KEPCO BHK-MG 200W (Full Rack) Series - Manual (Page 26)

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BHK-MG (OPR) 022014
to a dynamically changing load. The fast mode offers a faster response to step or dynamic pro-
gramming of the output voltage (in voltage mode), when the power supply is used as a power
amplifier. Fast mode is also recommended for current stabilization because of its fast response
to a dynamically changing load. Refer to PAR. 3.7.1 for more information.
1.4.9 EXTERNAL TRIGGER PORT
The external trigger port provides two functions: a trigger input can be used to restore the output
to previously defined settings using SCPI commands (see PAR. 3.3.4) and a shutdown input
can be used to immediately shut down the power supply output (see PAR. 3.2.7.3).
1.4.10 BUILT-IN PROTECTION
BHK-MG Series Power Supplies provide built-in protection against the following:
a. Overtemperature of the pass element. Heatsink temperature is monitored. If an overtem-
perature condition is maintained for more than 0.5ms, the following actions are initiated: the
pass element is cut off and latched off, the output capacitor is discharged, the LCD displays
the error message “BHK FAILURE“ and an error message is sent on the IEEE 488 Bus.
b. Overvoltage/overcurrent at the output. See PAR. 1.4.4
c. Uneven voltage/current in the pass element. Voltage is monitored across different transis-
tors of the pass element while current is monitored through the different branches. If uneven
voltage/current continues for more than 11ms, the pass element is latched off, the output
capacitor is discharged, the POWER circuit breaker is tripped to OFF and a flag is sent to the
host computer on a dedicated line (Status Port connector)
d. Fan failure. If fan current drops below predetermined value continuously for more than
16ms, the pass element is latched off, the output capacitor is discharged, the LCD displays
the error message “BHK FAILURE” and an error message is sent on IEEE 488 Bus.
e. AC line failure. If AC line is missing for more than 8 ms, a flag is sent to the host computer
on a dedicated line (Status Port connector). In addition, if the jumper at A7-J12 is installed
(default state), the pass element is latched off, the output capacitor is discharged, and the
POWER circuit breaker is tripped to OFF.
f. Interruption between the sensing and corresponding power output terminals. If there
is an interruption between the sensing and power terminals, two diodes connected in parallel
between the sensing lead and the corresponding power lead (one forward biased and one
reverse biased), allow the power supply to continue to function.
g. Overload of the main or auxiliary power transformer. If input current of the main trans-
former exceeds 7A a-c @ 115V a-c or 3.5A a-c @ 230V a-c, the input POWER circuit
breaker is tripped to OFF, the pass element is latched off, the output capacitor is discharged,
and a flag is sent to the Status Port connector. The reaction time is inversely proportional to
the input overcurrent: from a minimum of 10ms for 10 times nominal overcurrent, to a maxi-
mum of 100 seconds for 25% above nominal current.
If input current of the auxiliary power transformer exceeds a predetermined value, in most
cases the input POWER circuit breaker is tripped to OFF (if jumper A7J12 is installed), the
pass element is latched off, the output capacitor is discharged, and a flag is sent to the Sta-
tus Port connector. If the cause of the overload is a problem in the protection circuit, the input
POWER circuit breaker may not trip off: the pass element will be latched off and the output
capacitor will discharge more slowly, and a flag is sent to the status port. The reaction time in
this case is determined by PTC (positive temperature coefficient) thermistor A5R1 between
30 and 100 seconds.