KEPCO MBT Series - Manual (Page 112)

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MBTSVC111609
4.1.10 RETENTION OF PROGRAMMED VALUES
A non-volatile RAM located on the A3 Digital Control Board allows the MBT Power Supply to
retain the last programmed values for voltage and current when the unit is turned off. When the
unit is turned on, the last programmed values of voltage and current will be displayed on the
front panel, along with the message Output is OFF. For the M and MG option units, this
means that output voltage and current are set to zero; for MR and MRG option units, the output
relays disconnect the power supply output from the load. This allows the operator to readjust the
previously programmed values as desired, followed by the DC ON command to make the output
active. The non-volatile RAM also stores the data related to local programs.
4.1.11 OUTPUT ENABLE/DISABLE AND POLARITY REVERSAL RELAYS — MR, MGR MODELS
An important feature of “R” Option MBT Power Supplies is the output enable, disable and polar-
ity reverse functions. These are achieved by activating two power relays and two signal relays.
The two power relays connect, disconnect or reverse the power supply output at the Power
Supply rear panel OUTPUT and COMMON terminals (one relay for connect/disconnect, the
other for polarity reversal). The signal relays perform the same functions as the power relays but
they act on the sense leads (OUT S and COM S) instead of the power leads.
A special sequence is implemented in closing and opening these relays. With a Close com-
mand, the power leads are connected to the load first and then the sense leads are connected.
For the Open command the sense leads are disconnected first and the power leads afterwards.
To increase the reliability of the MBT Power Supply, a “Dry” switching technique is used. Any-
time a command is received from a Controller to Close, Open, or Reverse Polarity of relays, or
change the operating mode (voltage or current), the MBT software implements a special
sequence:
a) Store the previous or the new values for voltage and current.
b) Program the Voltage and Current References to zero (see PAR. 4.1.5).
c) Wait until zero volts output is established.
d) Close, open or reverse polarity.
e) Reprogram the output voltage and current to the stored values.
During the above sequence, flags that trigger error messages are inhibited (masked out of the
error buffer).
4.1.12 OUTPUT ENABLE/DISABLE
NOTE: For both voltage or current modes of operation, the command to Enable the output at
the load is Close, and to Disable the output from the load is Open. These definitions for
Enable and Disable apply specifically to MBT Power Supplies.
4.1.12.1 M, MG MODELS The non- “R” option units operate locally only as a commanded voltage
source. The actual mode, voltage or current, will depend on the programmed values for output
voltage and current and the value of the load. The output is disabled by setting the output volt-
age and current to zero.
NOTE: Refer to PAR.s 3.1.1 and 3.1.2 for an explanation of actual and commanded modes.