VARIAC? With valves!

[(*steve*)]

I just came across this rather interesting piece of equipment. I claims to be a VARIAC, but it's not like one I've seen before.



It has no controls other than an input lead and an output socket. Oh, and a power switch.



Inside, it's more interesting



Three tubes, what looks like a large selenium rectifier, and...



...a collection of passive components. And, a bunch of transformers



Three transformers, one of which is probably the power supply for the electronics.

Ok, it's clear that it regulates the output AC voltage for a reasonable range of input AC voltage.

Anyone know how these work?

Time for some googling me thinks.

 

[crutschow]

That certainly is not a Variac as the term is now used (for an adjustable autotransformer that allows the output voltage to be varied).

From the label, it appears to give a stable 230VAC output within 0.15% (!) for a 200-250VAC varying input voltage from the mains (which was probably typical of early main's voltage variations).

Notice that it's rated for 40c/s(Hz), which has probably not been used as a power line frequency for a century.
Is there a date anywhere on it?

As to how it works, that's anyone's guess.
It might use some type of saturable reactor which has a DC control winding to adjust the saturation point and thus the output voltage.

 

[Nanren888]

not been used as a power line frequency for a century.

The Claude Lyons Group was founded in 1918 ....
Might be right
Search on their site for the part number did not return any hits.

 

[(*steve*)]

I've sent an email to them with a couple of photos. Maybe they'll get back to me.

 

[(*steve*)]

...And Thanks to Martin of Lyons Instruments, I have a little more information:

This was a early type of Voltage Stabiliser manufactured by Claude Lyons prior to the Servo Mechanical designs.


Very interesting to see this although I am sure I have seen pictures of it on an old Claude Lyons catalogue but I cannot be sure of the date.

 

[MHW]

Steve I have some further information regarding the device. The device is a BAVR-200 electronic stabiliser, in which a saturable reactor is controlled by a valve feedback circuit, with stabilisation in terms of RMS. Originally developed for control of x-ray apparatus heaters where the high distortion was irrelevant, it found a limited range of applications in the 1950s. The Frequency range was detailed as 45 - 65 Hz, so it was suitable for both 50 and 60 Hz nominal supplies.
The Attached copy of an old Claude Lyons Catalogue offers some more details and was kindly passed to me by William Lyons.
The Allendale Group are in the process of producing a new Claude Lyons Website and it is intended that once complete this will include some data on historic products as well as the new ranges.
Any information relating to Claude Lyons your members might be able to share would be very welcome.
Martin

 

[(*steve*)]

Thanks a lot @MHW That is GREAT information.

Please keep us updated as to when the website with the historical information will be available to look at.