Joerg wrote: =============> > > ** Have you tried a Variac? > > > > Work just fine with most kinds of induction motor fans. > > > Yes, sorry, that was in an answer to John and not in the original post. > There is a UPS up front and that doesn't even like the smallest variac I > have.** FFS - so the real story has nothing to do with fan speed control ?????> The inverter in the UPS starts to buzz and then issues an overload > shut-off even without any fans connected to its tap-off. The UPS is a > small one with a modified sine inverter, no space for anything bigger there. > > This was a puzzler to me because that same variac runs fine on a smaller > 200W modified sine camping inverter, with and without fans connected. >** Betcha the "modified sine" has a significant DC offset. Variacs are just like toroidal transformers and insanely sensitive to offsets on the AC supply. A pair of reverse parallel electros in series with the Variac will eliminate such offsets. See page from my colleague Rod Elliott: https://sound-au.com/articles/xfmr-dc.htm ...... Phil
Small single-phase VFD for 120V?
Started by ●October 12, 2021
Reply by ●October 12, 20212021-10-12
Reply by ●October 12, 20212021-10-12
On 10/12/21 2:57 PM, Phil Allison wrote:> Joerg wrote: > ============= >> >>> ** Have you tried a Variac? >>> >>> Work just fine with most kinds of induction motor fans. >>> >> Yes, sorry, that was in an answer to John and not in the original post. >> There is a UPS up front and that doesn't even like the smallest variac I >> have. > > ** FFS - so the real story has nothing to do with fan speed control ????? >It does. The variac was never that great, fans become a bit louder at lower speeds. A VF drive would solve two problems, better fan control (more quiet) and it should run fine with any UPS. I was always on the lookout for a VFD even before buying this UPS.> >> The inverter in the UPS starts to buzz and then issues an overload >> shut-off even without any fans connected to its tap-off. The UPS is a >> small one with a modified sine inverter, no space for anything bigger there. >> >> This was a puzzler to me because that same variac runs fine on a smaller >> 200W modified sine camping inverter, with and without fans connected. >> > > ** Betcha the "modified sine" has a significant DC offset. > Variacs are just like toroidal transformers and insanely sensitive to offsets on the AC supply. > A pair of reverse parallel electros in series with the Variac will eliminate such offsets. > > See page from my colleague Rod Elliott: > > https://sound-au.com/articles/xfmr-dc.htm >Good point, could be a design flaw in the UPS. I can check that. -- Regards, Joerg http://www.analogconsultants.com/
Reply by ●October 12, 20212021-10-12
On Tue, 12 Oct 2021 12:04:21 -0700, Joerg <news@analogconsultants.com> wrote:>On 10/12/21 9:55 AM, Joerg 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. >> >> Even when typing in "VFD 120V single phase" all I get as results are >> three-phase and mostly for 220V. I am looking for something simple in >> the $50-100 range that doesn't have to deliver more than 100W but should >> vary the frequency, ideally in a frequency-voltage ratio that I can >> tweak with a potmeter. Simple knob to change the speed, ideally not some >> menu-driven panel. >> >> Of course I know how to build that or hack a camping inverter but I >> don't want yet another project. Modified sine would probably be good >> enough and I can filter that. >> > >Basically something like this but much smaller and for 120V, not 220V: > >https://www.amazon.com/SIPUN-SPVF-1-5G-S2-Variable-Frequency-Converter/dp/B0972NFCSF/Try this: .<https://www.automationdirect.com/adc/overview/catalog/motor_controls/ac_variable_frequency_drives_(vfd)/micro> It's best to get a small 3-phase motor for this. VFDs really do not like their motor circuit opening and closing, as with a centrifugal switch. I suppose one could use one phase and ignore the others; the manufacturer will know if this is supported. Joe Gwinn
Reply by ●October 12, 20212021-10-12
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 ? Or just got no idea what a Papst AC fan is? ...... Phil
Reply by ●October 12, 20212021-10-12
On Tue, 12 Oct 2021 14:24:31 -0700, Joerg <news@analogconsultants.com> wrote:>On 10/12/21 2:13 PM, John Larkin wrote: >> On Tue, 12 Oct 2021 11:19:41 -0700, Joerg <news@analogconsultants.com> >> wrote: >> >>> On 10/12/21 10:29 AM, John Larkin wrote: >>>> On Tue, 12 Oct 2021 09:55:29 -0700, 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. >>>>> >>>>> Even when typing in "VFD 120V single phase" all I get as results are >>>>> three-phase and mostly for 220V. I am looking for something simple in >>>>> the $50-100 range that doesn't have to deliver more than 100W but should >>>>> vary the frequency, ideally in a frequency-voltage ratio that I can >>>>> tweak with a potmeter. Simple knob to change the speed, ideally not some >>>>> menu-driven panel. >>>>> >>>>> Of course I know how to build that or hack a camping inverter but I >>>>> don't want yet another project. Modified sine would probably be good >>>>> enough and I can filter that. >>>> >>>> Do you think frequency control will work on those fan motors? They may >>>> be some modern electronic things. >>>> >>> >>> These are traditional AC fan motors sans electronics. They work >>> acceptably though not ideal with a variable transformer but the UPS up >>> front does not like the variable transformer for some reason (overload >>> shutdown). >> >> Do you need full range control? You could get two speeds with a series >> R or C, or even putting fans in series. >> > >In theory yes and I thought about it. However, I need at least four >speeds and that really gets old when you have to cram a bunch of big >caps into a box. All of which have to be 120V AC rated. Resistors would >becomes very toasty and for whatever reason the UPS does not like inductors. > >I was looking for something that can dial in a speed via a potmeter. >What I find strange is that such small VF drives are available for 230V >but not for 120V. > > >> I'm doing a fan speed controller right now, but with 24 VDC fans, >> driven by a DAC and an opamp. Planning to adjust fan speed based on >> box internal temperature. >> >> We'll have a DAC value integer with low and high limits. Once every >> second, if the temp is below setpoint, tick down, and vice versa. That >> is a low-drama control loop. >> > >With a meaningful hysteresis that should indeed be low-drama.No hysteresis. It's a 1-LSB bang-bang loop. -- If a man will begin with certainties, he shall end with doubts, but if he will be content to begin with doubts he shall end in certainties. Francis Bacon
Reply by ●October 12, 20212021-10-12
On Tuesday, October 12, 2021 at 2:24:37 PM UTC-7, Joerg wrote:> On 10/12/21 2:13 PM, John Larkin wrote:> >>>> Looking for a "better dimmer" to speed-control two small AC fans....> What I find strange is that such small VF drives are available for 230V > but not for 120V.It's not so strange; many items that benefit from variable frequency drive are tools for metalwork where cutting depends critically on speed, and half-horsepower is tiny (but well over the 100W class), and 240V power is common. Either use an inductive-rated dimmer and universal (with brushes) motor (drill motor, or other handheld power tool), or grab a DC supply suitable for a stepper motor with its controller. Regulated DC not required, but you'll want isolation, so regulation is kinda... free. Heck, a UPS is involved? So, you have battery power you could tap?
