KEPCO ATE-DMG SERIES - Manual (Page 41)

ATE-DMG 042314 3-7
3.3 OVERVOLTAGE CROWBAR, SETUP AND CHECK
The overvoltage crowbar circuit protects the load from momentary or long-term overvoltages.
The crowbar SCR conducts across the power supply output, and the A-C POWER
SWITCH/CIRCUIT BREAKER is tripped if such overvoltages occur. The setting of the front
panel LEVEL control determines the “threshold” between the actual operating voltage of the
power supply and the level at which the crowbar circuit will be activated. The LEVEL control can
be set from 3 volts to 110% of the rated output voltage. The LEVEL control may be adjusted very
close to the operating voltage (minimum threshold = 2% of rated output voltage or 0.5 volt,
whichever is greater). The operation of the crowbar circuit can be checked without actually trig-
gering the crowbar. All operating controls are accessible at the front panel (refer to Section 2,
Figure 2-1).
3.3.1 SETUP AND CHECK PROCEDURE
1. Without connecting the load to the power supply turn Crowbar LEVEL control fully clockwise.
2. Turn A-C POWER SWITCH/CIRCUIT BREAKER on. Press VSET key, then use the keypad
to enter the desired value at which the crowbar must trigger (NOT to the actual operating
voltage), then press ENTER.
3. Depress the DISABLE button (and keep it depressed) white turning the LEVEL control coun-
terclockwise, until the crowbar INDICATOR energizes (simulated crowbar action).
4. With the DISABLE button still depressed, press VSET key, then use the keypad to enter the
actual operating voltage and press ENTER key. Release the DISABLE button.
NOTE: This last adjustment established the “threshold” i.e., the difference voltage between the
output voltage and the voltage at which the power supply will “crowbar.” For minimum
“false triggering” use the largest threshold your load can tolerate.
5. To check the adjusted crowbar trigger level, depress DISARM push button. Press VSET key,
then use the keypad to enter the voltage trip point, minus 1%, then press ENTER.
6. Depress the

key and note the voltage at which the crowbar INDICATOR lamp energizes.
Correct LEVEL adjustment as described above if necessary. Use VSET to reduce power
supply output voltage to its operating value.
NOTE:1 Readjustment of the LEVEL control may be required after load and power supply have
reached thermal equilibrium.
NOTE:2)If an exact crowbar point at a remote load must be established, remote error sensing,
as described in PAR. 3.2.3 must be used.
3.4 LOCAL MODE OPERATION (KEYPAD OPERATION)
The following paragraphs explaining local mode operation include a description of the interac-
tion between the LCD and the front panel keypad (see PAR. 3.6 for remote mode programming).
Each key of the front panel is described, with a reference to a paragraph detailing the use of that
key. Local operation of the ATE-DMG Power Supply is accomplished via the 24 key keypad on
the front panel. All indications are provided by the 2-line LCD.