Step up, step down transformers

Discussion in 'Shop Talk' started by Ken Scharabok, Jan 25, 2005.

  1. Ken Scharabok

    Ken Scharabok In Remembrance

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    Please take a look at this eBay listing (5951529944). It says these transformers can be used to either step from 110 to 220 or down from 220 to 110. I have been restricted from sending any U.S. electrical appliance (such as a small microwave) to my relatives in Croatia because they use the 220, 50 HZ current.

    I believe the current there is DC, not sure, so would these even work?

    Would the HZ difference affect something like a microwave with a simple dial setting?

    This is way out of my knowing much about so I may not have the questions even properly stated. Please keep any reply in kitchen english.
     
  2. fordy

    fordy Well-Known Member

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    ....................First off , If the whole electricial system is predicated upon 50 cycle , I don't think any electrical device\appliance will work on 60 cycle that the USA system is based upon , and vice versa . Next , the 50 cycles per second implies too me that the system is AC voltage or alternating current. DC on the other hand is a constant voltage\current with NO cycling back and forth between positive<>negative voltage(s) . Some electrical items like drill motors , saws and other items I'm not familiar with will work with either DC or AC current . A transformer that has a primary winding input voltage on 120vac and an output of say 240 vac at 60 cycles will produce the same 240vDC output if fed by DC current , I Believe . fordy... :)
     

  3. daeve

    daeve Well-Known Member

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    Ken,

    The transformers you have posted about won't work for a microwave.

    You will need a step down transformer rated for 50/60 Hertz (cycles) and 220/240 to 110/120. A transformer that is rated at 60 Hz only, will have to work harder if running on 50 Hz. It may work for a while but WILL fail if used anywhere near its max current/wattage rating.

    The small microwaves that are being sold now are in the 500 to 700 Watt range which means that they are pulling around 4 to 6 Amps at 120 volts. If you need 5 amps at 120, the 240 volt supply (and step down transformer) will need to be rated AT LEAST 2.5 amps. It's best if you can get a step down transformer rated about double the required current/wattage just for long life.

    You also need to be careful that the equipment is rated for 50/60 Hz. A lot of todays electronics will work with no problem at 50 Hz if it DOESN'T have a transformer or clock that depends on the power line frequency to work. On a microwave I would make sure that the label stated that it is rated for operation at 50 Hz.

    Hope this is at least clear as mud... ;)
     
  4. mightybooboo

    mightybooboo Well-Known Member

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    Daeve,you fell into a common mistake about microwave ratings.The 500-700 watt range is the COOKING output,not what the machine actually uses,which is higher.Folks using inverters often underrate the inverter using those cooking numbers as the power consumption number.
    Other folks have tested their machines to prove this,I havent,but might be a nice test to do,eh?

    Just a friendly FYI,not trying to 'dis' you :)

    BooBoo
     
  5. mistletoad

    mistletoad Well-Known Member Supporter

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    How about buying them a power inverter - you can run most anything off a car battery. I saw one online AC 220-240v, 50Hz, 200W continous power - $79.
     
  6. Cosmic

    Cosmic Well-Known Member

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    Nope those transformers are only rated at 250 watts. Probably not enough for even the most smaller microwave.

    Do the relatives a flavor. Send them them the entire microwave. Lot of variation between models and manufacturers. Get one rated for 220 VAC 50 HZ or one that is a dual use model. Lots of choices, just be sure it says they are rated for foreign use.

    See here.

    http://www.interconmktg.com/pages_appliances/export.htm

    Plus microwaves are one of the most dangerous things a fellow can work on if you really don't know what you are doing. For the money, get them something that will probably work for a good while. Many of these countries also have quite unstable electrical systems. Voltages that are out of spec, even being off frequency a tad at times. Start with the best thing for the job and hope for the best.
     
  7. Big country

    Big country Well-Known Member

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    A transformer can only change AC voltage (up or down) it cannot change the frequency (Hz) 60Hz in = 60Hz out!! A transformer connected to DC is a dead short! Don't do it.
     
  8. John Hill

    John Hill Grand Master

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    Too right, dont even think of putting DC onto a transformer!

    I live in a 50Hz environment and there are some pieces of 60Hz equipment around here. As already stated the 60Hz transformer will overheat if operating on 50Hz although a really good transformer may tolerate this for many years.

    A microwave has a rather large transformer inside and would not like 50Hz if it has been designed for 60Hz. A transformer to do the job will weigh almost as much as the microwave and my recommendation is to go for a 50Hz 220v unit.
     
  9. daeve

    daeve Well-Known Member

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    And you, good sir, are absolutely correct. I worked on the things for years and HAVE tested it. I looked at that current 2 or 3 times knowing there was something wrong and still posted it. Brain fart I guess. :rolleyes:

    The values should have been in the 7 to 10+ amp range for the el-cheap-o units. I did see one at wallyworld a while back that claimed 5.5 amps at I believe 450 watt cooking output. There was almost room in the cavity for a small bag of popcorn so they may have been telling the truth but I suspect the current was measured at a high line voltage.

    The older units often ate up 12 to 15 amps to cook at 700 to 800 watts. The efficiency of the transformers and magnetrons has gone way up in the past few years but there is still a substantal difference between the total wattage consumed and the cooking wattage rating.

    Thanks for the FYI :worship:
     
  10. Big country

    Big country Well-Known Member

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    One more note on microwave safety, don't ever operate a microwave that doesn't have the "screen" over the window in the door. If you look closely you'll see that it is a metal shield with small round holes in it, (round holes block EMF radiation square holes don't.)