View single post by EVPDave
 Posted: Jan 28th, 2010 08:34 PM
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Joined: Mar 7th, 2007
Location: USA
Posts: 206

 The package for the relay may have a printout to identify the four connection points similar to the schematic diagram I supplied. It can be wired one of two ways, as I have shown with one set of contacts. Or, using both sets of contacts in a parallel configuration. The parallel wiring would lengthen the life of the relay contacts as two sets would be used instead of one set.

 How this works. As it's wired the relay will energize and de-energize finding a mechanical self resonance oscillation. You will also see arcing taking place at the contacts with back emf of the coil being a contributor. The arcing should also contain 60hz energy to help modulate the arc. The variac is like a light dimmer in function in that it can lower the 120 vac line voltage to the relay device so it will last longer. Lowering the voltage will also change the frequency of the relay oscillation . A mechanical adjustment can also be made on the internal spring on the moving part of the relay known as the 'clapper'.  

Hope this helps a little,