KEPCO KT 3126-3130S User manual

©2011, KEPCO, INC 1
Data subject to change without notice 228-1631 REV 1
INSTRUCTION MANUAL
KT
KEPCO
KEPCO, INC.  131-38 SANFORD AVENUE  FLUSHING, NY. 11355 U.S.A.  TEL [phone]  FAX [phone]
http://www.kepcopower.com  email: [e-mail]
An ISO 9001 Company.
SENSE RESISTOR
KT 3126-3130S
KT 3130-3131S
CURRENT SENSING RESISTORS
GENERAL DESCRIPTION (Refer to Figures 1 and 2)
Kepco Model KT 3126-3130S and KT 3130-3131S Current Sensing Resistors are precision, wire-wound components
with low temperature coefficients and integral heatsink used for calibrating Kepco Power Supplies
SENSING RESISTOR SELECTION
The value of the sensing resistor (RS) is selected according to the desired output current range, such that a I-volt sam-
ple is provided at the maximum output current (lOMAX):
INSTALLATION
Refer to Figure 1 for Sense Resistor connections. The two sense resistors are mounted on a heat sink. If the actual
power dissipation (MAXIMUM OUTPUT CURRENT TIMES ONE VOLT) exceeds one-tenth of the power rating,
additional cooling by means of an air stream or an oil-bath should be provided to keep the heat-rise in the
sensing resistor to a minimum. To minimize output ripple (“pick-up”) mount the sensing resistor assembly as close to
the power supply as practicable. Use shielded cable to connect the current control resistor to the null junction of the
power supply and connect the shield (single-ended) to the common signal ground.
INTERCONNECTIONS
The simplified connecting diagram (refer to Figure 2) shows the electrical connection of the Sensing Resistors to a typ-
ical Kepco Power Supply. The nomenclature used in the diagram coincides with that used on all Kepco Power Sup-
plies. Refer to your Kepco Instruction Manual when in doubt about interconnections or terminal designations.
CALIBRATION
The sense resistors are calibrated at Kepco. A label installed on the heatsink for RS1 and RS2 shows actual resistance
at various current ratings. For example, label for the 0.01 ohm resistor shows the calibrated resistance for operation
between 1A and 8A, between 8A and 15A, and between 15A and 25A. This means that if you are testing a 10 Ampere
power supply (e.g., BOP 20-10-4886) use the 0.01 ohm resistor and use the resistance recorded for between 8 and 15
Amperes.
TABLE 1. KEPCO SENSING RESISTORS
MODEL RESISTANCE
(OHMS)
RECOMMENDED OUT-
PUT CURRENT RANGE TERMINATION OUTLINE
DIMENSIONS
LOW HIGH
KT 3126-3130S 0.5A TO 20A
SCREW 8"L X 4.4”W X 1.75”HRS1 0.1 0.5A 8A
RS2 0.01 8A 25A
KT 3130-3131S 10A TO 100A
SCREW 8"L X 4.4”W X 1.75”HRS1 0.01 8A 25A
RS2 0.001 25A 100A
RS
1 Volt
IOMax.
--------------------= (See Table 1 for values.)

2228-1631 REV 1 111411
KEPCO, INC.  131-38 SANFORD AVENUE  FLUSHING, NY. 11355 U.S.A.  TEL [phone]  FAX [phone]
http://www.kepcopower.com  email: [e-mail]
FIGURE 1. SENSE RESISTOR CONNECTIONS
INOTE: If the load must be protected from excessive compliance (output) voltage, a zener diode, rated to
conduct at the desired voltage, should be connected as shown in FIG. 2.
FIGURE 2. EXTERNAL CURRENT SENSING AND CONTROL USING THE VOLTAGE MODE AMPLIFIER
CAUTION
WIRES BETWEEN POWER SUPPLY
OUTPUT AND SENSE RESISTOR MUST
BE RATED TO CARRY THE RATED
OUTPUT CURRENT OF THE POWER
SUPPLY. AWG#6 IS RECOMMENDED.
NOTE:
RSshould be physically located as
close to the (+) output terminal of the
power supply as possible. In this
case, the link (+) OUT – (+) SENSE
CAN BE CLOSED and the connec-
tion (+) SENSE to terminal P of RS
can be deleted. If RSmust be
located some distance from the
power supply, the sensing connec-
tion as shown must be used (link
(+) OUT – (+) SENSE removed) and
the (+) terminal of the output capaci-
tor (COmust be internally recon-
nected from the (+) sensing to the
(+) output terminal.