Installation 2
Series E4360 User’s Guide 37
Parallel Programming Cautions
CAUTION
To avoid possible tripping of the crowbar SCR, do not turn parallel
outputs off while they are operating in SAS
or Table mode. Program all
outputs to Fixed mode and set the voltage to zero
off.
If a follower output experiences a shutdown condition such as over-
temperature or over-current, it will not automatically shut down the
master output unless you have coupled output protection on the
mainframe as explained in chapter 3. Outputs on paralleled
mainframes will not shut down unless you have connected and
enabled the Fault/Inhibit system protection as explained in Appendix
B.
Note that if the OVP circuit of an output trips, its crowbar circuit will
draw current from all of the other units. Depending on the number of
outputs, the additional current may damage the internal SCR of the
tripped unit. Use one of the following methods to avoid problems.
1. Program the OVP of all follower outputs to maximum. This
minimizes the chance that the follower OVP circuits will trip. Then
program the OVP level of the master output to the desired
protection level (below the maximum programmable level.
2. Us e the built-in protection diodes. If you connect all outputs to the
load through the series diodes (as previously illustrated) and a
crowbar SCR trips, it will not draw current from other outputs.
Connecting Outputs in Series
WARNING
Only connect output modules in series that have identical model
numbers and options. Floating voltages must not exceed
240 Vdc. No
output terminal may be more than 240V from chassis ground.
CAUTION
Series connections should NOT be used in applications where the output
voltage is repeatedly and rapidly changing as is the case in a series or
shunt regulator application. This can result in overheating and damaging
the resistors of internal RC networks that are connected to ground.
Each output has a reverse voltage protection diode. If a reverse voltage
is applied, the unit cannot control the current conducted through this
diode. To avoid damaging the unit, never connect it in such a way that a
reverse voltage can force it to conduct current in excess of the unit’s
output current rating.
The following figure shows how outputs can be connected in series for
higher voltage output. Series connections are straightforward in this
case. Program each output independently. Program each output for 50%
of the total output voltage. Set the current limit of each output to the
maximum that the load can handle without damage.
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