A new type of GTO thyristor assisted tap changer is outlined which addresse
s the problems of traditional schemes, The scheme minimizes conduction loss
es in the solid state devices and also permits a fast response speed throug
h the adoption of fast actuator driven vacuum switches. This paper describe
s a prototype tap changer for a low voltage 300 kVA transformer using the n
ew method of tap changing. The prototype operates at current levels similar
to those at which a full scale tap changer would work, Test results are pr
esented.