Technical question - CPAP motors

Please pardon this business-type question, but I'm hoping to get some technical advice regarding motors used in CPAP machines. My startup has developed a medical device that produces HEPA filtered air (totally unrelated to the CPAP arena). Our problem is that the motor we use is very loud and large. We need to develop about 1500 FPM at 4" H2O pressure. We've had a hard time finding a suitable performing motor that is small-ish and quiet. Any help with finding a motor vendor would be greatly appreciated.

Maybe the reason you have had trouble finding a quiet small motor is your air volume and pressure requirements call for a bigger stronger motor than a XPAP Machine. I think the requirments in flow and volume are quite different. The choice is a quiet product with a low power fan the won't no much of a job or a higher powered product that works better. Jim

sdself wrote:Please pardon this business-type question, but I'm hoping to get some technical advice regarding motors used in CPAP machines. My startup has developed a medical device that produces HEPA filtered air (totally unrelated to the CPAP arena). Our problem is that the motor we use is very loud and large. We need to develop about 1500 FPM at 4" H2O pressure. We've had a hard time finding a suitable performing motor that is small-ish and quiet. Any help with finding a motor vendor would be greatly appreciated.

There used to be a company in the US that produced motors for blowers under contract to several of the former well known machine providers.
I know of the company but not its name.

The motors used are brushless DC motors but, the noise typically comes from the fan not the motor.

Resmed took a novel approach to the noisy fan problem by placing a blower fan at each end of the motor shaft. DC brushless motors can deliver enormous power in a small package. It all comes down to airflow required and fan design.

Most Cpaps peak at around 30 CMs. Hospital ventilators can go a lot higher.

If I were looking for a motor that delivers more air than that put out by a cpap I'd be looking inside a hospital ventilator & trying to track down the blower supplier.

Good luck.

DSM

sdself wrote:We need to develop about 1500 FPM at 4" H2O pressure.

10cms H20 is well within the scope of xPAP motors but AFAICT the flow rate requirement is much higher than xPAP, so you are probably going to be out of luck in terms of using motors designed for xPAP use.

Cheers,

Bill

I don't think that motor noise in a fan is really a problem, it is the blower and air flow that cause the noise. An off balance blower can also cause additional noise. There is a relationship between fan size and noise; for a give output volume and pressure; the smaller the fan, the louder it will be. Another place to look for quieter blowers are hair dryers, their output volume is closer to what you are looking at. There is a segment of the hair dryer/blow drier market that is looking for quieter machines.

To get the airflow required would probably take 50 to 100 XPAP motors, that would be costly, and probably noisy. Most brushless motors have low output, for torque a perm magnet motor D/C have more power in a smaller size and use less electricty.

I am going to guess that for the volume of air you are moving, a squirrel cage fan is probably going to be the quietest and most efficient for the size. You want the faan to be as physically large as your application will allow, so that your motor RPM will be as low as possible.

For that amount of air, you are probably best going with an AC motor. You are definitely in induction motor range at that CFM. This motor will be about the size of a typical furnace blower motor. They also make relatively small variable speed AC motors that require a drive inverter, if you need speed control.

timbalionguy wrote:I am going to guess that for the volume of air you are moving, a squirrel cage fan is probably going to be the quietest and most efficient for the size. You want the faan to be as physically large as your application will allow, so that your motor RPM will be as low as possible.

For that amount of air, you are probably best going with an AC motor. You are definitely in induction motor range at that CFM. This motor will be about the size of a typical furnace blower motor. They also make relatively small variable speed AC motors that require a drive inverter, if you need speed control.

Tks TLG

Good thinking and better advice than I was offering. I hadn't thought as much about the volume involved.

Cheers

DSM