A fail-safe power control apparatus for supplying power between an energy source and the motor of a transport system. The power control apparatus includes a power supply circuit, which has at least one converter containing controllable change-over switches, and the power control apparatus has a controller for controlling the converter change-over switches, a data transfer bus, at least two controllers adapted to communicate with each other, and a control arrangement for controlling a first braking device, and possibly a control arrangement for controlling a second braking device.