KEPCO MBT Series - Manual (Page 65)

MBTSVC111609
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it is necessary to view status by pressing SHIFT then (.) on the keypad). If the load forces the
power supply to operate in Current mode, the CURRENT control adjusts actual output current.
3.2.1.8 SETTING VOLTAGE MODE OR CURRENT MODE
Although all MBT Power Supplies automatically switch between Voltage mode and Current
mode depending upon the programmed values for output voltage/current, the voltage/current
limit values, and the value of the load (see PAR. 3.2.1.7.1), commanding the power supply to go
into Voltage mode or Current Mode causes the internal microcontroller to monitor either voltage
or current, respectively, for fault and overload error conditions. If an error condition is detected,
an error message is stored in the error buffer (this has no effect when operating in Local mode).
3.2.1.8.1 M, MG MODELS
The M and MG models can be commanded to Voltage mode from the front panel. Current mode
can not be set from the front panel, but units installed in a remote configuration can be com-
manded to go into Current mode using remote commands. If the power supply was commanded
to be in Current mode before being set to Local mode, the slew keys will adjust current (see
PAR.s 3.2.1.6.4 and 3.2.1.7.4). For the slew keys to adjust voltage it is necessary to command
the unit to be in Voltage mode as follows:
1. The display should be reading either “Output is off” (PAR. 3.2.1.5.1, step 1) if the out-
put is disabled, or “Keypad control” (PAR. 3.2.1.5.1, step 2) if the output is enabled.
2. To ensure that the power supply is set to Voltage mode, press SHIFT then Vadj keys. The
message “No relay present” appears briefly, then the display will revert back to either
“Output is off” if the output is disabled, or “Keypad control” if the output is enabled.
(Pressing SHIFT then Iadj will cause the same messages to appear, but will have no other
effect.)
3.2.1.8.2 MR, MGR MODELS
The MR and MGR models can be commanded to either Voltage Mode or Current mode from the
front panel. Internal relays within the power supply act to establish the commanded mode. For
Voltage mode the relays will either connect (output enabled) or disconnect (output disabled) the
load. For Current mode the relays either short the output internally with the load connected (out-
put disabled) or remove the short with the load connected (output enabled); refer to PAR.s
4.1.11 and 4.1.13 for details regarding enabling and switching sequences.
VOLTAGE MODE — Commanding the power supply to go into Voltage mode causes the inter-
nal microprocessor to compare the output voltage to the programmed voltage and the output
current to the current limit to determine when an error condition has occurred. While the power
supply is in Voltage mode with the load enabled, the output voltage will remain constant at the
programmed value, while the current will vary depending on the value of the load. If the load is
less than the programmed voltage divided by programmed current, the power supply will oper-
ate in Current mode (forced).
Commanding the power supply to go into Voltage mode (with output disabled) from Current
mode causes the output relays to disconnect the load and remove the internal short across the
power supply output. With the output disabled the VOLTAGE MODE indicator will go on and the
CURRENT MODE indicator will go off. If the output is enabled, the actual mode will be deter-
mined by the programmed voltage and current values relative to the load (see PAR. 3.2.1.7.1).
To command the power supply to go into Voltage mode, proceed as follows: