ASEA Model UZBLN 250/300 UZB , One resistor – asymmetrical 3MVA trafo, 44kV tap changer UZB , One resistor – asymmetrical L – Linear regulation N- at neutral 250kV impulse 300A rated

Asymmetrical pennant

Raising the voltage = up

Lowering the voltage = down

Linear regulation Linear = adding the turns or subtracting the turns for DC testing this is important, because : Raising voltage when subtracting turns, you are switching onto position with voltage but lower resistance (due to the voltage drop) and current is higher each position (UP) Peak up - current jumps, when connecting to the point with voltage

Lowering - DOWN Lowering voltage Peak down - current drops when adding turns, you switch onto the position without voltage but higher resistance, and the current is lower each position (DOWN) Peak down - current drops when connecting with point without voltage

Peak-up : going up T breaks S makes T makes

up T breaks S makes T makes

up T breaks S makes T makes

up T breaks S makes T makes

Peak-down : going down T breaks T makes S breaks

down T breaks T makes S breaks

down T breaks T makes S breaks

down T breaks T makes S breaks

Photos found on the internet

Before repair

After repair