On 14/10/2021 11:51 am, Anthony William Sloman wrote:> On Thursday, October 14, 2021 at 8:29:18 PM UTC+11, palli...@gmail.com wrote: >> I have a common 40W pedestal fan with a 13 inch dia fan blade. >> Tested a few minutes ago: >> >> At 240VAC rms current is 163mA. >> at 200VAC it became 144. >> at 100VAC it become 76. >> at 50VAC it become 33. >> >> by which time the blade was no longer turning. >> Not far off linear, you *must* agree. > > Far enough off to make it perfectly clear that you haven't got a clue about what was actually going on. When the fan is no longer turning, there isn't any back EMF, so the motor windings are just inductors - and not very good inductors, particularly when the magnetic path through the iron gets warm. as it does when the fan isn't rotating. >True, there may be no back EMF. But as Phil Allison showed at 50VAC the fan was consuming less than 2W - that is not going to make any serious heating problem. I think Phil has done us a big service by making actual measurements! piglet
Small single-phase VFD for 120V?
Started by ●October 12, 2021
Reply by ●October 14, 20212021-10-14
Reply by ●October 14, 20212021-10-14
piglet wrote: =========- Anthony William Sloman = Raving Psychotic asshole wrote: ================================= palli...@gmail.com wrote:> >> I have a common 40W pedestal fan with a 13 inch dia fan blade. > >> Tested a few minutes ago: > >> > >> At 240VAC rms current is 163mA. > >> at 200VAC it became 144. > >> at 100VAC it become 76. > >> at 50VAC it become 33. > >> > >> by which time the blade was no longer turning. > >> Not far off linear, you *must* agree. > > > > Far enough off to make it perfectly clear that you haven't got a clue about what was actually going on. When the fan is no longer turning, there isn't any back EMF, so the motor windings are just inductors - and not very good inductors, particularly when the magnetic path through the iron gets warm. as it does when the fan isn't rotating. > >> True, there may be no back EMF.** Don't inductors produce " back emf" ? Though the things did.> But as Phil Allison showed at 50VAC the > fan was consuming less than 2W - that is not going to make any serious > heating problem.** Piglet is a fair dinkum genius.> I think Phil has done us a big service by making actual measurements!** Far from it - I just broke the cardinal rule of usenet debates. Which a s in war and politics - the truth is irrelevant . ...... Phil
Reply by ●October 14, 20212021-10-14
On Thursday, October 14, 2021 at 10:16:01 PM UTC+11, piglet wrote:> On 14/10/2021 11:51 am, Anthony William Sloman wrote: > > On Thursday, October 14, 2021 at 8:29:18 PM UTC+11, palli...@gmail.com wrote: > >> I have a common 40W pedestal fan with a 13 inch dia fan blade. > >> Tested a few minutes ago: > >> > >> At 240VAC rms current is 163mA. > >> at 200VAC it became 144. > >> at 100VAC it become 76. > >> at 50VAC it become 33. > >> > >> by which time the blade was no longer turning. > >> Not far off linear, you *must* agree. > > > > Far enough off to make it perfectly clear that you haven't got a clue about what was actually going on. When the fan is no longer turning, there isn't any back EMF, so the motor windings are just inductors - and not very good inductors, particularly when the magnetic path through the iron gets warm. as it does when the fan isn't rotating. > > > True, there may be no back EMF. But as Phil Allison showed at 50VAC the > fan was consuming less than 2W - that is not going to make any serious > heating problem. > > I think Phil has done us a big service by making actual measurements!He has. They were remarkably crummy measurements, and he didn't make any attempt to make any sense of them. If he'd acquired that sort of data in an undergraduate practical class, he'd have got a very low mark. He reminded us that he didn't do all that well at university, and left without getting a degree. That doesn't mean that he hasn't got useful skills, but he does seem to be pretty bad at making sense of what he is doing. -- Bill Sloman, Sydney
Reply by ●October 14, 20212021-10-14
