While relays are usually taught and more easily understood as DC devices, inpractice AC relays are commonly used. These relays typically employ shadedpoles, similar to the shaded pole induction motor. A shaded pole is a coil loopwhich is not separately excited by the relay source; it is excited by the flux onthe main relay coil. This coil then produces an opposing current, flux andvoltage (Faraday’s and Lenz’s law) which holds the contact during zero voltageintervals on the main coil. Failure of the shaded pole leads to “relaychatter”— a 120 Hz clicking that occurs every time the main relay voltagecrosses the zero point.
Interesting. So a diode on an AC control line might have an affect? I would think that would make it worst, as only half the waveform would be controlling the coil, and it would basically be zero voltage for half the period. Maybe I'm not understanding some (many) things about this.So, what's a 4 amp diode look like? Any particular part number I should try? I'm not familiar with ratings. I've used 1N4004 diodes on my DC relay coils, and some larger stud diodes on the headlights, but I don't really know the ratings any more on these. I would think the 1N4004 might be about right considering the coils draw something like 320 mA.