Reply by ●October 13, 20212021-10-13
whit3rd wrote: =============== Joerg wrote:> ... > > What I find strange is that such small VF drives are available for 230V > > but not for 120V. > > > Either use an inductive-rated dimmer and universal (with brushes) motor (drill > motor, or other handheld power tool), or grab a DC supply suitable for > a stepper motor with its controller. Regulated DC not required, but you'll > want isolation, so regulation is kinda... free. >** The OP needs an all metal, AC fan cos of the hot environment.> Heck, a UPS is involved? So, you have battery power you could tap?** BLDC fans are out - read ALL the posts in a thread sometime. A Variac is all he needs for speed control. Using a "modified sine wave" AC supply is his one issue. ..... Phil
Reply by ●October 13, 20212021-10-13
On Tuesday, October 12, 2021 at 10:04:57 PM UTC-7, palli...@gmail.com wrote:> whit3rd wrote: > =============== > Joerg wrote: > > ... > > > What I find strange is that such small VF drives are available for 230V > > > but not for 120V. > > > > > > Either use an inductive-rated dimmer and universal (with brushes) motor (drill > > motor, or other handheld power tool), or grab a DC supply suitable for > > a stepper motor...> ** The OP needs an all metal, AC fan cos of the hot environment. > ** BLDC fans are out - read ALL the posts in a thread sometime.The 'BL' in BLDC is for brushless, which isn't the suggestion.> > A Variac is all he needs for speed control.That's not speed control for induction motors, though, only universal or rectifier-to-DC types, with brushes... and a triac (like the speed control on a Dremel tool) is cheaper.
Reply by ●October 13, 20212021-10-13
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.>Or just got no idea what a Papst AC fan is?They seem to all be single-phase, with a start winding. Joe Gwinn
Reply by ●October 13, 20212021-10-13
On 10/12/21 4:52 PM, John Larkin wrote:> On Tue, 12 Oct 2021 14:24:31 -0700, Joerg <news@analogconsultants.com> > wrote: > >> On 10/12/21 2:13 PM, John Larkin wrote: >>> On Tue, 12 Oct 2021 11:19:41 -0700, Joerg <news@analogconsultants.com> >>> wrote: >>> >>>> On 10/12/21 10:29 AM, John Larkin wrote: >>>>> On Tue, 12 Oct 2021 09:55:29 -0700, 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. >>>>>> >>>>>> Even when typing in "VFD 120V single phase" all I get as results are >>>>>> three-phase and mostly for 220V. I am looking for something simple in >>>>>> the $50-100 range that doesn't have to deliver more than 100W but should >>>>>> vary the frequency, ideally in a frequency-voltage ratio that I can >>>>>> tweak with a potmeter. Simple knob to change the speed, ideally not some >>>>>> menu-driven panel. >>>>>> >>>>>> Of course I know how to build that or hack a camping inverter but I >>>>>> don't want yet another project. Modified sine would probably be good >>>>>> enough and I can filter that. >>>>> >>>>> Do you think frequency control will work on those fan motors? They may >>>>> be some modern electronic things. >>>>> >>>> >>>> These are traditional AC fan motors sans electronics. They work >>>> acceptably though not ideal with a variable transformer but the UPS up >>>> front does not like the variable transformer for some reason (overload >>>> shutdown). >>> >>> Do you need full range control? You could get two speeds with a series >>> R or C, or even putting fans in series. >>> >> >> In theory yes and I thought about it. However, I need at least four >> speeds and that really gets old when you have to cram a bunch of big >> caps into a box. All of which have to be 120V AC rated. Resistors would >> becomes very toasty and for whatever reason the UPS does not like inductors. >> >> I was looking for something that can dial in a speed via a potmeter. >> What I find strange is that such small VF drives are available for 230V >> but not for 120V. >> >> >>> I'm doing a fan speed controller right now, but with 24 VDC fans, >>> driven by a DAC and an opamp. Planning to adjust fan speed based on >>> box internal temperature. >>> >>> We'll have a DAC value integer with low and high limits. Once every >>> second, if the temp is below setpoint, tick down, and vice versa. That >>> is a low-drama control loop. >>> >> >> With a meaningful hysteresis that should indeed be low-drama. > > No hysteresis. It's a 1-LSB bang-bang loop. >Then the hysteresis is one LBS :-) -- Regards, Joerg http://www.analogconsultants.com/
