AU657098B2

AU657098B2 - Circuit arrangement

Info

Publication number: AU657098B2
Application number: AU83394/91A
Authority: AU
Inventors: Rudolf Wiesenbacher
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1991-08-28
Filing date: 1991-08-28
Publication date: 1995-03-02
Anticipated expiration: 2011-08-28
Also published as: EP0600874A1; AU8339491A; CA2116528A1; CN1070066A; JPH06509932A; WO1993005558A1

Description

OPI DATE 05/04/93 AOJP DATE 10/06/93 APPLN. ID 83394/91 PCT NUMBER PCT/DE91/00681 AU?1 83394 (51) Intemationiile Patcntkassifikation 5 (11) Internationale Verbrrentlictiungsnummer: WO 93/05558 H02H 9/04, HOIT 1/14 Al (43) Internatlonales Vertiffentlichungsdatum 18. M'drz 1993 (18.03.93) (21) Internatlonales Aktenzeichen: PCT/DE91/00681 Ver~ffentlicht Alit internationalcmi Rclwrclicnbericlu.

(22) Internationales Anmeldedatum: 28. August 1991 (28.089 78 (71) Anmelder (ffir alle Besfinungssalen ausser US): SIE- MENS AKTI ENGESELLSCHAFT [DE/DE]; Wittelsbacherplatz 2, D-8000 Milnchen 2 (DE).

(72) Erfinder; und Erfinder/Anelder (hurfl~r US) WIESENBACI-!ER, Rudolf[DE/DE]; Brandeniburger Sir. 42, D-8555 Adelsdorf

(DE).

(74) Gemcinsamcr Vertreter: SIEMENS AG; Postfach 22 16 34, D-8000 Mflnchen 22 (DE), (81) BestlImm ungsstaaten: AU, CA, JP, US, europflisches Patent (AT, BE, CH, DE, DK, ES, FR, GB, GR, IT, LU, NL,

SE).

(54)Title: CIRCUIT ARRANGEMENT (54) Bezeichnung: SCHALTUNGSANORDNUNG (57) Abstract In order to improve the ratio between efficiency and complication in the best possible way in a circuit arrangement i:la, Ib) with a parallel circuit (3a, 3b) made of a power component (Sa, 5b) and an overvoltage arrester (7a, 7b), for a predetermined operating voltage (UB) the technical complication in the power component (Sn, Sb) and in the overvoltage atrester (7a, 7b) is reduced, a forced cooling system being fitted to the overvoltage arrester for compensation purposes. Alternatively, for the same technical complication, the operating voltage can be increased.

(57) Zusammenfassung Urn bei einer Schaltungsanordnung (Ia, Ib) mit einer Parallelschaltung (3a, 3b) aus einemn Leistungsbauelement (Sa, Sb) und elnem tOberspannungsableiter (7a, 7b) das Verhilltnis zwischen Leistungsvermi~gen und Aufwand optimal zu verbessern, wird bei ciner vorgegebener, Betricbsspanning (UB) der technLsche Aufwand beim Leistungsbauclement (Sa, Sb) und beim Oberspannungsableiter (7a, 7b) verringert, wobel zumn Alusgleich der Oberspannungsableiter (7a, 7b) zwangsgektlblt ist. Alternativ kann bei gleichbleibendem technischemn Aufwand eine Erholhung der Betriebsspannung erzielt werden.

WO 93/05558 1 PCT/DE91/00681 Circuit arrangement The invention relates to a circuit arrangement having a parallel circuit comprising a power module and a surge arrester.

It is known to connect electrical power modules to surge arresters to protect the power modules from overvoltages. The surge arrester is designed here in such a way that it generates a minimum of heat loss given a normal operating voltage. The power module is then designed according to the maximum voltage occurring which is limited by the surge arrester.

For a given operating voltage, it is desirable here to keep the technical outlay for the power module as small as possible, or to achieve an increase in the electrical power characteristics for the same technical outlay.

In a circuit arrangement of the type mentioned at the outset, the object of the invention is to improve optimally the ratio between power capability and outlay.

The starting point for the solution of said object is the realization that, for optimization, the difference between the maximum voltage occurring at the power module and the operating voltage can be reduced.

This can be achieved by reducing the maximum voltage by using a surge arrester with a lower limit voltage. Since in power electronics the surge arresters are composed of individual disks, correspondingly fewer disks are therefore used. As a result, however,

IY

-2the surge arrester for a given operating voltage then has a working point with an increased operating current so that it generates an increased heat loss. This, however, is not desirable.