On Wed, 13 Oct 2021 11:51:07 -0700, Joerg <news@analogconsultants.com> wrote:>On 10/13/21 7:54 AM, Joe Gwinn wrote: >> On Tue, 12 Oct 2021 16:12:58 -0700 (PDT), Phil Allison >> <pallison49@gmail.com> wrote: >> >>> Joe Gwinn wrote: >>> ================ >>> >>>> It's best to get a small 3-phase motor for this. >>> >>> ** Giant HUH ??? >>> >>>> VFDs really do not >>>> like their motor circuit opening and closing, as with a centrifugal >>>> switch. >>> >>> ** You feeling OK ? >> >> I'm OK. The issue is that while VFDs intended for machine tools may >> be able to drive a single-phase induction motor as well, but it's best >> to short or bypass the centrifugal switch if using the start winding >> of a single-phase motor. >> > >They might signal a fault and shut down if one or more connections are >seen open. Like when you only connect one of the output phases to a load.True. Some VFDs allow one to program to disable that fault.>> >>> Or just got no idea what a Papst AC fan is? >> >> They seem to all be single-phase, with a start winding. >> > >Just shaded-pole motors, usually. > >A problem with the small drives from Automation Direct is the same all >the others I looked at have. Aside from transfering 1-phase to 3-phase >even the 120V versions put out 230V max. That's a recipe for magic smoke >even if you tell everyone never to go past 50% or program in a limit. > >https://cdn.automationdirect.com/static/specs/cfw100acdrive.pdf > >Beats me why this is. There are so many applications for variable speed >of smaller induction motors. Such as heated water circulation, cooling >systems et cetera that only need small motors to overcome a miniscule >gravity load. They are single-phase and run on regular mains voltage.The main application for 120 Vac single phase in to 220 Vac three phase in small sizes is to allow three-phase industrial machines to be run from US domestic single-phase power. Three-phase 220 Vac industrial equipment is cheap and plentiful on the used market in the US. One common use is bench grinders and sanders and drill presses, where the variable speed is an added big advantage. One sees a lot of these machines on Craigs List. One can also get three-phase fans and circulation pumps, which are intended to be driven by a VFD which is commanded by some kind of PID (Proportional Integral Derivative) temperature controller, versus the more common bang-bang controller. Joe Gwinn
Reply by ●October 14, 20212021-10-14
On 10/13/21 2:57 PM, Phil Allison wrote:> Joerg wrote: > =========== > re: using a Variac: >>> >>> That's not speed control for induction motors, ... >> >> It's not ideal and causes hum at lower rpm > > ** Bullshit !!!! >For a test I drove this with an aerospace test setup (frequency- and voltage variable) and after finding the sweet spots there was considerably less hum from the fans at reduced RPM. Hence, I'd like that kind of setup in a tiny box instead of 19" rack size and that's why I started this thread.> >> Phil suggested it could be residual DC but I measured it with a lowpass >> and the UPS doesn't have a DC offset. > > ** Monitor the AC current in the Variac primary. > > Bet you see a different story. >Ok, thanks, I can do that. -- Regards, Joerg http://www.analogconsultants.com/
Reply by ●October 14, 20212021-10-14
On 10/13/21 5:55 PM, Cydrome Leader wrote:> Cydrome Leader <presence@mungepanix.com> wrote: >> Joerg <news@analogconsultants.com> wrote: >>> On 10/12/21 10:51 AM, Cydrome Leader wrote: >>>> Joerg <news@analogconsultants.com> wrote: >>>>> Looking for a "better dimmer" to speed-control two small AC fans. They >>>>> do not seem to like any kind of dimmer, fan-rated or not. What happens >>>>> is that they stall out and start "speed-pumping" in the 40-80% range. >>>>> The old ones did fine but the new fancy ones from Papst don't. >>>> >>>> Sounds like you're not dealing with a plain AC fan motor anymore. Papst >>>> the cooling fan maker? >>> >>> >>> Yes, that company. They are plain AC motors, IIRC the shaded-pole kind. >>> >>> >>>> ... just change to a DC fan with speed control. VFDs on >>>> small motors is completly pointless anyways. >>>> >>> >>> This is a bit more challenging. The fans are in an environment that's >>> too hot for electronics, which is also why they are completely metal. >> >> How many speeds do you need?Four would be fine if I can adjust each one to a target speed.>> ... I've never seen a weird speed pumping or >> racing issue with a decent speed controller (not a light dimmer, those are >> garbage, always) on even crap fan motors. They mighy run loud, or over >> heat at lowspeeds, or close to stall but that's about it. >>It's not a dimmer but made for AC fan control. Not sure how hot it is, it came with the fan assembly that was in there previously. The pumping sounds like stall - catch up - stall - catch up. Only in the 40-80% RPM range, outside that it's fine.>> The Dart Controls 55AC series is as good as it gets for a triac based >> speed controller. Built well, handles high currents, easy to fix and >> sometimes real cheap on ebay- >> >> https://www.dart-controls.com/category-s/162.htm > > scratch that bogus URL. > > The manufacturer is > > https://www.dartcontrols.com/products/55ac-triac-ac-motor-speed-control/ >Thanks. It a pricey test though :-) -- Regards, Joerg http://www.analogconsultants.com/
