VFDs

Hi all, First of all, thank you all for your great support. I finally could find the problem. There was something wrong with the SD cards. My Unitronics dealer sent me a manual on how to initialize the card using Diskpart commands and it worked. Now the Unistream is archiving the samples and CSV files correctly. Thanks again and best regards. DaveB

I'll check with the team and get back to you 🙂  

I'll try to fantasize a little on this topic. You have an AC fan. There are two points in such devices. The first - the fan is guaranteed to start only after reaching a certain supply voltage. Second - by slowing down the fan you can go to a voltage lower than the starting voltage and the fan will still rotate. Therefore, I recommend determining the PWM at which the fan will start if you gradually add voltage. Conversely, determine the PWM when it stops when the voltage drops. I think that's all you need to know. By setting the adjustment within (minimum starting voltage + some margin) up to 100% PWM - you will have everything your fan can. However, in general, it is said that it is illogical to apply a voltage below 40% of the nominal voltage to the fan - because the fan no longer creates an air flow.

John, different motors need different speed controls.  I don't know the term "boxer" (you americanos not talking aussie) but perhaps it means shaded pole?  I doubt that it's going to work immediately without something else.  It's a bit of a minefield.  One of the reasons motors are hard is that the windings and the way they work is essentially an inductive device that generates all sorts of odd things.  Couple that with all the different starting methods and caps involved or not and it gets messy.  My first phone call is to the maker if possible.   Even then, my final hardware backstop for some speed control of motors that supposedly can't be done is multi-tap transformers.....a seemingly long forgotten method that's been replaced by electronics.....except they often generate hum that the tranny doesn't! However, put your clamp meter on the line at full speed, do some measurements and then play, starting at the lowest PWM you can and increase slowly.  See what the fan does and whether current draw seems odd for what is being achieved.  If it IS a simple motor then it might just work if the draw bears a linear relationship to speed.  If you have an infrared temp gun, check the motor body as well for anything odd compared to normal full speed running.  Don't forget that fans rely on the inherent flow over the motor to keep things cool.  Even though at slower speeds the motor should be using less power, sometimes it isn't enough flow to compensate. A zero-crossing ssr might also help, but you can imagine the conflicts involved if your pwm is not near the line Hz rate. You wanted a simple answer, but sadly not as easy as one might think. cheers, Aus  

Hey All, I'm playing with one of my home projects where I have a 6" "boxer" fan (120vac 85W) cooling some components. The fan is currently controlled from my PLC with a PNP output turning on a random crossing SS relay (AD-SSR810-DC-48R). I would like to slow down the speed of the fan, and seems it should be just a matter of adding HSO/PWM to the output? But I've not done this before, so before I let the smoke out of things here, I figured I'd ask for opinions... What do you'all think??