Although it is known from US 4,262,319 to provide the surge arrester with gas cooling, no mention is made therein of the particular object we are concerned with here. Mereover, the technical outlay resulting from the cooling is obviously out of all proportion to the surge arrester disks saved due to better utilization.

The object is achieved by the features of Claim 1 and of Claim 2.

The inventor has namely recognized that the technical outlay for the power module can be reduced overproportionately by a saving on surge arresters with simultaneous forced cooling to compensate. Accordingly, it is also possible to increase the power utilization of the power module while maintaining the same technical outlay for the power module and surge arrester, in which case the latter is however force-cooled. The overdimensioning caused by the maximum voltage can be reduced.

A preferred dimensioning is stated in Claims 3 and 4. Lower limits from which a substantial improvements [sic] can then be achieved are set in this way. It is favorable here if the forced cooling means consists of a water cooling circuit. This provides an economic solution for optimization. The power module can likewise have a forced cooling means which can be coupled to the forced cooling means of the surge arrester by means of thermic measures. In this way it is also possible to keep the outlay for forced cooling low. Further advantageous refinements are stated in Claims q'I -t N -3- 6 to 8. The combination of all claims constitutes a preferred embodiment. This solution is characterized by a large saving on power modules.

Further advantages of the invention will be described in greater detail below with reference to exemplary embodiments, in which: FIG i shows a parallel circuit having a power module and a surge arrester, FIG 2 shows a current/voltage diagram, and FIG 3 shows a further development of the circuit arrangement according to FIG 1.

The circuit arrangement la shown in FIG 1 consists of a parallel circuit 3a comprising a power module and a surge arrester 7a. The surge arrester 7a protects the power module 5a from overvoltages here. To optimize the ratio between power capability and outlay, the surge arrester 7a is provided with a forced cooling means 9a. This may be designed, for instance, as gas cooling of the [sic) as liquid cooling. To illustrate the method of operation, FIG 2 will now be discussed in greater detail, the starting point of which is a reduction in the technical outlay for the power module FIG 2 applies analogously to an increase in the operating voltage.

The current/voltage diagram according to FIG 2 shows a given operating voltage UB, with which the parallel circuit 3a is to be operated. The curve U., represents here the current/voltage curve for a conventional surge arrester that is only cooled by its natural convection. The maximum voltage is therefore U1 here. U4 denotes the voltage difference between U1 and the operating voltage UB. The design of the power module 5a was based on the maximum voltage, that is to say Ul in the present case.

j~ 4 Given the operating voltage UB, a current I, is therefore produced in the surge arrester 7a. The surge arrester 7a ixl dimensioned here in such a way that said current Ii produces a thermally stable working point.

To reduce the technical outlay for the power module 5a, the maximum voltage must be reduced in the present example. This is achieved by selecting a surge arrester for a lower voltage, namely U2. For the given operating voltage UB, accordingly a current 12 is however set in the surge arrester 7a. This produces an increased heat loss in the surge arrester 7a, which must be eliminated by the forced cooling means 9a. It has proved particularly favorable if the maximum voltage across the parallel circuit 3a is greater than the operating voltage UB by at most a factor of 1.7, preferably by a factor of Alternatively, the forced cooling means 9a can also have a cooling capacity which is greater than the cooling capacity of the surge arrester with natural convection by a factor of 3. The cooling capacity is preferably increased by a factor of between 10 and 100.

FIG 3 shows a further circuit arrangement Ib with a parallel circuit 3b. The power module 5b may consist of a plurality of power modules here. These may be, for instance, semiconductor modules, in particular thyristors, connected in series. These are connected in series depending on the maximum voltage required. In the present case, the surge arrester 7b consists of a plurality of arrester disks lla arranged one above the other. The arrester disks lla are preferably manufactured from ZNO. The forced cooling means 9b consists of a cooling box 13a which is arranged between the ar:-ester disks lla and is connected to a cooling device 16 via lines 15. The forced cooling means 9b thus has a cooling circuit that can preferably be operated with water. If the power module 5b also has a cooling circuit, then these can be coupled to one another by means of thermic measures. For this purpose, in FIG 3 the power module 5b and the cooling device 16 are connected diagrammatically to one another via a line 17. The thermic coupling may also consist of the one surge arrester 7b and the power module having a common cooling circuit.

