BS 9727:1985 download free.Sectional specification for power transformers of assessed quality for use in electronic equipment for capability approval.
BS 9727 specifies inspection requirements and tests from which a selection is made when preparing a detail specification for power transformers to be released under the terms of BS 9720 capability approval. It includes a blank detail specification (BDS), which shows the format, and indicates which tests are considered to be appropriate to this type of component, although the final selection of tests to be included in the inspection schedule is at the discretion of the specification writer. It also lists appropriate ratings and characteristics.
The components covered by this standard are concerned with the maximum transfer of power at a single frequency with an essentially symmetrical waveform.
2 Related documents
BS 2011, Basic environmental testing procedures.
BS 6001, Sampling procedures and tables for inspection by attributes.
BS 9000, General requirements for a system for electronic components of assessed quality.
BS 9720. Specification for custom-built transformers and inductors of assessed quality: generic data and
methods of test.
PD 9002, BS 9000 and BS CECC qualified products list.
NOTE BS 6001 and 138 9720 should be available for reference when preparing detail specifications.
3 Preparation of the detail specification
3.1 General
A detail specification shall be prepared in accordance with 2.6.1 of BS 9720:1983.
NOTE I The detail specification should take the form of the BPS shown in clause 5, particularly in respect of the front page format and. in principle, in respect of the presentation of the inspection requirements.
NOTE 2 All the tests shown in the BDS are taken from BS 9720. Those shown in bold type concern operating characteristics of fundamental importance and it is strongly recommended that these are selected by the specification writer for inclusion in the detail specification. The tests shown in plain type are listed for the convenience of the specification writer, and tests should he selected from them according to the particular application of the component.
NOTE 3 Over.specification may carry an economic penalty. However, the specification writer may speci1’ tests and sampling levels different from, less than, or additional to those given in the BDS.
3.2 Particular requirements
3.2.1 Where additional tests of a type not defined or invoked in BS 9720 are required, these shall be fully specified in the detail specification.
3.2.2 Any tests considered as being destructive shall be so denoted in the test schedule by the addition of the notation “(D)”.
NOTE The use of this notation is not illustrated in the lIDS.
3.2.3 Tests shall be grouped in the schedule according to the level of sampling required and, where indicated [see 4.1 b)], in the order of testing required. Where 100 % testing is not required, inspection levels and acceptable quality levels shall be selected from BS 6001.
3.2.4 The completed detail specification shall be allocated a component identity number and issue status by the originator.
NOTE 1 This number is chosen by the originator (manufacturer or customer) within his own system. It is thus not subject to any external rules or codification.
NOTE 2 In the special case of a manufacturer’s detail specification for a standard catalogue item which the manufacturer wishes to be listed in PD 9002. BSI will allocate an appropriate number in accordance with 15.11 of BS 9000-1:1981.
3.2.5 Additionally the detail specification shall include a number allocated by the component manufacturer comprising this specification number, his factory identification code letters and a unique number within his registration system, e.g. BS 9727/XYZ11234.
NOTE After a detail specification has been allocated the manufacturer’s reference number in accordance with 3.2.5. it is to be considered a contractual part of an order, Copies of all such detail specifications are to be retained by the manufacturer’s chief inspector.
3.3 Ratings and characteristics
3.3.1 Ratings. In the case of customer originated detail specifications, customer and manufacturer agreement shall he obtained on the ratings to be ascribed to the component in the detail specification. These ratings shall not exceed the scope of the manufacturer’s capability approval
(see also 1.1.12 of BS 9720:1983).
3.3.2 Characteristics. A customer shall prescribe in the detail specification any characteristic required for a component.
3.4 Outline drawings and winding schematic diagram
3.4.1 The detail specification shall incorporate a drawing of the transformer showing important features, such as those dimensions affecting interchangeability, restrictions on mounting and marking requirements.
3.4.2 The detail specification shall incorporate a schematic diagram showing all windings. screens, taps and phasings and giving termination identification.
3.4.3 Where the transformer is intended to be connected to a circuit supplying direct current, full details of this circuit shall be given together with load and component values.
4 Inspection requirements to be listed in the detail specification
4.1 Conformance inspection
The detail specification shall incorporate the following notes.
a) Sampling inspection is to be carried out in accordance with BS 6001, normal inspection.
b) Tests in a group may be carried out in any order except where otherwise indicated (see 3.2.3).
c) Components submitted to any tests marked (D) may not be released under BS 9720 capability approval. (D = destructive).
d) The values given for measurement limits are absolute values: measurement uncertainty is to be taken into account.
4.2 Design verification
The tests to be detailed under this heading are those which the specification writer considers to be inappropriate to lot-by.lot release, but appropriate to the verification of new and original designs. Accordingly, they are to be performed only when specifically so stated in the order, and the detail specification shall carry a statement to this effect.
If design verification is required, the number of specimens and that there shall be no failures shall be stated in the detail specification.
NOTE Two specimem will normally be required.
5 Detail specification
The BDS which follows, when completed in accordance with clause 3. forms the relevant detail specification.
NOTE The front page of the BIJS has been based upon the need for a customer’s detail specification. Where a manufacturer’s detail specification is required, some changes will be necessary, but the basic format should be retained.