AMWEI thermistor Sensor-China manufacturer of PTC NTC thermistors,temperature sensor probe, Pressure Sensor  
MAIN   |  PRODUCTS   |  ABOUT US   |  CONTACT US

Thermistors Search
Thermistors Sort:
Keyword:
 
Technical Information
NTC Thermistor
Inrush Current Limit N...
NTC Thermistors Charac...
NTC Sensor Select Refe...
NTC Thermistor Tempera...
NTC Thermistor Manufac...
NTC PTC Thermistors Li...
PTC NTC Thermistors Co...
NTC thermistors Chargi...
PTC Thermistor
PTC Thermistors Manufa...
PTC Thermistors Glossa...
PTC Thermistors Charac...
PTC Thermistors Protec...
PTC Limit Temperature ...
PTC thermistors Limit ...
PTC Thermistor Overloa...
PTC Thermistor Protect...
PTC Thermistor Current...
PTC Thermistors Applic...
 
 /  PTC Thermistor  /  NTC Thermistor  /  Pressure Sensors


PTC Thermistors for Circuit Overload Over-current Protection

What is PTC Thermistor Circuit Protector?

Ceramic PTC (positive temperature coefficient) thermistors are used instead of conventional fuses to protect load, such as motors, transformers, or electronic circuit, against overcurrent for circuit protection. PTC thermistor protector not only respond to inadmissibly high currents but also if a preset temperature limit is exceeded. PTC thermistor over-current protector limits the power dissipation of the whole circuit by increasing their resistance and thus reducing the current to a harmless residual value. In contrast to conventional fuses, PTC thermistor resettable fuses do not have to be replaced after elimination of the fault but resume their protective function immediately after a short cooling-down time.

PTC Thermistors for Circuit Over-current Overload Protection Application

It applies in the over-current overload and short circuit protection of transformers, battery charger, switches, switch power supply, adaptor, meter, instrumentation, apparatus, electronic coils, control panels, air conditioner, automotive electron, etc.

How PTC Thermistor Resettable Fuse Protect Circuit against Overload Over-current Work? Operating Principle

The operating principle is as indicated in the following. When a circuit is in the normal status, the current through PTC is lower than the rated current and PTC thermistor protector is in the normal state with small resistance value, which will not affect the normal operation of the protected circuit. In case of some fault in the circuit and the current is greater than the rated current, the PTC thermistor protector will become hot quickly and present a high resistance state, which sets the circuit relatively "off" to protect the circuit from damage. After the fault is removed, PTC thermistor protector will automatically restore its low resistance state and the circuit will resume normal operation.

Normally, when PTC thermistor is used as an overcurrent protection component, it is preferred to select maximum operating current, maximum operating voltage and proper specifications. Furthermore such factors should be taken into consideration as the dimensions of the components, rated zero-power resistance, operating temperature range, etc.

Relation between operating temperature, operating current and non-operating current is as shown in Fig.2. Operating current is normally 2~3 times non-operating current, and both of the currents will be reduced as operating temperature increases.

Fig. 3 is Voltage-Current Curve and Load Curve in normal operating state. From point A to point B, the voltage on PTC thermistor protector increases gradually, current through PTC thermistor current limiting device also increases linearly, it indicates that PTC thermistor protector resistance keeps almost unchanged, in low resistance state; From point B to F, the voltage increases gradually, PTC thermistor protector resistance increases sharply due to heating, current through PTC thermistor current limiting device decreases rapidly, it indicates that PTC thermistor current limiting device in protection state. Normal load curve lower than point B, PTC thermistor over current protection device won't enter into protection state.

PTC thermistor Protective Threshold Current Range PTC thermistor operating current vs ambient temperature
Fig.2 PTC thermistor Non-trip current versus ambient temperature

3 types over-current and overload protection PTC Thermistor circuit protector carries.

1. PTC Thermistor for current overload protection(Fig. 4):RL1 is the loading current in normal operating state, When overloading resistance decreases, such as transformer short circuit, loading curve changes from RL1to RL2 , exceeding point B, PTC thermistor protector will enter into protection state.
2. PTC Thermistor for voltage overload protection (Fig. 5): Power voltage increases, such as increases abruptly from 220V to 380V, loading curve changes from RL1to RL2 , exceeding point B, PTC thermistor protector will enter into protection state.
3. PTC Thermistor for temperature protection(Fig. 6): When ambient temperature increases exceeding certain temperature, PTC thermsitor voltage-resistance curve changes from A-B-E to A-B1-F, loading curve RL , exceeding point B1, PTC thermistor protector will enter into protection state.