Reply by ●October 14, 20212021-10-14
On 10/14/21 7:52 AM, Joe Gwinn wrote:> On Wed, 13 Oct 2021 11:51:07 -0700, Joerg <news@analogconsultants.com> > wrote: > >> On 10/13/21 7:54 AM, Joe Gwinn wrote: >>> On Tue, 12 Oct 2021 16:12:58 -0700 (PDT), Phil Allison >>> <pallison49@gmail.com> wrote: >>> >>>> Joe Gwinn wrote: >>>> ================ >>>> >>>>> It's best to get a small 3-phase motor for this. >>>> >>>> ** Giant HUH ??? >>>> >>>>> VFDs really do not >>>>> like their motor circuit opening and closing, as with a centrifugal >>>>> switch. >>>> >>>> ** You feeling OK ? >>> >>> I'm OK. The issue is that while VFDs intended for machine tools may >>> be able to drive a single-phase induction motor as well, but it's best >>> to short or bypass the centrifugal switch if using the start winding >>> of a single-phase motor. >>> >> >> They might signal a fault and shut down if one or more connections are >> seen open. Like when you only connect one of the output phases to a load. > > True. Some VFDs allow one to program to disable that fault. >Ah, that may be an option. The other job would be to make 110% sure that it can never go past 120V because most VFDs put out 230V max, even those for 120V input.> >>> >>>> Or just got no idea what a Papst AC fan is? >>> >>> They seem to all be single-phase, with a start winding. >>> >> >> Just shaded-pole motors, usually. >> >> A problem with the small drives from Automation Direct is the same all >> the others I looked at have. Aside from transfering 1-phase to 3-phase >> even the 120V versions put out 230V max. That's a recipe for magic smoke >> even if you tell everyone never to go past 50% or program in a limit. >> >> https://cdn.automationdirect.com/static/specs/cfw100acdrive.pdf >> >> Beats me why this is. There are so many applications for variable speed >> of smaller induction motors. Such as heated water circulation, cooling >> systems et cetera that only need small motors to overcome a miniscule >> gravity load. They are single-phase and run on regular mains voltage. > > The main application for 120 Vac single phase in to 220 Vac three > phase in small sizes is to allow three-phase industrial machines to be > run from US domestic single-phase power. Three-phase 220 Vac > industrial equipment is cheap and plentiful on the used market in the > US. > > One common use is bench grinders and sanders and drill presses, where > the variable speed is an added big advantage. One sees a lot of these > machines on Craigs List. >Yes, that may be the reaon. Probably not enough market for driving 120V motors.> One can also get three-phase fans and circulation pumps, which are > intended to be driven by a VFD which is commanded by some kind of PID > (Proportional Integral Derivative) temperature controller, versus the > more common bang-bang controller. >This situation requires the small muffin-style fans. -- Regards, Joerg http://www.analogconsultants.com/
Reply by ●October 14, 20212021-10-14
"the concepts "male" and "female" are essentially social constructions" (Bill Sloman) "the Mueller investigation was about Trump only because Trump made it so" (paraphrased) Bozo the Clown... -- Anthony William Sloman <bill.sloman@ieee.org> wrote:> X-Received: by 2002:ac8:14a:: with SMTP id f10mr4864043qtg.9.1634200685209; Thu, 14 Oct 2021 01:38:05 -0700 (PDT) > X-Received: by 2002:a25:d94d:: with SMTP id q74mr4596274ybg.196.1634200684924; Thu, 14 Oct 2021 01:38:04 -0700 (PDT) > Path: eternal-september.org!reader02.eternal-september.org!news.uzoreto.com!tr1.eu1.usenetexpress.com!feeder.usenetexpress.com!tr2.iad1.usenetexpress.com!border1.nntp.dca1.giganews.com!nntp.giganews.com!news-out.google.com!nntp.google.com!postnews.google.com!google-groups.googlegroups.com!not-for-mail > Newsgroups: sci.electronics.design > Date: Thu, 14 Oct 2021 01:38:04 -0700 (PDT) > In-Reply-To: <1fea09a0-cbbd-4237-b617-6664a297eb04n@googlegroups.com> > Injection-Info: google-groups.googlegroups.com; posting-host=14.202.25.252; posting-account=SJ46pgoAAABuUDuHc5uDiXN30ATE-zi- > NNTP-Posting-Host: 14.202.25.252 > References: <islt03Fdtb9U1@mid.individual.net> <5bhbmgl61ctm1mhlnfmqo9658os1iufmo5@4ax.com> <ism1tuFerkoU1@mid.individual.net> <q8ubmg5cunq14rpqg33lkphirep7u3altr@4ax.com> <ismcohFgt8nU1@mid.individual.net> <d0f5b915-90e5-490c-875a-91bf2a27ff9an@googlegroups.com> <66f8470c-6c50-4101-b9ae-7157a8e93701n@googlegroups.com> <e4c7ad52-5915-4db3-8a3d-cdd56e81ac6cn@googlegroups.com> <de8f4f80-6455-4a58-8756-49c3e21604f1n@googlegroups.com> <89c2dc68-cbfd-449c-8847-a35be5f1a0d6n@googlegroups.com> <sk8iih$clf$1@dont-email.me> <f450c032-de59-4302-bb62-0e80d6c9e158n@googlegroups.com> <dc2978bc-aa95-432c-b95d-3561ed35c7edn@googlegroups.com> <1fea09a0-cbbd-4237-b617-6664a297eb04n@googlegroups.com> > User-Agent: G2/1.0 > MIME-Version: 1.0 > Message-ID: <1d79963e-0387-4367-8b88-d882b2e97545n@googlegroups.com> > Subject: Re: Small single-phase VFD for 120V? > From: Anthony William Sloman <bill.sloman@ieee.org> > Injection-Date: Thu, 14 Oct 2021 08:38:05 +0000 > Content-Type: text/plain; charset="UTF-8" > Lines: 20 > Xref: reader02.eternal-september.org sci.electronics.design:649084 > > On Thursday, October 14, 2021 at 7:09:55 PM UTC+11, palli...@gmail.com wrote: >> whit3rd wrote: >> ============================= >> piglet wrote: >> =========== >> > > > >> > > > Perhaps, but to burn the motor takes a lot of power and surely running >> > > > the motor from a variac at reduced voltage reduces the liklihood of heat >> > > > damage? >> > >> > >> > > ** Motor current drops in line with applied AC voltage. >> >> > No, of course it doesn't; >> >> ** FFS is their no end to the vile lunatic Google troll. > > Phil seems to be the vile lunatic troll here. He doesn't seem to understand how AC motors work, and he does get very upset when this pointed out. > > -- > Bill Sloman, Sydney >
Reply by ●October 14, 20212021-10-14
Joerg <news@analogconsultants.com> wrote:> On 10/13/21 5:55 PM, Cydrome Leader wrote: >> Cydrome Leader <presence@mungepanix.com> wrote: >>> Joerg <news@analogconsultants.com> wrote: >>>> On 10/12/21 10:51 AM, Cydrome Leader wrote: >>>>> Joerg <news@analogconsultants.com> wrote: >>>>>> Looking for a "better dimmer" to speed-control two small AC fans. They >>>>>> do not seem to like any kind of dimmer, fan-rated or not. What happens >>>>>> is that they stall out and start "speed-pumping" in the 40-80% range. >>>>>> The old ones did fine but the new fancy ones from Papst don't. >>>>> >>>>> Sounds like you're not dealing with a plain AC fan motor anymore. Papst >>>>> the cooling fan maker? >>>> >>>> >>>> Yes, that company. They are plain AC motors, IIRC the shaded-pole kind. >>>> >>>> >>>>> ... just change to a DC fan with speed control. VFDs on >>>>> small motors is completly pointless anyways. >>>>> >>>> >>>> This is a bit more challenging. The fans are in an environment that's >>>> too hot for electronics, which is also why they are completely metal. >>> >>> How many speeds do you need? > > > Four would be fine if I can adjust each one to a target speed.hmm, maybe just some relays and a small power transformer in buck mode would be fine. Fan motors are almost the opposite of a synchronous motor, always run at extreme amounts of slip, and voltage control is the easiest way to slow them down. The only catch is you need to sort of trace out the curve of speed to voltage for these fans. Some drop speed with 10% line voltage loss, some do nothing at all until you drop to 80% line voltage. They're all different and you will never get a nice linear "0-10" speed control with these, ever. To go real cheap, try a furnace transfomer. You can buck them to get something like 80% line voltage with one switch or relay. ... I've never seen a weird speed pumping or>>> racing issue with a decent speed controller (not a light dimmer, those are >>> garbage, always) on even crap fan motors. They mighy run loud, or over >>> heat at lowspeeds, or close to stall but that's about it. >>> > > It's not a dimmer but made for AC fan control. Not sure how hot it is, > it came with the fan assembly that was in there previously. The pumping > sounds like stall - catch up - stall - catch up. Only in the 40-80% RPM > range, outside that it's fine.Odd. Are the motors themselves OK? High heat is a killer for small bearings and motors. Not sure you can relube them or not. Luckily Papst stuff is top quality to start with though.>>> The Dart Controls 55AC series is as good as it gets for a triac based >>> speed controller. Built well, handles high currents, easy to fix and >>> sometimes real cheap on ebay- >>> >>> https://www.dart-controls.com/category-s/162.htm >> >> scratch that bogus URL. >> >> The manufacturer is >> >> https://www.dartcontrols.com/products/55ac-triac-ac-motor-speed-control/ >> > > Thanks. It a pricey test though :-)Maybe you can call and ask for a loaner. They're surpringly responsive to odd requests. zoro.com is usually the cheapest legit dealer if you buy new.
