Need some help with coils in a centrifugal fan speed controller - Page 1
Forum section: electronics / beginners

author: Mientje
author_rank: Newbie
timestamp: November 10, 2021, 06:32:02 pm
content: I have a speed controller for a 1 phase AC motor (centrifugal fan).I know the type I have works on the motors I have, but I would like to have several more and I can't find the existing one I have.I made the schematic based on the one I have.It's base around a triac BTA26-600B.https://drive.google.com/file/d/1IerlQw6sJtgD3kznou2jTKDyvAf1HFuN/view?usp=sharingMy biggest hurdle are the two coils that are being used.1. The blue one, connected to mains, has two seperate windings,each 13 turns.Outer diameter= 25.4mmInner diameter= 14.5 mmwire diameter = 0.9mmcore section = 5.3mm width x 10.9 mm height2. The second coil is the yellow one, this one consists only of one winding around the coreOuter Diameter= 27mmInner Diameter= +- 15mmnumber of turns = +-46wire diameter = 1.2mmcore section = +-6mm widt x x11.3 mm heightWould someone be so kind enough two explain what the purpose is of both coils, and what their inductance/value is?The controller is rated at 230 Volts / 10 Amps

author: Jwillis
author_rank: Super Contributor
timestamp: November 11, 2021, 01:06:50 am
content: Being a novice a TRIAC myself I believe both coils are for filtering . The blue one is a common mode choke to filter noise , coming from the TRIAC circuit , from entering the supply lines . The second is a Radio Frequency Interference (RFI) coil to reduce radio noise .Maybe someone here can explain this better .

author: Ian.M
author_rank: Super Contributor
timestamp: November 11, 2021, 02:21:48 am
content: The yellow core inductor may well be to prevent commutation failure. See the section "(c) Exceeding the max rate of change ofcommutating current dICOM/dt" on page 12 of the collected Philips technical notes for Thyristors and Triacs, 1997:https://rmorais.utad.pt/RMPDFFiles/PDFDatasheets/SC03.pdfIts inductance can be measured with a LCR meter, and its DC resistance with a four wire ohmmeter. Determining its saturation current is a bit trickier . . .

author: Jwillis
author_rank: Super Contributor
timestamp: November 11, 2021, 06:46:25 pm
content: Quote from: Ian.M on November 11, 2021, 02:21:48 amThanks Ian . I learned something new . You're of course refering to rule #5 on page 13 ?

author: Ian.M
author_rank: Super Contributor
timestamp: November 11, 2021, 07:43:52 pm
content: Quote from: Jwillis on November 11, 2021, 06:46:25 pmYep.

author: Mientje
author_rank: Newbie
timestamp: November 12, 2021, 05:22:09 pm
content: There is an LCR meter on its way, so I will be able to measure the inductance. Is it right if I say that both cores (because they are colored) are powder iron cores?

author: Ian.M
author_rank: Super Contributor
timestamp: November 12, 2021, 08:22:38 pm
content: Unfortunately toroidal core color codes are not standardized, so you'd need to know the core manufacturer to be certain what the core material is. As the other toroid is a common mode choke, there's an appprox 80% probability that one is a MnZn Ferrite core.

author: Mientje
author_rank: Newbie
timestamp: November 13, 2021, 03:19:22 pm
content: Quote from: Ian.M on November 12, 2021, 08:22:38 pm1. So i desoldered the yellow/white coil. That's when I saw it was yellow/white and not just yellow.I used the online calculator on coil32.net:https://coil32.net/online-calculators/ferrite-torroid-calculator.htmlThis is a ferrite torroid calculator, but since I can put in the 'relative magnetic permeability', I guess I can also use it for the powdered iron versons.The measurement I got was 206 uH (micro Henry). When I put all the info in the calculator I got N=45.471 which is pretty close to the 46 turns I counted. So I guess this is a match.https://drive.google.com/file/d/1sstmN49_HmmVA_ZHYF9sKDb2TeS41o-8/view?usp=sharing2. For the choke coil (entrance main voltage) I measured an inductance of 1,615 mH.The highest permeability I could find was Amidon Material 75 (permeability 5000).That would give me the desired inductance with 16 turns (I counted 14).https://drive.google.com/file/d/12Pl-62Qw8fFAJW0ZM8b_Oyv5PyCue-59/view?usp=sharingAm I on the right track here?

author: Ian.M
author_rank: Super Contributor
timestamp: November 13, 2021, 06:33:42 pm
content: At the moment you are just guessing. You'd need to set up a jig to measure saturation current before you could specify an equivalent inductor with a reasonable expectation it would perform the same in-circuit.