Why major appliances like refrigerators, air conditioners and washing machines need a "3-tap" or "triple-tap" transformer

Most major appliances with fractional horsepower motors (like a washing machine or dishwasher) or compressors (like a refrigerator or air conditioner) can be safely used abroad with a voltage transformer. However, these kinds of appliances require a special type of voltage transformer known as a "3-tap" or "triple-tap" transformer.

  • Large motors and compressors are sensitive to the difference between 60Hz and 50Hz AC frequency
  • When used with incorrect AC frequency, motors and compressors perform inefficiently, and will eventually burn out
  • "3-tap" voltage transformers work around this issue by increasing or decreasing the actual supplied voltage by roughly 10% to compensate for the difference in frequency

Alternating current (AC) electricity moves in a sine wave, alternating between positive and negative poles. AC frequency, expressed as hertz (Hz) refers to the number of times per second completes a full cycle between these positive and negative poles. A byproduct of these cycles is heat.


50 Hz vs. 60 Hz AC Line Frequency

Sometimes frequency really does matter. A lot.

AC frequency varies by region. In the United States, Canada, and most (but not all!) other countries operating on 110-120 volt electrical systems, the AC frequency standard is 60 Hz. On the other hand, in most other countries operating on 220-240 volt electrical systems, the AC frequency standard is 50 Hz. There are oddball exceptions though.

In the vast majority of cases, the difference in frequency is negligible, if not completely irrelevant.

Most electronics are perfectly capable of operating normally on either frequency. Even if they're not built to be fully compatible with both frequencies, it usually doesn't matter very much anyway.

The difference in frequency applies mainly to clocks/timers and motors. And even then, small motors like those in small kitchen appliances like mixers, blenders, food processors, etc. aren't significantly affected, because they're small, and usually aren't used for long periods of time. A blender or mixer may not operate quite as effectively, but it's usually not a big deal.


50 Hz vs. 60 Hz AC Line Frequency

So do I really need a special type of transformer for a refrigerator, freezer, air conditioner, washing machine, dishwasher, etc.?

In a word: yes.

Why? Because larger fractional horsepower motors (FHP motors) and compressors are particularly heat-sensitive to the difference in the frequency (60 Hz vs. 50 Hz) of the alternating current. Particularly ones that either run non-stop (refrigerators) or that continuously stop-and-start (washing machines.) These motors will overheat and burn out in short order if the difference in frequency isn't compensated for.

A triple-tap transformer is an effective workaround for that issue.

To avoid overheating these FHP motors and/or compressors, a 60 Hz motor should be run at roughly 10% lower voltage when operated on 50 Hz frequency. So, for example, a 115V 60 Hz motor should be run at roughly 100-105V 50 Hz. The reverse is also true of a 50 Hz motor being operated on 60 Hz.

A triple-tap transformer will compensate for the difference in frequency, allowing the motor to run at the precise RPMs it was intended to, thereby protecting the motor from overheating and eventual burnout.

Chances are, if you're going to the trouble of bringing a major appliance abroad, it's because it's important to you. And it's probably expensive. Replacement parts, particularly compressors and motors, are also expensive. Not to mention the cost of having that part shipped internationally, and then having a repair tech install the new one.

Don't let it happen to you. Use a triple-tap transformer to ensure that your major appliance gets the electricity it requires and lives a long life.