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Ceramic PTC Thermistor for High Voltage Current Surge Protection

Ceramic positive temperature coefficient PTC thermistors help provide protection against power cross, power induction surges and lighting surge defined in ITU, Telcordia, UL. Available in chip, radial-leaded coated and non-coated configuration. This thermally sensitive semiconductor resistor provides reversible, self-resetting fuse protection against over-currents short circuit for telecommunication line protector units, improve the reliability of custom premises and network equipment.
PTC Thermistors Current Limiting Protection Device can be found providing resettable line protection at the exchange, monitoring hot spots and protecting ringers, battery feeds, transformers, switches and relay circuits. Also used extensively to protect the mobile phone's battery pack against overcharging in land-based and radio mobile communications.

Advanced developments in telecom equipment in recent years have radically altered the protection requirements of both exchange and subscriber equipment. PTC Thermistor Current Protector must protect the telephone line circuit against overcurrent, which may be caused by the following examples:
Surges due to lighting strikes on or near to the line plant.
Short-term induction of alternating voltage from adjacent power lines or railway systems, usually caused when these lines or systems develop faults
Direct contact between telephone lines and power lines.
To provide good protection under such conditions, a PTC thermistor is connected in series with each line, usually as secondary protection; However, even with primary line protection (usually a gas discharge tube), the PTC thermistor must fulfill severe requirements.
Surge pulses of upto 2KV can occur and in order to withstand short term power induction, the PTC thermistor must withstand high voltages. If the line has primary protection, a 220V to 300V PTC thermistor is adequate. Without primary protection, 600V PTC device is necessary. We can manufacture a series of PTC thermistor fulfilling both requirements.

High Voltage Current Surge Protection PTC Thermistor Application in Telecommunication Equipment

Central Office Switching Equipment (C.O): analog and digital line cards, POTS, T1/E1 equipment, xDSL modems and splitters, multiplexers, CSU/DSU, servers.
Primary Protection Modules: MDF (main distribution frame) modules, network interface devices (NIC).
Custom Premises Equipment, also known as subscriber terminal equipment (T.E.), IT equipment: Modem, phone sets, fax machines, phone wall outlet (plugs), alarm systems, answering machine, PBX systems, ADSL Splitters, internet appliance, POS terminals.
Access Network hardware, LAN WAN equipment, Powered Ethernet systems, VoIP (voice over IP equipment), integrated voice data (IVD), Set-top box (S.B), etc.

PTC Thermistor Current Protector Features

Compliant with ITU-T K20 K21 K45

--Basic level lightning surges (10/700s)
--Basic level power Induction (600V,1A,0.2S)
--Power contact criteria A/B (230V,15min.)
Suitable for continuous connection to main voltage 110/230 VAC in tripped (high ohmic) condition.
Round leadless disk thermistor available for combined usage of PTC and primary protection, e.g gas arrestor.
Thermistor disk coated non-coated construction, diameter 5mm to 10mm.
Typical Resistance @25C (R25) 10 ohm, 12 ohm, 18 ohm, 20 ohm, 25 ohm, 50 ohm, 55 ohm.
Matching available with narrow resistance tolerance.
Tight resistance tolerance maintained after switching.
Negligible resistance drift after soldering or switching.

PTC Thermistors Overload Surge Current Protection Electrical Performances

Rated zero-power Resistance(R25)
Operating temperature range: 252, Within the allowable tolerance.

Non-operating characteristic
Operating temperature range: 402. In static air for 30min.Max. voltage: 60VDC. Non-operating current. Energized time: 60min. (R-R25)/R2550%

Over-current operating characteristic
Operating temperature range: 252,Max. voltage of power supply: 220Vrms.Test the time for the current decrease to limited value. See the spec. Table.

Over voltage withstanding (Power line contact)
Voltage of power supply: 250VAC, Initial current: 3A,Energized time: 30min . Restore time in room temperature is 4 hours, then test the R25. R/R2520%.

Over current withstanding
Max. voltage of supply: 220VAC, Initial current: 3A. ON 60S, OFF 600S,Cycle:30 times, Restore time in room temperature is 4 hours, then re-test the Rn.
R/Rn20%.

Surge current withstanding
Current waves: 10/1000S, Minimum opening circuit voltage: 1.0kv, Peak current: 25A, Interval: 3min, Cycle:30 times, Restore time in room temperature is 4 hours, then re-test the R25. R/R2520%.

Induction voltage current withstanding (Only for maximum voltage more than 600V)
Max. voltage of supply: 650VAC, Initial current: 1.1A.,ON 60S, OFF 600S,Cycle:10 times, Restore time in room temperature is 4 hours, then re-test the R25. R/R2520%.

Fail Model
I. Voltage of power supply: 250VAC. Initial current: 10Arms,
II. Voltage of power supply: 600VAC. Initial current: 15Arms.
III. Voltage of power supply: 650VAC. Initial current: 10Arms.
Energized time: 30min. High resistance or open circuit is allowable. Low resistance state or firing is not allowed..

Restore time
The necessary time of a PTC to return to twice of R25. 60S.

PTC Thermistor Current Protector Outline and Dimensions (unit:mm)

Fig.1

Fig.2

Fig.3

Fig.4

Telecom PTC Thermistors round chips drawingTelecom PTC Thermistors round chips thickness

Telecom PTC Thermistors rectangluar chips drawingTelecom PTC Thermistors rectangluar chips thickness Telecom PTC Thermistors radial leaded resin coated formTelecom PTC Thermistors radial leaded resin coated form Telecom PTC Thermistor radial leaded non-coating construction
Twin Surface Mount PTC Thermistor Outlook, telecom protect Twin SMD PTC Thermistor Telecom Protect Engineering Drawing
Fig.5 Twin Surface Mount PTC Thermistor for Telecom Protection AMZ26 Outlook and Dimension

PTC Thermistor for Telecom Line Card Protection Application

Part number

Resistance @25C
R25

Ohm

Non-trip current
IntmA

Trip current
@25C

It

mA

Tripping time at max current

(Seconds)

Max. current
Imax

(A)

Max. voltage
Vmax

(V)

Fail model Dimension mm
@25C @40C Dmax Tmax d
AMZ23-10RM130 10 ohm 130mA 100mA 260mA <0.2s 2.0A 250V 250V/10A 7.5 4.0 0.6
AMZ23-10RM150 10 ohm 150mA 100mA 260mA <0.3s 2.0A 250V 250V/10A 9.0 5.0 0.6
AMZ23-12RM130 12 ohm 130mA 100mA 260mA <0.3s 2.0A 250V 250V/10A 9.0 5.0 0.6
AMZ23-12RM090 12 ohm 90mA 60mA 160mA <0.2s 2.0A 250V 250V/10A 9.0 5.0 0.6
AMZ23-20RM100 20 ohm 100mA 80mA 200mA <0.2s 3.0A 250V 250V/10A 9.0 4.0 0.6
AMZ23-35RM090 35 ohm 90mA 75mA 180mA <0.2s 3.0A 250V 250V/5A 9.0 5.0 0.6
AMZ23-40RM080 40 ohm 80mA 70mA 160mA <0.2s 3.0A 250V 250V/5A 9.0 5.0 0.6
AMZ23-50RM070 50 ohm 70mA 60mA 150mA <0.2s 3.0A 250V 250V/5A 9.5 5.0 0.6
AMZ23-50RM075 50 ohm 75mA 60mA 150mA <0.2s 3.0A 650V 650V/10A 9.5 5.0 0.6
AMZ23-55RM070 55 ohm 70mA 60mA 150mA <0.2s 3.0A 650V 650V/10A 9.5 5.0 0.6
AMZ25-9RM160 9 ohm 160mA 130mA 330mA <0.8s 3.0A 250V 250V/10A 10.5 4.5 0.6
AMZ25-25RM100 25 ohm 100mA 80mA 220mA <0.2s 3.0A 250V 250V/10A 6.6 4.0 0.6
AMZ25-25RM120 25 ohm 120mA 100mA 300mA <0.4s 3.0A 250V 250V/10A 8.2 4.0 0.6
AMZ26-35RM080SMD 35 ohm 80mA 60mA 180mA <0.2s 2.5A 250V 250V/10A / / /
Note: Standard Resistance @25C (R25) allowable tolerance +/-20%, if not specified.

PTC Thermistor for Telecom MDF (Main Distribution Frame) Protection Application

Part number

Resistance @25C
R25

Ohm

Non-trip current
Int

mA

Trip current @25C
It

mA

Tripping time at max current

(Seconds)

Max. current
Imax

(A)

Max. voltage
Vmax

(V)

Dimension mm
@25C @40C Dmax Tmax d
AMZ21-10RM150 10 ohm 150mA 130mA 350mA <4.0s 3A 230V 7.2 1.5 /
AMZ21-18RM110 18 ohm 110mA 90mA 220mA <0.15s 3A 250V 5.5 1.5 /
AMZ21-18RM125 18 ohm 125mA 110mA 250mA <0.18s 3A 250V 5.5 2.0 /
AMZ21-18RM130 18 ohm 130mA 110mA 260mA <0.18s 3A 250V 6.2 2.0 /
AMZ21-18RM135 18 ohm 135mA 110mA 270mA <0.2s 3A 250V 6.6 2.0 /
AMZ21-20RM085 20 ohm 85mA 70mA 170mA <0.18s 3A 250V 6.2 2.0 /
AMZ21-25RM055 25 ohm 55mA 45mA 110mA <0.4s 2A 230V 5.3 2.0 /
AMZ21-25RM060 25 ohm 60mA 50mA 120mA <0.4s 2A 230V 5.3 2.0 /
AMZ21-25RM085 25 ohm 85mA 75mA 170mA <0.7s 2A 230V 5.3 2.0 /
AMZ25-25RM055 25 ohm 55mA 45mA 110mA <0.4s 1A 230V 5.3 4.0 0.6
AMZ25-25RM060 25 ohm 60mA 50mA 120mA <0.4s 1A 230V 5.3 4.0 0.6
AMZ25-20RM145 20 ohm 145mA 100mA 250mA <0.2s 3A 250V 6.6 4.0 0.6
AMZ25-10RM130 10 ohm 130mA 110mA 260mA <4.0s 1A 230V 6.6 4.0 0.6
AMZ25-10RM150 10 ohm 150mA 135mA 300mA <7.0s 1A 230V 8.2 4.0 0.6
AMZ25-18RM125 18 ohm 125mA 110mA 250mA <1.0s 1A 230V 5.5 4.0 0.6
AMZ23-18RM135 18 ohm 135mA 110mA 270mA <0.2s 3A 250V 7.5 4.5 0.6
AMZ23-18RM110 18 ohm 110mA 90mA 220mA <0.2s 3A 250V 9.0 4.5 0.6
AMZ23-20RM100 20 ohm 100mA 80mA 200mA <0.2s 3A 250V 9.0 4.5 0.6
AMZ23-25RM085 25 ohm 85mA 75mA 170mA <0.7s 1A 230V 6.5 5.0 0.6
AMZ23-25RM090 25 ohm 90mA 70mA 180mA <0.2s 3A 250V 9.0 4.5 0.6
Note: Standard Resistance @25C (R25) allowable tolerance +/-20%, if not specified.

AMWEI Telecom PTC Thermistor Code

Typical telephone line showing where PTC thermistors can be used for overcurrent protection

Typical telephone line showing where PTC thermistors can be used for overcurrent protection

PTC Thermistors telecom protection circuit

An example of PTC Thermistors for telecom circuit protection


Keep Reading: ‘Power NTC Thermistors for Inrush Current Limiting Surge Supression’ »


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