Impedencce voltage is nothing but self induced voltage in
reverse direction acting against the applied voltage( across
primary)
That is why after switching ON, the current intake reduces.

Impedance voltage of a transformer is the voltage required
to

short circuit the secondary winding terminals of the
transformer and apply voltage gradually from zero at
primary winding.increase the voltage gradullay till the
full load current flows in the secondary.The voltage at
which full load current flows that voltage is the impedance
voltage of the transformer.This is required for short
circuit calculations.You can find on the transformer name
plate as Impedance voltage or percentage impedance.

impedence voltage is that voltage which is applied through
primary side and full load current is flowing in secondary
side whwnever short Ckt. of secondary side

This is the voltage required to drive full load current in a
winding of a transformer when the other winding is short
circuited.
for example if percentage impedance of a 33/11kv transformer
is 6%. it means that 33x6/100=1.98KV would be required to
drive full load current in 33kv winding when 11kv winding is
short circuited.

Impedance voltage of a transformer is the voltage required

to

short circuit the secondary winding terminals of the
transformer and apply voltage gradually from zero at
primary winding.increase the voltage gradullay till the

full load current flows in the secondary.The voltage at

which full load current flows that voltage is the impedance

voltage of the transformer.This is required for short
circuit calculations.You can find on the transformer name

plate as Impedance voltage or percentage impedance

Imedance voltage is the amount of voltage required on
primary side to produce rated current on secondry side of
transformer when secondry is short circuited.

Or
amount of voltage drop accros primary side when rated
current flows through it

Simply it is the percentage of the normal terminal voltage
required to circulate full-load current under short circuit
conditions, or can also be consider as the voltage drop of
the trafo..