307C Overcurrent Thermistors
PTCR Overcurrent Protection
Vishay Cera-Mite
Fig P-6
Fig P-5
PTC THERMISTORS FOR
TELECOMMUNICATIONS
C.O. Ring
C.O.
Tip
Ground
Over-Current
PTC Thermistors provide protection
for large digital switches.Vishay Cera-
Mite has pioneered this field with
ceramic PTC thermistors working
closely with major telephone equip-
ment and telephone protection
manufacturers. The requirements are
dynamic, as switch makers continually
strive to protect at lower levels.Vishay
Cera-Mite participates with industry
standard technical committees to
establish common definitions and
understanding of this new tech-
nology.
Line
Tip
Pressure
Contact
Leaded PTCR
Pressure
Contact
Over-voltage
PTCR
C.O. Tip
OV
PTCR
Line Tip
C.O. Tip
OV
C.O. Ring
PTCR
PTCR
To Battery
C.O. Ring
Line Ring
Fig P-8
PTC THERMISTOR PELLETS FOR TELECOMMUNICATIONS
Table 2
Time-Trip Curves for Popular Telecom Pellets
100
PTCR
Scope
VISHAY
Fig P-7
HOLD (IH) TRIP (IT) RESISTANCE SWITCH SIZE (D) CERA-MITE
Solid Ceramic
Disc
RL
CURRENT CURRENT
R25
Ohms
30
TEMP. NOMINAL
PART
1/2
mA
mA
°C
105
70
mm
6.5
8
NUMBER
Time To
110
100
100
110
120
140
110
130
140
150
220
200
200
220
240
280
220
260
280
300
307C1127
307C1128
307C1126
307C1268
307C1129
307C1435
307C1134
307C1130
307C1436
307C1437
Note 3
Base
Electrode
10
15
D
307C1130
20
80
8
307C1129
307C1128
307C1126
307C1127
Silver
Electrode
18
80
8
15
80
8
15
15
15
9
105
70
80
70
80
8
1
T
9.5
9.5
9.5
9.5
2.5mm
Rated Voltage = 60 VDC
Rated Current = 3A
10
Maximum Voltage = 220 Vrms
Note 1
Note 2
0.1
0
.05
1
1.5
Current (Amperes)
Operating Time to 50% Current
2
2.5
3
Note 1
Hold and trip currents
are specified at
Note 3
Note 2
25 is nominal zero power
resistance at 25°C with
All pellets have silver elec-
trodes suitable for pressure
contact mounting.
R
25°C ambient.
tolerance of ± 20%.
Fig P-10
INTERRUPTING CAPACITY ESTIMATES
Under unusual circumstances, telecommunication lines may
be subjected to high surge currents as might occur from
lightning effects or accidental crossing with power lines or
transformer primaries.
Time VS. Current Curves for High Current Surges (25°C)
10,000
10 ohm, 80°C Pellets for
Diameters (mm
Fig P-10 shows trip time curves for higher currents.Estimated
interrupting capability data is also shown in Table 3 and
is expressed as “I2 t Let Through” based on test data
conducted in accordance with UL 497A and CSA 22.2 No.
0.7-M1985.
14.5mm
12.5mm
11.0mm
9.5mm
8.0mm
6.5mm
1,000
The data shown is for reference. Specific short circuit data or
interrupting capability is partially determined by the mounting
means and circuit application.
100
Fig P-9
15
85
275
PTCR
Current
Limiter
A
B
C
Variable
Voltage
Source
0-600V
60Hz
Current
Probe or
26 AWG
Pair
A = 1.5 sec.
10
Timed Interrupter B = 5 sec.
C = 30 min.
2
4
6
8
10
12
14
16
18
20
Current (Amperes)
2 t Let Through
Document Number: 23089
Revision 14-May-02
www.vishay.com
13
ceramite.support@vishay.com
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