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3. SYSTEM DESCRIPTION
This section points out the main components of the Uninterruptible Power System and discusses the
theory of operation of the unit.
3.1 PRINCIPAL COMPONENTS
The principal components in the Mesta Electronics UPS system are identified in Figure 6. On the front
panel, the 16 key keypad and the LCD readout are found, along with two locks for securing access to
the system. Accessible from the front panel, when the door is closed, are the power controls: two
battery breakers (Main Battery and optional External Battery), rotating transfer switch, and AC line
breaker. On the back of the cabinet are the communications I/O connectors: serial communications
port, custom I/O port and ports for dry relay contact outputs.
Other major components (from top to bottom) are: cooling fans, terminal block connectors, heat sinks
with power semiconductors, circuit boards for controlling the system, capacitor bank, transformer and
its high frequency filtering inductors, and battery shelves (size 1 cabinet with 20 batteries is shown). A
size 1 cabinet with 18 batteries is similar except the bottom battery shelf has only 3 trays of batteries. A
size 2 cabinet is also similar except the 20 battery system has 5 trays of batteries on each of the two
shelves, while the 18 battery size 2 cabinet has 5 trays on one shelf and 4 trays on the other shelf. A
size 3 cabinet does not contain any internal batteries.
Figure 6 Typical Location of Principal Components
