"StickThatInYourPipeAndSmokeIt"


Tell us, idiot... How many REAL WORLD applications in a test lab call
for hooking up a variac, yet keeping it set to 1:1. Isolation needs?
Nope, one uses an isolation transformer for that.

Even when testing an auto-switching power supply, one swings from 85 V
thru 265 V, and only stops at 1:1 momentarily to glance at the working
performance parameters at that set point.

Most folks use a variac at nearly any setting except 1:1, and even
though that maker might make some lame declaration of a slightly higher
capacity when set at 1:1, the fuse will still blow at its rated break
point.


** An audio repair workshop will typically use a medium size ( like 500
VA or 1kVA ) variac to bring items like power amplifiers that are known to
be faulty OR have just undergone repairs up to AC line voltage - watching
for smoke or other signs of trouble as they go.

IF all is well, then the variac is set to exactly 1:1 - so the item
under test can be put through its paces with the variac's windings causing
the LEAST possible increase in AC supply impedance.

The reason is, few if any variacs have a bypass switch and it is tedious to
keep removing the AC plug from the variac and moving it onto an AC wall
outlet in order to get a low impedance AC source - essential for measuring
the power output of a large audio amplifier with accuracy.



...... Phil