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Recent content by AG-PPI

  1. AG-PPI

    Corrosion on cable trays.

    I understand it doesn't have to be 8.8 and stainless. That's why I said for example. The metals do not have to be immersed in order for galvanic corrosion to occur either. Rainwater, or even moisture from a high humidity atmosphere is sufficient enough to begin the process. If the equipment is...
  2. AG-PPI

    Corrosion on cable trays.

    When I see specific localised rusting like this, it screams 'galvanic corrosion' to me. This occurs when two metals of significant difference on the anodic index are used together in the presence of an electrolyte (in most case, moisure). The more 'anodic' metal will act as a sacrifice, rusting...
  3. AG-PPI

    Two 250 VDC 1200A rectifiers feeding multiple crane rails - is it OK to put the outputs in parallel ?

    As these are diodes, then yes as a few have already said, it will be incredibly difficult to get these rectifiers to share equally. Even less likely if the diodes being used in the new rectifier are from a different manufacturer/part number from one rectifier to another. If all diodes were...
  4. AG-PPI

    Two 250 VDC 1200A rectifiers feeding multiple crane rails - is it OK to put the outputs in parallel ?

    Hi waross, Regarding voltage control, this is why I suggested the use of that control board. It has many control features, one being phase-angle control which I believe reduces RMS voltage on the output. That control board is designed to work in exactly these kind of situations. However, this...
  5. AG-PPI

    Two 250 VDC 1200A rectifiers feeding multiple crane rails - is it OK to put the outputs in parallel ?

    I am assuming the rectifiers are standard 3-phase AC to DC? I'm a little rusty but I believe you can connect the DC outputs in parallel to share the load, but it is not as simple as shown in your diagram The AC input on one rectifier must be delta, the other must be star. They cannot both be...
  6. AG-PPI

    Suggestions Needed: Thermal switch on live MV heatsink

    I am currently working on putting together a design draft for an MV inverse-parallel thyristor controller assembly. The assembly itself would be running at 7920Vac nominal, 50Hz 90A. The thyristors we will be using are 'hockey puck' style, single side cooled on a suitable aluminium heatsink. Our...
  7. AG-PPI

    Small AC-DC bridge popping

    Closing this thread. I told them to shift R1 to go across C1 like a normal discharge resistor should. Now seems to be working fine.
  8. AG-PPI

    Small AC-DC bridge popping

    It is. I probably should have taken that out for the purposes of taking a screenshot. I ran the simulation on Multisim just to see if any errors popped up, and it requires a ground point for that. No errors popped up though, so I was a little more confused after that.
  9. AG-PPI

    Small AC-DC bridge popping

    I have checked the diodes they put into the veroboard. Everything seems fine there. The capacitor in use is a 400Vdc electrolytic, so not concerned about voltage there. The resistor in use is a 3W resistor with a max working voltage of 500V, so not a concern there either. The 110Vdc relay...
  10. AG-PPI

    Small AC-DC bridge popping

    My companys test department needs a DC power supply to give 110Vdc to power a DC relay for testing purposes, and they don't want to buy a purpose built one. Up until now our test department has been chaining a couple of 30V dual output DC power supplies in series to get the voltage needed but...
  11. AG-PPI

    200A Fuse in a 400A FDS

    400A is likely the absolute maximum rating for the FDS. Using a smaller fuse could be a simple way of derating the FDS dependant on load size. But yes, as dpc says, ensure the fuse that has been fitted has been suitably selected.
  12. AG-PPI

    3ph Parallel Thyristor Rectifier Not Sharing Current

    Thanks everyone for the replies, much appreciated. I kinda suspected that the forward voltage drop difference would have been the issue here. I thought perhaps that if they were close enough then they would share but unequally, but it seems not to be the case here. The thyristors did actually...
  13. AG-PPI

    3ph Parallel Thyristor Rectifier Not Sharing Current

    Good afternoon all, I have a problem which has really melted my brain this afternoon and I am hoping someone can offer some insight. My company had recently designed and built a three phase thyristor bridge rectifier for our customer. One of our customers requests was that each thyristor had...
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