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power filters

Discussion in 'Electronic Basics' started by CptDondo, Jul 17, 2007.

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  1. CptDondo

    CptDondo Guest

    I've got a PLC (a little controller) that runs off a generator. The PLC
    keeps locking up; we suspect it's due to spikes from the generator.

    The PLC only draws a tiny amount of power - less than an amp at 120vac.

    Is there an inexpensive filter we can get or build for this thing?

    Thanks,

    --Yan
     
  2. Tom Biasi

    Tom Biasi Guest

    Maybe. Filtering keeps something out. Maybe you need something in. Like a
    solid sinusoidal 120 VAC.
    There could be many things glitching up your PLC.
    Specs on the unit and the generator would help.
    Tom
     
  3. Tom Biasi

    Tom Biasi Guest

    The cheap, low power UPS may cause him the same problems.

    Tom
     
  4. Jamie

    Jamie Guest

    Get your self a cheap low power UPS just to operate the PLC.
     
  5. Jamie

    Jamie Guest

    We use industrial mini ups supplies on our PLC's at work, they work
    just fine. They are not intended to run the PLC for any length of time,
    just produce a nice sine wave 120 V AC . the unit actually shuts off if
    it detects constant power loss after a set time on the front panel..
    we set ours on most for aprox 1 min. and will restart when power is
    returned for at least 1 min .
    noise activities and short drop outs can get very erratic and these
    things just keep supplying with no problem.
     
  6. Tom Biasi

    Tom Biasi Guest

    Hey, If they work, Fine.
     

  7. You aren't running them off a small generator that drifts in
    frequency. Also, some UPS check the line frequency to make sure the
    supply is stable before switching. Unless you are using a very
    expensive (And large) online UPS it is still running off the line input,
    through a simple LC line frequency filter to remove line noise. Small
    and cheap UPS are all off line design, so all you are doing is switching
    to battery backup to replace the occasional missing cycles. Read the
    documentation of your UPS to see what you are really using.


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
  8. zack

    zack Guest

    mabe you could use a active power conditioner
    transformer type.
     
  9. CptDondo

    CptDondo Guest

    Do you have a manufacturer / source for these? I'll see if they want to
    spring for them....

    --Yan
     
  10. Jamie

    Jamie Guest

    Let me explain here.
    the units we use derive their source from the inverter internally
    which is battery back-up. the AC does nothing but keep the battery
    charged and supply the inverter.
    The cycle change does not effect these units, voltage dips do not
    effect these units. I've repaired 2 of these units due to mother nature
    whacking our facility. It did nothing but take out the fuse between the
    charging circuit and the battery. the battery absorb along with the TVS
    units the over surge which force the fuse link to open and also took out
    the charging circuit how ever. The unit keeps on operating just fine for
    it's preset time before it shuts off.
    The charging system is a very simply 60 hz xformer with a bridge, a
    couple of resistors, TVS and fuse protection. They're nice little bricks
    that sit on the din rail..

    Argue all you want, facts are facts.
     

  11. So, these don't even try to match the line frequency or phase before
    they switch over? What a nasty design.


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
  12. CptDondo

    CptDondo Guest

    I think you're missing the point. If I understand this correctly, there
    is no "switch".

    The "UPS" takes AC to DC, charges a battery. Then there is an inverter
    that takes DC from the battery and provides AC.

    There is no AC - AC connection or switch; the unit is *always* fed from
    the inverter, and *never* from the grid.

    --Yan
     

  13. Sorry, but you don't understand.


    You are missing the point. There are TWO types of UPS. Off line and
    on line. Small UPS systems are typically off line type, where they do
    switch the inverter on and connect it to the load when there is a
    problem.


    Only in 'on line' UPS systemms. BTW, the smallest online UPS I've
    seen was 15 KW. Even then, there were manual switches to bypass the
    system, for maintanence.


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     

  14. http://en.wikipedia.org/wiki/Uninterruptible_power_supply has a very
    simplified explaination of most types of UPS.


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
  15. CptDondo

    CptDondo Guest

    A bit of googling will find them as small as 500va.
     
  16. Jamie

    Jamie Guest

    I'm glad some one understands it. :)
     
  17. Jamie

    Jamie Guest

    No , they don't match the line freq. the output is from the inverter at
    all times. the inverter is operating from a DC supply which is the
    battery which gets charged from the line..
    Our units we use have an option to turn off after a set time when the
    UPS has determine that line voltage is absent and not just being
    erratic. We do this to prevent some sensitive systems like PLC's,UC etc,
    to shut down and restart properly when power is lost.
    The one we use for our Wonderware is connected to the serial port to
    instruct it to shut down so that windows is properly terminated before
    it losses power.
     

  18. At what price and efficiency?


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     

  19. That can cause problems with some equipment but if you want to use
    junk, feel free.


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     

  20. My first APC last for over five years on the OEM battery. Sine then,
    I've had so many given to me that I haven't needed to buy batteries in
    over 10 year. Yes, the batteries do fail, especially when the electric
    goes out often, and the computer isn't set up to shut down.

    Right now I have at least 12 spares with usable batteries, and I could
    probably get several hundred more per year, for free. Replacement
    batteries aren't that bad, bought in bulk. APC is very high, compared
    to OEM and surplus sources. I used to pick up used Gates battery packs
    from a Diebold repair center, and sell them to amateur radio operators
    for standby power. they still bug me for more cheap batteries, but the
    source is gone. I also have several new 17 AH 12 VDC gel cells from
    those portable starter packs for cars. I'm tempted to use them as
    external batteries on a pair of old 1000 VA APC UPS I have in storage
    for my server and web design computers. The 650 VA APC can't handle the
    computer and HP 1130 monitor, and odds and ends in my office.


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
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