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| Subject - ups | |
| komaraiah |
Dear All We have a 200KVA UPs Its normally 50%load if power failurehow much time it will give the back up power plase tell me formuleu komaraiah |
| LIVEWIRE | Check one of your batteries. The battery should have a rating that indicates a given load (amps or watts) that it can carry for a given period of time (minutes or hours). The more batteries that you have, the longer that period of time will be. Compare this against your normal 100KVA load. |
| komaraiah | The UPS Details Are 200KVA-UPS 12V,130AH Lead acid batteries-34no.s Average load is 50%on the UPS Plz tell me how to calculate back up time of the UPS |
| JimmyDee | A 130 amp hour battery should give you 1 amp for 130 hours or 130 amps for 1 hour. That is in theory. So if I understand you correctly, and you have 34 of these batteries, you should be able to draw 130 amps @ 12 volts for 34 hours. If we series 10 batteries together to get 120 volts, we would have equivalent to a battery that will deliver 130 amps @ 120 volts for one hour. We could them make 3 of these 120 volt systems and then parallel these together and would have the capability of 390 amps @ 120 volts for 1 hour. We will use the additional batteries for voltage peaking when the batteries start to be used up or to make up for the inefficiencies of the UPS. 100 KVA, if the voltage is 120 volts (thats what we would use in the US) is 100,000/120 = 833 amps. So if my thinking is correct in this, you would have a little less than 1/2 hour (28 min) which is usually enough time to systematically shut down everything. Someone else please check these figures and see if I'm close. Jim |
| Scott Vickrey | 28 minutes would presume the inverter did not waste any energy in creating the sinewave. Of course, we know that semiconductors do not work this way. So we will have a great variation from manufacturer to manufacturer for each UPS depending on their inverter's efficiencys. This is information that will have to be obtained from the manufacturer of the UPS. Also, a 130 amp hour battery will hold more or less than 130 amphours depending on its condition. PS Nice math Jimmy. |
| Scott Vickrey | Furthermore, there are many diferent types of UPSs and they emlopy several diferent ways of generating the used voltages. I was told about one that uses a flybacks xformer that was supposed to be the ultimate in UPS applications. Supposedly the transformer acts like a flywheel making for a perfectly bumpless transfer. Some UPSs just reroute power some create a squarewave on the generated side of the UPS. I'm not sure about the next sentence so someone stop me when I'm lying. an active UPS uses it "secondary" circuit all the time to supply power to what it's protecting and a passive UPS just switches to the "secondary" circuit when the power fails or becomes otherwise unusable. I know there is a better word for secondary here. What is it? |
| JimmyDee | quote:The UPS's produced power or circuit. Yes you are correct than most of these work that way. It acts as a great spike filter when connected that way. Jim |
| sijagur | Dear Komaraiah, I think this UPS that we talk is similar with UPS in my company. If i didn't wrong, we have similar voltage rating here in Indonesia, so i hope this can help. The batteries of UPS set are always connected in series to get phase to phase voltage about 380 volt, and voltage rating of 1 phase load is 220 volt. I will calculate load current in total 3 phase, so 50% of 200kVA UPS draw total current about 100,000 : 220 = 454.5 A. Total capacity of batteries are 34 x 130 AH = 4420 AH. So, theoritically your UPS can back up your supply to feed load about: 9 hours 42 minutes. But please carefully noted, this is theoritically calculation, the back up time is very depended on each battery quality, the efficiency of battery is not 100%, and time after time it become less in efficiency. And please carefully noted too that a 130 AH battery, in practice never feed 130 A load in an hour. So, approximately your UPS set can back up aroud 4-5 hours. If anyone have correction, please don't hestitate to make comments. regards, -andi- |
| sijagur | Sorry, I think i'm over estimate about back up capability of this UPS set. Based on information from my friend who know better in practice, he said that this UPS set may back up load for only half an hour, because most of battery has poor efficiency. And i'm agree with him 
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