Switched reluctance motor driver? - Page 1
Forum section: electronics / projects

author: liquibyte
author_rank: Frequent Contributor
timestamp: January 03, 2014, 09:53:17 pm
content: I've got this motor I believe to be a switched reluctance type. Four wires with varying resistance between all of them but definite continuity. I had previously asked about this over at CNCZone but never went further than identifying what it was. What I'd like to do is throw together a circut to get this thing rotating but really don't have any specs on it. What I do have is what's printed on the motor and a few pictures I took years ago. Anybody have any experience working with these types of motors or seen one like this or have a circuit to drive one of these? It's got a gearhead on top of it that comes off easily enough if needed to minimize starting torque.Code:80045/188469-26834000531SERIALCEDAR ENGINEERING DIV.CONTROL DATA CORP.SYNCHRONOUS MOTOR - GEARHEADTYPE NO. SYG18016

author: Feanor
author_rank: Regular Contributor
timestamp: January 04, 2014, 03:30:50 pm
content: I would start by taking it apart if possible.If you do then please take more pictures.

author: liquibyte
author_rank: Frequent Contributor
timestamp: January 04, 2014, 03:52:17 pm
content: Sorry for the crappy quality, it's the only camera I have and it doesn't do pictures very well.

author: Kremmen
author_rank: Super Contributor
timestamp: January 04, 2014, 07:16:36 pm
content: Well, Control Data Corp passed into history a long time ago, so you won't easily find documentation about their stuff.Since it plainly says "synchronous motor" and there are 4 wires, then let's assume it is one and there are 3 phase leads and a neutral. What specifically lead you to think it was anything else?To make more certain, can you check the resistances to find out if there actualy is a central neutral wire? It means that you should find 3 leads with resistance R between any two, and one wire with resistance ~R/2 when measured against any of the previous three.

author: liquibyte
author_rank: Frequent Contributor
timestamp: January 04, 2014, 07:55:01 pm
content: This thing has been amusing to say the least. I can't figure it out but I also don't have a lot of experience with motors.54.6 ohms = Black-Green & Red-Green42.8 ohms = Black-Red32.6 ohms = Black-White & Red-White22.6 ohms = Green-WhiteBear in mind that my multimeter isn't the best so these readings may be a bit off but probably are close enough. The ohm symbol comes out as ?

author: calexanian
author_rank: Super Contributor
timestamp: January 05, 2014, 07:29:26 am
content: Thats a synchro motor. One winding is directly connected to AC and the other side via a capacitor to set up the phase shift. You are missing all the important data there such as voltage and capacitor value.

author: Kremmen
author_rank: Super Contributor
timestamp: January 05, 2014, 09:50:41 am
content: I agree. The numbers would suggest that white could be a common wire and black and red phase wires. Then a single phase motor would be connected so that N goes to common, L into one phase and via a phase shift cap into the other phase. Depending from which phase wire gets the direct voltage, the motor turns this way or that. I have in my CNC mill a couple of this kind of motors from Oriental Motor to drive e.g. the tool magazine.But what the green wire is then supposed to do escapes me at the moment. Unless there is an extra winding to excite something but what. Or it could be for voltage selection...The 42.8 ohm value between black and red looks a bit fishy. Are you sure? (see the diagram below - by naive calculation the resistance should be 65.2 ohms). If your original measurement is accurate then there is something else going on and the internal connections cannot be just coils connected in a star.https://www.dropbox.com/s/wc7tuslgx5yqnmm/Circuit%20-%20Page%203.png

author: woodchips
author_rank: Frequent Contributor
timestamp: January 05, 2014, 10:55:22 am
content: I agree, looks like a standard 2 phase 400Hz servo motor to me, size 11 with body about 1.1" in diameter?One winding connects to the fixed 400Hz, can only be 115V, and other winding is at 90 degrees phase shift and varies from 0 to about 20-30 volts 400 Hz giving the speed.The four windings are two for motor, two for tachogenerator. Similarly one connected to 115V 400Hz, the other will give a voltage proportional to speed.Which wires are which is easiest sorted by looking at the stator assembly.

author: liquibyte
author_rank: Frequent Contributor
timestamp: January 05, 2014, 03:26:24 pm
content: The resistance measurements are correct. I've measured twice, several years apart with two different meters. It's 1.75in in diameter. I can tell you that the windings are all electrically connected, or at least I believe so. I can measure a voltage across any two wires when spinning the shaft and connecting them gives the usual shaft resistance. The motor came in an assembly with gears and encoders and was originally an aircraft part. I'd like to try and get this thing spinning. Anyone have any ideas how to do so simply?

author: Zero999
author_rank: Super Contributor
timestamp: January 05, 2014, 05:25:58 pm
content: Aircraft normally operate at 115V 400Hz so you need an inverter to convert the 60Hz mains up to 400Hz.

author: liquibyte
author_rank: Frequent Contributor
timestamp: January 05, 2014, 05:42:10 pm
content: I do remember a thread here somewhere talking about 400Hz aircraft frequency. I'm starting to think this thing might just not be worth trying to get running. I'll hang on to it and play around with later on I guess. The usefulness of 400Hz to me isn't enough to be worth the bother of building something that I have very little need for, at least right now. I had thought of using this for a pcb drill or something but, given that I don't really have specs for it, I'm not sure it's feasable.

author: calexanian
author_rank: Super Contributor
timestamp: January 05, 2014, 06:14:06 pm
content: I do not believe its 400hz. It looks like a standard synchro motor. Are the two coils completely separate? If they are thats a dead giveaway. they do that so you can reverse polarity of one of them thats fed with the cap to change directions.

