User`s guide

3 - Installation

The overvoltage protection circuit senses voltage near the output terminals, not at the load. Therefore the

signal sensed by the OVP circuit can be significantly higher than the actual voltage at the load. When

using remote sensing, you must program the OVP trip voltage high enough to compensate for the voltage

drop between the output terminals and the load. Also, if the sum of the programmed voltage and the load-

lead drop exceeds the dc source’s maximum voltage rating, this may also trip the OV protection circuit.

Stability

When the unit is configured for remote sensing, it is possible for the impedance of the load wires and the

capacitance of the load to form a filter, which becomes part of the unit’s feedback loop. This can degrade

the unit’s stability and result in poor transient response performance. In extreme cases it may also cause

oscillations. The wiring guidelines previously discussed under "Wire Considerations" will eliminate most

stability problems associated with load lead inductance. If additional measures are required:

♦ keep the load capacitance as small as possible

♦ use larger diameter load wires to reduce resistance

OVP Considerations

The dc source’s OVP circuit contains a crowbar SCR, which effectively shorts the output of the dc

source whenever the OVP trips. If an external voltage source such as a battery is connected across the

output and the OVP is inadvertently triggered, the SCR will continuously sink a large current from the

battery, possibly damaging the dc source.

To avoid this, program the OVP setting to its maximum value to prevent it from inadvertently tripping.

Additionally, an internal fuse is connected in series with the SCR. This fuse will open to prevent large

currents from damaging the SCR. If this internal fuse has opened, The FS status annunciator will be set.

Refer to the Service Manual for instructions about replacing this fuse.

In addition, the OVP circuit’s SCR crowbar has been designed to discharge capacitances up to a specific

limit. This limit is:

Agilent 6611C

127,000 µF.

Agilent 6613C

20,000 µF.

Agilent 6612C and 66312A

50,000 µF.

Agilent 6614C

10,000 µF.

If your load capacitance approaches this limit, it is recommended that you do not intentionally trip the

OVP and discharge the capacitance through the SCR as part of your normal testing procedure, as this

may lead to long-term failure of some components.

INH/FLT Connections

This rear panel connector, has a fault output port and an inhibit input port. The fault (FLT) output, also

referred to as the DFI (discrete fault indicator) signal in the front panel and SCPI commands, is an open

collector circuit that pulls the positive output low with respect to the negative (chassis-referenced)

common. The high impedance inhibit (INH) input, also referred to as the RI (remote inhibit) signal in the

front panel and SCPI commands, is used to shut down the power supply output whenever the INH + is

pulled low with respect to the INH (chassis-referenced) common.

The connector accepts wires sizes from AWG 22 to AWG 12. Disconnect the mating plug to make your

wire connections.