Slide 1 Slide 2 Slide 3 Slide 4 Slide 5 Slide 6 Slide 7 Slide 8 Slide 9 Slide 10 Slide 11 Slide 12 Slide 13 Slide 14 Slide 15 Slide 16 Slide 17 Slide 18 Slide 19 Slide 20 Slide 21 Product List
Varistor - Slide15

Here are a few key design considerations that manufacturers need to address when developing products to comply with UL1449.  For safety, the device cannot explode, expulse molten material or catch fire when exposed to an abnormal condition per section 39 of the standard. For short circuit testing, the manufacturer can use a rugged enclosure, backfill with sand or epoxy, or add fusing to the suppression component in order to disconnect it form the circuit. For abnormal overvoltage, the designer could use a higher rated MOV that will not break over during the test. Other options are to add a thermal disconnect device located next to the suppression component, or beef up the enclosure. For operation, a key parameter for any SPD is the VPR rating. The lower the VPR, the better the level of protection for the end application. Typically, designers will select the lowest possible rated MOV or other suppression component to achieve a lower VPR. Other types of components such as TVS diodes or a GDT in combination with a MOV can also achieve lower VPR ratings, but there are other issues that can arise if these are not selected properly.

PTM Published on: 2012-08-31