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Darkwood

[ElectriciansForums.net] Mystery Item thread.... What am i?[ElectriciansForums.net] Mystery Item thread.... What am i? This is out of an old Russian lathe it has 4 contacts on it 2 x NC and 2 x NO it has a coil and on top it has a sealed oil filled reservoir.
What is its function!

Spoiler alert!!! Answer in post 9!!!
 
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As its multi-tapped windings i assume this is maybe used for selection of speed in some way ...as noted theirs a rectifier on the right, adjustable resistors above .... but without seeing what is used to select speed its a wild guess.

Is the speed selected by a multi position switch or by a pot'

Yep! il say its the old fashio speed control..... just pre-set speeds using the adjustable resistor rods.... ???
 
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The speed is controlled by a pot. AFAIK none of the windings is tapped, they are just five separate windings. The selenium rectifiers are related to the mystery item and they are the only semiconductors in the speed controller.
 
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Nope, the power supply transformer is to the right of the DIN terminals. The windings on the mystery device connect to the speed control pot, the main motor, a DC supply, the AC control supply, and one field winding of the cross-field servo-generator on the M-G set via the rectifier.
 
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Thats a cracker bit of kit there. Old gear is cracker. Us, being men, like taking things apart...and seeing what some old things like leccy gear is really interesting, even if it is confusing. A good example is Microwaves.Years ago, built with a nice high voltage transformer in them , made in england,now, replaced by "inverter technology" crap , made in china, and the old microwave will outlive the new one by 30 years. Its interesting to see how things have developed and moved on though, and a small lightweight circuit board has the same capabilities of a heavy, copper wound transformer.
 
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Well it's lasted 56 years so far, I've tickled up a few relay and contactor contacts in the last dozen years, changed the brushes and one resistor and that's about all. The rectifiers were replaced in the 1970s. When the machine moved premises a few years ago I did think about putting on a VFD to save having to install the Ward-Leonard set but as it works perfectly it seemed a shame not to use it.

Final clue for the evening - see the pic of the M-G set on which I have labelled the four units. The cross-field machine amplifies the servo demand signal but it's not sensitive enough to give good closed-loop control from the pot output and a small feedback signal. That's where our mystery device comes in.
[ElectriciansForums.net] Mystery Item thread.... What am i?
 
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Signal amp' or some kind of damper to stabilise speed then if your speed ref is't accurate enough the motor can cycle up and down with speed chasing its self ....
 
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Signal amp
Click to expand...

Bingo! Not wild guesses at all... It's a magnetic amplifier. The core is magnetised to half its saturation level by a winding carrying DC. The speed pot sends DC through another winding, the feedback circuit sends DC through a third with opposite polarity, so the steady flux level represents the difference between the two. The degree of saturation controls the power transfer from the AC energising circuit to the rectifier, which produces a DC output to excite the servo-generator, which in turn controls the main generator field and hence the output fed to the spindle motor. 7 hp of stabilised speed control without a thyristor or transistor in sight.

Lucien
[ElectriciansForums.net] Mystery Item thread.... What am i?[ElectriciansForums.net] Mystery Item thread.... What am i?
 
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Lucien Nunes said:
Bingo! Not wild guesses at all... It's a magnetic amplifier. The core is magnetised to half its saturation level by a winding carrying DC. The speed pot sends DC through another winding, the feedback circuit sends DC through a third with opposite polarity, so the steady flux level represents the difference between the two. The degree of saturation controls the power transfer from the AC energising circuit to the rectifier, which produces a DC output to excite the servo-generator, which in turn controls the main generator field and hence the output fed to the spindle motor. 7 hp of stabilised speed control without a thyristor or transistor in sight.

Lucien
View attachment 20032View attachment 20033
Click to expand...



yeah, just like the hadron collider. lucien, you obviously have no idea what you're doing and i would suggest that you stop now. how are you going to explain your actions when you produce a super-duper massive blackhole that swallows the entire universe??
 
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Lucien I know that germanium rectifier looks the part but if it’s in use get rid of it (hide a silicon bridge behind it). I had several burn out, the brown smoke that comes out of them is both toxic and a cacogenic.
PS it tastes foul!
 
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