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What exactly is a power flicker, and how can it be simulated?

  1. May 27, 2009 #1
    You guys have all seen a tiny flicker in the lights, where they either go dim or shut off completely for a very small period of time - usually less than half a second. It typically does not cause computers to shut down.

    What duration of abnormal power is usually associated with this? What voltage drop is normal? (If it helps, I am referring to residential power systems in the US)

    Also, does anyone have any quick suggestions on how to simulate this with a few 120VAC relays?
  2. jcsd
  3. May 27, 2009 #2
    I was working in a plant that made circuit breakers for high tension lines. Their circuit breakers could break and make the circuit up to three times a second and are responsible for the flicker in the lights when lightning strikes. They used a blast of high pressure nitrogen to blow out the arc when the circuit breakers opened.

    How much current will be in the circuit you are breaking?

    You may be able to simulate it by putting a momentary switch in series with the coil of your relay.
  4. May 27, 2009 #3
    The simulated flicker will depend on the phase of the voltage when the interruption occurs. So you may need a zero crossing trigger plus delay. If you use DPDT relays with 6 volt dc coils, a simple RC delay might work. I can inadvertantly cause flicker by turning on a 1 HP single phase motor.
  5. May 27, 2009 #4


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    Staff: Mentor

    There are IEEE standards for power sag, voltage flicker, etc. on AC power mains, as well as ways to characterize their severity and surveys of frequency of occurance in the US. Here is the main website:


    Unfortunately, it looks like you need a registration or membership to gain access to the docs. You might see if your local technical library has access...
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