Watlow QPAC Modular SCR Power Control Service - Manual (Page 14)

14
WATLOW QPAC Service Manual
Operation Theory, Chapter 3
Cards
BV - Burst fired with a
Variable Time Base (08-5342)
The BV card is time proportioning with a vari-
able (very fast) time base. At 50% power, one
full cycle is ON, and one full cycle is OFF. At
25% power, it is ON one cycle and OFF for
three. At 90%, it is ON nine cycles and OFF for
one. As the command signal gets farther from
50% power, the time base gets longer. The
maximum cycle time is 1 of 360 cycles. The BV
card is standard, setup for 4 - 20mA into 250
Ω
.
It can be changed to 1 - 5 VDC by removing the
resistor on the plug located on the back of the
card, adding a small circuit board (08-7210)
containing bias and gain pots allow the card to
be adjusted for any voltage from 0 - 3VDC to 0 -
15VDC or current between 0 and 25mA. The
card output is removed if the emergency shut
down signal is low.
CA - Contactor with an
AC Input Signal (08-5285)
The CA control card operates the same as the
CD card except it requires a 120VAC input
command signal. The CA can be special
ordered for 24VAC or 240VAC if required. The
QPAC can be kept OFF if the emergency shut
down signal is held low.
CD - Contactor with a
DC Input Signal (08-5286)
The CD control card operates the QPAC power
control as a zero cross solid state contactor. A
3 - 30VDC input signal is required to switch ON
the QPAC and a 0 - 1VDC is required to switch
it OFF. The QPAC can be kept OFF if the
emergency shut down signal is held low.
Figure 13 -
QCA Board Layout
Figure 14 -
QCD Board Layout
Figure 12 -
QBV Board Layout