Lambda LJS-12 Series Instruction Manual page 9

Programmed Voltage Connections, Using External Resistor, Figure 5. Discrete voltage steps can be
programmed with a resistance voltage divider valued at a nominal 1000 ohms/volt change and a shorting-tvpe
switch as shown in figure 5. When continuous voltage variations are required, use a variable resistor with the
same 1000 ohms/volt ratio in place of the resistive voltage divider and shorting-type switch. Use a low
temperature coefficient resistor to assure most stable operation.
Before programming, adjust programming resistor for zero resistance and set voltage adjust control to the
minimum rated output voltage. Output voltage of programmed supply will nominally be minimum output
voltage plus 1 volt per 1000 ohms.
As shown in figure 5, voltages can be programmed utilizing either local or remote sensing connections, as
desired.
Programmed Voltage Connections Using Programming Voltage, Figure 6. The power supply voltage output
can be programmed with an externally connected programming power supply. The output voltage change of the
programmed supply will maintain a one-to-one ratio with the voltage of the programming supply. If the output
voltage control of the programmed supply is set to minimum output voltage, output voltage of the programmed
supply will be minimum output voltage plus voltage of programming supply.
The programming supply must have a reverse current capability of 1.1та. minimum.
Alternatively, when supplies with less than 1.1ma. reverse current capability are used, a resistor capable of
drawing 1.1ma. at the minimum programming voltage must be connected across the output terminals of the
programming supply. This programming supply must be rated to handle all excess resistor current at the
maximum programming voltage.
Connections For Series Operation, Figure 7.
The voltage capability of LJS-12 power supplies can be extended by series operation. Figure 7 shows the
connections for either local or remote sensing in a series connection where the voltage control of each unit
functions independently to control the output.
A diode, having a current carrying capability equal to or greater than the maximum current rating of the
supply, must be used and connected as shown in figure 7. The diode blocking voltage should be at least twice
the maximum rated output voltage of the supply. See table I, of SPECIFICATIONS AND FEATURES, for
power supply current and voltage ratings.
OPERATION AFTER PROTECTIVE DEVICE SHUTDOWN
Fuse Shutdown. Fuse will blow when the maximum rated current value for the fuse is exceeded. Fatigue failure
of fuses can occur when mechanical vibrations from the installation combine with thermally induced stresses to
weaken the fuse metal. Many fuse failures are caused by a temporary condition and replacing the blown fuse
will make the fuse protected circuit operative.
Overvoltage Shutdown. When the power supply output voltage increases above the overvoltage limit, the
overvoltage protection circuit will short circuit output of the supply and shut down inverter operation. After
eliminating the cause(s) for overvoltage, resume operation of the supply by momentarily interrupting the AC
input circuit.
IM-LJS-12 5