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  • Users: BigBill53
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  1. BigBill53

    Detecting inter-turn short circuits in rotor on wind turbine

    Hello, I have a wind turbine that is overheating on the rotor. The rotor consists of 60 separate electromagnetic coils, all connected in series. There is a separate DC circuit used to excite the coils. I have other machines that don't get hot, and they are using much less current to excite the...
  2. BigBill53

    Air blowing back out of fan (the wrong way)

    Hi, I have an inline fan that is being used for dust extraction. The fan is 1200mm wide with a 55kW motor (1400rpm). There is a cone/hood on the inlet side of the fan that is around 1m long and is slightly larger than the diameter of the fan (not sure exactly how much larger, around 400mm...
  3. BigBill53

    RS-232 Data Parity Confusion

    Hey, I have an old software package that runs on MS-DOS. Needless to say it is tricky getting DOS to work on modern machines. So I had the bright idea of making a virtual machine of DOS and running it on a modern computer. This software talks to a number of machines via RS232 (actually it is...
  4. BigBill53

    DC Surge Protectors

    Hi, Does anybody know the difference between DC surge protectors and AC surge protectors? I am designing a standalone piece of equipment that has some solar panels charging a battery bank, and then some equipment being powered off these batteries. I want to know if I should put DC surge...
  5. BigBill53

    Calculating cascading on circuit breakers

    Hey, I am trying to work out the cascading on an old Merlin Gerin CM1600 circuit breaker. Basically, the product is so old that there are no cascade tables so I can't find out if the downstream breakers can withstand the fault current. Does anybody know how to calculate this? I normally just...
  6. BigBill53

    Solar system using grid for peak demand

    Hey guys, Does anyone know about an inverter for a solar system that will supply power to an installation, but if more power is required it gets it from the grid? I am an electrical engineer, but I haven't had a lot to do with solar. Typically what I have seen is things like houses with solar...
  7. BigBill53

    Pressure setpoint for VFD control on refrigeration compressor

    Hi, I have been asked to control some refrigeration compressors with VFDs to save power. I've done a lot with VFDs over the years, but this has never come up yet. I've done a fair bit of research and am pretty confident I have everything figured out - I was going to control the compressor...
  8. BigBill53

    Contactors tripping RCD

    Hi, I have an old resistive starter that has been overhauled. We installed 8 new 250A contactors, all with 240VAC coils. When we were testing the starter the main RCD to the board would trip when the third contactor turned on. It should be noted that we did not have the motor connected at this...
  9. BigBill53

    Enercon Wind Turbines and OPC

    Not really a PLC question, but there are no forum categories for SCADA and I know most of you guys will (like myself) do a lot with SCADA... I need to talk to an Enercon wind turbine. The correct way to do this is via an OPC server that communicates using the IEC 61850 standard for talking to...
  10. BigBill53

    Power factor correction unit totally blown up

    Hi all, I have a bit of an unusual one here, and I was wondering if anybody has come across something like it (or maybe a PFC expert could point me in the right direction). I recently took a look at a power factor correction unit that had pretty much totally blown up. All of the capacitors have...
  11. BigBill53

    High Voltage Automatic Transfer Switch?

    Hello, I have a problem that I think is a bit out of my league - I deal with mostly LV stuff. A customer of mine has gone out and bought some large generators, with the intention of powering their farm when there is no mains power. The farm is very spread out, and so it has around 30 small...
  12. BigBill53

    Input/Output Multiplexer with Digital and Analog

    Hi, I have a system where a number of digital inputs (10 of them) are multiplexed and sent across 2 wires back to the control room. The customer now wants a few 4-20mA signals sent back as well. Running more wires is not an option here - it's going to be too expensive. Does anyone know of a...
  13. BigBill53

    How long would you run a VFD after issuing a stop command?

    Hi, I've come across a situation in a pumping station and was wondering if I could get a few opinions. Basically, we have a VFD that has a line contactor supplying it power. The idea is that after issuing a stop command to the drive we turn off the contactor. Some people here are of the...
  14. BigBill53

    Surge arrestors and circuit breakers

    Hello, I have a colleague who is causing quite a bit of a stir at the moment. He is insisting that you need to connect a circuit breaker in series with a surge arrestor. He insists it is a new law or standard that he heard about that is coming into effect in my country (Australia). Since most...
  15. BigBill53

    Cascading fuses with circuit breakers

    Hello, I have heard that you can cascade fuses with circuit breakers to increase the kA breaking capacity, much like you can do with cascading circuit breakers. From what I can tell this is called "series rated". However, I really can't find much information from manufacturers about it. For...
  16. BigBill53

    Pump pressure at low flow

    Hello, I have a pump system that is giving me some headaches and I can't figure out why. This pump is controlled by a VFD, because the load varies quite a bit. The VFD has been set up to vary the pump speed in order to maintain a constant pressure. The pressure sensor is downstream from a...

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