Power Dissipator Operation
Power supply models rated at 1 kW, require one Keysight N7909A power dissipator to sink 100% of
their rated current. Power supply models rated at 2 kW, require two Keysight N7909A power
dissipators to sink 100% of their rated current. 2 kW models connected to one power dissipator can
sink 50% of their rated output current. Refer to Connections-Power Dissipator for installation
information.
l Each N7909A unit has a total power dissipating capacity of 1 kW.
l Current sinking requires a minimum operating voltage as shown in the output quadrant char-
acteristic.
l The N7909A does not have an On/Off switch. It turns on and off with the power supply. An LED on
the unit will indicate that the unit is connected and operational. See Power Dissipator at a Glance
for information about the front panel LEDs. The power dissipator must be connected before the
power supply is tuned on, or it will not be recognized and does nothing. If the power dissipator is
connected but not working, the power supply indicates a self-test error.
l The only operating difference for the power supply when the power dissipator is connected is that
the sink current capability is increased from 10% to 100% of the rated current, and the negative
power protection limit (CP-) is also increased.
l If the N7909A is disconnected during operation, the power supply indicates that a self-test error
has occurred and reduces the sink current capability to 10% of the rated current. The negative
power protection limit (CP-) is also reduced, which may cause the unit to go into a CP- protection
mode.
l The cables connecting the N7909A to the power supply cannot be longer than 1 meter. This limits
the distance that the N7909A can be located away from the power supply.
l The temperature sensor information from the power dissipator is combined with the temperature
sensor information from the power supply. The minimum difference between the internal tem-
perature sensors and the over-temperature trip level is reported by the OUTPut:PROTec-
tion:TEMPerature:MARGin? query.
Querying the Power Dissipator
Other than looking at the front panel LED of the power dissipator, the only way to know if the unit is
connected and operating correctly is to query the negative current limit of the power supply.
Front Panel Menu Reference SCPI Command
Not available To query the negative current limit:
CURR:LIM:NEG? MIN
Notethat the MIN parameter returns the most-
negative current value.
Keysight N6900/N7900 Series Operating and Service Guide 175
4 Using the Advanced Power System
To Next Page
Loading...
Need help?
General
