John, I didn't mean to say you said all that, just that the new inverters are cheap. I wrote that I thought some ran at around 1 kHZ, as I had an old one that did, and used a toroidal transformer in it. The new ones, as far as I am aware, are similar to the new-style switching power supplies, like the ones Maxim and a few others show in their app notes.
Best, Will *********** REPLY SEPARATOR *********** On 6/25/2011 at 12:37 PM J. Forster wrote: >> Chris, > >No I didn't say the output was 1000 Hz. No way. > >What I said (a bit amplified) was that the cheapie inverters use a high >frequency, think 50 KHzish, DC-DC converter to make about 170 VDC, then >use that to feed an "H" bridge, driven with either a square wave or a >modified square wave, to make the output. You snmply need to vary that >drive frequency to get 50, or 60, or any frequency you want. > >There is no output transformer. In fact, that is the cleverness of the >design... no big, heavy, expensive magnetics. > >-John > >=================== > >> As John mentioned earlier, the el-cheapo inverters are pretty much >> junk, and run as high as 1 kHz, if I recall. They were made to run small >> TV's, etc, that don't require a fixed line frequency, since they all have >> hot chassis now that don't use isolation transformers. >> >> Best, >> >> Will >> >> *********** REPLY SEPARATOR *********** >> >> On 6/25/2011 at 11:55 AM Chris Albertson wrote: >> >>>> The reason for using 12 Vdc, is that you can pick them up, and 24 Vac >>>> CT >>>> transformer, on the cheap >>> >>>That's a good point. So use two of them. One to power a high >>>current amp that produces a 12V AC signal from a high precision 60Hz >>>input. Then the other to convert the 12V to 120V. This avoids the >>>need for a high voltage DC power supply. Likely cuts the total cost >>>in half at least. So just use use 12V supply to the amp and then a >>>cheap 12V transformer connected "backwards" to step up to the desired >>>voltage. >>> >>>The second advantage of this design is that you can connect a lead >>>acid gell cell battery in parallel to the 12V DC supply and if the AC >>>fails the battery will power the amp for a while. This way there is >>>no switching so the 60Hz wave remains continuously even if AC mains >>>fails. >>> >>>This is something most UPS don't do but for this application you don't >>>want the 60Hz sine wave to be broken. >>> >>>As long as the load is only a few milliamps of AC this should not be >>>hard to do. >>> >>> >>>-- >>> >>>Chris Albertson >>>Redondo Beach, California > > > >__________ Information from ESET Smart Security, version of virus signature database 5851 (20110206) __________ > >The message was checked by ESET Smart Security. > >http://www.eset.com _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
