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  1. electricuwe

    Inverters for solely Syncing / Sourcing VARS

    Large PV inverters can be used as VAR compensators. Usually this function is advertised as "Q at night" and can generate some additional income from grid support. However, I never checked if it is feasible to install a PV inverter just for this purpose. You can by "Active filters" for this...
  2. electricuwe

    Directly from 30 kV to 0.4 kV? Or step down the voltage in stages, typically from 30 kV to 6 kV, then from 6 kV to 0.4 kV.

    From my point of view the choice depe nds on the power you need per LV bus: In case you need more than 10 MVA per LV bus, then direct 30/0.4 kV transformation is reasonable In case you only need a few 100 kVA per LV bus it is more reasonable to have an intermediate step. You have to consider...
  3. electricuwe

    VFD increasing the motor winding temperature

    Surprised how you can discuss this topic with a lot of posts without even asking for the switching frequency. In nearly all VFDs the switching frequency is user-adjustable. low fs --> reduces inverter losses, reduces EMI high fs --> reduces motor winding losses, reduces acoustic noise, improves...
  4. electricuwe

    Fault current capability of DFIG generators

    Yes, I fully agree to Propot. The exact details how the control in fault mode works is valuable manufacturer IP. However, everthing you need to integrate wind turbines in a grid should be available from the utility (grid code) or the supplier documentation - at least from the established suppliers.
  5. electricuwe

    Transformerless Inverters and BESS

    Basically the decission to operate a system ground or ungrounded has three implications: - voltage stress across isolation - capacitive currents driven by common mode voltages - fault currents If you compare PV and batteries, PV is not able to drive large fault currents from the DC-side, hence...
  6. electricuwe

    Excitation current on induction motor as a generator via VFD

    My guess is that exiting the generator with quite small external power via an VFD will work quite well. You just have to provide the losses during the startup process. But the issue is feeding into the grid. Usual active frontends are not designed to work without a grid. You need a grid forming...
  7. electricuwe

    [Active Front End Rectifier] Leading current issues

    My experience with synchronizing to the grid is that solutions that somehow mimikry the behavior of a rotating mass work fine. This is robust against errors or short term disturbance. We implemented this as a three-phase PLL on 16 bit µC more than 25 years ago, but the concept was already...
  8. electricuwe

    Fault current capability of DFIG generators

    For type 3 the stator winding is able to provide a significant SC current as described by wcaseyharman. However, this is not mandatory in most areas and it creates significant stress to the rotor side inverter, making its design challenging.
  9. electricuwe

    Fault current capability of DFIG generators

    Look for the keywords "low voltage ride through" or "grid code". These regulation define how wind turbines have to behave during a fault. In general they have to stay online for a defined duration and feed in a little more than nominal current during that time. Power from the turbine has to...
  10. electricuwe

    Heathrow power outage

    Fully agree to thermionic1. Askarel/PCB was by far more a curse than a benefit in regard to safety. But there are other fluids where at least no sever health or environmental risks are known although they are in use for several decades. I have worked on units of several 10 MVA using silicone oil...
  11. electricuwe

    power factor issue

    You have to be aware that poor power factor can be caused by inductive load (lagging) or by capacitive load (leading). Unless you know your power factor without any capacitors connected you can`t decide. Maybe you just pay the penalty for the capacitorys causing leading power factor.
  12. electricuwe

    Heathrow power outage

    Let me provide some background on disaster protection related to transformers. - the usual liquid for cooling transformers is mineral oil as it provides excellent isolation and cooling - however this oil is flammable - protection and regular maintenance, e.g. derived from regular oil analysis...
  13. electricuwe

    power factor issue

    From your description of load there is no reason to use a capacitor bank. Your (small) welder most probably uses power electronics may even provide power factor correction and the grinder has low power and might rune in worst case at a power factor of 0.6 or 0.7.
  14. electricuwe

    Transformer impedance indexed to k-rating

    Lucas, it would be helpful if you could post other data from the name plate. Is the kVA-rating identical for k = 1 and of k = 8 ?
  15. electricuwe

    KW rating of 4 pole motor at highest speed is low.

    Power is proportional to the product of speed and torque. As for electric motors torque is given by the rotor dimensions, lower speed motors have lower ratings.
  16. electricuwe

    Hydrogen electrolysis aka green hydrogen

    Green hydrogen is extremely important to achieve climate targets, but not for putting into lots of new applications, but to replace the hydrogen currently generated by steam reforming. Only when we have achieved this replacement we should start to think about hydrogen or hydrogen derivates for...
  17. electricuwe

    Pulse generation

    Such kind of power supplies is quite common for electroplating. Look for a "pulse plating power supply" and you may find something suitable for your application at reasonable cost.
  18. electricuwe

    Electrical Aluminum DC Busbars - Joint Coating of silver, tin or nickel

    A busbar joint is much more complex as commonly considered. The performance is a combination of busbar material, coating,clamping hardware and maximum temperature. I can confirm that in US silver is preferred, at least on Cu, whereas the rest of the world prefers other coatings. Some of our...
  19. electricuwe

    Powerflex 755 (15 hp) IGBT SMOKED!

    At 15hp drives rarely use IPMs. More likely the drive uses a PIM - a module containing all power semiconductors including the input rectifier. But often in this power class the driving circuit is not done by isolated drivers but by level shifters (similar like in a IPM, but outside the module)...
  20. electricuwe

    Led time large power transformer

    I'm afraid for this size you have to expect at least twice the time estimated by DPC.

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