Hello.
I have a mains(230VRMS 50Hz) driven fan and it's speed is controlled by a digital fan-speed controller that implements phase control with a Triac, the problem is that this speed-control technique is creating a lot of noise in the motor. I am not bothered by the noise that the air moving through the fan is creating but that buzzing weird noise that the phase control is creating is a big problem and I want to get rid of it. Others have told me that the only option to a digital fan-speed controller is to use a Variac which I simply refuse to believe to be true,sure I could get a Variac and mounting on a stepper motor to turn the shaft or something but that doesn't make a lot of sense.
I have read a lot online but no I can't find more than loosely described schemes but it sounds to me as I should be able to use a controlled rectifier(or even the same circuit that is used in a Triac phase control) together with a capacitor/filter to create a adjustable crude DC rail that would adjustable between pretty much 300VDC and 0VDC(probably not 0V but some very low voltage).
Then I want to feed that DC voltage to an inverter that would chop it up into AC and create a sinewave such as a pure sine-wave inverter or even modified sine-wave inverter though I really would prefer a pure sine-wave inverter since maybe a modified sine-wave inverters output waveform could possibly also produce some noise?
I don't know a lot about inverters but if I had a inverter with a output that was classified as a modified sine-wave, then I could use a filter to filter it into a 50Hz "pure sine-wave" right?
But I can't find any clues as to how to construct a inverter who's output amplitude is dependent simply on the input DC voltage amplitude.
The fan in question a rated for: 230VRMS @ 0,13A or 30W, so the inverter current output doesn't have to be very high but it would of course be a good idea to over-dimensions the circuit to maybe 0,5A or something(depending upon what that would require in terms of circuit & components), 0,15A would be fair enough.
Question 1:
Would a simple single Triac + filter circuit connected to the 230VRMS mains be sufficient to generate an adjustable(actually programmable) <=300VDC or do I need to use something like 4 SCR's in a rectifier bridge configuration?
Question 2:
Can you imagine a DC-AC inverter that features an output amplitude that's dependant upon the input DC voltage amplitude?
If so can anyone suggest to me which topology I should look into first or any other directions to give me?
If anyone have a better idea(simpler/easier to implement) for achieving an adjustable sine-wave voltage that can be programmed as high as or close too 230VRMS?
Even though I know very little about inverters I have some knowlagde about them although my interest are mainly focused around AC-DC or DC-DC SMPS, a single Triac phase control circuit is easy to make and program with a microcontroller and from what I have seen a controlled rectifier isn't that much of a leap from there, but I would very much like to get some thoughts about this idea before I dive into the prototyping. I'm sure I am capable to figure this out with some advice.
I hope you all are having/have had/going to have a very nice day.