Brian, Actually, the fuses do trip on the first pulse that engages the MOVs (between 1.5kV and 2kV). The I2t is such that it doesn't take much (Littelfuse 508.500). Since this is a voltage measurement terminal not powered by the Mains it is measuring, we use as small a fuse as we can. We would use smaller, but the resistance of the fuses introduce too much error into the measurement.
Rob From: Kunde, Brian [mailto:[email protected]] Sent: Wednesday, August 05, 2015 10:14 AM To: [email protected] Subject: Re: [PSES] IEC 61010-2-030 Transient Overvoltage Testing Robert, Your fuses should not blow, and we always test 5 positive and 5 negative at 0º, 90º, 180º and 270º. We also test at lower voltage levels, starting at 500V, the increasing to 1kV, 2kV, 3kV, and so on. By the time you get to 8kV your circuit would have been hit hundreds of time. You can probably change out your circuit as a point where you think your MOVs have served out its usefulness. But we have tested such circuits under thousands of hits without the MOVs failing, so just be aware. When the MOVs fail short, your overcurrent protection device will normally trip because once the Gas Tubes conduct they won't let go once the MOVs short. The Other Brian From: Rob Oglesbee [mailto:[email protected]] Sent: Tuesday, August 04, 2015 3:23 PM To: [email protected]<mailto:[email protected]> Subject: [PSES] IEC 61010-2-030 Transient Overvoltage Testing I have a circuit I'm using to reduce the Overvoltage Category Level from 600V/CAT IV to 600V/CAT II before hitting an instrumentation transformer. I wish to test it per IEC 61010-2-030 Clause 14.101 (Circuits or components used as Transient Overvoltage limiting devices in measuring circuits used to measure Mains). The requirement is 5 positive and 5 negative impulses from a hybrid impulse generator at 8000V (1.2/50us O.C., 8/20us S.C., 2 ohms) while Mains is applied. Up to a minute is allowed between impulses. The pass criteria for the test is that no Hazard shall arise, and that the Mains breaker is not tripped. My circuit is a combination of MOVs and GDTs with fast fusing on both input legs. On the first impulse the protection circuitry will blow the fuses. My first question is, do I replace fuses between impulses (I think not)? My second question is, what phase angle should I perform the test at (I think worst case, +90 for positive and +270 for negative)? Thanks, Robert A. Oglesbee Radian Research, Inc. (765) 449-5505 This message, and any attachments to it, may contain information that is privileged, confidential, and exempt from disclosure under applicable law. If the reader of this message is not the intended recipient, you are notified that any use, dissemination, distribution, copying, or communication of this message is strictly prohibited. If you have received this message in error, please notify the sender immediately by return e-mail or call 765-449-5500 and delete the message and any attachments. Thank you. - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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