HSF (M) 300W 042315
15
5.1
ADJUSTING THE VOLTAGE
NOTE: Refer to the RA 19-4C Rack Adapter manual for alternatives to the standard master/
slave parallel configuration described below.
To adjust the paralleled units, turn off all the units except one (designated as the master) and
adjust to desired voltage using the front page trimmer and monitoring the front panel voltmeter.
•
Each slave must be adjusted to a slightly lower voltage than the previous unit. The differ-
ence between the master and the lowest voltage slave must not exceed 2% of E
NOM
.
•
The voltage separation between master and subsequent slave(s) (V
SEP
) = 2% E
NOM
/ N
where N = number of units in parallel.
Adjust the first slave V
SLAVE1
to E
NOM
- V
SEP
. Adjust the second slave V
SLAVE2
to V
SLAVE1
- V
SEP
.
Adjust the third slave V
SLAVE3
to V
SLAVE2
- V
SEP
and so on.
As an example, for three HSF 24-27M units in parallel, 2% of E
NOM
is 0.48V and V
SEP
is 0.48/3 =
0.16V. Turn off the master, then turn on another unit (slave 1) and adjust for 160mV less than the
master. Turn off slave 1 and turn on slave 2 and adjust for 160mV less than slave 1.
When all units are turned on, the unit adjusted to the highest voltage will be the master. The
meters of all units read the voltage on the bus. If a unit fails, the VDC ON indicator of that unit is
either off or red, however the meter of a failed MZ Model may continue to read the voltage on the
bus since it is powered by a separate internal power supply.
5.2
PARALLEL CONNECTIONS, M MODELS
When using parallel-connected M Models, a minimum load is required to avoid the slave becom-
ing “idle.” When the slave is idle, the output is off, no lights are lit, and the alarm is set. The mini-
mum load (Amperes) = N x (I/10) where N = the number of units in parallel, I = Nominal current
rating of individual power supply (Amperes). For applications requiring either no load or lower
than minimum load conditions, the MZ Models are recommended.
5.3
PARALLEL CONNECTIONS, MZ MODELS
If parallel-connected MZ models are controlled individually, either a minimum load or voltage set
restrictions are required to avoid slave “idle” or slave “oscillating output” conditions; the idle and
oscillating output conditions show slightly different indications depending on the position of SW1
position 7 as defined below.
NOTE: If the minimum load is maintained, voltage set restric-
tions are not required.
If position 7 of SW1 is set to off (default, see PAR. 3.1), the VDC ON indicator is powered from the
output; therefore when a slave is idle, the output is off, VDC ON is off, and the alarm is set. The
oscillating output condition means that the unit alternates between briefly idle and output on (the
VDC ON indicator will appear dim as it goes on and off, and the toggling relay will be audible).
If position 7 of SW1 is set to on (see PAR. 3.1) so that the VDC ON indicator is powered from the
internal power supply, when a slave is idle, the output is off, VDC ON lights red, and the alarm is
set. The oscillating output condition means that the unit alternates between briefly idle and output
on (the VDC ON indicator will toggle between briefly amber and green, and the toggling relay will
be audible).
