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View Poll Results: What brand would you consider?
APC 7 70.00%
Tripp Lite 1 10.00%
OEM / Roll your own 2 20.00%
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Old September 3rd, 2002, 02:16 PM   #1
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Question UPS for PLC (off topic)

I'm looking for some ideas for a UPS (uninteruptible power source) for a PLC. We have an AB PLC-5/40L with an external power supply (1771-P7) running some critical processes and need to prevent the PLC from rebooting during short losses to the supply power. I know this forum is for programming issues but I'm hoping that someone has run across this and I'm for some pointers in the right direction.
Thanks in Advance
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Old September 3rd, 2002, 02:40 PM   #2
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I voted for APC because it's the only one I've heard of.
Although Perpetual Motion is great when you can get it.
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Old September 3rd, 2002, 10:30 PM   #3

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I've been in similar situations in the past.
However, I found that careful use of memory areas, and ensuring the battery backup was working correctly, allowed the PLC to recover from a power outage and resume operation without needing a UPS.
I don't know about AB PLCs, but if you find a way of doing it you could avoid installing another piece of equipment.

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Old September 4th, 2002, 08:28 AM   #4
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Short Losses......

Your solution lies in the exactness of your problem. What type of time period does "short losses" entail? Have you thought of also going with redundant PLC's (if the process is that critical) in case of problems with the main processor. There is a section of configuration in AB PLC's (DIP switches on the rack) where you can configure the I/O to remain in it's last state when hardware failure occurs. A UPS would also ensure that your process remains safe. I would opt for all of the above actions.
Will Wilson
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Old September 4th, 2002, 08:53 AM   #5
Jiri Toman
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I have used the following UPS: ONEAC #ON400XRA-SO

ONEAC used to make a UPS specifically for PLC's but for some reason
they have stopped making them. The above model does a good job,
it will hold up for at least 15 minutes.

For some projects it is necessary to have UPS and not
just a tracking filter or a good clean power supply.
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Old September 4th, 2002, 09:16 AM   #6
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UPS Specification

I prepare submittals based upon specifications prepared by the consulting engineering firm. Frequently a UPS will be in the spec. Sometimes they will give a minimum time that the system must run on battery. I do maximum load calculations and come up with a VA number. I like Powerware and Best. I have been using them for a few years.
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