1、EIA TENTSTDLZ 73 m 3234b00 00072b 2 m / JEDEC Tentative Standard No. 12 Suggested Standard for Selenium Surge Suppressors November 1973 Published by ELECTRONIC. INDUSTRIES ASSOCIATION Engineering Department 2001 Eye Street, N. W., Whiagton, D. C. 20006 EIA TENTSTDL2 73 = 3234600 O007270 9 3 TITLE: S
2、UGGESTED STANDARBS FOR SELENIUM SUPPRESSORS PREPARED BY: JC-22 COMMITTEE ON SELENIUM SURGE SUPPRESSORS TASK FORCE MEMBERS: Chairman: C.E. Arnold - GENERAL ELECTRIC COMPANY C.B. Geib - INTERNATIONAL RECTIFIER COW. N. Farb - GENERAL INSTRUMENT COMPANY C.L. Maloney - WESTINGHOUSE CORP. C.F. Seyer - POW
3、ER CONVERSION PRODUCTS INC. G.E. Weber - FMC - SYNTRON DIVISION F.T. Zoerner - SARKES-TARZIAN, INC. Revised: 5-13-70 7-23-70 10- 9-70 5- 6-71 8-29-72 2-27-73 -1- EIA TENTSTDL2 73 3234b00 0007271 O W TABLE OF CONTENTS - 1.0 SCOPE 2. O DEFINITIONS 3.0 MINIMUM REQUIRE?!fJ3NTS 4.0 RECOMMENDED TEST CIRCU
4、ITS 5.0 SYMBOLS 6.0 USERS GUIDE 6.1 GENERAI, 6.2 SUPPRESSOR SELECTION GUIDE 6.3 SPECIAL APPLICATIONS 6.4 CONTACT PROTECTION AND ARC SWPWSS%ON 6.5 UNUSUAL SERVICE CONDITIONS 6.6 MUT=,TIPLE SUPPRESSOR EEEMXNT CELL APPLICATION . 6.7 FUSING 6.8 INSTALLATION TIPS 6.9 SUPPRESSOR CELL SIZES 6.10 TYPICAL NO
5、MENCLATURE -2-. - -f -i EIA TENTSTDL2 73 m 3234600 O007272 2 m SELENIUN SURGE SWPEESSORS 1.0 SCOPE: The Suppressor furnished under this Standard shall be a product which has been tested and meets the definitions and minimum requirements specified herein. 2.0 DEFINITIONS: The following definitions sh
6、all apply to the various technical terms wherever such terms appear in this specification, 2.1 SELENIUM SURGE SUPPRESSOR CELL: A Selenium Surge Suppressor Cell is a polycrystalline semiconductor having an asymmetrical voltage- current characteristic, The cell functions as a surge suppressor when it
7、is operated in the reverse region of the voltage-current characteristic. 2.2 SELENIUM SURGE SUPPRESSOR: A Selenium Surge Suppressor is an integral assembly of one or more selenium surge suppressor cells with appropriate terminal connections. 2:3 POLARIZED SELENIUM SURGE SUPPRESSOR: A Polarized Selen
8、ium Surge Suppressor is an integral assembly of one or more surge suppressor cells with terminal connections in which the suppressor cells are connected in series in one conducting direction. 2.4 NON-POLARIZED SELENIUM SURGE SUPPRESSOR: A Non-Polarized Selenium Surge Suppressor is an integral assemb
9、ly of two or more suppressor cells with appropriate terminal connections in which half of the cells are connected in series in the opposite electrical direction to the other half. available connection for joining the suppressor into the circuit. 2.5 TERMINAL: A terminal of a Selenium Surge Suppresso
10、r is the externally 2.6 POSITIVE TERMINAL: The positive terminal of a Selenium Surge Suppressor is that terminal that is to be connected to the positive side of the circuit to which it is to be applied. When color coded it will be Red. 2.7 NEGATIVE TERMINring table gives safe estimated values . 6.2.
