3-2
MST-MHT SERIES 071320
3.2
OPERATING MODES
MST-MHT power modules permit the user to select the operating mode as either Voltage Mode
or Current Mode, depending upon the characteristics of the load being driven by the power
module. The following paragraphs describe the characteristics and method of selecting the
operating mode; note the following:
•
only one operating mode may be selected at a time.
•
operating mode selection affects only the operation of the fault detector and not the rect-
angular operating characteristic of the power module.
•
the MODE indicators on the front panel indicate the real-time operating mode of the
Power Module.
3.2.1
VOLTAGE MODE
In this mode, the Power Module is programmed to behave as a voltage source. The user pro-
grams an operating voltage XX with a current limit YY based on the required voltage stabiliza-
tion point and the maximum anticipated load current. The Power Module is now programmed to
provide a stabilized output voltage XX to a load impedance greater than or equal to XX/YY; the
VOLTAGE MODE indicator LED is on for these load conditions.
Load impedances below XX/YY are considered to be overloads, and the Power Module will
modulate the output voltage between zero and XX as necessary to maintain the load current at
YY. Operation with load impedances below XX/YY will result in the CURRENT MODE indicator
LED going on and the VOLTAGE MODE indicator going off; a status query at his point will indi-
cate a device overload condition. Increasing the load impedance to a value greater than or
equal to the critical value indicated above will result in automatic return to normal operation.
3.2.2
CURRENT MODE
In this mode, the Power Module is programmed to behave as a current source. The user pro-
grams an operating current YY with a voltage limit XX based on the required current stabilization
point and the maximum anticipated load voltage. The Power Module is now programmed to pro-
vide a stabilized output current YY to a load impedance less than or equal to XX/YY; the CUR-
RENT MODE indicator LED is on for these load conditions.
Load impedances greater than XX/YY are considered to be overloads, and the Power Module
will modulate the output current between zero and YY as necessary to maintain the load voltage
at XX. Operation with load impedances greater than XX/YY will result in the VOLTAGE MODE
indicator LED going on and the CURRENT MODE indicator going off; a status query at his point
will indicate a device overload condition. Decreasing the load impedance to a value less than or
equal to the critical value indicated above will result in automatic return to normal operation.
3.3
OUTPUT POLARITY REVERSAL
NOTE: Although MST-MHT Power Modules include Polarity Reversal relays, this function is
not available for modules controlled by the MST 488-27HT Controller.
MST-MHT Power Modules are designed to permit reversal of output terminal polarity via a
remote command. Polarity reversal is achieved via relay switching of both power and signal
lines, and can be employed in both Voltage and Current operating modes. Polarity reversal can
be programmed in advance of output activation (Standby) or “on-the-fly” (Active) while the out-
put is enabled; both methods employ a “dry-switching” scheme in order to extend relay life.
Содержание MST 100-2MHT
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