Hello from San Diego:
> 2.9.4.4 stipulates the following: > * allows wound components without interleave insulation if the > winding wire is insulated with polyimide or FEP and complies with > annex U. > > * three constructional layer of insulation (of polyimide or FEP) > satisfy the criteria for reinforced insulation. > > * two such wires crossing at an angle between 45 and 90 degrees only > require an insulating sleeving or sheet material to relieve > mechanical stress at the crossover point. > > This clause appear to indicate that the creepage distance requirement > per table 6) for reinforced insulation between the primary and > secondary windings does not apply to this type of construction (using > triple insulated wire for the winding). Is this a valid assumption?? Creepage distance is the shortest distance between two conductors measured across the surface of insulation. For conventional magnet wire, the insulation is considered brittle. For safety purposes, conventional magnet wire is considered uninsulated. Therefore, the transformer construction must incorporate the applicable creepage distances between primary and secondary magnet wires. For multiple-insulated magnet wire, the insulation is considered robust. Primary and secondary insulations may be in intimate contact with each other, i.e., need not comply with creepage requirements because the insulation is considered solid insulation. In a transformer employing multiple-insulated magnet wire, creepage distance applies to the UNINSULATED (stripped) conductor, not to the insulated conductor. > Does clause 2.9.4.4 imply that both the primary and secondary windings > of the transformer must be the triple insulated wire or does clause > 2.9.4.4 allow the use of triple insulated wire for the primary and an > enameled magnet wire for the secondary (or enameled magnet wire for the > primary winding and triple insulated wire for the secondary winding)?? > Comments please... Sub-clause 2.9.4.4 states that insulation complying with Annex U is considered to be BASIC or SUPPLEMENTARY insulation. Two such wires that are adjacent to each other are considered to be separated by DOUBLE insulation. If your secondary winding is intended to be SELV, then you must use triple-insulated magnet wire for BOTH primary and secondary windings. In such construction, the primary wire insulation is considered BASIC insulation, and the secondary wire insulation is considered SUPPLEMENTARY insulation. If your secondary winding is either ELV or more than ELV, then you only need BASIC insulation. In this case, the secondary winding can be ordinary enamel insulation. Best regards, Rich ------------------------------------------------------------- Richard Nute Quality Department Hewlett-Packard Company Product Regulations Group San Diego Division (SDD) Tel : 619 655 3329 16399 West Bernardo Drive FAX : 619 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com -------------------------------------------------------------
