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I'm going to replace current resistor potentiometer with arduino-controlled triac scheme, probably this module.

I'm going to load it with 6 motors , 300W each.

  1. How bad the EMI gonna be (would I be able to plug audio amlplifier to the same line)?
  2. Would it substantially influence reactive power section of my electricity bill? I am located in industrial building in the country that has charges for reactive power.
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    \$\begingroup\$ Note that the dimmer module you linked is specifically designed for resistive loads, which motors are not. \$\endgroup\$ – uint128_t Mar 2 '16 at 16:25
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    \$\begingroup\$ @uint128_t I would think so too, but the description includes "or fan speed" \$\endgroup\$ – Gleb Mar 2 '16 at 16:27
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What are the risks of powering fan AC motor with Triac dimmer?

  1. The speed control may not work very well. Nearly all AC fan motors are induction motors. Induction motors are inherently designed to operate at a speed determined by frequency with very little controllability by voltage reduction. However, low-powered fan motors of the shaded pole and permanent split capacitor (PSC) type of induction motor can be controlled that way. Your 300 watt motors are a little larger than the usual motor (150 W or less) that is controlled that way and may overheat if they are not designed for that duty. They may also have a more limited range of control.

  2. Electronic voltage reduction distorts the waveform of the current drawn from the source.

I'm going to replace current resistor potentiometer with arduino-controlled triac scheme, probably this module.

It appears that you will need to program phase-back firing control for each fan. Have you considered that?

How bad the EMI gonna be (would I be able to plug audio amlplifier to the same line)?

You will need to design filtering to deal with the EMI

Would it substantially influence reactive power section of my electricity bill?

A distorted load current has an effect similar to reactive current and will reduce the total power factor, but not the displacement power factor. It is likely that the effect on the meter will be to increase the reactive section of the bill. The percentage increase may be small depending on other loads. The addition to the reactive power is not arithmetic, but proportional to the square root of the sum of the squares of the distortion current and the conventional reactive current.

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  • \$\begingroup\$ What do you mean by "phase-back firing control for each fan"? The program code for Arduino to delay opening of the triac after zero-crossing is ready for this scheme, and I'm planning to use it. Or do you imply that I need more complex algorithm like NXP's Single Phase AC Induction Motor Control Reference Design \$\endgroup\$ – Gleb Mar 3 '16 at 15:17
  • \$\begingroup\$ I mean conduction angle control or variable delay of gating after zero crossing. If you have the program code for that, you have simply to implement that for each fan. \$\endgroup\$ – Charles Cowie Mar 3 '16 at 16:51
  • \$\begingroup\$ The international standards for motor parameter identification call for the full-load output mechanical power to be marked on the motor rating plate. I have assumed that "6 motors , 300W each" are motor that will produce 300 watts of mechanical power. If you have motors that require 300 W electrical input and produce 150 W mechanical power, they are more in the range of fan motors that are commonly used with slip-control methods. \$\endgroup\$ – Charles Cowie Mar 3 '16 at 16:58
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It won't work because you need random turn on SSR for motor, not zero cross. Motors will constantly jerking.

EDIT: actualy I'm wrong, the SSRs aren't zero cross, rather the MCU has an input from zero cross detector on board, but without schematics I can't say more, but probably is going to work.

The opto triac is probably MOC3051 as seen from other boards of same brand, which is an enhanced opto triac to work with inductive loads. If problems can occur, you can still mount snubbers between L and outputs L.

  1. The EMI: you can install additional EMI filter on mains side if you will encounter problems.
  2. Nowdays a phase angle control is still widely used in industry. The phase angle control itself doesn't generate extra reactive power, rather it generate high order harmonics which can be eliminated with use of choke or filter.
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  • \$\begingroup\$ The module linked by the OP has TRIACs with random-turn on control. It just also includes a zero-cross detector that is exposed to the connected microcontroller (which means you'd have to implement the timing logic yourself). \$\endgroup\$ – marcelm Mar 2 '16 at 16:27
  • \$\begingroup\$ Universal motors can be speed controlled with triacs just fine, it's how most of the speed controlled power tools like drills, sanders, saws, grinders etc. are speed controlled. \$\endgroup\$ – jms Mar 2 '16 at 16:28
  • \$\begingroup\$ @jms But the board lacks of snubbers and probably the opto hasn't the aditional RC circuit on trigger side, used for inductive loads control. \$\endgroup\$ – Marko Buršič Mar 2 '16 at 16:32
  • \$\begingroup\$ Correct, OP's light dimmer isn't suitable for driving inductive loads. The triggering topology has nothing to do with it however. You misunderstand what zero crossing-delayed turn-on and random turn-on are: they are two alternate approaches to controlling the average voltage with triacs, with random turn on being the cruder, cheaper approach. See electronics.stackexchange.com/questions/18163/… \$\endgroup\$ – jms Mar 2 '16 at 16:33
  • \$\begingroup\$ @jms Where did you get this feeling that I misunderstood the difference between ZC and random, just curious. \$\endgroup\$ – Marko Buršič Mar 2 '16 at 16:38

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