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
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
The cheap, low power UPS may cause him the same problems.
Tom
Get your self a cheap low power UPS just to operate the PLC.
-- "I\'m never wrong, once i thought i was, but was mistaken" Real Programmers Do things like this. http://webpages.charter.net/jamie_5
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.
-- "I\'m never wrong, once i thought i was, but was mistaken" Real Programmers Do things like this. http://webpages.charter.net/jamie_5
Hey, If they work, Fine.
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
mabe you could use a active power conditioner transformer type.
Do you have a manufacturer / source for these? I'll see if they want to spring for them....
--Yan
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.
-- "I\'m never wrong, once i thought i was, but was mistaken" Real Programmers Do things like this. http://webpages.charter.net/jamie_5
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
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
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
-- 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
A bit of googling will find them as small as 500va.
I'm glad some one understands it. :)
-- "I\'m never wrong, once i thought i was, but was mistaken" Real Programmers Do things like this. http://webpages.charter.net/jamie_5
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.
-- "I\'m never wrong, once i thought i was, but was mistaken" Real Programmers Do things like this. http://webpages.charter.net/jamie_5
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
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
That's why most people have to settle for off-line UPS equipment. I could have bought a used online sine wave UPS big enough to power everything in my house for $100. It was almost two tons, and only needed about $5000 worth of new batteries that had to be replaced every two years. So, it would have cost over 2.5 times my current electric bill, plus the cost of extra electricity for air condoning.
-- 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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