MST-MHT SERIES 071320
3-5
redundant applications, the user can reduce overall power system operating stress by increas-
ing the number of modules above N.
For parallel operation, all Power Modules should be same model. The module d-c outputs and
error sense leads are wired in parallel to the load; the load share terminals from each DC Output
connector are daisy-chained together. The user must ensure that the load and sense wiring min-
imizes loop inductance to prevent stray pickup from injecting noise into the load share signals.
Twisted pairs (shielded, if necessary) should be used for both power and error sense leads
when remote error sensing is used, with all error sensing lines terminated to the same physical
location; if possible, the user should employ local error sensing.
Program each module for Voltage Mode operation at identical output voltage and current limit.
The load sharing circuitry will automatically select the “load master” as the module with the high-
est “effective” voltage supplying power to the output bus; all other modules operate as slaves
and are indicated as such by the CURRENT SHARE indicator LED on the front panel of the
power module. Since MST-MHT Power Modules are enabled sequentially, the enabled modules
will generate output voltage errors until the minimum number of modules (N) are turned on; the
user should ignore these error flags until all modules are enabled (SCPI provides a method of
masking these flags using software). The same is true if modules are disabled sequentially.
3.6
SERIES OPERATION
MST-MHT Power Modules are designed to allow series operation to achieve higher output volt-
age if desired. Series operation requires detailed investigation into all possible output conditions
which may result from either normal or abnormal operation to ensure that the power supplies
are not exposed to undue stress, especially voltage. This need is increased for MST-MHT
Power Modules which, because of the sequential turn-on characteristic, may be exposed to
greater risk during output enabling and disabling sequences. Users wishing to operate MST-
MHT Power Modules in series are directed to contact Kepco Applications Engineering for spe-
cific guidance.
3.7
FAULT PROTECTION
In addition to providing protection against externally generated faults, MST-MHT Power Mod-
ules incorporate fault protection circuitry which protects the load in the event of an internal fail-
ure or malfunction which may result in loss of output control. The fault classifications are output
overvoltage, output overcurrent, internal overtemperature, source power loss and open sense
lead. A description of the fault detectors associated with these faults is provided in the following
paragraphs.
The response of the Power Module to any of these faults (except for open sense/power lead) is
a fault shutdown procedure consisting of the following:
a. Fault Shutdown with Flag - Any of the faults (except open sense leads)
•
All output power and signal relays are immediately opened, isolating the Power Module
from the load;
•
Output voltage and current are programmed to zero;
•
The dc-dc converter which powers the output stabilizer is latched off;
Summary of Contents for MST 100-2MHT
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