I purchased a fan (https://www.acinfinity.com/smart-cooling/axial-fans-accessories/115v-ac-axial-hs1238a-muffin-fan-120mm-x-38mm-high-speed/#product-warranty) and I was wondering what the simplest method would be to reduce the RPM of the motor in order to quiet it down if need be.
I've read there are certain ways to control AC motors unlike DC motors and if not done properly you can damage the motor and/or it's windings.
From what I understand is that most AC motor controllers chop the AC waveform up to either reduce or increase the HZ provided. Is this correct?
Here are my thoughts on ways to control the motor, and I was wondering if anyone could tell me if they are the correct way. If not provide a better simpler way.
1) Simply add a resistor in series. This will drop the voltage supplied, but likely increase current draw on the windings?
2) Add some capacitance some how to adjust the power factor of the motor to increase/reduce torque?
3) Triacs to chop up the wave form to reduce the ON time the motor receives.
Are any of these correct? If not what is the simplest solution to drop the RPM. I am not looking for variable adjustment, just a simple reduction when inserted into the circuit.
If any of the above are correct, what would the schematic look like for 2 or 3.