Siemens sitop uninterruptible power supplies ups ups500s ups500p siemens 6ep1933 2ec41 the siemens 6ep1933 2ec41 is a sitop ups500s 25kw uninterruptible mode power supply that is essential for guaranteeing the productivity of automated plants and machines but in order to protect 24v loads from longer power failures as well the power supply can be upgraded with dc ups modules a maximum of 3 sitop ups501s expansion modules rated at 5kw can be connected in parallel to increase the buffer