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- From: smckinty@sunicnc.France.Sun.COM (Steve McKinty - Sun ICNC)
- Newsgroups: sci.electronics
- Subject: Re: AC power inverter questions?
- Date: 15 Sep 1992 08:03:51 GMT
- Organization: SunConnect
- Lines: 46
- Sender: smckinty@France.Sun.COM (Steve McKinty - Sun ICNC)
- Distribution: world
- Message-ID: <1945d7INNneo@grapevine.EBay.Sun.COM>
- References: <1992Sep14.210900.1@acad2.alaska.edu>
- NNTP-Posting-Host: hardy.france.sun.com
-
- In article <1992Sep14.210900.1@acad2.alaska.edu>, aslt@acad2.alaska.edu writes:
- > This is probably a stupid... *ahem*, well, a question that reveals how just how
- > much I have forgotten, but it is one that I have thought about frequently
- > over the years, and the discussions about power supplies and dynamotors
- > and whatnot resurrected it in my mind...
- >
- > Many inverters use square waveforms rather than sinusiodal waveforms.
- > Intuitively, though, it seems that significantly less energy will be
- > transferred from the primary to the secondary of the transformer using
- > square waves (input changes at discrete places in the waveform) than
- > would be transferred using sinusoidal waveforms (input continuously changing)
- > What am I missing?
-
- I don't think you're missing anything, square waves are used simply because
- they're easier & cheaper to create. As far as efficiency goes, an oscillator
- producing square waves will have switching elements (usually transistors)
- either on or off, so they run cool. Generating sine waves requires the
- transistors to operate in a linear fashion, and for most of the cycle they
- will be only partially on. As a result they will dissipate a lot of heat
- which calls for big transistors, and also a lot of wasted (and precious if
- coming from a battery) power.
-
- As a thought, could you do do something creative with pulse-width-modulation
- to create pseudo sinewaves, with only switching transistors? Integrate them
- in the transformer?
-
-
- >
- > Along the same lines, presumably the outputs of inverters are square waves
- > rather than sinusoids (I'm speculating, I don't know). It seems you could
- > do some serious damage to the motors in some devices, drills, margarita
- > blenders, refrigerators, freezers, and such. Any comments?
-
- I'd expect motors to be OK, they have enough inertia to ride out the
- square ends of the waveform. Anything which relied on sinewave input
- for phase-control of voltage (drill controllers, light dimmers, some TV's)
- would have problems.
-
-
- Steve
-
- --
- Steve McKinty
- SUN Microsystems ICNC
- 38240 Meylan, France
- email: smckinty@france.sun.com BIX: smckinty
-