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PTC SERIES SPECIFICATION
Common Glossary:
Rate Zero-power Resistance (Rn):DC resistance value of the thermistor measured under 25℃ by adopting
sufficiently low power consumption.
Maximum Operating Voltage (Vmax) The maximum rated voltage the PTC thermistor can continuously
endure at 25℃.
Maximum Inrush Current (Imax) The maximum current (effective value) through the PTC thermistor under
max.rated voltage. Exceeding this current may result in damage to the PTC components.
Reference Temperature (Tsw) The temperature at which the resistance value of the PTC thermistor increases
to twice Rmin, also called Curie temperature.
Non-trip Current (Int) Rated current or holding current, at maximum operating temperature, this is the
maximum current value that doesn’t trip the PTC to the high resistance state. Under these conditions, PTC
performs as a fixed resistor.
Trip Current (It) The minimum current value that will cause the PTC to trip to the protective high resistance
state.
Operating Temperature Range The ambient temperature range in which PTC can be used when the maximum
voltage is applied. Range is -10℃to+60℃.
Temperature Coefficient of Resistance(aT) The Temperature coefficient is calculated from the linear range at
the steepest portion of resistance (Tb-Tp) as illustrated in Fig.1. aT=(InRp-InRb)˙100/(Tp-Tb) (%/℃)
Dissipation Factor (δ) The ratio power dissipation change to temperature change of PTC thermistor(in mw/
℃). δ=p/(T-Tr)
Where P=dissipation power
T=thermistor body temperature
Tr=room temperature
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MZ2 Series for overcurrent protection in telecom
Advanced developments in telephony equipment in rencent
years have radically altered the protection requirements for
both exchange and subscriber equipment. The PTC
thermistor must protect the telephone.line circuit against
overcurrent, which may be caused the following examples:
¾ Surges due to lighting strikes on or near to the line plant.
¾ Short-term induction of alternating voltage from adjacent power lines or railway systems
,usually caused when these lines or systems develop faults.
¾ 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; see Fig.1. However, even with primary line protection (usually a gas
discharge tube ),the PTC thermistor must fulfill severe requirements.
Surge pulses of up to 2 KV can occur and in order to withstand short-term power induction the PTC
thermistor must withstand hign voltages. If the line has primary protection, a 220V to 300V PTC thermistor
is adequate. Without primary protection,600V PTC device is necessary..
Fig.1
Fig.2
Component outline
Fig. 3
Fig. 4
Fig.5 Examples of application
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