General > General Technical Chat
US Ceiling Fan Efficiency Rule Proposal
wraper:
--- Quote from: Nominal Animal on September 04, 2023, 01:41:40 pm ---
--- Quote from: Zero999 on September 04, 2023, 01:30:36 pm ---I can't say I've ever noticed any whine from a BLDC motor, even when I was much younger and could hear over 20kHz.
--- End quote ---
Nevertheless, it is a well known phenomenon. Microchip even made an appnote (AN771: Suppressing Acoustic Noise in PWM Fan Speed Control Systems) about it in 2002. Feel free to ignore me (many do, and that's okay), but please do read that appnote to understand the issue I'm trying to bring up. It affects slow high-current/high-load (large fan assembly) fans in particular, so therefore definitely does apply to BLDC ceiling fan motors also (or rather, their control circuitry, which is basically the only part manufacturers can cost-cut anymore, with just about everything else being basically standard).
--- End quote ---
Idiot engineer phenomenon. Appnote about of how to make ridiculous garbage a little bit less of garbage. You cannot safely PWM power of 99% of brusheless fans to begin with. Brusheless fan speed must be controlled through its PWM wire (if present) or by adjusting DC voltage, not PWMing it's power. Yet some engineers think it's fine despite fans generally having an electrolytic capacitor across their power and driver IC which are not supposed to be abused this way. Heck, Sunon even explicitly forbids it in their datasheets, I guess because there are enough idiots who think otherwise.
Nominal Animal:
--- Quote from: wraper on September 08, 2023, 12:15:33 pm ---
--- Quote from: Nominal Animal on September 04, 2023, 01:41:40 pm ---
--- Quote from: Zero999 on September 04, 2023, 01:30:36 pm ---I can't say I've ever noticed any whine from a BLDC motor, even when I was much younger and could hear over 20kHz.
--- End quote ---
Nevertheless, it is a well known phenomenon. Microchip even made an appnote (AN771: Suppressing Acoustic Noise in PWM Fan Speed Control Systems) about it in 2002. Feel free to ignore me (many do, and that's okay), but please do read that appnote to understand the issue I'm trying to bring up. It affects slow high-current/high-load (large fan assembly) fans in particular, so therefore definitely does apply to BLDC ceiling fan motors also (or rather, their control circuitry, which is basically the only part manufacturers can cost-cut anymore, with just about everything else being basically standard).
--- End quote ---
Idiot engineer phenomenon. Appnote about of how to make ridiculous garbage a little bit less of garbage. You cannot safely PWM power of 99% of brusheless fans to begin with. Brusheless fan speed must be controlled through its PWM wire (if present) or by adjusting DC voltage, not PWMing it's power. Yet some engineers think it's fine despite fans generally having an electrolytic capacitor across their power and driver IC which are not supposed to be abused this way. Heck, Sunnon even explicitly forbids it in their datasheets, I guess because there are enough idiots who think otherwise.
--- End quote ---
Agreed; and those engineers get paid to do that only because it is cheaper than doing it properly.
On the PC fan side, those motor designs got kicked in the teeth as users basically rejected them, and even the cheapest mass producers have shifted to more sensible driving schemes.
Ten to twenty years ago, there were only very minor differences between fan blade designs, with quiet fans just having blade geometry well matched to their motor. Nexus was the bees knees back then for general use. Gentle Typhoon had optimal geometry for intake fans, as they could deal with filters' airflow impedance without becoming noisy. 3-pin (voltage controlled, no PWM) fans were quieter and with nicer noise spectrum than 4-pin PWM-controlled fans, as you can find out yourself by looking at fan noise comparisons back then (by SPCR for example). Noctua started with good CPU heatsink designs, with well matched fans; and then went on to optimize their fans for low noise and good airflow by both working on the motor designs (their sinusoidal BLDC drive ICs, bearing designs) and later even on the blade geometry. Now several manufacturers design their own blade geometries with both noise and airflow in mind.
Since this already happened with PC fans, taking a decade from the arrival of PWM-controlled fans to actually good motor and blade designs to be available, I'm just afraid something similar will happen with ceiling fans. The current ceiling fan AC motors may not be as efficient as possible, but they for sure are reliable and quiet; the two things that matter to me personally more than the exact power usage. To me, it would be a HUGE step backwards to replace a perfectly good, reliable, quiet ceiling fan with one that has a one-year warranty, a high-pitch squeal I can hear when trying to sleep in the summer, much higher price (due to the more complex construction and electronics), but with lower energy consumption.
Sure, I could be wrong. But when something similar has already happened in the past, history tells us things tend to repeat the same way.
bdunham7:
--- Quote from: Siwastaja on September 08, 2023, 11:12:11 am ---Instead, we should demand reliable electronics, because the 99% of cases show that this is entirely possible.
--- End quote ---
In fact, to the extent that the government causes the issue by mandating levels of efficiency that sometimes results in less reliable products, they should mitigate the problem by requiring very long warranty periods. After all, if their goal is to save energy and the environment, surely long-lived appliances results in less manufacturing (consumption of energy and raw materials) and less waste. Recycling is a poor substitute for long product life.
By long warranty periods I mean refrigerators/dehumidifiers/AC units - 20 years, clothes washers/dryers/dishwashers - 10 years. Ceiling fans - 50 years.
wraper:
--- Quote from: Nominal Animal on September 08, 2023, 01:45:02 pm ---Agreed; and those engineers get paid to do that only because it is cheaper than doing it properly.
--- End quote ---
And then you have failing fans, whiny noise and rattling sound during fan start. The problem is that I've seen this not only in cheapest devices but where such economy makes not economical sense. I'm pretty sure it's more of incompetency rather than saving $0.05 BOM cost.
wraper:
--- Quote from: Nominal Animal on September 08, 2023, 01:45:02 pm ---To me, it would be a HUGE step backwards to replace a perfectly good, reliable, quiet ceiling fan with one that has a one-year warranty, a high-pitch squeal I can hear when trying to sleep in the summer, much higher price (due to the more complex construction and electronics), but with lower energy consumption.
Sure, I could be wrong. But when something similar has already happened in the past, history tells us things tend to repeat the same way.
--- End quote ---
BLDC is more reliable in general because there is no run capacitor that degrades and they do not heat nearly as much due to high efficiency. Shaded pole motor that is most common in AC fans on other hand is cheap but super inefficient, heats like hell and that heat kills bearings. Not surprising due to ~25% efficiency.
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