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Step-up transformers in homes

  1. Dec 12, 2009 #1
    In poor countries, the domestic electricity supply is inconsistent, and even though the country's standard voltage may be 220V, it is not unusual for the voltage to go quite a bit below this level, say around 150V.

    So normally, households buy step-up transformers, so that they can increase the incoming voltage high enough to allow reliable usage of 220V AC rated appliances. However, I have a friend who lives in such a poor country, and she says her father refuses to buy a step-up transformer because it would 'take away the amount of electricity going in to other homes'. As a result, their refrigerator does not operate most of the time, and food goes bad quickly.

    I think this is nonsense - a step-up transformer only increases the incoming voltage. It does not increase the electrical power coming into the house from the power station, and thus does not 'take away electricity' from other homes. I'd like to know if my reasoning is correct. Thanks for your time.
  2. jcsd
  3. Dec 12, 2009 #2


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    I don't think you could give a definite answer to this.

    If you increase the voltage on most appliances, they will draw more power. So, more current must enter the primary of the step-up transformer than if you just connected the appliance directly to the mains.

    A refrigerator is a problem, though. It may draw more current on less voltage (due to back EMF effects in the motor) and it may operate continuously to try to get down to the right temperature rather than turning off when it reaches the temperature. So, it could actually use more power on a lower voltage.

    Now, whether this extra current matters depends on why the power supply voltage is dropping. If it is due to excessive current, then yes, increased current in one house could cause a slight drop in voltage for the other houses.

    If your house has such a stepup transformer, you could check whether the lights of the house get dimmer when the refrigerator turns on.
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