On 03.05.16 13:32, andy pugh wrote: > On 3 May 2016 at 13:29, andy pugh <bodge...@gmail.com> wrote: > > Until I googled just now I thought that this was what was meant by > > MOV. The data sheets for Varistors seem to specify an activation > > voltage and a power dissipation, but no off-state resistance > > measurement to calculate the power dissipation. Or is the resistance > > so low that this can be ignored? > > And I now see I was reading a voltage/current graph as a > voltage/resistance graph. Ignore that question.
Yup, a MOV goes across the triac, to clamp voltage spikes. It's high impedance until a spike makes it conduct while there is enough voltage across it. It has only a limited life if hit with big surges, IIRC. A Transorb (transient suppressor diode) is also good for protecting triacs and MOSFETs, but the application of suppressors is roughly: Gaseous arrestors on lines going outdoors, for clamping induced voltage from nearby lightning; MOVs after that, and on mains circuits, for example; transorbs for final protection of other semiconductors after the edge of really big spikes has been taken off by primary protection. Erik ------------------------------------------------------------------------------ Find and fix application performance issues faster with Applications Manager Applications Manager provides deep performance insights into multiple tiers of your business applications. It resolves application problems quickly and reduces your MTTR. Get your free trial! https://ad.doubleclick.net/ddm/clk/302982198;130105516;z _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
