Odd two-phase induction motor in aerospace gyroscope, need help understanding - Page 1
Forum section: electronics / beginners

author: Haatveit
author_rank: Regular Contributor
timestamp: June 20, 2018, 11:31:01 pm
content: I got my hands on a Soviet era gyroscope, similar if not identical to a type used on the Soyuz spacecraft, among many other things. See attachment image. I might post more about it elsewhere when I figure more out, it's a fascinating piece of hand-built, hand-tuned gear that's for sure. My hope is to figure out how it all works, and maybe make it do something interestingFor now, I'm trying to work out how some of the motors on it work. One of them was burned out / broken, and I'm trying to locate a replacement. If anyone in Russia or Ukraine feel like helping me, I'd appreciate it - I can find replacement motors there, but I can't order them, partly because I don't understand anything....!Meanwhile, I need to understand exactly how this motor (there are 2 of them in the gyroscope) is supposed to function.... It doesn't seem to be obvious. It's also incredibly hard to find information about this that isn't written in Cyrillic, so if anyone can read it clearly, feel free to help with that too!Here is the schematic for the motor (I can confirm that the motors are wired exactly this way):I was expecting a "two-phase" motor to have two separate windings, driven out of phase. The technical information I found seem to suggest exactly that. But I am woefully unfamiliar with these types of things, I admit complete cluelessness when it comes to magnetics and motors and all that type of jazz.Some info about the motor here.But as the two main windings seem to be connected in ... series? And there's a tertiary winding (This must be the "control winding" they refer to).This is a very small motor for what it's worth:

author: Dubbie
author_rank: Unknown
timestamp: June 21, 2018, 01:17:50 am
content: Just asked the Russian here at work and she said that the type on the schematic simply says:it is 'designation/name of the exits'

author: amyk
author_rank: Super Contributor
timestamp: June 21, 2018, 01:37:00 am
content: This video shows the inside of one along with some driving circuitry. Unfortunately, no explanation:Here is an article with more information and driving circuitry:https://ingeneryi.info/shemy/prochie-shemy/1748-400-gercovyy-generator-dlya-pitaniya-elektrodvigateley-did-05.html...and even more schematics:http://ttonons.appspot.com/did-0-5ta-shema-vklyucheniya.html

author: wasyoungonce
author_rank: Frequent Contributor
timestamp: June 21, 2018, 02:34:39 am
content: Haven't really had a good look but maybe a "fast erect winding"...to position the motor to a known start position.

author: Haatveit
author_rank: Regular Contributor
timestamp: June 21, 2018, 03:48:04 am
content: Quote from: wasyoungonce on June 21, 2018, 02:34:39 amThis would make a lot of sense in a gyroscope application, I'll keep that in mind. Although there are feedback potentiometers as well so they may not be using it that way.Quote from: amyk on June 21, 2018, 01:37:00 amThose are great links, thank you! I'll sit down and try to figure this out once I have time.I have a pair of pretty beefy general purpose amplifiers that I hope to be able to use to power these. I'll generate whatever I need on my arb gen, and amplify that to the voltages (and currents obviously, the arb gen can't do much there) I need. Should be interesting

author: Jwillis
author_rank: Super Contributor
timestamp: June 21, 2018, 03:49:08 am
content: Wouldn't they be used for steering ? By changing the pitch or yaw of the gyroscope you essentially steer your rocket , satellite or space capsule. Roll is controlled by slowing or speeding up the flywheel. so the motors would be used as steppers. Just a guess mind you.

author: Haatveit
author_rank: Regular Contributor
timestamp: June 21, 2018, 04:23:01 am
content: Quote from: Jwillis on June 21, 2018, 03:49:08 amThis is a sensor unit, pretty much like an artificial horizon. Similar in design to many western ones in that regard. There is a gimbal limit of around ~75 degrees on this one.What you are thinking of are reaction control wheels - and they require a near perfect vacuum to work, and usually spin at a couple thousand RPM nominally, and usually have no gimbal limits (continous rotation in all axes). Reducing / adding speed to the wheels cause the spacecraft to change orientation in another axis (torque applied at 90 degrees off the gyro axis). Although they are also gyroscopes essentially, but very different mechanism for a different purposeI know the exact purpose of this unit itself, but it's the internal parts that I'm trying to understand, and failing to do so

author: woodchips
author_rank: Frequent Contributor
timestamp: June 22, 2018, 06:05:38 pm
content: Looks like a standard size 11 servo motor to me. Search for two phase servo motor, lots of info around. Probably runs off 400Hz, so don't try 50/60Hz, will burn it out.