11、3.1.3 Rated Transformer Secondary Current o to SOA 50 to . 2008 200 to 1000A Over 1000A Calculate Im - u .- IM x sec Percent Magnetizbng Current (% 4) - 8% 477 3% 2% RRM - Peak Surge Current %IM - Percent Magnetizing Current - Rated Secondary Current sec 6.2.3.1.4 From the value of the peak surge cu
12、rrent (IRm) calculated above, select the cell size from a specific manufacturers data sheet. c t EIA TENTSTDL2 73 m 3234600 0007282 5 m 6.2.4 6.2.4.1 6.2.5 6.2.5.1 6.2.6 6.2.6.1 6.2.6.2 6.3. 6.3.1 6.3.2 a ESTIMATION OF CIRCUIT CLAMPING VOLTAGE: Each manufacturer of surge suppressors has prepared and
13、 published the reverse E-I characteristic of his suppressor Ifne. In most cases, this characteristic will be presented as a plot of voltage per cell vs. peak surge current. An alternate method of obtaining Vc is to multiply the rated steady-state voltage (V V ) by the clamping factor. Ref er to para
14、graph 6.2.3. R(RMS) or R(DC) By using the estimated value of peak surge current from the E-.I reverse plot, the clamping voltage per cell (V,) is easily determined. The circuit clamping voltage (V ) equals the product of the number of series cells (N) times the clamping voltage per cell (Vc). Expres
15、sed as: - S Vs = N x VC From the estimated circuit clamping voltage, other components can now be properly selected. See para 6.2.6. MANUFACTURER S SURGE SUPPRESSOR IDENTIFICATION : Each manufacturer has his am coding system for Selenium Surge Suppressors. Refer to section 6.10 for some of the variou
16、s coding sys tems . SELECTINGTHESEMTCONDUCTOR REVERSE VOLTAGE RATING: Al1 Semiconductor Devices must have a higher reverse voltage rating than the maximum circuit clamping voltage (V ) as calculated in section 6.2.4. This will insure that the transient power (P ) of the surge will be absorbed by the
17、 suppressor rather %an by the semiconductor. If suppressor selection is based upon- circuit voltage alone, the maximum value of Vs as defined in Section 6.2.4.1 should be used. SPECIAL APPLICATIONS: MAGNETIC LOADS: The energy stored in a magnetic type load, such as a reactor, is (1/2)L2 . If this en
18、ergy is to be discharged by the SuPPressor because of a polarity reversal of the load, the current to be discharged by the suppressor Lll be about one-half of the full load dc current. The energy to be discharged, however, may. call for a higher current rated surge suppressor due to the decay time o
19、f the surge. Consult manufacturers energy dissipation curves. SYNCHRONOUS MOTOR LOADS: experienced by a synchronous motor field, the suppressor must be capable of dissipating the power of the transient and holding the voltage at a level low enough to protect the semiconductor. The following circuit
20、illustrates this application. To successfully clamp the induced voltage - 13 - EIA TENTSTDL2 73 M 3234b00 0007283 7 M . 6.3.2. Continued .- . : A dc Surge Suppressor is shownacross the output of a synchronous motor field exci tation,.rectifier. It .will protect the main rectifier against overvoltage
21、 from the motor field when the field discharge resistor . Is not in the circuit. . . . :_- i u 2 -1 4- -. EIA TENTSTDL2 73 m 3234600 0007284 9 W a 6.3.2 Continued If the ield energy level can be determined, the manufacturers data sheet should be consulted for a Power vs. Time curve and the cell size
22、 selected directly from the information. If the field energy level cannot be determinedsthe selection of - cell sizemay be done on the basis of field current. The suppressor should be capable of an instantaneous current twice the rated field current at a voltage value equal to OF less than the clamp
23、ing voltage. The number of cells required in series is as outlined .in para 6.2.2. 6.3.3 THYRISTORS: The following examples are the preferred methods for protecting thygistors. Based upon field experience, they have proved to be the most reliable methods. 6.3.3.1 TRANSFORMER SECONDARY APPLICATIONS :
24、 6.3.3.1.1 6.3.3.1.2 6.3.3.1.3 6.3.3.2 6.3.3.2.1 6.3.3.2,2 CELL SIZE: same means as in para 6.2.3. SUPPRESSOR VOLTAGE RATING-: means as in Para 6.2.2. The size of the suppressor cell is determined by the This rating is determined by the same LOCATION AND TYPE OF SUPPRESSOR: must be used in most circ
25、uits across each thyristor to prevent false firing due to transienkin the forward direction and to protect the reverse blocking capability from transients in the reverse direction. See Figures 1-A,B, 61 C for examples. In half-wave capacitive circuits, the preferred location is across the secondary
26、o the transformer. See Figure 2. If placed across the thyristor, a suppressor of twice the steady-state rating would be needed to block the sum of the capacitor voltage plus input voltage. Non-polarized suppressors TRANSFORMER PRIMARY CONTROL APPLI-CATIONS: CELL SIZE: Since Energy levels are not eas
27、ily calculated, an estimate based on the size of most transformer substations be used. Experience has shown that for 24Q volt service, cells with seven square inches or more of active area (3“ x 3“ or slightly larger) may be used. Experience has also shown that for 480 volt- service, two inch square