author: liquibyte
author_rank: Frequent Contributor
timestamp: January 05, 2014, 06:30:44 pm
content: Quote from: calexanian on January 05, 2014, 06:14:06 pmI get continuity between all four wires so that can't be it. I wish there were a way I could test this but I have no idea how other than just unwinding the thing to see how it's made.

author: calexanian
author_rank: Super Contributor
timestamp: January 05, 2014, 07:25:40 pm
content: Continuity from all 4 wires. Hmmm..... Could be a 3 phase synchro with one being the middle. Those were common in some systems.

author: calexanian
author_rank: Super Contributor
timestamp: January 05, 2014, 07:29:00 pm
content: I might just try putting 12vdc on it and twist the shaft and see what it felt like, then try the same with 24vac and give the shaft a spin. If it keeps spinning its just a regular old AC motor with many taps. If it just sits there or feels like its stuck there its a synchro or other type of polyphase or similar type.

author: liquibyte
author_rank: Frequent Contributor
timestamp: January 05, 2014, 07:50:24 pm
content: Quote from: calexanian on January 05, 2014, 07:29:00 pmHooking up any two wires results in the shaft not being able to be rotated by hand at 12VDC. I've got a 25.2 RS center tapped transformer that should work ok. I'll do that test later on because I have to build a nice way to hook everything together without holding the wires by hand.

author: SeanB
author_rank: Super Contributor
timestamp: January 05, 2014, 07:55:18 pm
content: If it is an aircraft part it will be a 400HZ part, never anything else or it will be 28V and have brushes in it. You might have a 4 wire maths part, there are some that do sine/cosine conversion, addition and such operations. Hard to say without a spec sheet.Making a 400Hz inverter is very easy. Just take a regular 115V transformer and run it in reverse feeding the secondary with it's rated voltage at 400HZ. I did that as a quick and dirty inverter, using a 115VAC to 12V transformer and using a 555 timer to drive it via a 2N2219 and some tuning caps on the primary side. 1uf IIRC was fine to get close to a sine wave output. Transistor ran a little warm but otherwise fine with a clip on heatsink.

author: liquibyte
author_rank: Frequent Contributor
timestamp: January 05, 2014, 08:30:33 pm
content: Hooked it up to 25VAC and it spins. It does not matter which leads I use, it spins regardless. Cool beans.QuoteKnowing what I just found out, would the frequency matter? I'm assuming that to drive this thing correctly that some sort of phase transitioning would have to be done between the coils to make it opererate within its specs. Now that I've gotten it turning, I'm intruiged. I'll bet with the gearbox on this thing, it would make a great pcb drill.

author: SeanB
author_rank: Super Contributor
timestamp: January 05, 2014, 08:38:36 pm
content: Those generally require between 100-130VAC at a frequency between 380 to 420HZ to operate at full torque. With lower voltage you can drop the frequency, but if you are going to use 50/60Hz you are limited to 12V maximum to prevent core saturation.Attached is a 115VAC 400Hz variac, but it is limited to 12VAC at 50Hz otherwise the magic smoke will leave. I use it as an adjustable AC source.

author: liquibyte
author_rank: Frequent Contributor
timestamp: January 05, 2014, 08:51:31 pm
content: Quote from: SeanB on January 05, 2014, 08:38:36 pmThanks for the help. I'll see if I can get something working at 400Hz and around 120VAC or so and see how it goes. The gearbox should give this thing some nice torque with the right power going to it. I think I'll try and make a tiny drill press out of this.

author: Zero999
author_rank: Super Contributor
timestamp: January 05, 2014, 09:34:24 pm
content: Quote from: liquibyte on January 05, 2014, 08:30:33 pmAt 60Hz it will run at 62/3of the speed.

author: liquibyte
author_rank: Frequent Contributor
timestamp: January 05, 2014, 09:55:03 pm
content: From what I've been reading, the most I should put through this at 60Hz is <=15VAC or risk damage. The thing that's giving me fits is whether or not I'll have to figure out a three phase system for it. I have exactly 0% experience with this type of thing and am having trouble finding circuits. I may be using the wrong search terms. If this is three phase, wouldn't I have to power each leg 120 degrees out of phase with the others more or less?Look what Ifound. I'm not even going to ask about your status there.

author: liquibyte
author_rank: Frequent Contributor
timestamp: January 05, 2014, 10:47:18 pm
content: I've foundthispage that has a circuit to take 12VDC to 115VAC @ 400Hz. Could someone a bit more knowledgeable than me have a look at this circuit and let me know what you think?Edit: Found a 3 phase version too.

author: calexanian
author_rank: Super Contributor
timestamp: January 05, 2014, 11:42:08 pm
content: Many ac motors were 24 volt.

author: liquibyte
author_rank: Frequent Contributor
timestamp: January 06, 2014, 12:20:28 am
content: Quote from: calexanian on January 05, 2014, 11:42:08 pmLooking around I found a similar looking motor onEbay. They're calling it a "SYNCHRO CONTROL TRANSFORMER 5RS901-1A SINGER KEARFOTT 11.8VAC/22.5VAC 400HZ" but it looks like a motor to me. I don't understand the stator input 3 phase 11.8V and rotor output 1 phase 22.5V on it. I may have to open mine back up and remove one of the snap rings to see what that looks like inside there.

author: liquibyte
author_rank: Frequent Contributor
timestamp: January 06, 2014, 01:14:56 am
content: I did a bit of a test and the white-green pair hooked up to the 12VAC has the most torque.I'd rate from 1-3 the amount of torque delivered per pair (3 = highest) as:1 = black-green, red-green, black-red2 = black-white, red-white3 = white-greenThe last one has enough torque that I have to grab the shaft fairly hard to stop the motor.