Crash_Override Posted January 5, 2015 Share Posted January 5, 2015 Hi, I'm in need of some information about this transformer we have between mains power and sound power. My main question is: Do we need it there? It's using quite a lot of electricity even when nothing is powered on. It's a three phase system. Talking in Amps: Transformer draws almost equal amount from every phase: 6A. Everything after transformer uses about 0,6A, on every phase. Info on the transformer: MUUNTOSÄHKÖ OY Helsinki NO: JTA99/188 Malli: 3K23-31,5K (model)Ensiö: ABC 400V 50Hz (primary)Toisio: abcn 400V 31,5kVA (secondary)Kytk. Dyn11 Link to picture of the lable: I hope you understand what I mean. Link to comment Share on other sites More sharing options...
themadhippy Posted January 5, 2015 Share Posted January 5, 2015 Maybe,hows the primary and secondary wired? could be you only have a 3 phase without a neutral so the primary will be delta wired and the secondary star wired to gain a neutral and give you 240v between phase and the star (neutral point Link to comment Share on other sites More sharing options...
Andrew C Posted January 5, 2015 Share Posted January 5, 2015 Hi, I'm in need of some information about this transformer we have between mains power and sound power. It is going from a delta system without a neutral to a star system with. You might be able to do away with it, but not without some investigation of your wiring. Link to comment Share on other sites More sharing options...
Dmills Posted January 5, 2015 Share Posted January 5, 2015 And most of that 6A will be magnetising current rather then real power, so depending on how the rest of your buildings network behaves it might actually be saving you money by improving the power factor..... Regards, Dan. Link to comment Share on other sites More sharing options...
adam2 Posted January 5, 2015 Share Posted January 5, 2015 Maybe,hows the primary and secondary wired? could be you only have a 3 phase without a neutral so the primary will be delta wired and the secondary star wired to gain a neutral and give you 240v between phase and the star (neutral point That sounds possible but we need more information to be certain. OTOH a supply without a neutral seems a bit unlikely, what about lighting or d0m3stic appliances ? how are these powered ? Link to comment Share on other sites More sharing options...
GR1 Posted January 5, 2015 Share Posted January 5, 2015 Why don't you ask the people who installed it exactly what it is there for? They should be able to give you a full answer. Link to comment Share on other sites More sharing options...
Brian Posted January 5, 2015 Share Posted January 5, 2015 So, looking at the label... The primary is delta wired (ABC)The secondary is star wired (abcn) ...my guess would be that it's being used to derive a clean mains supply for your sound equipment. By re-deriving the neutral, and presumably grounding it somewhere, you'll be keeping a lot of crap out of the sound kit, along with the fact that large transformers don't pass HF crud easily. Link to comment Share on other sites More sharing options...
dbuckley Posted January 6, 2015 Share Posted January 6, 2015 And in addition to all those good answers, it may also be required by the utility to keep neutral harmonic currents under control. Non-linear loads generate harmonic currents, which end up in the neutral, and they can exceed the phase current, and by some margin. They eventually get dissapated as heat somewhere, and that somewhere is almost always a transformer. Between the source and the transformer they heat up the neutral wiring, and some old stuff is woefully underrated. And utilities dont like neutral current at all. Link to comment Share on other sites More sharing options...
Andrew C Posted January 6, 2015 Share Posted January 6, 2015 Worth bearing in mind that the OP is in Estonia. Their wiring practices could vary considerably from the UK, or indeed, New Zealand! Link to comment Share on other sites More sharing options...
AdrianW Posted January 6, 2015 Share Posted January 6, 2015 And most of that 6A will be magnetising current rather then real power, so depending on how the rest of your buildings network behaves it might actually be saving you money by improving the power factor..... Regards, Dan. Really? Unless the OPs building is net capacitive (unlikely), I don't think this transformer will improve the overall pf. No argument that the current is the mag current which will be mostly reactive .... but its going to be lagging not leading. Link to comment Share on other sites More sharing options...
Dmills Posted January 6, 2015 Share Posted January 6, 2015 I was thinking about all those cheap and shonky switchmode supplies that are everywhere these days, buildings coming in leading overall are not unheard of. Of course it is possible the OP is not actually being charged for KVAr, in which case the best thing to do is just to keep quiet. Regards, Dan. Link to comment Share on other sites More sharing options...
dbuckley Posted January 6, 2015 Share Posted January 6, 2015 Worth bearing in mind that the OP is in Estonia. Yeah, I did note that, mainly to make sure that he wasn't in Norway, with their weirdo 240V delta mains, where a delta to star tranny to run "normal" kit might not be uncommon! But 400V delta to star makes me think that they must have a power system resembling the European standard... Link to comment Share on other sites More sharing options...
pmiller056 Posted January 11, 2015 Share Posted January 11, 2015 The transformer will most likely be used to provide a clean, low noise supply to the audio equipment. The secondary neutral should be connected to a local clean earth/ground. The transformer rating would suggest it is intended to power the whole sound system in a reasonable sized venue. A delta primary will have been chosen (even if a neutral is available in the source power system) to limit the amount of 3rd order harmonics coupled from the primary to the secondary - particularly from a thyristor controlled stage lighting system. If an interwinding screen is provided, then the star output from the transformer will be very clean. You should take care to ensure that any equipment connected to the secondary is only interconnected to other equipment supplied by the transformer for electrical noise and safety reasons. Regards Peter Link to comment Share on other sites More sharing options...
Crash_Override Posted January 12, 2015 Author Share Posted January 12, 2015 Well, I took the cover off today. And this is what I saw:All grounds are together and all neutrals are together. So both Neutral and Ground are also connected to main fuse panel ground and neutral.Picture from inside Link to comment Share on other sites More sharing options...
Crash_Override Posted January 15, 2015 Author Share Posted January 15, 2015 As seen on picture. Then if both neutrals are connected together is there any point of keeping this transformer connected? Link to comment Share on other sites More sharing options...
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