KEPCO MBT Series - Manual (Page 113)

MBTSVC111609
4-7
4.1.12.2 MR, MGR MODELS The “R” option units operate either as a commanded voltage source or a
commanded current source. The actual mode, voltage or current, will depend on the pro-
grammed values for output voltage and current and the value of the load (see NOTE above).
Enabling or disabling the output differs from the voltage mode to the current mode. When con-
sidering a voltage source, a no-load condition (infinite resistance) is ideal. This is equivalent to a
disabled voltage source since no output current flows to the load and a set output voltage is
maintained. Enabling the voltage source is followed by energizing the power relay that connects
the power supply to the load.
For a current source to operate properly there must be a load at the output terminals. A current
source without a load will transfer itself into a voltage limit source. The ideal load for a current
source is a direct short at the output terminals. This is achieved by energizing both power relays
and is equivalent to a disabled current source. No output voltage will be present, no current will
flow into the load and the set current will flow freely through the short.
Enabling the current source is achieved by deenergizing the power relays to remove the short
across the Power Supply output terminals and to permit a current flow through the load.
4.1.13 LOCAL CONTROL
The local controls consist of the POWER circuit breaker which applies source power to the unit.
VOLTAGE and CURRENT controls are used to increment output voltage/voltage limit in Voltage
mode/Current mode, and output current/current limit in Current mode/Voltage mode, or pro-
grammed values for voltage and current when the output is Disabled. A numeric keypad with
additional dedicated keys can also be used to program the MBT. Five STATUS LEDs provide
direct indications for operating mode (Voltage or Current), polarity reversed, remote mode, and
output enabled; an alphanumeric LCD display provides status messages and programming
instructions in response to keypad entries. The following paragraphs indicate the functions
available.
4.1.13.1 SET OUTPUT VOLTAGE/CURRENT LIMIT (VOLTAGE MODE) When operating in the Volt-
age mode, output voltage can be set in three different ways:
NOTE When the output is Disabled, the following controls affect the programmed output and
limit values for voltage and current.
1. The VOLTAGE control is an optical encoder that digitally increments (clockwise rotation) or
decrements (counterclockwise rotation) the programmed voltage value, which will be dis-
played on the LCD display.
2. The slew keys ( , ) on the keypad also increment the voltage value displayed on the
LCD display; the increment is programmable (see PAR. 3.2.2.6).
3. Pressing the Vadj key, then using the numeric keypad to enter the precise numeric value
for output voltage.
Current limit can be set in two ways:
1. The CURRENT control is an optical encoder that digitally increments (clockwise rotation) or
decrements (counterclockwise rotation) the programmed current limit value which will not
be displayed on the LCD display. The new current limit can be viewed by using the STA-
TUS function (SHIFT then “.” key).
2. Pressing the Iadj key, then using the numeric keypad to enter the precise numeric value for
current limit.