Robert, As I understand the requirement in IEC 601-1 para 20 and following, only those parts which provide safety function need to be tested. My experience has been that MOV's are used for the purposes of the EMC directive for various surges and line spikes and actually provide not safety function. However the mains input insulation does need to be tested as a routine test. This includes any wire insulation, terminal blocks, circuit breakers, fuse holders, EMI filters and so on. This would be "basic" insulation and the test voltages of table 7 row 1 are used. If the insulation test exceeds the clamping value of the MOV then you are allowed to temporarily remove the component for the test, but the test still needs to be performed. In other words the protection provided by the MOV's is separate and distinct from the insulation being tested.
As a side note be careful using MOV's. If you are using agency rated MOV's such as VDE, then you should be in good shape. If you are not using rated MOV's then there may be trouble. Especially if your input current protection is over 16 Amps. The MOV's can become a safety problem. Under certain conditions they may catch fire, explode or sputter metal onto nearby insulating surfaces. My safety inspector recommends MOV's protected with thermal fuses or placing a spark gap in series with the MOV. Doug Powell ----------------------------- Advanced Energy Industries, Inc. [email protected] ---------- From: Robert Rovai To: [email protected] Subject: Insulation test and EMC protections List-Post: [email protected] Date: Monday, June 09, 1997 5:30PM While testing an apparatus (of class I) for EN-60204-1, at the voltage test session i meet the 1000V insulation test between the live conductors and the protection earth. As the apparatus has an internal electronic circuitry protected with MOV'S from line to line and line to ground i ask myself if the 1000V withstand test is applicable or not to equipments with this kind of protections... or whether such a protection is in contrast with basics safety standards. Robert Rovai Electronic Department S.E.Q.W Pisa - Italy
