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Anonymous Poster #1

Designing Or Sizing A Single Phase (50 Hz) UPS System

12/22/2014 4:48 AM

I read the old postings about UPS in CR4 but no good...So I would like to ask as I am uploading a simple standby UPS system diagram by Electrical Engineering World forum to get the point straight. (a) I may take a rated UPS to fit my needs (b) I may design my own for the load....Lets go both ways:

Assuming: I have a single phase critical load of 1500 W which would be supplied by the UPS in an event of main utility power shut down for at least 3 hours on on and off basis of main power load shedding...

(1) What sort of batteries? Parallel or series? I know it but not much my specialty :)

(2) Need to design or size an inverter to output 220 V single phase (no fluctuation)?

(3) Rating of inverter in KW and how much of input DC voltage be better suited, 12 V, 24 V or ...

(4) Sizing charger for the said batteries?

(5) You could see in the diagram that the main AC is feeding the charger before power failure. Any under/over voltage on the main before shut down hasn't been addressed. It's a fact that under voltage on the main happens on daily basis, so need to size an AVR/AVS or else on the main AC input? Wouldn't I need one on the inverter output of 220 V in case of battery back up system during main shut down?

(6) Would prefer Static Transfer Switch over ATS for electro-mechanical failure reasons? Any suggestions?

(7) Any recommendation on a control systems to make everything function etc. CPU, dial-up modem etc.

(8) Charging and discharging times?

(9) etc.

Thanks in advance!
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Anonymous Poster #1
#1

Re: Designing or Sizing a single phase (50 Hz) UPS System

12/22/2014 4:52 AM
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cuba_pete
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#8
In reply to #1

Re: Designing or Sizing a single phase (50 Hz) UPS System

12/22/2014 2:36 PM

What? No safety ground!?!

Preposterous!
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tcmtech
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#2

Re: Designing or Sizing a single phase (50 Hz) UPS System

12/22/2014 6:28 AM

Why bother building one when you can go out and buy a commercial one for far less that will work right the first time and every time?

Most any 2000 VA or larger commercial unit will carry 1500 watts as long as what ever battery bank you have it attached can hold it up.

Price would be around $200 - $300 American (you will never build one for less) fora good used one plus what ever your battery bank sets you back.
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Fredski
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#6
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Re: Designing or Sizing a single phase (50 Hz) UPS System

12/22/2014 10:27 AM

I second that notion
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Crabtree
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#7
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Re: Designing or Sizing a single phase (50 Hz) UPS System

12/22/2014 12:31 PM

I third it.

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Brave Sir Robin
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#9
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Re: Designing or Sizing a single phase (50 Hz) UPS System

12/22/2014 11:04 PM

Fourth it.
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lyn
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#3

Re: Designing Or Sizing A Single Phase (50 Hz) UPS System

12/22/2014 9:04 AM

Take your requirements/questions to three different UPS suppliers and ask therm.

Even if someone here tried to explain it to you, you'd still need thehelpofyouru PS supplier.
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Original_Macgyver
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#4

Re: Designing Or Sizing A Single Phase (50 Hz) UPS System

12/22/2014 9:09 AM

Try APC!

They most likely have a solution for you off the shelf!

http://www.apc.com/tools/wizard/home/zoneForm.cfm?ISOCountryCode=us&gclid=CJz95srp2cICFROTfgodVysADQ

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Noudge79
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#5

Re: Designing Or Sizing A Single Phase (50 Hz) UPS System

12/22/2014 10:13 AM

Ametek has sorts of products like this. Powervar their user manual has its diagram and basic features you could find as a reference to your design. Nothing special about it other than switching ac to dc inverter power in times of interruption, although some design adds up surge protection and flitering features. You could even google some wiring diagrams of this stuff. Use google image.

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Brave Sir Robin
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#10

Re: Designing Or Sizing A Single Phase (50 Hz) UPS System

12/22/2014 11:41 PM

I recommend an on-line UPS where the inverter is always supplying the load and the only thing that changes is the battery charger stops working when the utility power is not up to snuff. These are also sometimes known as dual conversion as well. Some loads will not operate correctly when an off-line UPS switches from the mains to the inverter. The delay that invariably occurs can cause all kinds of problems. All depends on the nature of your load. For three hours of load backup, you will need a substantial external battery bank. For rough estimates, you will need 27 amp hours at 220 volts (2 kVA) multiplied by an efficiency penalty factor of about 1.2 to account for inverter losses.

A GC2 6V battery for a golf cart is about 200 amp hrs for an approximate energy of 1.2 kW-hrs. Of course that is discharging the battery down to nothing which does not make for good battery life. A good rule of thumb is to take about half its capacity per event. So if each GC2 battery is good for about 0.6 kW-hrs, and you need about 7.2 kW-hrs then twelve GC2 lead-acid batteries will make for a robust UPS.

That's only 744 pounds or 338 kilograms of batteries.

You can shave the battery down in size if you can add an automatic start generator that will pick up the battery charging if the power is off for more than five or ten minutes. Short outages will be carried by the smaller battery bank and the generator keeps things going for the longer outages.
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vsar
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#11

Re: Designing Or Sizing A Single Phase (50 Hz) UPS System

12/23/2014 1:28 PM

What you have described as well as shown in your drawn wiring diagram is an emergency power source, NOT a UPS! Similar to an emergency light scenario, will operate only when regular power source is interrupted... It is battery powered that get recharge via regular power source.

In a real sense of true UPS system, the load is always connected to it, (need No transfer switch), regardless whether the outside commercial power is available or not. The pre-conditioned UPS output power is always provided, with or without commercial source, and until a predetermined length of time which is typically dependent on the type of battery used and its state of charge condition!

This type of system is more elaborate to design or expensive to acquire. Mostly recommended for critical loads and applications!

Good luck!

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Anonymous Poster (1); Brave Sir Robin (2); Crabtree (1); cuba_pete (1); Fredski (1); lyn (1); Noudge79 (1); Original_Macgyver (1); tcmtech (1); vsar (1)

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