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Forum Index : Electronics : Need help testing Transformer
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| BenandAmber Guru  Joined: 16/02/2019 Location: United StatesPosts: 961 |
I got my 52 lb Transformer in the mail today I powered it up using a 1 20.3 volts out of my wall socket I put a small old-style light bulb in series on one leg not sure what the wattage is on the light bulb but on the output low side it put out 18.68 volts one the light bulb I got a reading of 88.3 this is right after the light bulb in series on one side and the other side connection Mains to Transformer so the voltage out of the wall was 120.3 the voltage after the light bulb was 88.3 the output on the low side of the Transformer was 18.68 the amperage reading was 0.06 I had a small jumper hooked up to by pass light bulb when I tried to bypass it made big spark so I did not do it I would greatly appreciate any input I could get from the experts on here and I thank you very much for all the help be warned i am good parrot but Dumber than a box of rocks |
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LadyN Guru Joined: 26/01/2019 Location: United StatesPosts: 408 |
OK. I am very exicted to see you going so fast. AWESOME! First, I really recommend putting in spaces and returns/enter key in what you type so it's easy to read for everyone. Once you make it easy to read, people will help you more. I used to have the same challenge years ago and someone took time to teach me this so I am trying to do the same. Hope you like it :) I took the liberty of doing this to your above post: Did I reformat it correctly and convey your post properly? It might be possible things got lost in translation so please don't get upset but tell me what I did wrong and I will try again. |
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| LadyN Guru Joined: 26/01/2019 Location: United StatesPosts: 408 |
Now, before we proceed, you must understand that at these voltages and currents, you WILL kill yourself and anyone around you including setting things up on fire if you make ANY mistakes so make ABSOLUTELY sure to run by any and all plans you have by an electrician before you plug anything into mains. I also highly recommend either buying or making an isolation transformer. If you are interested, we can make an isolation transformer together and the people here will help us do it, so let me know what you think. An isolation transformer with proper safety features reduces somewhat but does not make 0 the chances that you will kill yourself and anyone around you. I also highly recommend starting off with lower voltages and currents first and then once you understand everything, make a higher voltages and current version. |
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| LadyN Guru Joined: 26/01/2019 Location: United StatesPosts: 408 |
OK, now you must start drawing things. As they say, pictures are worth a thousand words, so let me draw, very roughly, what you said: It would have been better if I drew a picture. The two wires coming out off the top of the transformer is the secondary winding (if it has only one secondary winding). I am assuming you measured 18.68v across this transformer secondary winding Did I get ALL of it right? If I am wrong in even one thing, you have to tell me. In that case: Mains provide 120.3 volts If the voltage after the light bulb was 88.3V, it means there was a drop of (120.3 - 88.3) = 32V across the bulb. This also means that the transformer saw only 88.3V of the possible 120.3 volts. Check if this is the case. Since you got 18.68 out of the transformer secondary winding after feeding it 88.3V at the input, it's a 88.3/18.68 = 4.73:1 step down transformer. My guess is that if you connected it directly to mains (DONT DO THAT YET!) you would have got 120/4.73 = 25.37V. We need more information to help you: 1. What's the cold resistance reading of the bulb? IF you safely can, measure the warm resistance reading of the bulb by connecting it directly to the mains and measuring the ampere. Make sure the meter you are reading can go upto 15A and that it has a working fuse 2. What's the specification of the transformer? For example do you have a picture of the eBay listing? Or do you have a link to the product page? (your eBay purchase history should have this information) |
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| LadyN Guru Joined: 26/01/2019 Location: United StatesPosts: 408 |
I have to eat dinner and then go to sleep soon but I thought about this experiment and have two questions myself: i. Why did you get a reading of 0.06A from the transformer output? Since there was no load connected, you should have got 0. Does this mean 0.06A is the current consumed by the secondary winding itself? ii. IF you shorted the secondary winding, would 0 volts appear across the transformer? Probably not because the transformer is not ideal and has some loss, but how much would that be? iii. Consequently, would the bulb brigten up when the secondary winding was shorted? By how much visibly (given our vision is logarithmic not linear)? I will wait upon the Gurus on this forum to provide insight |
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| BenandAmber Guru Joined: 16/02/2019 Location: United StatesPosts: 961 |
