The power envelope is set to give 62V/7A, 42V/10A and 20V / 20A under all supply conditions
(both outputs loaded); at lower output voltages the output power is restricted by the 20A current
maximum.
When the power limit is exceeded, the status indication will change from CV or CI to UNREG. For
example, if the supply is set to 20V, with the current limit at maximum, and is connected to a 2
Ω
load, 10 Amps will flow and the supply will be in CV mode. As the voltage across the load is
increased, the power into the load increases until, at about 29V, the power limit is exceeded and
the supply changes from CV to UNREG.
Connection to the Load
The load should be connected to the positive (red) and negative (black) OUTPUT terminals. Both
are fully floating and either can be connected to ground.
Remote Sensing
The unit has a very low output impedance, but this is inevitably increased by the resistance of the
connecting leads. At high currents this can result in significant differences between the indicated
source voltage and the actual load voltage (two 5m
Ω
connecting leads will drop 0.2V at 20 Amps,
for instance). This problem can be minimised by using short, thick, connecting leads, but where
necessary it can be completely overcome by using the remote sense facility.
This requires the sense terminals to be connected to the output at the load instead of at the
source; insert wires into the spring-loaded SENSE terminals and connect directly to the load.
Switch the LOCAL/REMOTE switch to REMOTE. To avoid instability and transient response
problems, care must be taken to ensure good coupling between each output and sense lead. This
can be done either by twisting the leads together or by using coaxially screened cable (sense
through the inner). An electrolytic capacitor directly across the load connection point may also be
beneficial.
The voltage drop in each output lead must not exceed 0.5 Volts.
Switch the LOCAL/REMOTE switch back to LOCAL when remote sensing is not in use.
Series or Parallel connection with other units
The outputs of the power supply are fully floating and may be used in series with other power
supply units to generate high DC voltages up to 300V DC.
WARNING!
Such voltages are exceedingly hazardous and great care should be taken to shield
the output terminals for such use. On no account should the output terminals be touched when
the unit is switched on under such use. All connections to the terminals must be made with the
power switched off on all units.
It should be noted that the unit can only source current and cannot sink it, thus units cannot be
series connected in anti-phase.
The unit can be connected in parallel with others to produce higher currents. Where several units
are connected in parallel, the output voltage will be equal to that of the unit with the highest output
voltage setting until the current drawn exceeds its current limit setting, upon which the output will
fall to that of the next highest setting, and so on. In constant current mode, units can be
connected in parallel to provide a current equal to the sum of the current limit settings.
Note that the output terminals are rated at 30A maximum; if two or more outputs are operated in
parallel to source higher currents than this the junction should be made at a separate point, not
one of the terminals.
Protection
Overvoltage protection (OVP) is fully variable within the range 10% to 110% of the supply's
maximum output level. The OVP limit is set via the screwdriver adjustable SET OVP preset
potentiometer, accessible through a hole in the front panel. Rotating the preset clockwise
increases the limit, which can be read directly on the user display by pressing the button beneath
the preset. If the voltage on the output exceeds the set OVP for any reason, including an
externally forced voltage, the output will be tripped off.
The output will also be tripped off if an attempt is made to draw power from the sense wires.
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