KEPCO JQE 150-1.5MVPY-26956 Half Rack - Manual (Page 30)

3-6 JQE SPECIAL SVC 081111
The ratio of termed the “CONTROL RATIO,“ gives the current (in mA) needed to obtain
one Ampere of output current where R
S
is in Ohms and R
CF
is in KOhms.
3.5 GENERAL RULES FOR REMOTE PROGRAMMING
All remote programming applications require the observance of a few basic rules to insure
proper functioning of the power supply in the particular mode of operation selected. These rules
should be remembered before each application, and especially if malfunctioning of the program-
ming set-up is experienced.
3.5.1 GROUNDING
Ground loops due to multiple and indiscriminate grounding of various equipment are the cause
of the majority of complaints about "high ripple or noise." They can be easily avoided by ground-
ing the power supply at one point only to which all shielded cables and equipment cases are
connected. If possible, one side (preferable the positive one) of the power supply output should
also be grounded.
3.5.2 CONNECTIONS
All external connections, especially the rear barrier strip terminal screws, must be tight. Series
malfunctions may be caused by open feedback loops, error sensing lines or programming con-
nections.
3.5.3 PROGRAMMING RESISTORS
Programming resistors should be high quality wirewound units with temperature coefficients of
20 parts per million or better. Their wattage rating must be at least 10 times the actual power
dissipated. Although the control current through these resistors is only 1 mA, an error current
spike exists when programming large voltage excursions. The peak of the current is limited by
the internal 500 Ohm resistor and depends upon the magnitude of output voltage swing. The
time constant is determined by the internal 500-Ohm resistor and the unit’s output capacitance
given in Table 1-1 for current mode.
3.5.4 EXTERNAL SWITCHING
If step-switch devices are used in resistance programming, they must be of the "make before
break" variety to avoid programming infinity. Programming resistors must have a voltage rating
at least equal to the maximum output voltage of the power supply.
3.6 OUTPUT VOLTAGE PROGRAMMING WITH EXTERNAL RESISTANCE
The output voltage of the Power Supply may be controlled remotely by an external resistance,
replacing the built-in voltage control resistance which is disconnected at the rear barrier strip;
this is accomplished by removing the link between terminals RVC and RPV1 at terminal block
TB501 at the rear panel. Refer to Figure 3-5 and install a variable resistance across terminals
RPV1 and RPV2 of TB501. To maintain a calibrated “programming ratio” of 1000 Ohms/V, the
switch labelled E
OUT
LOCAL - E
OUT
REMOTE (accessible through the top cover) must be set to
E
OUT
REMOTE. The value of the programming resistance may be calculated by referring to the
transfer function derived earlier (Eq. 1)
(1)
RCF
KSRS
---------------
EO RVC
Er
Rr
------ Ч =