Reply by ●October 14, 20212021-10-14
On Thu, 14 Oct 2021 09:30:59 -0700, Joerg <news@analogconsultants.com> wrote:>On 10/14/21 7:52 AM, Joe Gwinn wrote: >> On Wed, 13 Oct 2021 11:51:07 -0700, Joerg <news@analogconsultants.com> >> wrote: >> >>> On 10/13/21 7:54 AM, Joe Gwinn wrote: >>>> On Tue, 12 Oct 2021 16:12:58 -0700 (PDT), Phil Allison >>>> <pallison49@gmail.com> wrote: >>>> >>>>> Joe Gwinn wrote: >>>>> ================ >>>>> >>>>>> It's best to get a small 3-phase motor for this. >>>>> >>>>> ** Giant HUH ??? >>>>> >>>>>> VFDs really do not >>>>>> like their motor circuit opening and closing, as with a centrifugal >>>>>> switch. >>>>> >>>>> ** You feeling OK ? >>>> >>>> I'm OK. The issue is that while VFDs intended for machine tools may >>>> be able to drive a single-phase induction motor as well, but it's best >>>> to short or bypass the centrifugal switch if using the start winding >>>> of a single-phase motor. >>>> >>> >>> They might signal a fault and shut down if one or more connections are >>> seen open. Like when you only connect one of the output phases to a load. >> >> True. Some VFDs allow one to program to disable that fault. >> > >Ah, that may be an option. The other job would be to make 110% sure that >it can never go past 120V because most VFDs put out 230V max, even those >for 120V input. > >> >>>> >>>>> Or just got no idea what a Papst AC fan is? >>>> >>>> They seem to all be single-phase, with a start winding. >>>> >>> >>> Just shaded-pole motors, usually. >>> >>> A problem with the small drives from Automation Direct is the same all >>> the others I looked at have. Aside from transfering 1-phase to 3-phase >>> even the 120V versions put out 230V max. That's a recipe for magic smoke >>> even if you tell everyone never to go past 50% or program in a limit. >>> >>> https://cdn.automationdirect.com/static/specs/cfw100acdrive.pdf >>> >>> Beats me why this is. There are so many applications for variable speed >>> of smaller induction motors. Such as heated water circulation, cooling >>> systems et cetera that only need small motors to overcome a miniscule >>> gravity load. They are single-phase and run on regular mains voltage. >> >> The main application for 120 Vac single phase in to 220 Vac three >> phase in small sizes is to allow three-phase industrial machines to be >> run from US domestic single-phase power. Three-phase 220 Vac >> industrial equipment is cheap and plentiful on the used market in the >> US. >> >> One common use is bench grinders and sanders and drill presses, where >> the variable speed is an added big advantage. One sees a lot of these >> machines on Craigs List. >> > >Yes, that may be the reaon. Probably not enough market for driving 120V >motors. > > >> One can also get three-phase fans and circulation pumps, which are >> intended to be driven by a VFD which is commanded by some kind of PID >> (Proportional Integral Derivative) temperature controller, versus the >> more common bang-bang controller. >> > >This situation requires the small muffin-style fans.I would hazard that you will need a DC fan for proportional control. If I recall, the speed controls in overhead fans (with 4-foot sweep diameter, consist of switched AC motor capacitors in series with the motor. I don't recall if I wrote the details down, but this was how the Hunter fan in one room in my house works. There are likely some patents on such. There are lots of circuits on the web. The underlying motor has two windings, and is not shaded pole. I suppose that for a shaded-pole induction motor in fan duty, a small variac would work, but would be a bit clumsy Maybe a tapped transformer. Joe Gwinn
