Distressed Nerd - How to increase Motor RPM

[Distressed Nerd]

Hello!
As an engineer who graduated #2 out of 10 in my class from a top tier university, yet I am completely, 100%, stumped on this electronics project and feeling like I a complete doo doo head and I am in dire need of help from my nerd comrades.
What I am trying to do is increase the RPM’s of this fan motor. Right now it has a 4 setting selector switch (off, speed 1, speed 2, and speed 3), but I need more power or RPM’s then the highest speed setting (speed 3) will give me. A picture and all the details is attached, anyone who can solve this problem I will worship you! Just let me know the parts and wiring and I will turn your words into a finished project.
If the rpm’s can not be increased using the motor I have now – then please let me know an easy motor setup I could install to give me more RPM’s then the current setup.
Thanks a ton guys!

 

[ArticCynda]

The method to increase RPM depends on the type of motor. Assuming it's a DC motor, increasing the voltage will also increase the RPM but at the same time lead to a higher power dissipation in the motor. Take measures to ensure the motor is sufficiently cooled.

 

[chuckey]

Its a single phase motor with a start winding supplied by the 9 MF capacitor. I suspect the IR block that does the speed control (two wires in and two wires out) is some sort of "cycle remover" .i.e. on full speed the motor gets 60 out of 60 cycles of the mains, at reduced speed it gets 40 out of 60 or 20 out of 60. The flywheel effect of the fan provides a flywheel action to keep it going, or it just reduces the voltage to the motor and as the motor struggles to rotate slows down.
Frank

 

[BradtheRad]

Rectify mains AC so it is DC.
Add a smoothing capacitor.
Send the DC through an H-bridge.
And you have an AC power supply, at any frequency you choose.



The rightmost scope trace shows that mains AC is 60 Hz, but the output is 80 Hz.

Square waves are easy to produce. However square waves are not the best waveform to power a fan. Therefore you may wish to add a filter, or modify the H-bridge, to obtain sinewaves.

- - - Updated - - -

It's hard to be sure which factor needs to be changed more, in order to increase your fan speed, whether it should be higher voltage, or higher frequency.

 

[D.A.(Tony)Stewart]

Hello!

What I am trying to do is increase the RPM’s of this fan motor.

You should learn quickly after graduating is that any design worth doing is worth documenting or follows a good spec. or least a measurable requirement to verify when done well.

Your spec is " a faster fan"

the fan draws 1.1A @ 120Vac 60Hz and is a shaded pole type. probably 2700~3200 RPM

Do you want higher air speed or volume flow or both? Then you need more power input with implied winding temperature rise.
DC Fans are more efficient but shaded poles are cheap reliable and quiet.

How is the squirrel cage fan air flow loaded? Do you want 1/8HP?

 

[chuckey]

The easiest way is to increase the supply voltage, but this will shorten the fans life. Borrow a mains to 12V 2 A transformer. Wire the 12 V winding in series with the 110V winding, apply mains to the 110V winding connect fan to free end of 12|V winding and the free end of the 110V winding. You will now have 110+ 12 V or 110 - 12V. Try out the fan, if its running slower, switch every thing off and cross over the connections to the 12V winding. Like I said you are not doing the transformer any favours!!
Frank