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Constant Current Regulator - Bad Regulation

  1. Nov 27, 2009 #1
    Hi There,

    I have a CCR (High Power) to feed current into a airfield lightning serial circuit which is having a lot of troubles trying to maintaing the current regulation.

    Basically the problem is that once the CCR is set up to highest step (Step 5: 6.6 A) with a maximum load (PF=0.98), the current start oscillating between 0.0 A and 6.6 A which produce the all lightning circuit to oscillate also.

    All Airfield lamps are connected to a remote control unit which in turn is connected to an isolation transformer secondary.

    The remote control unit feed the airfield lamp with the appropriate current when it receives a signal from the CADA system to turn ON the lamp, and it produce a secondary short circuit when the remote control unit is being commanded to turn OFF the lamp or when the lamp is broken.

    Of course, when we have all lamps OFF, the CCR is OFF, and the CCR goes ON when the lamps are commanded to be ON (the communication is going through the same power cable by using Power Line Carrier technology).

    We don't have the CCR ON at any state if we have all lamps OFF, which means the PF drops to 0.63. As far as we add up load to the serial circuit the PF improves (which is logical).

    What could be the reason for the system to oscillate in such a way?

    The minimum PF we have in normal conditions is 0.66 (with the minimum amount of lamps that could be ON).

    The IEC-61822 establish that the CCR for Airfield Lightning should be capable of regulating the current at any step (Table 1: step 1≈2.8 A / Step 2≈3.4 A / Step 3≈4.1 A / Step 4≈5.1 A / Step 5≈6.6 A).
    ----------------------
    5.3.2 Regulation – reactive loading
    The CCR shall maintain the current within the limits of table 1 for all current steps when the
    load has an inductive power factor of 0,60.
    ----------------------

    From this point of view, the system should be capable of regulating the current even in an inductive circuit with a PF of 0.60.

    What else could produce the CCR to oscillate?

    I observed that when I have a certain load (about 50% of the possible load) and we surpass the 900 V @ step 5, the system starts oscillating in current. The CCR is 15 KVA and the maximum load (with all lamps in ON state) is 7 KW which means that in worst case we do not reach the maximum load we might have on CCR.



    Regards,

    CL
     
  2. jcsd
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