General > General Technical Chat

US Ceiling Fan Efficiency Rule Proposal

<< < (5/13) > >>

Nominal Animal:

--- Quote from: Zero999 on September 03, 2023, 06:42:42 pm ---Lower speeds generally correlate with less noise and higher efficiency.
--- End quote ---
I've found that lower PWM duty cycles correlate with more noise, rather than less.

Zero999:

--- Quote from: Nominal Animal on September 04, 2023, 05:56:56 am ---
--- Quote from: Zero999 on September 03, 2023, 06:42:42 pm ---Lower speeds generally correlate with less noise and higher efficiency.
--- End quote ---
I've found that lower PWM duty cycles correlate with more noise, rather than less.

--- End quote ---
I wasn't talking about PWM, but air speed i.e. velocity. Consider two fans, both moving the same amount of air per second. One is 2m in diameter and the other 200mm. The 200m fan will have to spin much faster, to move the same amount of air per second and therefore will make far more noise, than the 2m fan.

Nominal Animal:

--- Quote from: Zero999 on September 04, 2023, 07:20:21 am ---
--- Quote from: Nominal Animal on September 04, 2023, 05:56:56 am ---
--- Quote from: Zero999 on September 03, 2023, 06:42:42 pm ---Lower speeds generally correlate with less noise and higher efficiency.
--- End quote ---
I've found that lower PWM duty cycles correlate with more noise, rather than less.

--- End quote ---
I wasn't talking about PWM, but air speed i.e. velocity. Consider two fans, both moving the same amount of air per second. One is 2m in diameter and the other 200mm. The 200m fan will have to spin much faster, to move the same amount of air per second and therefore will make far more noise, than the 2m fan.
--- End quote ---
Sure, but that's obvious. You must agree that because we're talking about the motor technology of ceiling fans, interjecting that larger fans are quieter than small fans, is a bit odd.

I was explicitly talking about the motor noise.   The diameter of my "silent" ceiling fan (blades) is about 48".  I did verify last night that even with my ear right below the center hub, there is no hum or even bearing noise, at the lowest (my preferred) speed of about 50 RPM; the noise from the blades is a nice white-ish noise with no overtones (it's too quiet to record with my phone or microphones I have, so no spectrum analysis).  I don't want to take it down and check the motor type, though.  The hub alone has a diameter of 10"-12", and I can see lots of coil wires through the cooling vents.  The only "downside" is that the lamp shades are Grandma-style flowery "roses", heh.

I am extremely aware of the difference the fan size makes for devices, as I have built and maintained racks of HPC nodes (1U with lots of fans), as well as my own "silent" PC workstation enclosures.  I was not referring to the size-dependent noise characteristics –– smaller fans having higher RPMs and therefore also higher acoustic spectrum peaks –– but to the effects of PWM'ing the BLDC motor in these fans, and to the "squeal" at low duty cycles at the PWM frequency due to insufficient filtering/smoothing in the motor.  (All PC fans, both three and four pin ones, are BLDC motors.  Three-pin ones are supply voltage controlled, typically 7V-12V, and four pin ones PWM controlled; some are hybrids which can be controlled either by voltage or by PWM.  Nowadays, many PC PWM fans have excellent noise characteristics, and the "squeal" is only an issue with el-cheapo ones; but it used to be an issue with basically all early PWM-controlled PC fans.  Just go look at old SilentPCReview stuff, for example.)

Zero999:

--- Quote from: Nominal Animal on September 04, 2023, 08:18:59 am ---
--- Quote from: Zero999 on September 04, 2023, 07:20:21 am ---
--- Quote from: Nominal Animal on September 04, 2023, 05:56:56 am ---
--- Quote from: Zero999 on September 03, 2023, 06:42:42 pm ---Lower speeds generally correlate with less noise and higher efficiency.
--- End quote ---
I've found that lower PWM duty cycles correlate with more noise, rather than less.

--- End quote ---
I wasn't talking about PWM, but air speed i.e. velocity. Consider two fans, both moving the same amount of air per second. One is 2m in diameter and the other 200mm. The 200m fan will have to spin much faster, to move the same amount of air per second and therefore will make far more noise, than the 2m fan.
--- End quote ---
Sure, but that's obvious. You must agree that because we're talking about the motor technology of ceiling fans, interjecting that larger fans are quieter than small fans, is a bit odd.

I was explicitly talking about the motor noise.   The diameter of my "silent" ceiling fan (blades) is about 48".  I did verify last night that even with my ear right below the center hub, there is no hum or even bearing noise, at the lowest (my preferred) speed of about 50 RPM; the noise from the blades is a nice white-ish noise with no overtones (it's too quiet to record with my phone or microphones I have, so no spectrum analysis).  I don't want to take it down and check the motor type, though.  The hub alone has a diameter of 10"-12", and I can see lots of coil wires through the cooling vents.  The only "downside" is that the lamp shades are Grandma-style flowery "roses", heh.

I am extremely aware of the difference the fan size makes for devices, as I have built and maintained racks of HPC nodes (1U with lots of fans), as well as my own "silent" PC workstation enclosures.  I was not referring to the size-dependent noise characteristics –– smaller fans having higher RPMs and therefore also higher acoustic spectrum peaks –– but to the effects of PWM'ing the BLDC motor in these fans, and to the "squeal" at low duty cycles at the PWM frequency due to insufficient filtering/smoothing in the motor.  (All PC fans, both three and four pin ones, are BLDC motors.  Three-pin ones are supply voltage controlled, typically 7V-12V, and four pin ones PWM controlled; some are hybrids which can be controlled either by voltage or by PWM.  Nowadays, many PC PWM fans have excellent noise characteristics, and the "squeal" is only an issue with el-cheapo ones; but it used to be an issue with basically all early PWM-controlled PC fans.  Just go look at old SilentPCReview stuff, for example.)

--- End quote ---
In my experiance, the sound of the air moving throuh the fan blades, dominates that of the motor.

No mention of PWM was mentioned. I very much doubt noisy brushed motors driven by PWM will be used. They'll all use brushless DC, or perhaps a three squirrel cage motor, driven by a small inverter for higher power units.

gnuarm:

--- Quote from: NiHaoMike on September 02, 2023, 01:53:05 pm ---I think ceiling fans can get a lot more efficient merely by using a motor which is optimized for a single speed with low slip, the way multiple speeds is usually done is an ugly hack. And if BLDC ceiling fans become common, there likely would be a lot of generic driver boards for them like how there are a lot of generic ESCs for R/C motors.

--- End quote ---

If a fan isn't three speed, I won't buy it.  I almost never use a ceiling fan on high speed and even the second speed is seldom.  I don't like the feeling of the air on me.  It also tends to dry out my eyes.  On the lowest speed,  I have no problems with it. 

Most fans, I find are cranked up too much.  The ventilation fan in my car goes to 11... yes, 11.  I hardly ever use it above 4.  I would like to have settings equivalent to 0.5 and 1.5 though.  They never seem to give much thought that the lower settings need to be spaced closer together.   It's a bit like the logarithmic audio levels... which also run to 11 and are not really logarithmically spaced.

Navigation

[0] Message Index

[#] Next page

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod