ELECTRONIC FILM CAPACITORS, INC.
Reidville Industrial Park * 41 Interstate Lane
WATERBURY, CONNECTICUT 06705
PHONE (203) 755-5629
FAX (203) 755-0659
RESISTOR-CAPACITOR NETWORKS
APPLICATIONS
Noise suppression and contact protection
SERIES RC1313
R
N
R
L
L
R
L
OR
V
source
R
N
C
N
L
V
source
C
N
Fig. 1 (across the load)
Fig. 2 (across the contacts)
The circuit to be used is dependent upon particular situations. Either circuit may be enough protection for
your needs. For extreme situations, both "Load" and "Contact" protection may be required.
Recommendations
There are two types of discharges that can damage switching contacts and generate noise:
(1) "Glow Discharges" caused by the ignition of gases between contacts. These develop at about 320 volts at
about a 0.0003 inch gap range and can be sustained at a much wider gap range.
(2) "Arc Discharges" occur at much lower voltages, about 0.5 MV/cm. Minimum voltages and currents are
necessary for "Arc Discharges" to be sustained. Contact material also plays a role in sustained "Arc Discharges".
(see Table 1)
MATERIAL
Silver
Gold
Gold Alloy
Palladium
Platinum
MIN. (VA)
Arcing Voltage
MIN. (IA)
Arcing Current mA
12
15
9
16
17.5
400
400
400
800
700
The function of the RC network is to:
(1) Keep the voltage across the contacts below 300 volts. C> (I
L
/300)
2
L
(2) Keep the rate of voltage change below 1V/µs. C> I
L
x 10
-6
(3) Keep the current below that described in Table
1.
TABLE 1
Inductors do not instantly "let go" of a current. At the instant a contact opens, the current through the contact
does not want to change. Using Ohms Law (E = IR), we can see that when the contact is closed, the resistance
is essentially zero, making the voltage zero, as well. As the contact opens the resistance begins to increase.
This leads to the generation of a high voltage which is generally destructive to contact life.
Capacitors will restrict an instantaneous change in voltage. A capacitor, therefore is useful to counter the
destructive voltages generated at the switch contacts. When the contacts are closed, the capacitor is out of the
circuit. As the contacts are opened any change in voltage is restricted by the capacitor if its value is large enough
to restrict the voltage change to less than 1 V/µs.
A capacitor alone is not an ideal solution. When the contacts are open, the capacitor charges up to the supply
voltage. As the contact is "made", an inrush of current results limited only by a residual resistance and damage
may still result. For this reason, a resistor is configured in series with the capacitor. The higher the resistance
value the smaller the inrush current and the less effective is the capacitor. The voltage across the contacts when
opened is equal to the load current x resistance. (V = IR) It is recommended to keep V =< supply voltage.
In this case, the maximum resistance of the network (R
N
) will be equal to the load resistance (R
L
).
The above formulas are recommended for determining the RC network parameters. They do not identify all
of the subtleties but should serve as a guideline for effective results.
RESISTOR - CAPACITOR NETWORK NOMENCLATURE
RC 1313 EFR - N - .1 - 6.3 - 20 / 5 101
DIELECTRIC CODE
1313 - METALLIZED POLYESTER
RESISTOR VAL. (OHMS)
CAPACITANCE
IN MICROFARADS (µF)
µ
FIRST 2 DIGITS ARE SIGNIFICANT
FIGURES - LAST DIGIT IS NUMBER
OF ZEROS ADDED
(i.e. 101 = 100 OHMS)
CASE CODE
TC - WRAP & FILL - ROUND - AXIAL
TF - WRAP & FILL - OVAL - AXIAL
EFR - EPOXY CASE - FLAT - RADIAL
VOLTAGE
SIZE CODE
(SEE DIM. SPECS.)
2 - 200 VDC
4 - 400 VDC
6.3 - 630 VDC
RES. WATTAGE
2 - 1/4 WATT
5 - 1/2 WATT
6 - 1.0 WATT
7 - 2.0 WATT
CAP. TOLERANCE
R/C NETWORK
5 - 5%
10 - 10%
20 - 20%
ETC.
T
<
+
L _ .010"
>
< >
>
+ .010"
_
<
L + .010"
>
><
EFC
RC1313
R
<
S
+
.025"
_
>
R
_
H + .010"
1.00 "
MIN
EFC
RC1313
Insulated Leads
(All dimensions in inches)
DIMENSIONS AND RATINGS
Cap.
µ
F
0.10
0.10
0.25
0.25
0.50
0.50
1.0
1.0
VOLTAGE
DC
AC
200
630
200
630
200
630
200
630
125
250
125
250
125
250
125
250
RES. VALUE
(OHMS)
22-1000
22-1000
22-1000
22-1000
22-1000
22-1000
22-1000
22-1000
L
T
H
in. mm in. mm in. mm
.709
1.04
.709
1.04
1.04
1.26
1.26
1.26
18
26.5
18
26.5
26.5
32
32
32
.295
.335
.295
.394
.236
.512
.335
.670
7.5
8.5
7.5
10
6
13
8.5
17
.531
.669
.531
.748
.591
.866
.669
1.36
13.5
17
13.5
19
15
22
17
34.5
<
EFC PART NUMBER
RC1313EFR - H - .1 - 2 - _ / _ _ _ _
RC1313EFR - N - .1 - 6.3 - _ / _ _ _ _
RC1313EFR - H - .25 - 2 -_ / _ _ _ _
RC1313EFR - 0 - .25 - 6.3 - _ / _ _ _ _
RC1313EFR - L - .5 - 2 - _ / _ _ _ _
RC1313EFR - Q - .5 - 6.3 - _ / _ _ _ _
RC1313EFR - N - 1.0 - 2 - _ / _ _ _ _
RC1313EFR - V - 1.0 - 6.3 - _ / _ _ _ _
*
*
*
Denotes UL recognized parts
RESISTOR SPECIFICATIONS
POWER
(WATTS)
0.25
0.50
LEAD SPECIFICATIONS
(SOLID COPPERWELD)
L
(In.)
.709
VOLTAGE
(VAC)
250
250
TYPE
Carbon Comp.
S
(In.)
.562
.886
1.13
DIA.
(In.)
.031
.031
.031
LEAD LENGTH
(MIN. In.)
1.000
1.000
1.000
Carbon Comp.
1.04
1.26
RESISTOR TOLERANCE _ 10 % or better
+
EFC will manufacture to any non-standard value and size. Please consult factory for special requirements.
Embedded System
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EEWORLD
