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Synchronizing module lab volt Model 8110-20

  1. Aug 5, 2015 #1
    Hi im Ken. Nice to meet you. I would like to get some info on this synchronizing module. It has a 3 phase lamp for synchronizing an alternator. Any knows whats the theory behind that flashing lamp? what if the lamp blink very fast or blinking slow? the reason is frequency is out of phase but i want to know in details what cause it to blink? Thanks.
    Last edited by a moderator: Aug 6, 2015
  2. jcsd
  3. Aug 6, 2015 #2


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    I know about a module, that has 3 lamps ( an older analog version). These lamps are connected through a circuit to the 2 x 3 three phases. The circuit consist of resistors and capacitors in some arrangement ( don't remember how ). Of course the three lamps will flash when the frequecies are mismatched, but when the frequecies are matched and the phase is matched, the middle lamp will be switched of, and the two outer lamps will shine exactly equally.

    If your module acts different, I think that it could have been made, based on a μ-processor. Then there is a lot of methods, how to program the processor. The simplest way would be to measure when the 2 x 3 phases cross zero. Then to calculate/determine how your lamp should react ( the HMI, Human-Machine-Interface ).
  4. Aug 6, 2015 #3

    jim hardy

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    Simplest form is simply a light between the two machines.

    you can use three lamps, one per phase if you wish but one will do the job


    It should be obvious that when the machines are in phase there's no voltage across the lamps and they all 3 go out,
    so it's safe to close the switch when the lamps are out

    whenever the machines are not in phase there will be voltage across the lamps
    at any instant the voltage across a lamp will be the difference (vertical distance) between red and blue voltages
    and as phase shifts between 0 and 360 degrees, that voltage difference will grow from zero to twice peak than back to zero

    so your synch module must either :
    use lamps rated for twice voltage,
    or do what we did in the power plant - two lamps in series.

    Used to be in Great Britain they preferred to wire their lamps through transformers and swap phase so that the proper time to close the switch was maximum brightness instead of minimum. Sophie might know if that's still the practice.

    The lamps also tell you if there's a voltage mismatch - the they'll never quite go out.
  5. Aug 6, 2015 #4


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    I think it is very difficult to see if the lamps have gone completely out ( easier to see if two lamps have the same brightness ).

    Also it's difficult to estimate maximum brightness.
  6. Aug 6, 2015 #5

    jim hardy

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    The skill lies in timing the peaks (of brightness or darkness, whichever you prefer)
    you want the unloaded machine to be going very slightly faster than the bus to which you are about to connect it
    so that when breaker closes, it provides power rather than absorbing it
    because big generators have protective relays to disconnect them when they're "motoring"
    and it's really embarassing to synchronize successfully only to have the automatic protection equipment disconnect you a few seconds later

    so the operator adjusts governor valves to make the lights cycle through their dark-dim-bright-dim-dark cycle once every several seconds
    with his machine going just a few RPM faster than synchronous, maybe 3005 or 3610 RPM
    When he feels he's "Got the rhythm" he'll close the switch at the right moment.

    It's easier with a synchroscope, which is just a rotating phase angle meter
    this one's showing 90 degrees out of phase
    proper time to close is - needle rotating slowly clockwise and it reaches straight up
    we had our lamps immediately above the synchroscope
  7. Aug 6, 2015 #6


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    I've tried to google circuit+synchronize+alternator, but cannot find the circuit mentioned in #2.

    But I remember we had a question at some examination, how to design/calculate resistors and capacitors.

    That was easy. But since then, I've have become much older, so now it's not easy. :sorry:

    I'll think about it, then I will dream about it, ( must remember to have a pencil and sheet of paper ready, awaking from the dream in the middle of the night ).
    Last edited: Aug 6, 2015
  8. Aug 6, 2015 #7

    jim hardy

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    Is this it ?
    Looks like just lights...
  9. Aug 6, 2015 #8


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    This PDF appears to have some related information:


    Use the search feature to look for the instances of 8110-20 in the PDF file -- there are several with pictures.

  10. Aug 10, 2015 #9

    Thank you so much. Much appreciated
  11. Aug 10, 2015 #10
    Thank you for the info :D. But do you know what actually caused the flashing lamp to blink fast and slow? The reason behind it.
  12. Aug 10, 2015 #11

    yes this the one im using. Because im analyzing on an alternator synchronization. module needed is the synchronous motor/generator and DC motor/generator. So now I just to get the theory behind that flashing 3-phase lamps.
  13. Aug 10, 2015 #12
  14. Aug 11, 2015 #13

    jim hardy

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    The lamps are connected between the two generators, that is between the ed and blue sinewaves
    one lamp(or pair of lamps) for each of three phases
    when the voltage is high the lamps are bright indicating the two sine waves are not aligned vertically, ie in phase
    when the sine wavs come into phase , ie vertically aligned, the voltage across the lamps becomes zero so the lamps extinguish
    that's the time to close your breaker because zero volts means not much current will flow.
    Closing the breaker when voltages are out of phase causes high current and largetorques, it's a violent manuever.

    interesting video demonstration here with stroboscope
  15. Aug 11, 2015 #14

    Thank you so much Jim hardy. This is the part that I wanted. introduction and sync lamps. :smile::smile:
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