An electronic device manufacturer, said that using it with transformer is not recommended.

I don't understand why is that. There are products that work with both voltages, and I don't understand how the output of a transformer will be different from an "original" output.

Is that really true? If so, why is it?

‎The device is a singer sewing machine, which I want to use in the USA and in Europe, with different power outlets.

Even if regular transformer wouldn't work, I'll be glad to hear about other solutions.

  • 2
    \$\begingroup\$ This question is missing some essential information. The mention of a 220V-110V transformer in the subject line (but nowhere else) suggests you have a 110 VAC rated device and want to power it from 220VAC mains. If this is the case you should state it clearly. You should also say what the device is as there are a range of factors that may or may not be important depending on the device. Knowing power required would also be useful. Aspects like grounding, peak power drain, startup conditions and more may be relevant. \$\endgroup\$
    – Russell McMahon
    Jul 14, 2011 at 15:55

3 Answers 3


RE: why output of transformer is different ?

The difference is caused by non-ideality of transformers. Most noticable non-ideality is the leakage inductance. For switching load with some cable or filter capacitance like thryristor commutated load, there can be unpredictable runaway mode with circuit resonating at high frequencies.

Another non-idealities of tranformer is non-linearity, caused by saturation, which can clip the original sinusoidal waveform coming from source, asymmetric rectifier, which can magnetize core and saturate it even worse, simple raw peak rush currents, which can overload transformer.

Or for very simple case, it can be manufactures disclaimer to save user from misuse of little 90VA "autotransformer" when they plug 1000W hair dryier and cause all kinds of trouble.

What is the device in question ? Looks like it is something special

  • \$\begingroup\$ It's a singer sewing machine. Aren't there more expensive transformers that minimize those effects? \$\endgroup\$ Jul 14, 2011 at 16:58
  • \$\begingroup\$ Great. Then the reason is a thyristor, connected to the pedal. You will need a filter between transformer and machine. For even low powered motor it is very common to burn the thyristor on those machines \$\endgroup\$
    – user924
    Jul 14, 2011 at 17:13
  • \$\begingroup\$ Thanks! Can you please explain me in a way that a mere CS major can understand, how can I get this filter, and what should this filter, erm, filter? \$\endgroup\$ Jul 14, 2011 at 17:21
  • \$\begingroup\$ It is 3 wires input, 3 wires output board or little box with markings about UL certification. Should be 120V/60Hz say 1..3A rated. It filters everything except band 0..60Hz. Looks like arraysolutions.com/Products/nqnaclinefilter.htm or usefulparts.com/index.php?main_page=index&cPath=143_72_97 \$\endgroup\$
    – user924
    Jul 14, 2011 at 17:39
  • \$\begingroup\$ So, I just want to make sure I got you. I should use a transformer goo.gl/B0YOQ and to the transformer to connect the filter you've mentioned. To them I should connect the sewing machine, and I'm set, right? \$\endgroup\$ Jul 14, 2011 at 18:28

If the transformer is 1:1, usually called a "isolation transformer" because that's why you'd use it, then it shouldn't matter as long as the transformer is capable of delivering the required power.

If the transformer does something other than produce the same output voltage as input voltage, then it could matter. For example, 220V power tends to be 50 Hz with most 110V power being 60Hz. Some devices might not work well at the wrong line voltage frequency. For example, some clocks use the line frequency to keep time, but there can be other electrical reasons too.


Yes, it matters. That transform will put out half the input voltage at twice the current.

Some devices can take a wide range, but many others can't. And @Olin's point about 50/60 Hz is important too.

  • 1
    \$\begingroup\$ Yes, I wrote the @ too before user names in answers, but I learned that it has no function there, so you can simply call him Olin. In comments it's a different matter. \$\endgroup\$
    – stevenvh
    Jul 14, 2011 at 17:19

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