KEPCO MST 100-2MHT, Руководство оператора

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MST-MHT SERIES 071320
3-3
For programming polarity reversal in Standby mode, the user simply issues the polarity reversal
command prior to enabling the output; the Power Module will then present reversed output
polarity when enabled.
For polarity reversal while the output is enabled, the action is somewhat more complex although
essentially transparent to the user. Upon receipt of a polarity reversal command, the Power
Module control circuit stores the previous output settings (mode, voltage and current setpoints,
etc.). The output of the Power Module is immediately programmed to zero volts and zero amps.
A time-out delay of 2 seconds maximum is employed to allow for discharge of any load capaci-
tance through the Power Module's return supply; during this time-out interval, the power supply
waits for the output to reach zero volts. When zero volts is established, or at the end of the 2
second time-out, the relays are switched. The output is then reprogrammed to the stored set-
tings and operation continues. During this sequence, error message generation is inhibited.
Restoration of the output to normal polarity follows a similar path.
NOTE: The “return supply” current incorporated into MST-MHT Power Modules is limited to a
maximum value which may in some cases be inadequate to fully discharge all external
load capacitance. To ensure dry relay switching for all output conditions, the user must
ensure that the external load capacitance can be discharged completely within the 2
second time-out interval by the available current, or dry switching will not take place.
The maximum external capacitance value that can be discharged within the 2 second
time-out interval is calculated as follows (see Table 3-2):
where C = Maximum external capacitance allowed to maintain dry switching (Farads)
I = Return supply current (Amps)
V = Output voltage (Volts)
T = Time (Sec) = 2 seconds
CAUTION: FAILURE TO OBSERVE THE “DRY SWITCHING” CRITERIA NOTED ABOVE
WILL CAUSE DAMAGE TO THE RELAYS AND VOID THE KEPCO WARRANTY .
In order to allow for settling time, the user should wait approximately 300 milliseconds after com-
pletion of polarity reversal before sending a status query in order to avoid erroneous fault mes-
sages.
TABLE 3-2. MAXIMUM EXTERNAL CAPACITANCE VALUES TO ENSURE DRY SWITCHING
MODEL
RETURN SUPPLY CURRENT
(MILLIAMPS)
MAXIMUM EXTERNAL CAPACITANCE *
(

F)
MST 6-20MMHT 400 125,000
MST 15-12MMHT 400 50,000
MST 25-8MMHT 250 20,000
MST 36-5MHT 165 8,800
MST 55-3.5MHT 110 4,000
MST 75-2.5MHT 60 1,600
MST 100-2MHT 44 880
MST 150-1.2MHT 30 400
* Values shown for worst case: T = 2 seconds and

V = maximum voltage.
C
I T

V

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