28、 or &lightly larger cells may be used. should SUPPRESSOR VOLTAGE RATING: determine the voltage rating of the suppressor except when wye-connected transgormers with a neutral connection are used. In this case, line-to neutral voltage is used. See Para 6.2.2. The line-to-line voltage is used to _ _- I
29、 EIA TENTSTDL2 73 353qbOO 0007285 O EIA TENTSTDL2 73 = 3234b00 0007286 2 6.3.3 Continued 6.3.3.2.3 LOCATION OF SUPPBESSORS: Non-polarized Suppressors are placed across the thyristors to prevent false firing and reverse blocking failure See Figure 3. The suppressors are not placed line-to-line as the
30、y would not have the additional resistance of the transfomer windings in re- ducing the amount of energy of any transients from the lines. Other circuit configurations may be used, but the particular manufacturer should be consulted. 6.4. CONTACT PROTECTION AND ARC. SUPPRESSION: A forerunner to Sele
31、nium Surge Suppressors is the Selenium Contact Protector product line. It is not the intent of this specification to cover the character- istics of this established product. Each manufacturer has literature describing his products characteristics. It is noteworthy to indicate that the selenium cells
32、 used for arc suppression applications are similar to those described in this specification. 6.5 UNUSUAL SERVICE CONDITIONS: There are two general categories of transient voltages as described below. 6.5.1 CIRCUIT GENERATED TRANSIENT VOLTAGES: This specification describes the steps for calculating t
33、his source of transient voltages. These are, in general, of a nature that can-be estimated because the circuit parameters are known. 6.5.2 LINE GENERATED TRANSIENT VOLTAGES: These voltage transients are fed through the service entrance supply and may be caused by lightning or power company line swit
34、ching. In general these transient voltages have high energy content and for this reason are very difficult to identify. The Surge Suppressor is not intended to be a lightning arrestor, nor can a lightning arrestor be used in all cases to protect semicondhctor devices. 6.6 MULTIPLE SUPPRESSOR ELEMENT
35、 CELL APPLICATION: For many suppressor applications, multiple element devices are available that offer advantages over the use of single element devices. Examples are polarized bridges for protection of rectifier bridges and non-polarized bridges for protection of thyristor bridges. These protect ag
36、ainst surges originating in either the ac or dc circuits. 6.6.1 THREE PHASE BRIDGE PROTECTION: In a three phase circuit, the bridge connected suppressor will have a lower clamping voltage rating than the dcsuppressor, This is because of the lower voltage rating per cell of the dc suppressor and also
37、 the fact that the rms voltage is less than the dcvoltage. The duty on the bridge type unit is also light as only half the unit operates at a time, whereas the dc unit must discharge every surge. CAUTION: A suppressors of 60 volts or less rating which contain one or more polarized elements should no
38、t be used in parallel with diodes because of the possible diversion of rectifier load through the suppressor unit. -17- EIA TENTSTDL2 73 m 3234600 0007287 4 m 6.7 FUSING: Accepted practices such as National Electrical Code Requirements for fusing should be used at all times. It is always recommended
39、 that fuses be placed in series with the device or circuit to be protected and& in series with the surge suppressor. Fusing the suppressor may remove the suppressor from the circuit and would disable its protective function. Fuse ratings must be based on the circuit requirments, not on the suppresso
40、r ratings. 6.8 INSTALLATION TIPS: 6.8.1 For dimensions, mounting configurations and special enviromental conditions, consult the manufacturers catalogue. 6.8.2 Adequate cooling of the suppressor is of prime importance and the following illustrations emphasize methods to obtain proper suppressor cool
41、ing. - 18 - EIA TENTSTDL2 73 W 3234600 0007288 b = .6.8 Continued PROPER MOUHTING ORIENTATION OF RECTI FIER STACKS (NOTE: all diagrams are side views) a Right . Wrong Hount Cells or Stacks on Horizontal P1 ane for Uniform Cooling. Right F- FI STACK Mount Stacks under or to side of Transformer or oth
42、er heat generating devi ce. Right Perforate top and bottom of housing for proper circulation of cooling air. -Do not mount Stacks or Cells .one over the other. S TAa Wrong Do not mount stacks above Tr$nsformer or other heat generating device. Wrong Do not perforate sides of housing for ventilation.
43、- -_ EIA TENTSTDL2 73 3234b00 0007289 8 T 6.9 TYPICAL STIPPWSSOR CELL SIZES: 6.9.1 The following table lists typical avaflable suppressor cell sizes and approximate active cell. area. Diameter 9/32 1x1 1.6 x 1.6 2x2 3x3 4 ab 4 5x5 5x6 6 x 7 114 11% . Appssxba t e Active Area Square Inch 055 o 196 o 56 a, 75 3.QO 7.25 13.40 21.60 26,50 39.50 6.10 NOMENCLATURE : 6.10.1 Each manufacturer has his own nomenclature to identify each Thfs information is available on request suppressor model, from each manufacturer.
