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I am going to purchase an air condition for my home. I noticed some types of air-conditioners are AC Inverter.

What is the meaning of inverter? What I should know about it?

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    When they first came out they were called "freak drives", and were used to control motor and fan speeds from 0 to 100%. (just in case someone uses that term) – d.george Sep 8 '17 at 10:17
  • No, you heard "freak" - I'm quite sure people who had the vaguest clue what they were talking about called them "freq" as a shorthand for frequency as in variable frequency drive, which is what they are. – Ecnerwal Sep 8 '17 at 14:26
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    freak or freq; so what, freak is easier to understand for the average person. Lighten up!! – d.george Sep 8 '17 at 17:03
  • Yeah, don't be a spelling Nahtzee, be more like Ann Teefa. – Harper Sep 8 '17 at 17:51
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They are using the term "inverter" to describe the conversion of Alternating Current to Direct Current and then back to Alternating Current.

Industry uses a device called a Variable Frequency Drive to control the speed of Alternating Current motors for various purposes.

These VFD devices have become inexpensive enough to now be used to control light commercial and residential devices such as air conditioners and well pumps.

This use of a VFD in an "inverter" air conditioner makes it much more efficient than a non-inverter air conditioner since it can run at slower speed for lower demand. An old style air conditioner is either on at full speed or off. There is no speed control.

If you are updating your air conditioner then inverter technology will pay for itself over the life of the unit and save you money.

Read the article here for an overview.

Good luck!

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    Fifty years ago we called a device which converted mains power (50 - 60 Hz ac) into direct current a "power supply". It should really have been called a power converter. I don't recall there being any devices around which would do the inverse, and I'm sure that if anybody had asked about going the other way, most people would have thought it a nonsensical question. Later it was realized that this would be a useful operation, and when such devices were perfected and put into operation they were called "inverters" because the original widespread direction of transformation was ac-to-dc. – Jim Stewart Sep 8 '17 at 11:10
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    The output of most modern VFD's is not sinusoidal. It is Pulse Width Modulated (PWM). It fakes the motor into thinking it is a sine wave. en.m.wikipedia.org/wiki/Pulse-width_modulation The AC to DC section of the VFD is called the converter section instead of rectifier. – ArchonOSX Sep 8 '17 at 15:25
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    Freak or freq it's all the same pwm adjust the motor speed both lower and higher than 60hz. Not only can they save power they can ramp up to speed reducing damage to belts and gear boxes on equipment. + – Ed Beal Sep 8 '17 at 16:46
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    So @ArchonOSX is the mains power first converted to + and - DC supply, and then this is with PWM used to control the compressor motor? The frequency of the switching from + to - would then be the frequency that the motor is synchronized to? – Jim Stewart Sep 8 '17 at 23:40
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    @JimStewart Yes like that. In a single phase VFD it would turn one of two transistors on and off for the positive half of the simulated sine wave and the other transistor for the negative half. The pulse width is widened (modulated) for the middle of the alternation. And then thinned at the beginning and end of the alternation. Ditto for the negative alternation. The motor interprets this on / off switching of the D.C. supply as if it was a sine wave and synchronizes to the fundamental frequency. A three phase VFD uses 6 transistors 2 for each phase. – ArchonOSX Sep 8 '17 at 23:53

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