Parallel Operation Of Supplies - HP 721A Operating And Servicing Manual

Model 7 21A
Sect.n Page 3
2-5 PARALLEL OPERATION QF SUPPLIES
Two supplies may be operated in parallel to supply
loads in excess of 150 ma. Set the SHORT CIR¬
CUIT CURRENT switch of the first unit to maximum
(225 ma). The first supply becomes a 225 ma con¬
stant current source. The supply will furnish up to
this amount of current without harm, however the
regulation and ripple specifications can no longer
be guaranteed. Adjust the voltage of" the second
supply to be the same as the first unit before con¬
necting them together. The second supply can be
made to share load by advancing the VOLTAGE
ADJUST control slightly clockwise. The second
supply will furnish the regulation action up to the
limit of its capacity (150 ma).
The second supply may be loaded beyond the 150 ma
point up to a maximum of 225 ma, making a total of
450 ma available. The usefulness of this extra out¬
put capacity depends on the performance required
from the supplies. The supplies become constant
current sources when the SHORT CIRCUIT CUR¬
RENT limiting circuit is operating. At this point
the ripple, source impedance and voltage regulation
specifications cannot apply.
Operation of more than two instruments in parallel
is not recommended as the total current capacity
becomes greater and accidental gross misadjusted
controls may result in instability.