Forums

Small single-phase VFD for 120V?

Started by Joerg October 12, 2021
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.

-- 
Regards, Joerg

http://www.analogconsultants.com/
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. -- 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
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? just change to a DC fan with speed control. VFDs on small motors is completly pointless anyways.
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). -- Regards, Joerg http://www.analogconsultants.com/
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. -- Regards, Joerg http://www.analogconsultants.com/
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/ -- Regards, Joerg http://www.analogconsultants.com/
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. 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. -- 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
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. >
** Have you tried a Variac? Work just fine with most kinds of induction motor fans. .... Phil
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. -- Regards, Joerg http://www.analogconsultants.com/
On 10/12/21 2:16 PM, Phil Allison wrote:
> 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. >> > > ** 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. 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. -- Regards, Joerg http://www.analogconsultants.com/