Starting from a reduction in outlay, the number of arrester disks Ila are first reduced by means of the circuit arrangement lb. As a result, the number of power modules in the power module 5b can be reduced. In the case of thyristors used in converters, in particular high-voltage direct-current converters, these also include the associated module slots and auxiliary devices. Overall, therefore, a substantial reduction is produced for the power module 5b. In turn, the power module 5b is consequently made smaller, which leads to a reduction in the size of the circuit arrangement lb. In conjunction with the reduced maximum voltage across the parallel circuit 3b, a further reduction in the size of the circuit arrangement lb is possible by means of reduced insulation clearances. It is of course possible to use the forced cooling neans saved in the power module for the surge arrester 7b here, so that no additional new forced cooling means need be provided here.

By virtue of the simple technical alteration, namely the forced cooling of the anrge arrester, which in itself does not initially confer any decisive advantage, surprisingly upon closer examination a large number of simplifications and savings emerge, which permit a substantially more cost-favorable manufacture of the circuit arrangement lb. Moreover, further advantages are conferred of course with regard to the space requirement of the circuit arrangement.

4- I 6 The savings will be illustrated below with reference to a dimensioning example in Figures 2 and 3.

With a conventional design, a maximum voltage of 187 KV was obtained for a given operating voltage of 100 KV. The power loss of the associated surge arrester was 17 watts here. When the power module was formed in a 12-pulse current converter, this produced a series number of operations of 34 thyristors per bridge branch.

Now the calculation for the design with forced cooling. It was possible to reduce here the number of arrester disks in the surge arrester for an operating voltage reduced by 22%, that is to say from 100 KV to 78 KV. This resulted in a maximum voltage of 146 KV. The power loss occurring in the surge arrester is then 900 watts, and it was possible to reduce the series number of operations of the thyristors to 26.

8 thyristors are thus saved per series connection. In the present 12-pulse current converter, this series number of operations must be multiplied by 24 bridge branches, so that a total of 192 saved thyristors and the associated module slots is obtained. For the dimensioning of the modules, there is a non-linear relationship, on which the surprising effect is produced during optimization. The effect can be used to increase the operating values or to reduce the outlay.

Application of the present circuit arrangement is however also suitable for other power modules, or for high-voltage equipment such as motors or power-breakers for example. The forced cooling can also be operated here with other cooling media, for example also with sulfur hexafluoride (SF 6 A preferred use is in power converters of high-voltage direct-current converter systems.

:1k r ,T %e B c

Claims

1. Circuit arrangement having a parallel circuit comprising a power module and at least one surge arrester, which protects the former from overvoltages and has a maximum voltage Umax2 that is much lower than a maximum voltage 6 Umaxl corresponding to a given operating voltage UB of the power module, and wherein the at least one surge arrester is forced-cooled.

2. Circuit arrangement having a parallel circuit comprising a power module and at least one surge arrester protecting the former from overvoltage, wherein for a given maximum voltage Umaxl of the at least one surge arrester the to operating voltage UB of the power module is substantially higher in comparison to its previous operating voltage UB, and wherein the at least one surge arrester is force- cooled.

3. Circuit arrangement according to Claim 1 or 2, wherein the ratio between the maximum voltage occurring across lhe parallel circuit and the operating 16 voltage i. less than 1.7, preferably

4. Circuit arrangement according to any claim of Claims 1 to 3, wherein forced cooling means of the at least one surge arrester has a cooling capacity S" which is greater than the cooling capacity using natural convection by at least a factor of 3.

5. Circuit arrangement according to Claim 1 or 2, wherein the surge arrester comprises a plurality of arrester disks arranged one above the other, at least :one cooling box being arranged between these arrester disks.

6. Circuit arrangement according to ar, claim of Claims 1 to wherein the forced cooling means consists of a water cooling circuit. 26

7. Circuit arrangement according to any claim of Claims 4 to 6, wherein the power module likewise has a forced cooling means which can be coupled to the forced cooling means of the at least one surge arrester by means of a thermal measures.

8. Circuit arrangement according to Claim 7, wherein the power module and the at least one surge arrester have a common cooling circuit,

9. Circuit arrangement according to any claim of Claims 1 to 8, wherein the power module is at least one semiconductor module, preferably a thyristor. Circuit arrangement according to any claim of Claims 1 to 9, 36 wherein the at least one surge arrester is a ZnO arrester.

INAlibcc0021:HRW

11. Circuit arrangement according to any claim of Claims 1 to wherein the parallel circuit is part of a converter, preferably of a high-voltage direct- current converter.

12. Circuit arrangement having a parallel circuit substantially as described in the specification with reference to Figs. 1-3 of the accompanying drawings. DATED this Twenty-fourth Day of November 1994 Siemens Aktiengesellschiaft Patent Attorneys for the Applicant 0 SPRUSON FERGUSON *00 so W -I, INMU000IO219 MIW