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Recent content by BigBill53

  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)

    Datasheet of the fan is attached. Rotation of the fan is correct and it doesn't appear to be slipping on the shaft (it's held in place by a grub screw into a keyed shaft). The dust extractor that the fan is blowing air into contains a number of "socks". These are basically a long tube of...
  3. 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...
  4. BigBill53

    RS-232 Data Parity Confusion

    @badservo: I was starting to think the same thing - that this isn't a parity bit at all but some other way that the system is using to communicate with the devices (such as an address word, which indeed the first byte of data is). I will check the settings and come back to you (I am using...
  5. 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...
  6. BigBill53

    Need to upload from Quick Panel Jr. II

    I have very often had problems with the COM and USB ports not being mapped properly to the virtual machine. For example, say you have a USB to RS232 adaptor. When you plug it into your USB port it will map to the main computer, not the virtual machine. You need to configure your virtual...
  7. 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...
  8. 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...
  9. BigBill53

    Solar system using grid for peak demand

    Hey guys, sorry for being ambiguous (funny how it makes sense to yourself but then you explain it to other people and it doesn't come out clear!) 1) The network provider doesn't allow backfeed of any more than 5kW in this area. The site is grid connected. 2) This is for a very small factory...
  10. 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...
  11. BigBill53

    Control via OPC

    Step 1: In the PLC, if the variable changes to the defined value turn on a bit/flag Step 2: When flag is set turn off the bits of code you don't want to run In some PLC's you can deactivate whole programs at a time by setting a bit. Sometimes you can change the PLC state by setting a controller...
  12. BigBill53

    Pressure setpoint for VFD control on refrigeration compressor

    Sorry about the late reply to this thread - it took me a while to get the information I was after. The desired evaporator temperature is -17 degrees Celsius. The refrigerant is R404A. While I was snooping around the machine I found an existing pressure switch that may have the answers I am...
  13. 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...
  14. BigBill53

    Cast iron vs Aluminium

    My father was a motor rewinder, and working with him I have had quite a bit to do with both types. You will find aluminium motors are generally only in smaller frame sizes. I haven't seen one much larger than 3kW. They are usually a bit cheaper and easier to install (because they are lighter)...
  15. BigBill53

    Contactors tripping RCD

    Thanks, I will have a look into that. You never know sometimes. After looking more closely I suspect it may be related to a bad installation. Because they had to fit this to an existing board, they have used a huge CT to fit around the busbars, and one of the phases is much closer to the...

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