High Voltage Connectors for use in Laboratory Equipment -------------------------------------------------------
Reference: Chris Dupres' Recent Questions As you may surmise, high voltage connectors can involve several different tables and clauses in the IEC 1010. The applicable requirements can vary depending on the connector construction. For a homogeneous construction, the CLEARANCE required may be less than value derived from Table D.13 if the construction passes a peak (dielectric) test voltage at the potential specified in Table D.16 corresponding to the normally required CLEARANCE. In order to determine a specific required CLEARANCE value and/or the corresponding test voltage requirement, we need to know what type of circuit the connector is to be connected to; e.g. Type 1 (CAT. II) or Type 2 (CAT. III). If the connector is inaccessible during normal use of the equipment and the equipment is grounded, basic insulation is sufficient. Mr. Dupres is correct regarding the use of Table D.18 for CREEPAGE if the voltage is 15kV with respect to other circuits that are accessible (or in the area) and/or to ground. After all of this you may wonder how any practical connector could be obtained and utilized for voltages above 10kV. One possiblity is by adding suitable seemless insulating tubing over the entire connector assembly. Another (more commonly used) method is by applying the third paragraph of D.1 which essentially states that CREEPAGES and CLEARANCES for other than mains circuits that fail to meet Annex D may be accepted if compliance is achieved under the fault conditions described in 4.4 and if HAZARDOUS LIVE parts are not accessible after a fault. Fault testing would include causing the connector to arc to chassis. Practically speaking, this optional evaluation method "opens the door" to many connectors which do not meet the specified distances in Annex D of IEC 1010. I checked our CD ROM Library of all current IEC Standards and found some pertaining to connectors but not of the type relating to this application. I hope you find this information helpful. _________________________________________________________________ KENT JONES Underwriters Laboratories Inc. Voice : (408) 985-2400 x32371 1655 Scott Blvd. Fax: (408) 296-3256 Santa Clara, CA 95050 E-mail: [email protected] _________________________________________________________________