You done a very good job ladyN I am not very good at writing I am on a phone have no PC I apritiate the tips U answered my question ty I couldn't find my multimeter so I stuck my tongue to the output of the Transformer to make sure it was getting voltage you no kind of like you do on a 9 volt battery I'm just kidding. you did a very good job and I appreciate your concern for me I am a electrician so I got myself to help me lol my carelessness in the past has got me a couple times thank goodness the good Lord above was looking out for me had a plan for me still yet cuz I'm still here but I do have a great respect for electricity I really appreciate you doing the math for me sometimes I just can't get my brain to work no matter how hard I try I have my good days and I have my bad days bad days I get lost in my own hometown on bad days but that's neither here nor there You answer my question and I am very grateful you are very smart and awesome thank you and by the way I'll try to quit doing run-on sentences you gave me some good advice and I'll try to take it if I don't I'm sure you'll let me know LOL be warned i am good parrot but Dumber than a box of rocks |
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| BenandAmber Guru Joined: 16/02/2019 Location: United StatesPosts: 961 |
 Would this Transformer be good for a inverter project it is very heavy I tested the no load current on it it was 0.05 I tested it with volt metter clamp with no load on secondary you can leave it plugged in for days and it won't even warm up a little bit Would anybody have a guess to how many watts it may be the two to the left are 3000 va together out of smart apc ups are thay good for inverter I would appreciate any and all feedback on this subject thanks everybody be warned i am good parrot but Dumber than a box of rocks |
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| azhaque Senior Member  Joined: 21/02/2017 Location: PakistanPosts: 117 |
BenandAmber, The transfo looks a little beat up with possible shorted turns. To determine the usefulness of this for an inverter, please measure the physical size of the core, particularly its center leg plus the size of the stack, for an E-I or E-E core. I have an Excel sheet in another thread on this forum which helps to calculate the parameters of the transfo, by putting in the physical data in the Excel sheet's designated cells. If you don't have a PC, just copy the data here and we can do the calculation. azhaque |
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| BenandAmber Guru Joined: 16/02/2019 Location: United StatesPosts: 961 |
 This is the Transformer I'm trying to figure out the wattage Or what the core is capable of Thank you for your time be warned i am good parrot but Dumber than a box of rocks |
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| BenandAmber Guru Joined: 16/02/2019 Location: United StatesPosts: 961 |
 This is a Transformer Amber was working on the question here is She stacked for Transformer cores together and bonded them with epoxy the four Transformers cores where 250 VA a piece by stacking them this tall will it hurt the performance of these Transformers if so how second question is do you add the 250 v a four times to come up with the new VA or will it be different we have both research this and can't get no answers we found other people asking the same question but no answer thanks for your time I really appreciate it be warned i am good parrot but Dumber than a box of rocks |
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| BenandAmber Guru Joined: 16/02/2019 Location: United StatesPosts: 961 |
 This is like the transformer cores she stacked together They are made up of incredibly thin layers Sorry guys I still haven't figured out how to put two pictures together on the same post I would like to finish winding this Transformer for the little Chinese eBay board I am debating between this one the square one above or maybe some smart Apc UPS Square Transformers I have I think the toroid might be the most efficient If you have an opinion on this please let me know I would appreciate all opinions Thank you for your time be warned i am good parrot but Dumber than a box of rocks |
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| BenandAmber Guru Joined: 16/02/2019 Location: United StatesPosts: 961 |
 I left out one of the window measurements in the first pick I've been searching all over the internet I can't make heads nor tails of how calculate this va If anyone knows of a tutorial or something I can read somewhere that simple for someone like me to understand I would really appreciate it I know the width times the depth equals core area or something but that don't give me VA Thanks for your time be warned i am good parrot but Dumber than a box of rocks |
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| tinyt Guru Joined: 12/11/2017 Location: United StatesPosts: 438 |
Found this transformer tutorial with spreadsheet calculator Tried your transformer width and stack height, it gave me a VA of 871 at 60 Hz. I don't know if it is accurate. Not yet finished reading it. |
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| BenandAmber Guru Joined: 16/02/2019 Location: United StatesPosts: 961 |
Tinyt thanks for the link be warned i am good parrot but Dumber than a box of rocks |
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