phase firing angle formula for exhaust fan

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bagusdj

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hey guys. im trying to modify my exhaust fan using principal of phase firing angle. then i want to compare my experiment toward the theory.

to get the delay angle, i use this online calculator: http://www.sengpielaudio.com/calculator-timedelayphase.htm

then i found formula about pfa in this pdf View attachment pfa.pdf and use the formula (6).

why when i assign 90 degree for alfa, the rms is 155? is it suppose to be 110 right?

i live in a country with mains 220V 50HZ

my load is exhaust fan. is it inductive? resistive? or resistive capasitive?
 

RMS caluclations are onyl meaningful for resistoive loads, 155 V is correct in this case, 90° phase angle is half power or 1/√2 voltage, remember P = V²/R.

For AC motor drive, fundamental magnitude can be calculated as a first guess of phase angle control effect, you need to refer to fourier series. The relation to actual motor speed is much more complicated however.
 

i apply 5ms delay angle to my device, and i got 110V on my voltmeter screen. is this indicating what i am doing is already right? even when the formula gives 155V.
 

You have validated that your voltmeter measures rectified value rather than RMS and your circuit is most likely working correct.
 
is that means all of the voltage displayed on my DVM had to be divided by √2?
 

Not at all. The voltmeter will show the same reading as a true RMS instrument for sine waveform and different values for other waveforms.
 

i collect the average voltage after tested it 10 times each for particular delay(mS):
delay 5: 108.66
delay 4: 154.08
delay 3: 188.84
delay 0: 215.9

what would you say about these?

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updated:

i refer to this site https://elprojects.blogspot.com/2011/01/rms-voltage-control-circuit-with.html. it says the 110 is rms. in this case my 5ms delay is near 110. the formula on 1st post also said the vo is in rms too,but for 90 deg is 155. i dont really need to know actual fan speed. i just wonder, is there any formula to compared my work? (formula for phase firing angle using exhaust fan for load.)
 
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what would you say about these?
Click to expand...
Numbers like this are expectable with a non-RMS voltmeter.

it says the 110 is rms. in this case my 5ms delay is near 110. the formula on 1st post also said the vo is in rms too,but for 90 deg is 155.
Click to expand...
So obviously, only one of these can be right. I already told which one.
 

i think the result that i got and the pdf that i posted is different topic..

i found this picture in this forum

the graph said it is relation between power and delay. tahmid from edaboard said this graph can be used by assuming constant current. what would you say? im not so good with electric,i just dont get it how it can be right if current is constant?

example from the graph, 5ms delay= 50% power. assuming constant current , 5ms = 50% max voltage (220). im looking for 2nd opinion..
 

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