John, I forgot to add, that an H bridge could work for a clock motor, since those are used to drive ac motors in industry every day. You would have a sqauare wave though, unless it was modified. If I recall, that's the way a lot of the AC drives work today, using four sets of switching semiconductors, unless the motor is small enough to be ran off a power chip. In this case, I wonder how an AC drive would act if it ran a clock motor? Set it at 60 Hz, and be done with it?
Best, Will *********** REPLY SEPARATOR *********** On 6/25/2011 at 12:55 PM J. Forster wrote: >Certainly, the inverters can run that low, but if so they sing a lot. > >Best, > >-John > >================= > >> 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. >> >> > > > >__________ 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.
