Reversible DC power-supply systems with thyristor inverters are described. Design principles applicable to and technical difficulties encountered by the reversible DC power-supply system are discussed. To give an example of application, the power-supply system of Kobe Metro is described in detail, together with principal designs, solutions adopted to overcome the technical difficulties and some operational results. Some more examples of application in Japan are referred to as further experiences of the system. The designs described are supported by service experience.