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2 Installing the Instrument
leads or by load current transients acting on the inductance and resistance of the load lead. If it is
desirable to keep voltage transient levels to a minimum, place a high-voltage film capacitor, with an
approximate value of 10 microfarad per foot (30.5 cm) of load lead, right across the load.
Additional Load Considerations
Response Time with External Capacitor
When up-programming or down-programming the output voltage with an external load capacitor,
voltage response time may be longer than with purely resistive loads since the power supply may enter
constant current operating mode, which adds additional response time. By setting the proper voltage
slew rate when using an external capacitor, it may be possible to prevent mode crossover into constant
current. Use the following formula to estimate the additional programming response time:
Response Time =
(added output capacitor +Cx)X(change in Vout)
Model
RP7972A/ RP7982A
RP7973A/ RP7983A
Positive, Negative, and Floating Voltages
Either positive or negative voltages with respect to ground can be obtained from the output by
grounding (or "commoning") one of the output terminals. Always use two wires to connect the load to
the output regardless of where or how the system is grounded.
500 V units can operate with any output terminal ±500VDC including output voltage from ground
l
1 kV units can operate with any output terminal ±1 kVDC including output voltage from ground
l
1.5/2 kV units can operate with any output terminal ±2 kVDC including output voltage from ground
l
Keysight power supplies are optimized for grounding the negative output terminal.
Grounding the positive terminal may result in increased current measurement noise
and a reduction in current measurement accuracy.
The following additional restrictions apply when grounding (or commoning") one of the output
terminals.
Voltages applied must keep harmonics below the specified limit versus frequency along with the
fundamental as shown in the following figures. For common mode voltages with multiple harmonics,
keeping the fundamental and harmonics at 70% of the limit over all relevant frequencies is strongly
recommended.
78
(current limit setting)–(load current)
Internal capacitance C
x
8.8 μF/ 13.2 μF
2.2 μF/ 1.5 μF
Keysight RP7970 & RP7980 Series Operating and Service Guide
Model
RP7971A, RP7981A
RP7984A
Internal capacitance C
x
17.6 μF/ 26.4 μF
5.9 μF
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