Specifications

CONSTRUCTION
transformer of 32-amp primary rating, the
power of the UPS-cum-EPS can be in-
creased to 500 watts or 625 VA.
The transformer ratings as mentioned
above are applicable for squarewave out-
put. The transformer primary rating will
be 25 per cent higher in case of sinewave
output. Also the number of MOSFETs per
bank should also be correspondingly
higher. Provision is made for mounting 5
MOSFETs in each bank.
PCB and component
layout. A double-sided PCB
is proposed for the circuit
of Fig. 2. Except the op-
tional circuit of ‘no load pro-
tection’, all switches, fuse,
CB, LEDs, and transform-
ers are required to be
mounted inside the cabinet
and front-/
back-panels
of the cabi-
net suitably
(refer Fig. 1
for the proposed front- and
back-panel layouts). Large
battery terminals may be
used for terminating the
battery leads. The tracks
connecting drains and
sources of MOSFETs may
be suitably strengthened
by depositing solder over
the same.
The actual-size compo-
Fig. 8: Wiring diagram of chasis/panel mounted components to the PCB
nent-side and
solder-side
track layouts for
the PCB are
shown in Figs 5
and 6, respec-
tively. Fig. 7
shows the com-
ponent layout
scheme. The
wiring diagram
for the chassis
and panel-
mounted com-
ponents con-
nected to the
PCB via connec-
tors (and few di-
rectly to pads) is
shown in Fig. 8.
The pads for
a few compo-
nents are not
existing in the
PCB using ex-
isting pads/
tracks. The
same may have
to be mounted
externally using
the available
pads in accor-
dance with the
circuit diagram of Fig. 2. The affected com-
ponents are: (a) C9—across battery termi-
nals, (b) D8—reverse palarity battery pro-
tection diode, (c) C11 and C12—capacitors
across source and gates of bank 1 and
bank 2, (d) C2—across pole of
SW2 and neutral of transformer X1
secodary, (e) C8—positive end to junction
of R22 and gate of SCR1 and negative end
to ground.
Photograph of author’s prototype
Sinewave output waveform as seen on the oscilloscope
163