A combination of torodial transformer and C-core transformer. Its invention has been said to be a revolution of transformer in 90s. Core material used in R-core transformer is continuous, non-cut, grain oriented silicon steel strip, which has been completed the process of anneal treatment and soakage in insulating paint. The special feature of R-core transformer is there are two matched PBT fire retardant bobbins on each side of the core. Each bobbin is separated into two parts, which makes the primary winding and secondary winding. So they can enjoy complete isolation between them. By using special winding machines to roll the bobbins, copper wires can be wound into the bobbins uniformly.