Has anyone run bldc fans in series? I want to run three 12v fans from a 48v supply, with a resistor or something in series I guess I could be cautious and put a cap and a 12v TVS across each fan. Hmmm, 3 fans and 4 TVSs might work. Worst case, I can make a 48 to 12 switcher. Here's the idea: https://www.dropbox.com/s/5hx2hzrq4edd3ye/P944_Load_Module_1.jpg?raw=1 -- I yam what I yam - Popeye
fans in series
Started by ●January 12, 2022
Reply by ●January 13, 20222022-01-13
On 2022/01/12 7:48 p.m., jlarkin@highlandsniptechnology.com wrote:> Has anyone run bldc fans in series? I want to run three 12v fans from > a 48v supply, with a resistor or something in seriesUneven airflow loading could burn out a fan...> > I guess I could be cautious and put a cap and a 12v TVS across each > fan. Hmmm, 3 fans and 4 TVSs might work.This sounds like it would work. Should probably add a fuse to it.> > Worst case, I can make a 48 to 12 switcher.Zeners and pass transistors would also work. John :-#)#> > Here's the idea: > > https://www.dropbox.com/s/5hx2hzrq4edd3ye/P944_Load_Module_1.jpg?raw=1 >-- (Please post followups or tech inquiries to the USENET newsgroup) John's Jukes Ltd. MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3 (604)872-5757 (Pinballs, Jukes, Video Games) www.flippers.com "Old pinballers never die, they just flip out."
Reply by ●January 13, 20222022-01-13
On a sunny day (Wed, 12 Jan 2022 19:48:59 -0800) it happened jlarkin@highlandsniptechnology.com wrote in <hm5vtg599rmbp88m0smfr7bsd05e4nh18t@4ax.com>:>Has anyone run bldc fans in series? I want to run three 12v fans from >a 48v supply, with a resistor or something in series > >I guess I could be cautious and put a cap and a 12v TVS across each >fan. Hmmm, 3 fans and 4 TVSs might work. > >Worst case, I can make a 48 to 12 switcher. > >Here's the idea: > >https://www.dropbox.com/s/5hx2hzrq4edd3ye/P944_Load_Module_1.jpg?raw=1My system using Meanwell 7.5 V supplies in series allows any voltage output in steps of about 6 to 8 V. In your case and if customer has only 48 V, bolt an ebay 48 V to 12 V switcher in the housing, maybe something like this: https://www.ebay.com/itm/383691634312 add a fuse in primary..
Reply by ●January 13, 20222022-01-13
On 13/01/2022 14:48, jlarkin@highlandsniptechnology.com wrote:> Has anyone run bldc fans in series? I want to run three 12v fans from > a 48v supply, with a resistor or something in series > > I guess I could be cautious and put a cap and a 12v TVS across each > fan. Hmmm, 3 fans and 4 TVSs might work. > > Worst case, I can make a 48 to 12 switcher.You should use the switcher or buy 48V fans. More fancy fans have things in them to intermittently attempt to restart after they stall without running the windings continuously, and other fancy things. There is no reason to believe that the fans would each want to draw the same current at all times. If you put zeners across each fan, it might work, but in the event that one fan doesn't draw current (e.g. stalls and goes into intermittent restart attempts) the corresponding zener might get very hot.
Reply by ●January 13, 20222022-01-13
On Thu, 13 Jan 2022 22:16:20 +1100, Chris Jones <lugnut808@spam.yahoo.com> wrote:>On 13/01/2022 14:48, jlarkin@highlandsniptechnology.com wrote: >> Has anyone run bldc fans in series? I want to run three 12v fans from >> a 48v supply, with a resistor or something in series >> >> I guess I could be cautious and put a cap and a 12v TVS across each >> fan. Hmmm, 3 fans and 4 TVSs might work. >> >> Worst case, I can make a 48 to 12 switcher. > >You should use the switcher or buy 48V fans.Why? For some reason, 35mm fans only seem to come in 5 or 12 volts. They only need 50-90 mA. High voltage switchers are a nuisance. This might be OK: https://www.mouser.com/ProductDetail/XP-Power/SRH05S12?qs=w%2Fv1CP2dgqoB4ok%252BZU%252BVXg%3D%3D $7, if we can get them.> >More fancy fans have things in them to intermittently attempt to restart >after they stall without running the windings continuously, and other >fancy things. There is no reason to believe that the fans would each >want to draw the same current at all times. If you put zeners across >each fan, it might work, but in the event that one fan doesn't draw >current (e.g. stalls and goes into intermittent restart attempts) the >corresponding zener might get very hot. >But we have forced air cooling! -- I yam what I yam - Popeye
Reply by ●January 13, 20222022-01-13
On 13/01/2022 22:41, jlarkin@highlandsniptechnology.com wrote:> On Thu, 13 Jan 2022 22:16:20 +1100, Chris Jones > <lugnut808@spam.yahoo.com> wrote: > >> On 13/01/2022 14:48, jlarkin@highlandsniptechnology.com wrote: >>> Has anyone run bldc fans in series? I want to run three 12v fans from >>> a 48v supply, with a resistor or something in series >>> >>> I guess I could be cautious and put a cap and a 12v TVS across each >>> fan. Hmmm, 3 fans and 4 TVSs might work. >>> >>> Worst case, I can make a 48 to 12 switcher. >> >> You should use the switcher or buy 48V fans. > > Why?Well, if you are sure that your fans don't have anything smart in them and always draw current, monotonically increasing with voltage, or if the power of the fans is small enough that you can dissipate the same amount of power in a parallel zener if you need to, then fine you could put them in series. I have seen some fans that when you stall them, they go into some low-power mode and then every second or two, briefly have a go at restarting, so they are high-impedance most of the time then draw a big spike of current when they try to restart. I don't think these would work well in series without the zeners.
