Block st 230v to 42v transformers block st 250 23 42 the block 250va transformer 230v to 42v is a low inrush current control safety or isolation current transformer with screw connection terminals designed with a very good switch on behaviour thanks to reduced starting currents plus high performance for the volume thanks to compact design this high quality transformer also has excellent corrosion protection and low noise thanks to blockimpex vacuum impregnation block st 250 23 42 250va