Hello I have read many topics about fan speed control, but I can't tell what options I have in controlling this fan. Please, let me know if I can apply phase or group control here, or rather only the inverter is at stake. I care about the lowest possible RPM and to be able to control the RPM from the microcontroller. I have already tried with group control - however, the engine had clearly uneven revs (you could hear when it gets power) while with phase control it was possible to go down to low revs, however, the engine squeaked slightly and I do not know if it is the fault of the program or maybe I should not use such regulation in this blower .
I will not help you specifically, because I do not know the "Ventilation" industry. I have only minor attention to the phase regulation. As you know, for thyristor-triac triggering angles below 3/4 half of the power grid period, the input voltage of the receiver is a strongly distorted piece of sine wave. The smaller the angle, the greater the distortion and the more and more parasitic harmonics are generated. In my humble practice, most phase thyristor systems with phase control generated mechanical and acoustic effects. They were squeaks, humming, almost magnetostrictive vibrations of induction elements. The receivers had a power below 1000W - home appliances, e.g. light bulbs, food processor, some power supply with control in the transformer primary winding. Electromagnetic interference is a separate issue. If you wrote that at low revs you can only hear a slight squeaking engine, then maybe it is not bad at all. Of course, such a squeak should not be burdensome for living beings, and mechanical vibrations should not damage devices, e.g. bearings. My friend service technician-power electronics says that the most quiet and efficient are the so-called inverters, but you pay for it. On the other hand, power supply with phase control is relatively simple, possible to perform in "home" conditions. Despite this, the layout should be done carefully and do not skimp on filtering interference, otherwise life in the vicinity will become hell. It was supposed to be a minor remark, and talkativeness came out, for which I am sorry. Krzysztof Podstawa
I also know that in this blower the speed can be controlled to a really low level because I saw / heard how the Defro installed in the furnace works and it can spin very slowly there, but there are no strange noises and I doubt that there would be an inverter because the whole controller is quite small.
Phase control is normally used. I agree with my friend above, the phase regulation introduces a lot of interference if the appropriate filter (choke) is not installed in the controller. Most of the controllers for boilers that do not have them - with a blower operating at partial power, radio reception on medium and short waves is impossible, especially since these are disturbances conducted through the power network. And practically speaking, these blowers are a lime. Low engine power and high speed. It is necessary to slide down with phase regulation to be able to reduce the blower efficiency.
Thanks for the answers. As for the blower, the equipment is what it is and I would like to use what I have. Your answers show that I can use phase regulation - which also confirms a quick glance at the Defro controller. As for the audible disturbances (squeaks or engine humming) I did not observe them. I was able to look inside this controller for a moment but because of the construction of the whole system it is impossible to deduce. Rather, they certainly use phase regulation. At the blower connector there is a Pilkor capacitor on its line; 3,3uF; 305V AC, nearby is the 3062 opto-triac and the BT134 triac but I can't tell how it is connected to each other - I would have to screw up the controller strongly. Similarly, I did not see the choke there but I can not be 100% sure that it is not there. For now, my design is very simple Is it worth adding a capacitor in series after the triac at the output as in the furnace controller (will it help with blinking squeaks)? Where should I put the choke - on the microcontroller power supply or somewhere near the above elements?
In the search engine, under the key "triac triggering", various schemes appeared. Note those with RC filters (extinguishers) in parallel with the triac and chokes connected in series with the load. I think this is the minimum necessary to start designing and testing. In addition, the guides write that for stability, thyristors-triacs should be triggered by current pulses with good steepness of the front slope, appropriate amplitude and duration. Will such a simple optotriac key provide this? In industrial or semi-industrial systems, however, I saw separate generators, diacs or minimally switching diodes. Fact - a long time ago - thyristor bridges were common). KP
I read a bit but I'm still in the field. I tried to give the RC element - a 39Whm 0.6W resistor plus a 1uF 305V capacitor in series and the whole parallel to the triac (between 230V and the triac output on the blower) and with this connection the resistor starts burning. Is the culprit too large a capacitor or a too weak resistor? By the way, when I accidentally connected a capacitor without a resistor, the triac was damaged - here I don't understand a bit why the triac was damaged. I have found such a scheme
where is a similar RC circuit but the capacitor is much weaker (10nF) but I don't know what power the resistor is (whether 0.5W or stronger) and I see that the similar circuit is repeated a second time with a larger resistor and a larger capacitor although I don't know why items are 2 times.
In several publications that I reviewed, the parameters of the triac extinguisher for 230VAC were mostly similar. 10nF 630V capacitor. Resistor 39 Ohm and at least 2W. But I found this remark: "For highly inductive loads (power factor
For speed control, e.g. in heaters, autotransformers are used (the voltage for the fan is selected by a switch, it is a step control, typically 5 switch positions), the voltage supplying the fan is not deformed.
I tried with a 10nF 630V with a 39 Ohm 5W resistor and everything works OK - in the sense nothing burns. However, unfortunately this buzzing at low speed did not eliminate it. Regarding the autotransformer, the Defro furnace controller almost certainly does without it - I glanced at the controller a bit and as I wrote there is only electronics, besides the speed control is completely smooth from full power to very low speed and at almost low speed the fan can hardly be heard despite this, the engine does not hum.
Added after 1 [hours] 47 [minutes]:
And one more question: does such humming at low speed have any negative effect on the engine?
So, we would have a gasik implemented. The fire extinguishing system is the filter and protection of the thyristor circuit. However, a separate filtering system is needed for the receiver. Buzzing at low speed results from the shape of the current in the receiver. The "cut off" piece of the voltage sine wave, for angles below Pi / 2, more and more resembles a triangle shape. Ripples of the first harmonics are not negligible, and the currents in circuits with inductances already quite differ from smoothness. In my opinion, a good quality motor should handle this shape of the supply voltage and hence the currents in the windings. In addition, it is an AC voltage motor, i.e. even such triangles should have an average value close to zero. However, the use of LC (more precisely LCL) filters on the receiver may make sense, despite the fact that the motor winding with a magnetic tape can be considered a filter choke. The parallel capacity in the filter discharges some of the harmonic voltages back to the source, thus reaching the receiver with less energy. A few months ago, I read a post about Triacs on Elektroda, and something I didn't know about it. Well, the real characteristics of triacs are not perfectly symmetrical, which means that a DC component can be created in such a switched circuit. This is not good for the power supply or receiver because of the permanent magnetization of the core and entry into the more non-linear part of the characteristic. This can generate additional current distortions. Therefore, good quality triacs or thyristor systems must be used, because thyristors can be paired well. I could have twisted something, so possibly look for this thread. Krzysztof Podstawa PS. I found the forum "ventilation-heating", and in it a similar topic on blower speed control. I was looking for information about LC filters. Well, I didn't write electrons heresy, but times are newer than my knowledge. The practitioners there were not phase lovers, but inverters. They advised to check with the blower manufacturers whether the characteristics of the currently produced motor-blower assembly allow for phase control. I will not provide a link so that it does not turn out that I am infringing any copyright or market competition rules. KP
And one more question: does such humming at low speed have any negative effect on the engine?
It can reduce durability, but not much, the bearings will sit down earlier. Blowers should theoretically have better motors for phase control (more compact sheets and windings), but as it is in practice - it varies. As you are already experimenting and want the highest quality of the product, it is probably better to go towards the pseudo inverter - i.e. rectify the mains voltage and enter rectangles (pwm) with the filling fill in accordance with the sine wave, at a few kHz it is easy to filter such a signal and it will be almost like a sine at a changed frequency. It would be a challenge to develop such a system, but the engine would have what it likes