The on-board static converter PSB 550/28 (hereinafter referred to as PSB) is designed for installation in urban electric transport vehicles and for supplying 28 V DC consumers. The PSB output is a stabilized voltage source with maximum current limitation. The output characteristic of the PSB provides power to on-board consumers with simultaneous charging (recharging) of the battery. The range of regulation and the accuracy of maintaining the set values ​​ensure the possibility of normal operation with both alkaline (nickel-cadmium or nickel-iron) and maintenance-free (sealed) acid batteries.