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1、BRITISH STANDARD BS 7815:1995 IEC 1087:1991 Guide for evaluating the discharges from a charged surface Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 11:57:22 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7815:1995 This British Standard, having been prepared un
2、der the direction of the Electrotechnical Sector Board, was published under the authority of the Standards Board and comes into effect on 15 July 1995 BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference GEL/15 Draft announced in BSI News April 1995 ISBN
3、0 580 24197 1 Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee GEL/15, Insulating material, upon which the following bodies were represented: British Ceramic Research Ltd. British Industrial Ceramic Manufacturers Associati
4、on Electrical and Electronic Insulation Association (BEAMA Ltd.) Electricity Association Federation of the Electronics Industry Rotating Electrical Machines Association (BEAMA Ltd.) Transmission and Distribution Association (BEAMA Ltd.) Amendments issued since publication Amd. No.DateComments Licens
5、ed Copy: London South Bank University, London South Bank University, Fri Dec 08 11:57:22 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7815:1995 BSI 10-1999i Contents Page Committees responsibleInside front cover National forewordii 1Scope and object1 2Principle of the method1 3Test equipment1 4Cond
6、itioning and preliminary operations2 5Test procedure2 6Test results2 7Acceptance conditions3 8Test report3 Figure 1 Test specimen and test electrode3 Figure 2 Typical trace without discharges4 Figure 3 Typical trace with discharges4 List of referencesInside back cover Licensed Copy: London South Ban
7、k University, London South Bank University, Fri Dec 08 11:57:22 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7815:1995 ii BSI 10-1999 National foreword This British Standard has been prepared by Technical Committee GEL/15. It is identical with IEC 1087:1991 Guide for evaluating the discharges from
8、a charged surface, published by the International Electrotechnical Commission (IEC). A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of its
9、elf confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 4, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be i
10、ndicated in the amendment table on the inside front cover. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 11:57:22 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7815:1995 BSI 10-19991 1 Scope and object This Technical Report is used as a guide that applies to p
11、roducts, materials, plastic parts of equipment, electrically-insulated metal parts of such equipment, or complete equipment. It provides a test method to determine whether a product produces discharges when its surface has been charged, for example, by rubbing and thus be potentially the source of p
12、roblems arising from electrostatic charges and discharges. 2 Principle of the method The principle of the method consists, in a first step, in charging electrically by an appropriate procedure, for instance by rubbing the external part of the product placed on a large metallic plate (where this repr
13、esents an appropriate ground plane), and then, in a second step, in detecting if a discharge appears when an earthed test electrode approaches the charged area. When such a discharge appears, the electric charge transferred during the spark may be measured by an appropriate equipment and is compared
14、 to a limiting value, characteristic of a given electrostatic problem. Examples of relevant problems and risks are ignition of flammable gases, Interference with operation of electronic equipment and damage to semiconductor devices. 3 Test equipment The test equipment consists of three main parts: a
15、 charging device; a mobile test electrode which is driven at a given speed towards the test object; an electric equipment to measure and record the electric charge produced or transferred during the different steps of the test. 3.1 Charging device Any charging device, based on contact and separation
16、 such as rubbing or beating, can be used.1) The effectiveness of the charging device shall be verified in preliminary tests in that it can create a net surface charge approaching a density of at least 105 C/m2 on a highly insulating material, and an area of at least 200 cm2 shall be charged. The cha
17、rging device shall be specified with reference to the product and it would be described in the relevant individual standard. The charging can be achieved by hand with a suitable material with an appropriate shape. A rubbing speed and pressure providing maximum charge are used. For plane material sam
18、ples the rubbing materials shall be wrapped around a metal electrode with a flat lower surface with an area of at least 100 cm2 and a width of at least 7 cm. During the rubbing period there shall be a pressure on this lower surface between 400 Pa and 600 Pa. The charging device shall be electrically
19、 isolated from the operator and connected to earth by a measuring instrument. The operator shall be connected to earth by a wriststrap and hold the insulated rubbing electrode in his hand. The type of charging material shall be accurately described. Unless otherwise stated in the specification, thre
20、e types of materials should be used: a pure cotton fabric, wool or leather, as a conductive cloth; a material expected to produce a positive charge such as polyamide 11; a material expected to produce a negative charge such as polyacrylic fabrics. In some circumstances, d.c. corona charging may be u
21、sed. If tests are performed on site on a product on which there is already a charge, a charging device need not be used. 3.2 Moveable electrode Unless otherwise specified the electrode consists of a metal sphere 15 mm in diameter fitted on a motor driven vertical rod. The device is such that the sph
22、ere can be moved down and up at a constant speed. The test equipment is shown in Figure 1. The standardized characteristics are the following: speed of the electrode: 5 cm/s 1 cm/s; distance between sample and sphere at furthest extent: 300 mm 10 mm; drive reversal direction automatically switched o
23、n at a distance from the sphere to the product of 1 mm 0,5 mm to reach the same maximum distance of 300 mm 10 mm. 3.3 Charge meter The electric measurement circuit is shown in Figure 1. It consists mainly of a charge meter, which comprises a highly insulated and calibrated 10 nF to 100 nF capacitor
