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Remote Operation 71
Overvoltage (OV) Protection
The programmable OV is a protection feature which can be set by the operator to protect the load against excessive voltage.
When the actual voltage exceeds the programmed overvoltage setting for a given output channel, the OV is tripped. The
OV circuit will fire the SCR crowbar which shorts across the output and the output assumes a low impedance state.
For example, to program the OV of output channel 1 to 9.5 V send the following command:
OVSET 1,9.5
To find out the OV setting for output channel 1 send the following query and address the supply to talk:
OVSET? 1
To enable an output after it went into overvoltage, you must first remove the overvoltage condition and then send the OV
reset command.
To reset output 1 send:
OVRST 1
If you send the reset command without first removing the OV condition, the supply will fire the OV again.
NOTE If the programmable OV fails, the supply has a fixed OV circuit which will fire the SCR crowbar if the
voltage exceeds 120% of the maximum rated output. The fixed OV circuit will also fire the SCR crowbar
if the supply is off (line cord disconnected) and an external source is supplying voltage which exceeds
120% of the maximum rated output.
Overcurrent Protection (OCP)
The OCP is a protection feature employed by the power supply to guard against excessive output currents. When the output
enters the + CC mode and the OCP is enabled, the OCP circuit down programs the output voltage and disables the output.
To enable the OCP, for output channel 1, send the command
OCP 1,1
To disable the OCP, send the command
OCP 1,0
You can find out the OCP setting by sending the following query and addressing the power supply to talk.
OCP? 1
The response from the power supply is either a "0" to indicate that OCP is off or a ’’1" to indicate that it is on. To reset the
output channel after an overcurrent trip, you can either disable the OCP and send the reset command, or you can reduce the
output current below the programmed current and then send the reset command. To reset output 1, send the command:
OCRST 1
NOTE The supply can report a fault condition when an output is in overvoltage or overcurrent. Although the
OVRST and OCRST commands reenable the output, they do not clear the fault register. As a
housekeeping measure, it is advisable to always clear the fault register by querying its value after an OV
or OC reset.