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Selsyns 1

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buzzp

buzzp

Electrical
Nov 21, 2001
2,032
Anybody rememer 'selsyns'? The little synchronous motors made by GE used to transmit position or torque to another device (ie another synchronous motor so both would be in same position). Anyway I have dug up some info on these and heard claims that there is a product that accepts the signal (position) of these little guys to display the position on something more modern. I do not claim to understand these entirely but I gather they have 3 windings and hence 3 signal wires to be sent to another motor to properly position the motor. I am trying to find the device that accepts this position signal (3 wires) and displays it in a digital format. Anyone help?
GE site has some info and maybe they make a digital display but I was not able to find such an animal. If no luck here, I will have to call them (hate calling into GE's web of phones). Thanks

 
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How much accuracy do you need ? 60Hz ? How accurate in your line imput ?

<nbucska@pcperipherals.com>
 
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What I am trying to do, perhaps temporary, is to just have the position displayed on a digital meter rather than the analog unit it came with. The unit is powered with 115VAC 60Hz. I believe the accuracy of the unit is +-1 deg or it could be +-5 deg. The literature I have is not very clear and it was printed in the sixties. The meter could be powered with line voltage or DC voltage. We currently have 115VAC, 5VDC, and 125VDC available.

I will likely change out all these dated systems. Just now sure how quickly. I will replace them with absolute resolvers.
 
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The digital display:

1.) using 0-cross detector and high frequency counter.
Use the 3 input phases as reference and convert these
and the secondary to logic level square- wave.

You may improve accuracy by filtering the inputs.

2.) Use one or more analog multiplier(s), multiply the secondary with a phase used as reference, integrate for one period and convert it do digital.



<nbucska@pcperipherals.com>
 
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Not sure I understand what your saying Nbucska. These units have single phase 120VAC inputs (60Hz). The 'output' is on three wires (assumed to be used to move the motor hooked to this 'output' to the same position as the sending unit/motor). I really don't want to design a display. Was really wanting something off the shelf. If I have to desing something, I might as well spend that design time researching replacements for the whole system.
I did find this link after posting my original post that makes me hopeful there is a digital display. It also has some dwg's of what is going on. Although, it is concerned with torque, I beleive most principles apply.

Thanks
 
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I think you are after a syncro to digital convertor with display. The devices supply the R1-R2 reference and read the s1,s2,s3 and display and angle. I have see these before but do not know who makes them. The last time used them they where built into VMEbus cards. You need to
know if yours is single or dual speed. I think below is a company that sells them as plug ins for a computer.
 
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It looks like the above link does advertise the converter with digital display +488 bus!
 
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Thanks, I will check it out. Mine is single speed and it is very dated (60's).
 
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A selsyn consisted of a wound rotor
and as you said three distibuted coils on the stator connected in star with the other ends brought out to terminals.

A Ac volage was applied to the rotor which induced voltage in the stator. The Amount of voltage induced in each stator
winding being proportional to the rotor position.

If you conected the stator windings of one selsyn to the stator of another selsyn and then applied voltage to both
selsyn rotors the shaft of the remote selsyn would follow
any movement of local selsyn
 
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Thanks for all the info. I have found what I need from some companies I found on my own and some suggested above. Now to find the best for my app.
Selsyn is a trademark name used by GE to describe a synchro as suggested by IR.
 
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