author: jmelson
author_rank: Super Contributor
timestamp: June 22, 2018, 07:00:13 pm
content: OK, these things typically have 3 motor-like components. One is the main gyro motor (or may have several gyros mounted orthogonally on a stable platform). Then, on the gimbals, they will have resolvers and torque motors, which will look awfully similar. The resolvers will have a wound rotor, however, driven either by slip rings or a rotary transformer. The torque motor will be an induction motor, and thus NOT have windings on the rotor. (It will have shorting bars, however.)Complex inertial nav stable platforms may have gimbal locking motors or motors to turn the outer gimbal 90 degrees to accomplish alignment from the earth's rotation. And, I know NOTHING about space-based inertial nav systems, which probably get a lot messier (no earth rotation for alignment, and needs to run for months or years, using star nav to correct for drift.)Jon

author: Haatveit
author_rank: Regular Contributor
timestamp: June 22, 2018, 08:18:23 pm
content: Quote from: woodchips on June 22, 2018, 06:05:38 pmThanks, I'll have a look for that! And yes, I am running these things off of my function generator via a pair of amplifiers to get the correct frequency and voltage. Most aircraft avionics I've seen run off of 400Hz so I assumed these ones did too, and judging by old datasheets it looks correct! Good caution either way though.Quote from: jmelson on June 22, 2018, 07:00:13 pmThanks, interesting insight on these. So far I've located a plethora of large induction motors, with big huge diameters and windings. See attached pictures. I have no idea how to drive these, but that'll be something I work out later on I guess! I've managed to find the actual gyro mass itself, and it's motor - it's embedded in a vacuum chamber, looks kind of like a vacuum tube, but it's only similar in the sense of vacuum. Anyhow, there are at least 3 more large induction motors in the unit, neither of which I have any clue what they are forThey have a lot of wires going to / from them, so I guess it's more complex than the motor I posted originally about.The motors I'm asking for here though are, as far as I can understand, part of a self-correcting mechanism in the gyro, and play a role similar to a regular small DC motor, just these are more controllable I guess. It's hard to find info about this model of gyro, but I originally thought these small motors were for some kind of cockpit control - but from what I've managed to find about this model of gyro, I appear to be wrong! They are part of some kind of automatic self-correcting mechanism.If anyone is curious, the gyroscope is marked 'ГА-1М СЕРИЯ2' which translates to 'GA-1M series2', if I remember my Cyrillic correctly.

author: tpowell1830
author_rank: Frequent Contributor
timestamp: June 22, 2018, 09:26:42 pm
content: Could these motors be synchronous motors? They are used when you need very precise rotational speed. Unlike regular induction motors with torque established due to slip, these motors turn exactly at the input frequency as a function of given poles. Perhaps someone who reads Cyrillic could read the comments in the video and get a clue.Hope this helps...

author: Haatveit
author_rank: Regular Contributor
timestamp: June 23, 2018, 01:39:46 am
content: Quote from: tpowell1830 on June 22, 2018, 09:26:42 pmYou could very well be right. I managed to trace out the motor winding wires and they actually break out at the big huge military style connector on the housing of this unit, so either they wanted to drive them directly (these synchro-looking-ones), or they did some kind of sensing.Precise rotational speed sounds a lot like something you would want in a device like this.

author: amyk
author_rank: Super Contributor
timestamp: June 23, 2018, 03:00:57 am
content: The large "motors" are actually positional sensors:https://en.wikipedia.org/wiki/Resolver_(electrical)

author: Haatveit
author_rank: Regular Contributor
timestamp: June 23, 2018, 05:16:09 pm
content: Quote from: amyk on June 23, 2018, 03:00:57 amNow I feel stupid.You are right! And it makes a lot more sense, one for vertical, one for horizontal.. I guess for some reason I thought they were for adjustment or pointing of the gyro cage.

author: SeanB
author_rank: Super Contributor
timestamp: June 24, 2018, 05:50:23 am
content: Gyro drive will be 400Hz 3 phase, either 115VAC or 26VAC, as the precise speed of the gyro is not too critical, as it runs in a vacuum the slip will in any case be nearly zero after run up. The split phase motor and clutch driving a gear train will be for alignment of the gyro axis, as it will allow the cage to be rotated to a new fixed position even with the gyro running, allowing you to set the initial pointing direction of the whole unit after power up.From the looks of the wires your unit uses 115VAC for the gyro power, but the rest use 26VAC for all the resolvers and such. The enamelled copper windings are too thick for 115VAC, and most resolvers are 26VAC anyway, along with the synchro displays, and in any case almost all the synchro to digital converter blocks ( mostly you will find them marked Teledyne and potted in a block with a big blue top label giving pin out on there) accept 26VAC directly along with a reference 26VAC clock input.

author: Haatveit
author_rank: Regular Contributor
timestamp: June 24, 2018, 05:12:54 pm
content: Quote from: SeanB on June 24, 2018, 05:50:23 amThanks, very useful!Although I doubt I'll find anything marked Teledyne in this 70's Soviet era (design) gyroscope (;I've found that they liked to do things their own way, with little or no interest in how things were done in other areas of the world at the time, which is one of the things that make these old beasts so interesting. Although obviously a lot of things end up being very similar since, usually, there are only a limited number of ways to successfully achieve what you want.