KEPCO MST 100-2MHT, Руководство оператора

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MST-MHT SERIES 071320
3-7
3.7.5 A-C LOSS DETECTOR
Although MST-MHT Power Modules are designed to provide a minimum of 21.5 milliseconds of
output hold-up time (one full cycle of 47Hz power), loss of source power for extended periods
will eventually result in complete Power Module shutdown. Additionally, certain power loss inter-
vals can create a condition where the internal bias supply for the digital control circuitry decays
partially, but not enough to force a system interrupt and reset; when this occurs, it is possible
that digital communication and processing can be corrupted without warning or notice. To pre-
vent this, MST-MHT Power Modules incorporate a power loss detector which will initiate a fault
shutdown as described in PAR. 3.7a if the internal bulk d-c storage capacitor voltage falls to a
level where quality of the internal bias voltages is questionable.
3.7.6 OPEN SENSE/POWER WIRE PROTECTION
In the event that the error sense leads (+S, -S) become disconnected from the power leads, the
output voltage will attempt to rise uncontrollably. If the output voltage rises past the programmed
overvoltage protection setting (see Table 1-1), the programmed overvoltage protection
described in PAR.3.8.1 shuts down the unit. A hardware backup ensures that if the software
OVP fails, the unit will shut down upon reaching the OVP hardware .trigger value (see Table 1-
1), At the same time, bit 10 appears in the MST 488-27HT Controller Questionable register.
Depending on the output voltage rise time, either the programmable output protection as
described in PAR .3.8.1, or the fixed overvoltage detector as described in PAR. 3.7.2, will pro-
tect the unit. Observe the front panel OUTPUT FAULT indicator to determine recovery action. If
the indicator is on, refer to PAR. 3.7.1 for recovery. If the indicator is off, send
*RST
to recover.
The open sense/power wire protection circuitry can also be triggered by a power lead voltage
drop in excess of the 0.5V maximum specified headroom resulting in the same situation as
described above. . If the error sense lead connections appear to be correct, the user should
double-check the size of the power leads to verify adequate margin. Contact Kepco Applications
Engineering for assistance if necessary.
3.8 PROGRAMMABLE PROTECTION
The MST-MHT unit allows the user to set an arbitrary level for voltage protection (see PAR.
3.8.1). In addition, the MST-MHT gives users the option to shut down the unit almost immedi-
ately upon exceeding programmed current, instead of waiting until the unit exceeds pro-
grammed current by 10% (see PAR. 3.8.2).
3.8.1 PROGRAMMABLE OVERVOLTAGE PROTECTION
The
VOLT:PROT
command can be used to program the unit to shut down when actual output
voltage exceeds the protection level established by
VOLT:PROT
. For this case if the actual out-
put voltage exceeds the
VOLT:PROT
value, almost immediately upon detection, voltage and
current are programmed to minimum values and the output is disabled, bit 0 (2
0
) of the Ques-
tionable Condition register is set and no further commands are accepted until
*RST
is sent.
3.8.2 PROGRAMMABLE CURRENT MODE PROTECTION
If 10% Overcurrent as described in PAR. 3.7.3 is not acceptable, sending the command
CURR:PROT:STAT ON
makes it possible for overcurrent detection to be initiated as soon as the
programmed current exceeds actual output current. Almost immediately upon detection, voltage
and current are programmed to minimum values and the output is disabled, bit 1 (2
1
) of the
Questionable Condition register is set and no further commands are accepted until
*RST
is
sent.