Reply by ●January 13, 20222022-01-13
jlarkin@highlandsniptechnology.com wrote:> Has anyone run bldc fans in series? I want to run three 12v fans from > a 48v supply, with a resistor or something in series > > I guess I could be cautious and put a cap and a 12v TVS across each > fan. Hmmm, 3 fans and 4 TVSs might work. > > Worst case, I can make a 48 to 12 switcher. > > Here's the idea: > > https://www.dropbox.com/s/5hx2hzrq4edd3ye/P944_Load_Module_1.jpg?raw=1Don't do it. They will not share voltage and the losers will burn out on the first start. Been there, done that. Find 48 volt telecom fans or 24 volts ones and use individual series resistors. Fans are mechanical so don't increase your failure rate by using any sort of chain.
Reply by ●January 16, 20222022-01-16
On Thursday, January 13, 2022 at 5:34:42 PM UTC-8, Cydrome Leader wrote:> jla...@highlandsniptechnology.com wrote: > > Has anyone run bldc fans in series? I want to run three 12v fans from > > a 48v supply, with a resistor or something in series> Don't do it. They will not share voltage and the losers will burn out on > the first start.Yeah, it's the equivalent of a house with a floating neutral; well known for wild voltage fluctuations. If the fans are identical, after the first fails, will the others fail the same way, and make a short? Or will one or more fail open and leave everything unventilated pending combustion? I want to see that video. Meanwhile, enjoy this one <https://youtu.be/YSOpl4gG95w>
Reply by ●January 16, 20222022-01-16
On Fri, 14 Jan 2022 01:34:35 -0000 (UTC), Cydrome Leader <presence@MUNGEpanix.com> wrote:>jlarkin@highlandsniptechnology.com wrote: >> Has anyone run bldc fans in series? I want to run three 12v fans from >> a 48v supply, with a resistor or something in series >> >> I guess I could be cautious and put a cap and a 12v TVS across each >> fan. Hmmm, 3 fans and 4 TVSs might work. >> >> Worst case, I can make a 48 to 12 switcher. >> >> Here's the idea: >> >> https://www.dropbox.com/s/5hx2hzrq4edd3ye/P944_Load_Module_1.jpg?raw=1 > >Don't do it. They will not share voltage and the losers will burn out on >the first start. Been there, done that. Find 48 volt telecom fans or 24 >volts ones and use individual series resistors. Fans are mechanical so >don't increase your failure rate by using any sort of chain.The 35mm fans I want to use seem to only come in 5v and 12v. And the supply is 48. I suppose I can make a 48-to-12 switcher on this board. Still, a series string with shunt zeners ought to work. -- I yam what I yam - Popeye
Reply by ●January 16, 20222022-01-16
søndag den 16. januar 2022 kl. 16.30.17 UTC+1 skrev jla...@highlandsniptechnology.com:> On Fri, 14 Jan 2022 01:34:35 -0000 (UTC), Cydrome Leader > <pres...@MUNGEpanix.com> wrote: > > >jla...@highlandsniptechnology.com wrote: > >> Has anyone run bldc fans in series? I want to run three 12v fans from > >> a 48v supply, with a resistor or something in series > >> > >> I guess I could be cautious and put a cap and a 12v TVS across each > >> fan. Hmmm, 3 fans and 4 TVSs might work. > >> > >> Worst case, I can make a 48 to 12 switcher. > >> > >> Here's the idea: > >> > >> https://www.dropbox.com/s/5hx2hzrq4edd3ye/P944_Load_Module_1.jpg?raw=1 > > > >Don't do it. They will not share voltage and the losers will burn out on > >the first start. Been there, done that. Find 48 volt telecom fans or 24 > >volts ones and use individual series resistors. Fans are mechanical so > >don't increase your failure rate by using any sort of chain. > The 35mm fans I want to use seem to only come in 5v and 12v. And the > supply is 48. > > I suppose I can make a 48-to-12 switcher on this board. Still, a > series string with shunt zeners ought to work.once you add a switcher you can also stop it sounding like jet engine when it doesn't need to