Sorry, that should have said DC drive, as I was writing while brain storming. However, a variable AC drive, which does control the frequency, may be able to be used. I would have to look at this more, but it might be possible, and these can be bought on the cheap at surplus sellers.
Best, Will *********** REPLY SEPARATOR *********** On 6/25/2011 at 4:12 PM Will Matney wrote: >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. > >__________ 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.
