Heavy Voltage Stabiliser

[Wishiknewmore]

While stuck in lockdown in sunny France I have dug another treasure out of the shed, I didn’t really know what it was when I got it and not really so much wiser now.

I know from the label that it’s a 120v and/or a 220v voltage stabiliser, presumably used in the days when fluctuation in supply were a significant problem, I suppose when I picked it up I thought that there may have been a possibility that is was some form of isolation transformer, but obviously not as the input and output share a common terminal.

I am a bit nervous about asking how it worked as I probability won’t understand the answer, but I am asking anyway, and for any other suggestions what use it could be put to besides a very heavy doorstop (one transformer has three hand drawn red x’s on it so it may well be dead anyway)

Thanks in anticipation
Philip

[Skywave]

It's a constant-voltage transformer, often simply referred to a 'CVT'. Amongst other manufactures of such devices, Claude-Lyons is a well-known manufacturer.
If it is faulty, I would suspect the capacitor.

Al.

[kalee20]

Big transformer and big capacitor... Ferroresonant stabiliser?

Uses the fact that the transformer core saturates at a predictable degree of magnetisation, to stabilise the output voltage.

[Radio Wrangler]

Constant-voltage transformer aka ferroresonant AC stabiliser.

A transformer core is designed to saturate at a certain level and this stabilises the output voltage. To avoid it trying to pull the tops off the local mains a resonance trick is used. The saturation effect tends to give a truncated sinewave as output, but some people refer to it as squarewave output. If you're going to use it to feed rectifiers, this is very good for them, but if you feed motors etc, then some added magnetics are added to make a more sine-like output.

These things are not just useful for areas where mains voltage is iffy, they also work to remove spikes and transients up to the point where capacitive coupling dominates.

Claude Lyons were big UK makers also Advance (as in test gear) and Solar Electric.

Because it's resonant, the incoming frequency is critically important. Never never ever try to use one on a generator.

David

[Wishiknewmore]

Thank you all

I am a little wiser now, and it has lead me off onto some further reading, which I have to admit is straining the grey cells a little!
As yet I don't have any form of oscilloscope so won't be seeing any squarewaves, but eventually....

Philip

[Oldcodger]

Sounds very similar to the way High voltage power feeds for TAT1 /CANTAT 1 and the Anglo Swedish Cable was done. I've not worked on this part ofany of those systems, but from a brief read of the handbooks ,regulation was done by degrees of saturation of the core to maintain the circa 4.5/5Kv needed. Unfortunately I can't find any mention of the finer details.

[Herald1360]

Regulation by degrees of saturation of a core sounds more like some sort of magamp? An AC "series regulator" can be done by having a saturable reactor where you would normally have the series pass transistor so to speak.

[Wishiknewmore]

Update

Although not 100% on how it works, the good news is that on a quick test it appears that it does.
Using simple and inexpensive DMM the supply voltage is 234v and the output from the stabiliser is 220v(no load at the time of testing)

Philip

[Skywave]

Photo 1 gives info. in French; translations . . .

"Tension secteur" = the mains supply voltage.
"Puissance" = power (rating)
"tension filtree" = voltage filter

Quote: "No-load" at time of testing. A full load test would be worthwhile.
V-A rating is 210. So at 220 v.a.c O/P, you'll need (approx.) 220 Ω load rated at 220 watts. A large heat-sink + a fan spring to mind!

On account of this item's design, I would connect a 'scope across that load to monitor the waveform across it as the load is varied. The use of an isolation transformer powering that 'scope will be needed, since you reported that "the input and output share a common terminal."
And I was a bit surprised at that, since many years ago (during a particular employment), it was necessary to use a CVT manufactured by Claude Lyons on a daily basis. ISTR that between input & output there was complete isolation.

Aside: It would be interesting to see the cct. diag. of this item.

Al.

[Joe_Lorenz]

@ David: Just for curiosity, I would like to know what happens with this device fed by a generator

Regards, Joe

[Leon Crampin]

Ferroresonant transformers are intolerant of frequency deviations from their designed value. They also dislike excessive harmonic impurity. Both of these qualities are almost inevitably present in supplies from simple generators.

My lasting admiration for Tek scopes stems from using a 465 on top of a running engine in the rain, powered by a really flaky diesel generator. It didn't miss a beat.

Leon.

[Herald1360]

Originally Posted by Skywave

Quote: "No-load" at time of testing. A full load test would be worthwhile.
V-A rating is 210. So at 220 v.a.c O/P, you'll need (approx.) 220 Ω load rated at 220 watts. A large heat-sink + a fan spring to mind!

Al.

Or perhaps a couple of 100W bulbs (if you have any) other combinations of wattage would work.

[Radio Wrangler]

Originally Posted by Joe_Lorenz

@ David: Just for curiosity, I would like to know what happens with this device fed by a generator

They usually burn out. Get hot, smoke and fail if there is any significant frequency error. The resonating capacitors can also be destroyed.

They are quite high-Q and it doesn't take much to damage them. Look for a maker's plate with ratings on it, and pay close attention to the specified frequency range.

David

[Tractorfan]

Hi,
I remember seeing something similar made by 'Valradio'. It was in a steel perforated case and a 5 amp BS546 socket on the side. I can't remember what kind of input connector it had.
It didn't look particularly big but, by 'eck, it was heavy!
I could hardly move the br!
Cheers, Pete!