Introduction; Principle Functions; Normal Mode; Buffer Mode - Siemens SITOP DC UPS 6EP1931-2DC21 Considerations For Use

0. Introduction

The user notices accompany the operating instructions belonging to the scope of supply of every
SITOP DC UPS module. General information, protection notices, and warnings can be found in the
operating instructions of the respective SITOP DC UPS module. In these user notices, the functions
of the SITOP DC UPS module and its various application possibilities are described in detail.

1. Principle Functions

In case of a failure of the mains supply, the SITOP DC UPS module backs up critical consumers (Load 2 in
Figure 1) with 24 VDC from the connected battery.
Communication
Load 1 Load 2
Figure 1: Principle connection and function of the SITOP DC UPS module

1.1 Normal Mode

In the normal mode, the SITOP power supply provides 24VDC. This voltage is directly available at the
consumers (Load 1 in Figure 1) and at the input of the SITOP DC UPS module. The SITOP DC UPS module
loads the connected battery module and provides 24VDC for the critical consumer (Load 2 in Figure 1). The
green "OK" LED lights up and the X2.2 – X2.3 "OK" relay contact is made. When the charge of the connected
battery has reached a value of approximately 85%, the green "Bat >85%" lights up and the X2.7 – X2.8 "Bat
>85%" relay contact is made.

1.2 Buffer Mode

If the supply voltage at the input of the SITOP DC UPS module sinks below the value set as the cut-in
threshold, the module assumes the supply of the critical consumers (Load 2 in Figure 1) using the battery
module. The yellow "Bat" LED lights up and the X2.2 – X2.1 "Bat" relay contact is made. They are accordingly
supplied with backup power for the buffering time set via the DIP switches or until the maximum buffering time
is up (deactivation after the exhaustive discharge threshold is reached).
© Siemens AG, 2009 3/18