Abstract: There is disclosed a transformer, comprising a triangular wound core; a low voltage LV winding; and at least one high voltage HV foil disc winding and a method for manufacturing a transformer coil, comprising providing a high voltage HV inner mold assembly; and winding at least one HV foil disc winding on the HV inner mold assembly. There is also disclosed a mold for manufacturing a transformer coil, comprising side gears respectively arranged at top and bottom positions of a triangular wound core; a high voltage HV inner mold assembly connected to the side gears; and a HV outer mold assembly connected to the side gears, wherein the HV outer mold assembly has a top opening across a length thereof.