A power supply system having a power converter unit and a rack. The rack has a shelf and a shelf connection device. The power converter unit has a housing and a unit connection device, where the unit connection device is adapted to be releasably locked to the shelf connection device when the power converter unit is inserted into the shelf. The shelf connection device has a recess, and the unit connection device has a plate spring and an actuating device. A first end of the plate spring is connected to the housing and a second end of the plate spring is supported on or connected to the actuating device. The actuating device is arranged to move the plate spring between a locked position, in which the plate spring is protruding from the housing into the recess, and an open position, in which the plate spring is retracted from the recess.