UPS power with a rediculous duty cycle

[Strongarm]

I have been tasked with a challenge that requires me to maintain the power to a PLC and drive (VFD or Servo has yet to be determined) using a UPS or Capactior that will lose power for approximately 21 seconds on three occasions in a 5 minute cycle. This cycle will repeat 16 hours a day 365 days a year. Has anyone used anything that might possibly tackle this task?

 

[KalleOlsen]

Has anyone used anything that might possibly tackle this task?

Yes. An UPS. Must be big enough. What is the problem?

Kalle

 

[Strongarm]

The problem is the fact that the entire UPS will need to maintain a charge when it is being used 1 mintue out of every 5 minutes, 16 hours a day, 7 days a week, 365 days a year for at least 20 years. 7 out of the other 8 hours the power will be off, thus draining the unit. This thing need to charge quickly, not suffer any memory effect, and not be massive.

 

[Tharon]

Sorry I can't be of help, but I am curious what you are doing that will require control power being shut off 1 minute out of every 5 minutes of run time. I can't really think of anything off the top of my head that would require this.

 

[bkottaras]

Sorry I can't be of help, but I am curious what you are doing that will require control power being shut off 1 minute out of every 5 minutes of run time. I can't really think of anything off the top of my head that would require this.

Plus 1 here!
I'd look into what causes the frequent power failures before I think about a "patch" job.

 

[Strongarm]

Plus 1 here!
I'd look into what causes the frequent power failures before I think about a "patch" job.

These are not failures, they are planned. High vibration eliminates the ability to maintain an electrical connection. Sadly, I cannot discuss the equipment this will be used on, life would be much easier if I could. The drive doesn't need to run, I just don't have time to wait for the PLC and drive to boot, and then clear the faults once power is restored.

 

[Ken Roach]

What you need might not be physically possible: it depends on what you mean by "not massive". All the UPS'es I've seen that can supply power to AC drives are the sort that need a rack of batteries.

You definitely want to pursue a UPS that supplies bus voltage to the AC drive; just keeping the control board active isn't enough. Precharge cycles not only take time but also wear out the precharge rectifiers..... I wouldn't expect a drive to last more than a week under that service, maybe less.

Could you consider using another AC drive as a DC charge reservoir, with the buses connected together ? A typical small drive will hold up the DC bus after the main power is removed for 10 seconds... a big drive (say, 50 HP) will keep it up for several minutes. If you could use a high voltage UPS to keep the drive "topped up" and prevent the precharge from engaging, it might work.

Start by putting some numbers down: how many watts will the control system need, how many will the drive need, what kind of enclosure footprint do you have, and how many kilograms is "not too massive" ?

 

[Strongarm]

I was actually thinking about some sort of capacitor set up to keep the charge active on the 24V components for the time when the power disconnects will occur. It would be three 21 second losses throughout the sequence. I'm almost tempted to mount the drive off the vibrating unit and just use some sort of bus rail to connect the drive to the motor once the vibration stops.

 

[diat150]

good luck with your requirements. even if you could make something work I guarantee it wouldnt last 20 years. I am also pretty sure you will ruin your batteries pretty quickly by not properly charging them.

 

[mjmorrow]

Having spent some of my career in the Uninterruptible Power field,
you will not find a unit that will service those demands. Remember-
Gozinta-Gozoutta. You're way behind the curve just in battery charge time alone. Does all this have to be mounted on the device as in it is a mobile unit? Or if it is stationary, maybe the incoming power could be constantly on, with the VFD varying the motor speed?

 

[The Plc Kid]

Your best option would be to use stackable flywheel UPS system and you would need several of the larger units. If you need more you can kep adding up to buss capacity and no batteries are needed

 

[KalleOlsen]

The problem is the fact that the entire UPS will need to maintain a charge when it is being used 1 mintue out of every 5 minutes

Also you charge 4 mins interrupted by discharge 21+21+21s.

1: The 1 of 8 hrs that the system is still on; can you charge?
2: What load are we talking about 1,10,100 kW?
3: And voltage?


Perhaps you could use the equipment from a rapid chargeable ElCar?

Kalle

 

[tragically1969]

If the power truly is that unreliable then a generator has got to be the only option ?

 

[leitmotif]

What gets me is why you cannot leave normal power on YET you think the UPS will be able to supply power. I suppose this is the Top Secret part but until you tell me what TS is all about I do not see any ability to help.

Also if you are going to be discharging and recharging these cells at these intervals you should give some very heavy thought on how you are going to keep the battery cooled. At one time submarine batteries had internal cooling to enable fast recharge.

Dan Bentler

 

[rguimond]

I have been tasked with a challenge that requires me to maintain the power to a PLC and drive (VFD or Servo has yet to be determined) using a UPS or Capactior that will lose power for approximately 21 seconds on three occasions in a 5 minute cycle. This cycle will repeat 16 hours a day 365 days a year. Has anyone used anything that might possibly tackle this task?

Use flywheel UPS. Very little recovery time. You may need a bunch of them, but they're suitable for this task.