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Recent content by irmalcol

  1. irmalcol

    Fire in photovoltaic panel

    I'm not sure if you are asking specifically about this, but it is definitely possible for an individual solar module to light on fire. If there is a defect or damage in the module, a DC arc can form between two components within the module. Because the module is inherently current-limiting, a DC...
  2. irmalcol

    AC current when grounding AC and DC conductors in PV system?

    I agree with VE1BLL. Under normal operating conditions, there should be no current in the grounding/bonding conductors. I would like to add that it is important to note that bonding and grounding are different and serve different purposes. Bonding is the connection of all metallic (i.e...
  3. irmalcol

    Modbus RTU on Toshiba VF-AS1 VFD

    Yeah, I realize that. That's why I need this gateway, since it's designed to work with both half-duplex RS485 and specifically with Toshiba drives.
  4. irmalcol

    Panel wiring

    I agree with LionelHutz. It would be better to have the relays downstream of the smaller breakers. However, as far as violating code, you might be OK. Assuming the small conductors you are worried about are not more than 3 m long, they don't leave the panel, and they are rated correctly for...
  5. irmalcol

    Modbus RTU on Toshiba VF-AS1 VFD

    Thanks, danw2. I completely agree with you, and you are spot on. Perhaps I wasn't clear. The AS1 has an RJ45 jack via with which the drive can speak several different protocols with different signal standards. Modbus RTU over RS485 is one possibility and the one I am interested in. There are two...
  6. irmalcol

    Modbus RTU on Toshiba VF-AS1 VFD

    I'm working on a project where we have to replace some Toshiba G3 VFDs. Currently, the G3 drives communicate with the PLC/DCS using Modbus RTU over a standard 2-wire interface (screw terminal block and shielded 2-wire cable). The cables are already run, and the client doesn't want to pull new...
  7. irmalcol

    Harmonics with VFDs and Wye-Wye Transformer

    There is no neutral running to the VFDs, just 3 phases.
  8. irmalcol

    Harmonics with VFDs and Wye-Wye Transformer

    I've been wondering about capacitive effects as well. LiteYear, can you explain further how the current would return via the filter? I don't quite understand how that would work. Thanks for the good suggestions.
  9. irmalcol

    Harmonics with VFDs and Wye-Wye Transformer

    Thanks for the link, dpc. I hadn't found that one yet. HornTootinEE, The input to the VFDs is a 6 pulse rectifier. I don't know whether you want to think of that as delta connected or not. In any case, the VFDs are 3-phase loads, and are presumably balanced, notwithstanding the power...
  10. irmalcol

    Harmonics with VFDs and Wye-Wye Transformer

    There is no neutral bus in the MCC. Running from the transformer to the MCC, there are the 3 phase conductors and the secondary neutral (goes to the NGR which is installed in the MCC building). The MCC ground bus is attached to the MCC building ground, which is attached to the transformer...
  11. irmalcol

    Harmonics with VFDs and Wye-Wye Transformer

    Hello all, I have an update to this problem. A solution to the harmonics issues has been found, so there should not be any further problems with harmonic filters melting or VFDs failing. There is still, however, an interesting phenomenon observed with the ground and neutral current at the MCC...
  12. irmalcol

    Harmonics with VFDs and Wye-Wye Transformer

    The engineering company I work for was hired by the plant to investigate these problems. I have little access (and no immediate access) to the utility side of things (i.e., current in the primary neutral, the core configuration or nameplate of the transformer). After speaking with my supervisor...
  13. irmalcol

    Harmonics with VFDs and Wye-Wye Transformer

    All good things, HornTootinEE. Thanks again. One other important question I have is whether this configuration is likely or able to produce circulating currents in the transformer through the neutrals? I am fairly unfamiliar with wye-wye transformers, and the NGR is of unusual rating.
  14. irmalcol

    Harmonics with VFDs and Wye-Wye Transformer

    Thanks for the reply, HornTootinEE. For any interested parties, the VFDs are 6 pulse. This is really just for your information, though, as I am mainly concerned with the transformer here (others are looking into problems with the VFDs).
  15. irmalcol

    Harmonics with VFDs and Wye-Wye Transformer

    Hello, I am looking for some opinions regarding a plant distribution system I am investigating with the following configuration: There is a 1500kVA 25kV/480V wye-wye transformer feeding the plant. The bulk of the load is comprised of 2 600HP VFDs. The primary neutral of the TX is solidly...
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