Page 145 - Uninterruptible Power Supplies

Static Uninterruptible Power Supplies
Static Uninterruptible Power Supplies 143

switch, which may be used as subassemblies in many other circuits each
having its own properties and uses. These will be described in more detail
later in this chapter.

Subassemblies
Before detailing the various alternative circuits, a general description
of the subassemblies is given below, commencing with the rectifier/
battery charger.
This subassembly is designed to provide full-load power through the
inverter assembly , recharge a battery, and also cater for losses in the
system.

Rectifiers
As an example, a fully controlled six-pulse thyristor bridge is normally
used as shown in Fig. 5.2. Note the conduction point is varied to control
the dc output voltage. L in the diagram represents an impedance to
attenuate ripple which will affect battery performance.
The rectifier bridge offers the ability to ramp up power on start-up, thus
affording excellent loading conditions to a supporting diesel generator
set. Ramp up may be set from No Load to Full Load within 5 to 30 s.

L

FUSE

HARMONIC
REDUCTION
CHOKES
L
TO THYRISTOR GATES

MICRO PROCESSOR
MONITOR AND CONTROL

Figure 5.2

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