24、and a very high input resistance voltmeter, which is connected across the capacitor and has a range of 1 mV to 10 V, providing a time constant of at least 120 s. The output of the voltmeter shall be continuously recorded. 1) Different types of charging devices are under consideration in order to est
25、ablish their effectiveness and reproducibility. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 11:57:22 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7815:1995 2 BSI 10-1999 4 Conditioning and preliminary operations 4.1 General remarks The test product shall be
26、 cleared from all pre-existing electrostatic charges. This can be achieved by various means: either by conditioning in a wet atmosphere ( 70 % r.h.) for 24 h minimum; or by cleaning all the surfaces with a rag wetted with alcohol or demineralized water and earthed through the operator; or by using s
27、tatic eliminators. The absence of static charges on all the surfaces of the product is checked by the test procedure described in 5.1. Consideration should be given to the fact that the act of removal of all pre-existing charges may affect the surface and its ease of charging and discharging. 4.2 Am
28、bient conditioning Unless otherwise specified, the test product is then conditioned in an atmosphere of 35 % 2 % r.h. at 23 C 1 C at minimum for 24 h and the test is to be performed in the same environmental conditions. However, in many circumstances a dry atmosphere of 15 % 2 % r.h. and 23 C 1 C co
29、uld be more suitable. Pursuit of the test in a low humidity may enable high charge levels to be achieved, but if there is any chance that the character of the discharge could be affected by moisture in the atmosphere or absorbed on the surface, it is desirable also to check behaviour with a higher l
30、evel of humidity in this case. 4.3 Mounting of the test product After this conditioning, the test product is mounted in relation to a large metallic plate to simulate normal use conditions, and under these conditions the metallic plate should be connected to earth. In the case of a product with exte
31、rnal electrical connection, this connection shall be earthed. If charge decay in the sample within the test time scale is suspected, an independent measurement of the decay rate is required. 5 Test procedure 5.1 Preliminary measurements Test environment is the same as described in 4.2. When the prod
32、uct is ready for testing as described in 4.3, the absence of remanent charges is checked by moving the electrode towards the upper surface of the product. The reading of the charge meter connected to the electrode shall be less than 0,1 nC. The electrode is then moved up to a distance of 300 mm 10 m
33、m from the surface. 5.2 Sample charging In appropriate circumstances an area of at least 200 cm2 of the test product is then rubbed or beaten, according to 3.1 in order to create as large a charge as possible. This maximum level of charge should not decay by more than 10 % in 120 s. This is recogniz
34、ed by recording the output of the charge meter connected to the movable (but now fixed) electrode. Alternatively, it can be measured by using a field meter. 5.3 Discharge measurement The movement mechanism shall be switched on as soon as possible after charging is completed. The reading of the charg
35、e meter connected to the electrode is continuously recorded during both downward and upward motion. The operations described in 5.1, 5.2 and 5.3 are made at other locations on the sample, according to the indications given in the specification. In appropriate circumstances three tests are to be repe
36、ated on separate 200 cm2 areas of the sample for each of the rubbing materials. Between successive tests, the sample shall be discharged as described in 4.1. Careful consideration shall be given to any charges on the sample which may not be removed by the procedures described. 6 Test results The tes
37、t results are expressed by the output of the recording device under the following conditions. 6.1 Residual charge When no discharge has been observed, the pattern of the recording is smooth as is shown in Figure 2. The value recorded on the charge meter at the end of the experiment shall be less tha
38、n 1 nC (residual charge): Qr = C %Vr. 6.2 Transferred charge When a discharge has occurred, the pattern of the recording shows a form similar to the one reproduced in Figure 3. The sudden increase in voltage on the recorder is used to calculate the transferred charge Qt: Qt = C %Vt where %Vt is the
39、increase in voltage and C the capacitance of the charge meter. The value of the distance at which the spark occurred shall be measured. NOTEOnly the first discharge is to be taken into account, but if more than one discharge occurs, then an investigation with a larger sphere is advisable. Licensed C
40、opy: London South Bank University, London South Bank University, Fri Dec 08 11:57:22 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7815:1995 BSI 10-19993 7 Acceptance conditions The acceptance conditions shall be specified in individual standards. 8 Test report The test report shall include: descrip
41、tion of the product, including dimensions; description of the device used to ground the product, if any, and dimensions of the ground plate; description of the charging device and procedure; distance at which the spark occurred, if any; Qr as defined in 6.1 and polarity, or Qr as defined in 6.2 and
42、polarity; reference to any relevant particular specification on specific conditions; conditioning; environment conditions during the test; record of the number of tests and of the number of discharges. NOTEThis test has been shown to be repeatable in a given laboratory when conducted by experienced
43、operators. The reproducibility between laboratories is still under examination. Figure 1 Test specimen and test electrode Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 11:57:22 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7815:1995 4 BSI 10-1999 Figure 2 Typi
44、cal trace without discharges Figure 3 Typical trace with discharges Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 11:57:22 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7815:1995 BSI 10-1999 List of references See national foreword. Licensed Copy: London South
45、 Bank University, London South Bank University, Fri Dec 08 11:57:22 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7815:1995 IEC 1087:1991 BSI 389 Chiswick High Road London W4 4AL BSI British Standards Institution BSI is the independent national body responsible for preparing British Standards. It pr
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