Interesting transformer setup 0 110 0 110 130

Discussion in 'General Electronics Chat' started by BrainFog, Oct 18, 2011.

  1. BrainFog

    Thread Starter Member

    Jan 24, 2011
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    A few days ago as I was buying a few parts I chose to get a transformer that seemed fantastic value for what it is. http://uk.farnell.com/dagnall-electronics/d3652/transformer-20va-2x-15v/dp/3304231

    Anyway I am a bit puzzled by the logic behind the arrangement of the windings. It has 0-110 0-110-130. Why does it have the extra 130v winding on the primary? I have noticed they sometimes vary their primary side voltages but never really thought about it until now.

    Here in the UK mains voltage is 220-240v so do I wire it up 0-110-0-110 or 0-110-0-130?

    Thanks
     
  2. colinb

    Active Member

    Jun 15, 2011
    351
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    Hopefully it's safe to use on 240 V, since I don't see a maximum voltage in the specs.
     
  3. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    2,574
    230
    Looks like it is configured so that the primary side can run on 110, 130, 220, or 240VAC.

    Ken
     
  4. #12

    Expert

    Nov 30, 2010
    16,257
    6,757
    Why?

    Here in the states, it used to be (40 years ago) that you were lucky to get 115 VRMS on the power line. Now, I have 125 RMS at my house. I had to put buck transformers on my outdoor lights and change the heater element in my clothes dryer to a Calrod because the nichrome kept burning out.

    That's why transformers are sometimes equipped with 115 volt and 125 volt taps on the primary. You seem to have 110V and 130V taps.
     
  5. Adjuster

    Well-Known Member

    Dec 26, 2010
    2,147
    300
    You can only ever parallel identical voltage primary windings, or dangerous circulating currents will result, and the transformer will draw excessive current and burn out.

    That means the transformer can most likely only be used at full rating on 110V, with the 110V sections in parallel, or at 220V or 240V with the sections in series.

    Edit: Unless the 110V/130V section has heavy enough wire to be used as the sole primary at full rating, which seems unlikely.

    Finally to the OP: Put all the sections in, being careful to connect them in correct phase. 220V rating is not really safe for UK mains, even now we are officially 230V. The fact that we have 50Hz here, not 60Hz also increases the risk of saturation.
     
    Last edited: Oct 18, 2011
  6. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    #12,
    Have you talked to you power company? I'm not sure what their contractual voltage limits are.

    Ken
     
  7. #12

    Expert

    Nov 30, 2010
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    Been there, done that. The power company decided to declare their spec as: 240V +/- 5%.

    High limit is 252V. 126 for one phase. Nothing I can do about their end, so I fixed my end.
     
  8. BrainFog

    Thread Starter Member

    Jan 24, 2011
    122
    4
    Wow, I did not realise that mains voltages could vary so greatly. I thought that they had to be within a very specific boundary.

    #12 It really doesn't sound like the power company is supplying you with usable power. I don't see how they can get away with what they are doing. The Americans are famous for solving their problems with lawyers and if I were you I would consult one in regards to getting them to fix this problem.

    So 0-110-0-130v it is. Thank you

    I might as well bring this up as I have been wondering about it for a while. If we were to redo the entire national grid, from scratch, would we be better off discarding the current sinisoidal wave at a low frequency and replace it with lets say 100volts with a square wave at several kHz.

    I know it would never happen as it would render most electrical items useless.

    Also would it be safer or more dangerous if we were to electrocute ourselves?
     
  9. #12

    Expert

    Nov 30, 2010
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    I'll tell you what I tell people who say, "You should patent that".
    You pay the lawyers and I'll give you half the profits I make.
    In this case, you would stand to win one 40 VA transformer and half of an 1800 watt heater rod. I would not need these installed if only the line voltage was 115VRMS.

    Other subject: I agree that the low frequency of the mains was probably a poor choice, especially when I see the size of a 5 horsepower motor that runs on 400Hz. Hindsight, we have it.
     
  10. colinb

    Active Member

    Jun 15, 2011
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    Well, the grid itself has little to do with the actual voltage since power transmission absolutely must be done at very high voltages in the tens to hundreds of volts for acceptable efficiency.

    Even within buildings, higher voltage brings much greater efficiency and lower cost. For instance, 120 V rms power to an electric oven in your kitchen means you need MUCH larger wire to carry that twice-as-high current compared to 240 V. For lower power devices, the higher supply voltage and lower current of 240 V power mean less energy loss in the house wiring.

    Sure, it would be nice if we could have completely safe electrical systems in our homes that could not cause serious electric shock, but I don't know if even going to 100 V peak from 170 V peak is much better.

    I understand some of the benefits that higher frequency would provide (smaller transformers, smaller filtering capacitors on dc power supplies), but why would you want a square wave? The sine wave is an ideal form for electrical transmission and conversion, as I understand it.

    Any square wave would have tremendous harmonics resulting in huge EMI issues.
     
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