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| Subject - 3 phase transformer question | |
| Ryan_J |
At the request of Scott, here is another question: A transformer has a primary of 480 (Delta) and a secondary of 208Y/120. A 100A load is placed on the secondary. 1) What is the turns ration? 2) What is the minimum KVA rating that this transformer could be? 3) What is the current on the secondary? 4) What is the wattage being consumed on the secondary? 5) What is the wattage being consumed on the primary? Same transformer, assume 96% efficiency 6) What is the wattage of the load on the secondary? 7) What is the volt-amps of the load on the secondary? 8) What is the wattage of the load on the primary? |
| David Hyatt | Something seems wrong about this question maybe its me. Where is the 100a load, is it divided equal on all phases 33.33 per phase or is the 100amp load on one phase? I could answer this question if you had KVA load instead of 100 amp load. But I will give it a shot anyway. 1) ratio 4:1 2) 20.8 KVA? 3) sec line current?= 57.77 we already know current 100amps 4) 20,800 5) 12,000 I am going to stop here let me know if I am on the right track. I am really confused on the question. It is probably something simply and I am trying to complicate it. |
| iwire | A transformer has a primary of 480 (Delta) and a secondary of 208Y/120. A 100A load is placed on the secondary. 1) What is the turns ration? 2.3 2) What is the minimum KVA rating that this transformer could be? 36 3) What is the current on the secondary? Ah, you gave us that so I will give you primary current 43 amps 4) What is the wattage being consumed on the secondary? 36,025 5) What is the wattage being consumed on the primary? 100% efficiency? 36,025 Same transformer, assume 96% efficiency 6) What is the wattage of the load on the secondary? 100 amps, you told us that.  7) What is the volt-amps of the load on the secondary? 36,025 8) What is the wattage of the load on the primary? 37,178 |
| David Hyatt | 1) ratio 4:1 2) 208x100x1.732=36,025.6/1000= 36KVA 3) 100amps 4) 36,025 5) input va = output va @ 100% eff 36,025 6) eff goes up input goes down output stays same 36,025 7) 36,025 8) input= output/ eff 36,025/.96= 37,526 after looking at Bobs i think I got my head on straight is this right? |
| Ryan_J | I don't know! Did you want me to do the math too? Let me get back to you on this. :D :D :D |
| Ryan_J | Heres what I came up with: 1) 4:1 2) 36 KVA 3) 100A 4) 36,025 5) 36,025 6) 36,025 7) 36,025 8) 37,526.6 |
| David Hyatt | cool you through me at first with 100 amp load and I was trying to use a more advanced formula when all I needed was that basics. Iwire made me realize that when I seen some of his answers. This was probably an easier question that most we have had, but I made it hard on myself. Thanks. |
| Scott Vickrey | Shmeg! I had to work and missed my question. I missed another chance to show my soft underbelly. Bob, I'm glad to see you are not infallible. I hate to be the only one. David, You! Go! Boy! Ryan, Thanks for taking the time to write this question. There is no way of knowing how many electricians you have helped in the future. POWER TO THE PEOPLE! |
| iwire | quote: Not even close,  , I do know some things but I am not afraid to let it show that I still have things to learn.Anyone that thinks they have all the answers to all aspects of this trade is fooling themselves.  Bob |
| David Hyatt | Yea I know, see my first post. |
| LIVEWIRE | 1. 4:1 2. 35.9KVA 3. 100A 4. Need PF of load 5. Need PF of load 6. 34.54KW 7. 35.9KVA 8. 34.54KW |