AC Line Frequency: Explained So Well it Hertz


When electricity arrives at our homes and businesses, it shows up in the form of Alternating Current. Before continuing, it’s important to know that there are two kinds of electrical current: DC and AC. DC is the abbreviation of direct current. DC as its name implies moves directly and without any positive/negative polarity. Batteries operate with DC and the internal circuitry of electronic devices use DC as well.

AC, or alternating current, which was invented by super-genius Nikola Tesla back in 1880-something, is the preferred way to deliver electricity from the power plant along power lines for distribution to customers, due to it being more efficient and less expensive. It’s been this way for more than 100 years. Basically, AC power moves in sinewave-like fashion, alternating between positive and negative poles. Each positive-to-negative cycle finds electrons moving back and forth, positive (+) and negative (-) over the course of time. Ultimately, these cycles create electrical heat, or power dissipation. Regardless of which way the current is moving (i.e. forward or back, positive or negative), if there is enough current (amps) and force (voltage) produced to meet the demands of an electrical device, that device will work.

AC line frequency is the number of times per second that the AC current completes a full 360° cycle between the positive and negative poles. The graph below illustrates this.


(courtesy of

Cycles per second is measured by the unit Hertz (Hz), and AC frequency varies geographically according to country, and not necessarily the native voltage standard. For example, in the United States, Canada, and other countries with a standard line voltage of 110-120V, the frequency standard is 60 Hz. In most 220-240V countries, the frequency is 50 Hz, yet South Korea uses 220-240V with 60 Hz as does Peru, the Philippines, Saudi Arabia, and many Caribbean countries. Often, countries that have both 110-120V and 220-240V nonetheless use a 60 Hz AC frequency. They include Brazil, Cuba, Belize, and Guyana. Then there’s Japan, which has a voltage standard of 100V but an AC frequency of 50 and 60 Hz depending on where you are in that country. 

Often, most electronic devices can operate at 50 or 60 Hz. But—and it’s a big but—when it comes to motorized appliances that use bigger high-power motors, such as bigger refrigerators, freezers, coolers, washers and dryers, et al., the 10 Hz difference between 50 and 60 is also the difference between a motor burning out, food getting spoiled, and basically large machines not working at 100-percent efficiency. This is due to motors working either faster or slower than they were designed.

With the necessity of AC frequency conversion in mind, ACUPWR’s ADC and AUC step-down (220-240V to 110-120V) voltage transformers and step-up models respectively have a solution for the AC line frequency so your appliances with a motor will with the other frequency just fine. No other voltage transformer on the market does this! In the end, you can rely on ACUPWR for all of your international voltage (and frequency) conversion needs.

We’ll discuss the important electromagnetic principle of polarity in the next ACUPWR Papers blog post.

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  • Mike Bieber
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