PTC Thermistor for Protection of Telecom Apparatus

PTC thermistor for overcurrent and overload protection of telecom apparatus Z2 series

Brief Introduction:
Advanced developments in telephony equipment in rencent years have radically altered the protection requirements for both exchange and subscriber equipment.The PTC thermistors must protect telephone line circuit against overcurrent,which mainly caused by the following examples:
1)surges due to lighting strikes on or near to the line plant;
2)short-term induction of alternating voltage from adjacent power lines of railway systems,usually caused when these lines or systems occur faults;
3)direct contact between telephone lines and power lines.

Product Application:
They provide reversible,self-resetting protection against overcurrents in：
1.SPC exchange,PBX
2.Distribution frame,main distribution frame (MDF) 
3.Security unit
4.Telephone and outdorr telephone
5.Telecom equipment

Advantages:
1. Automatic protection,can resume steadily;do not need to be reset after protection
2. Contactless,noiseless and flameless;
3. Reacts fast;
4. With a better performance of withstanding voltage,can operate in 110/230V AC (high resistance state) continuously
5. Low rated current
6. Small steady resistance;
7. Narrow resistance tolerance (resistance matching)
8. Satisfy ITU-T K20 K21 requirement.
--Surge current（10/700µs）
--Induction voltage（600V,1A,0.2S）
--Power line contact（230V,15min.）
9.Long stability

Electronic feature:
Rated zero power resistance:
Ambient temperature: 25±2℃,within the allowable tolerance.
Non-trip characteristic:
Ambient temperature: 40±2℃，in still air for 30 minutes, power voltage 60VDC, maximum non-trip current ON for 60 minutes. （R-Rn）/Rn≤50%
Overcurrent trip characteristic:
Relation between trip current to trip time of PTC thermistor.
Over voltage withstanding:
Power voltage: 230 Vrms /250 Vrms, maximum current ON for 30 minutes. 4 hours after restoring in room temperature, retest zero power resistance, ΔR/Rn≤20%.
Over current withstanding:
Power voltage 220Vrms, maximum current 60S ON/600S OFF, cycles: 20, 4 hours after restoring in room temperature, retest zero power resistance, ΔR/Rn≤20%.
Surge current withstanding:
Short circuit wave: 10/1000μs, minimum opening circuit voltage: 1.0KV, peak current：25A, interval time: 3 minutes, cycles: 30,4 hours after restoring in room temperature, retest zero power resistance, ΔR/Rn≤20%.
Induction voltage withstanding (Only for maximum voltage over 600V):
Power voltage: 600 Vrms /650Vrms,initial current 1.1A, 2S ON/600S OFF, cycles: 10, 4 hours after restoring in room temperature, retest zero power resistance, ΔR/Rn≤20%.
Fail model:
Ⅰ. Power voltage: 250Vrms，initial current: 10A.
Ⅱ. Power voltage: 600Vrms ，initial current: 15A
Ⅲ. Power voltage: 650Vrms，initial current: 10A
Energized time 30 minutes, high resistance state or open circuit is allowable. Low resistance or firing is not allowed.
Restore time:
The time necessary for PTC thermistor returning to twice Rn. Lower than 60 seconds is required.

Many specifications for choice,and samples&orders can be custom made per customers' requirement.