Hi,
This questions is a quite open-ended one:
Seebeck-Peltier type fanless coolers are not considered as Air has to be moved.
If you have liked an Ultra-Quiet Fan or Tools or Biomedical Equipment or similar, please let me know.
Possible Specifications (can be changed somewhat if the motor is really quiet):
(1) Load is Fan Type (Load torque is proportional to Speed^2), Fixed Criterion.
(2) Power is less than few Horse Power (HP), fractional HP motors are candidates as well.
(3) Speed between 900 rpm to 3600 rpm.
Which are Ultra-Quiet Motors (Rotary or possible Linear) that you know, used or have heard of (rather not heard of)?
Motor can include:
(1) Motor/Servo Motor,
(2) Bearings and mounting brackets,
(3) Motor Drive Inverter/SCR Rectifier,
(4) Balance of motor and Fan,
(5) Motor, Pulley and Belt, etc.
The type of motor can be:
(1) Induction, 3 phase or Single Phase,
(2) AC Synchronous
(3) Brushless DC (this seems to be the most promising category),
(4) Brushed DC,
(5) Brushed DC Universal Motor,
(6) Stepper,
(7) Switched Reluctance (these are usually noisy)
Promising motors seem to be:
(1) SDT (Brushless motors achieve quiet efficiency), only 35 dBA, company now seems to be closed.
(2) Moog(http://www.moog.com/products/motors-servomotors/brushless-motors/inside-rotor-brushless-dc-motors/bn-series/bn17/),
(3) Buehler, etc.
Thank you for your inputs and suggestions!
Best Regards,
RK