14) wound around a cable (13) connecting electrolytic capacitors (6) to (10). It is composed of things.

 Next, the operation of the present embodiment will be described.

In the steady state, since the same-phase current flows through the electrolytic capacitors (6) to (10), the sum of the secondary currents of CT1 (1) to CT5 (5) is 1/5 of the total current.

Generally, when the number of parallel electrolytic capacitors is N, N =
It is known that if an even number, the sum of the secondary currents = 0, and if N = odd, the sum of the secondary currents = the total current × 1 / N × CT ratio, and that only a small current flows.

When an internal short circuit occurs in the electrolytic capacitor (6), as shown in FIG.
CT2 (2) to CT5, which detects the current 12 to 15 flowing in (10)
The secondary current of (5) is canceled because it is connected to the opposite polarity to zero, but CT1 (1) detects the value of the short-circuit current I1 itself.

Therefore, a current obtained by multiplying the short-circuit current by the CT ratio flows through the second CT (11).

That is, in the second CT (11), in the steady state, at most (when N is an odd number) at most the current of only about the rated ripple current (several 10A) of one electrolytic capacitor flows, Sometimes a current of several KA flows, so that the detection sensitivity is good, and a short circuit can be sufficiently determined even with a simple CT of the air core in which the cable is simply wound into a fixed size as shown in FIG.

In the above embodiment, the number of electrolytic capacitor rows is five, but the present invention is not limited to the number of electrolytic capacitor rows.

When a plurality of electrolytic capacitor rows are short-circuited at the same time, the above-described detection cannot be performed. However, such a thing is unlikely to occur and there is no practical problem.

[Effects of the Invention] As described above, according to the present invention, each of a plurality of electrolytic capacitors arranged in parallel or a plurality of electrolytic capacitors connected in series by a plurality of electrolytic capacitors is provided for each column. Since the short circuit of the electrolytic capacitor is detected by a plurality of first current detecting means in which the polarity is alternately connected to the positive polarity and the reverse polarity, the short circuit of the electrolytic capacitor is detected immediately, and the reliability of the inverter is improved. Can be improved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of an electrolytic capacitor short-circuit detecting device according to one embodiment of the present invention, FIG. 2 is a diagram showing a current when an electrolytic capacitor is short-circuited, FIG. 3 is a perspective view showing a configuration of a CT, FIG. 4 is a circuit diagram showing a general example of a voltage-type inverter, and FIG. 5 is a diagram showing a plurality of rows of electrolytic capacitors connected in series. In the drawing, (1) to (5) are first current detecting means, and (6) to (6).
(10) and (18) are electrolytic capacitors, (11) is second current detecting means, and (12) is a detecting circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

(57) [Claims] 1. A current path for each of a plurality of electrolytic capacitors connected in parallel or a current path for each of a plurality of columns of electrolytic capacitors connected in series, each having a polarity alternately provided. A first current detecting means connected to the positive polarity and the opposite polarity; a second current detecting means for obtaining a sum of output currents of the first current detecting means; and an output current of the second current detecting means. An input detection circuit, wherein the first current detection means includes a short-circuit when a short-circuit current flows through a capacitor by means of an air-core loop-shaped coil part of which is disposed close to the current path to be detected. An electrolytic capacitor short-circuit detecting device, wherein a current corresponding to the current flows, and the detecting circuit detects a short-circuit of the electrolytic capacitor based on an output current of the second current detecting means.