Mystery variac wiring

[Joe P]

My father-in-law, who's a bit of a hoarder of ancient elctronics, dug up an old variac. Wiring diagram attached. Also attached is how I interpret it, is that right? What about the earth connector, would that be for grounding the (no longer existing) enclosure? And connection Z, would that be for 120V mains, or what?
This thing is probably of either Swedish or German origin, there's a lot old German stuff floating around here.

[mat janssen]

This Variac is a Philips variac from the netherlands. Whrn the mains is connected to N and L  and the output to N and T this transformer goes from 0 to 260 volts. Z is the middle point of this transformer. When the mains is connected  to N and K this transformer goes from 0 to 220 volts. The attaches schema where the mains is connected top L and N and the output between L and T then this tranformer goes when turning Clockwise from 220 to 0. So it's a reverse use connection. And Yes the ground connection was for the housing. Please look out the black metal turning plate can be "hot". So use it carrefully

[Joe P]

This Variac is a Philips variac from the netherlands. Whrn the mains is connected to N and L  and the output to N and T this transformer goes from 0 to 260 volts. Z is the middle point of this transformer. When the mains is connected  to N and K this transformer goes from 0 to 220 volts. The attaches schema where the mains is connected top L and N and the output between L and T then this tranformer goes when turning Clockwise from 220 to 0. So it's a reverse use connection. And Yes the ground connection was for the housing. Please look out the black metal turning plate can be "hot". So use it carrefully

Ah, OK.
Philips is also extremely common in Sweden, btw.
Thanks for the heads up on the plate, would that be affected by which way you orient the plug in the wall socket?

[mat janssen]

In principle NO, but if you want to know where the phase is then ofcource you can mark that.

[PRR]

I do not know this type of variac. However the two near-end taps and the Z center-tap *suggest* it was intended to support 230V-0V-230V (through zero) settings. So then one way is one phase and the other way is reversed phase (polarity). This could be used on a 2- or 3-winding AC motor to slow and *reverse* rotation. Perhaps the feed on a power tool which cuts both ways.

If that is so(?), then the end-to-end rating might be 520V. However I doubt you want to mess with 480V lines. Working a 520V variac at 230V is a "waste" of potential output (and weight and original cost); however this beast seems ample for almost *any* "appliance" (guitar amp etc) you would want to variac.

In any case, I would experiment with a 100 Watt incandescent lamp between the wall and this thing, so you can't burn-up wires or burn-down house. It won't deliver high power with a lamp limiter, but you could power say a 25W incandescent lamp or basic solder-iron to experiment.

[mat janssen]

Here is the datasheet for this variac. The data is from the .1 version. You have the .2 version with a smal change, but no big changes otherwise the type number will change.

[Tony Bones]

If that is so(?), then the end-to-end rating might be 520V. However I doubt you want to mess with 480V lines. Working a 520V variac at 230V is a "waste" of potential output (and weight and original cost); however this beast seems ample for almost *any* "appliance" (guitar amp etc) you would want to variac.

Running a variac (or any power transformer) at less than its max rated primary voltage does seem like a waste of iron, but I can say that in the case of old variacs, they will often run quieter. I have a bunch of vintage units that all work fine, but the 120V units tend to hum when plugged into 120V. I have a monstrous 240VAC unit on my bench that is plugged into 120V. Obviously, the numbers on the dial are off by a factor of two, but the variac itself runs quiet. I don't move it around, ever, but it is the one that gets used when I need variable AC.

[Williamblake]

Having excessive iron in a variac may flip your fuse in the breaker box so you might need a surge limiter for turning this on even if you have little load connected to it.