Guizhou Changzheng Electric Co., Ltd. is a new and high-tech enterprise specially engaged in research, development, manufacture, sale and service of transformer on load tap changers and off-circuit tap-changers. Our company was the earliest manufacturing enterprise who began to manufacture the tap changer. We began to independently develop on load tap changer in the early 1970s, now we independent researched on load tap changer of ZVMD, ZVM, ZMD, ZM, ZV and etc......