PTC Thermistors protector for over-current and overload protection PTC thermistor current temperature protection
PTC thermistor current temperature protection
PTC Thermistor engineering drawing
PTC Thermistor outline and dimension (mm)

Circuit protection using PTC Thermistor over-current protection devices examples

PTC Thermistors circuit protection for transformer power supply motor

PTC thermistor inrush current limit circuit
PTC thermistor inrush current limit circuit

AMWEI PTC Thermistor for Circuit Overload Over-current Protection 265V/250V Series Data

Part number

Resistance
@25C
R25
(OHM)

Non-trip
current
IntmA

Trip current
@25C
It
(mA)

Max.
operating
voltage
Vmax
(V)

Max.
current
Imax
(A)

Reference
temperature
Tref
(Centigrade)

Dimension
(mm)
@25C @60C Dmax Tmax d
AMZ11-20P2R6H265 2.6 ohm 650mA 500mA 1300mA 265V 4.3A 120C 22.0 5.0 0.6
AMZ11-20P3R7H265 3.7 ohm 530mA 430mA 1050mA 265V 4.3A 120C 22.0 5.0 0.6
AMZ11-20P5RH265 5.0 ohm 480mA 370mA 970mA 265V 4.3A 120C 22.0 5.0 0.6
AMZ11-16P5RH265 5.0 ohm 420mA 320mA 840mA 265V 3.1A 120C 17.5 5.0 0.6
AMZ11-16P6RH265 6.0 ohm 390mA 300mA 780mA 265V 3.1A 120C 17.5 5.0 0.6
AMZ11-16P7RH265 7.0 ohm 350mA 280mA 700mA 265V 3.1A 120C 17.5 5.0 0.6
AMZ11-13P10RH265 10 ohm 300mA 200mA 600mA 265V 1.8A 120C 14.0 5.0 0.6
AMZ11-13P12RH265 12 ohm 270mA 180mA 540mA 265V 1.8A 120C 14.0 5.0 0.6
AMZ11-13P15RH265 15 ohm 240mA 160mA 500mA 265V 1.8A 120C 14.0 5.0 0.6
AMZ11-13P50RH265 50 ohm 130mA 100mA 260mA 265V 1.8A 120C 14.0 5.0 0.6
AMZ11-12P7RH265 7 ohm 320mA 250mA 640mA 265V 1.8A 120C 14.0 5.5 0.6
AMZ11-12P8RH265 8 ohm 300mA 230mA 600mA 265V 1.8A 120C 14.0 5.5 0.6
AMZ11-12P9RH265 9 ohm 290mA 220mA 580mA 265V 1.8A 120C 14.0 5.5 0.6
AMZ11-12P10RH265 10 ohm 250mA 200mA 500mA 265V 1.8A 120C 14.0 5.5 0.6
AMZ11-12P12RH265 12 ohm 240mA 180mA 480mA 265V 1.8A 120C 14.0 5.5 0.6
AMZ11-12P15RH265 15 ohm 200mA 160mA 400mA 265V 1.8A 120C 14.0 5.5 0.6
AMZ11-12P27RH270 27 ohm 120mA 90mA 350mA 270V 1.8A 120C 14.0 5.5 0.6
AMZ11-12P101H265 100 ohm 50mA 40mA 100mA 265V 1.8A 120C 14.0 5.5 0.6
AMZ11-10P12RH265 12 ohm 230mA 160mA 460mA 265V 1.2A 120C 11.5 5.0 0.6
AMZ11-10P15RH265 15 ohm 180mA 140mA 350mA 265V 1.2A 120C 11.5 5.0 0.6
AMZ11-10P18RH265 18 ohm 170mA 130mA 340mA 265V 1.2A 120C 11.5 5.0 0.6
AMZ11-10P39RH265 39 ohm 130mA 100mA 250mA 265V 1.2A 120C 11.5 5.0 0.6
AMZ11-08P15RH250 15 ohm 150mA 120mA 300mA 250V 0.8A 120C 9.5 5.0 0.6
AMZ11-08P22RH250 22 ohm 135mA 110mA 270mA 250V 0.8A 120C 9.5 5.0 0.6
AMZ11-08P25RH265 25 ohm 130mA 100mA 250mA 265V 0.8A 120C 9.5 5.0 0.6
AMZ11-08P35RH265 35 ohm 115mA 90mA 225mA 265V 0.8A 120C 9.5 5.0 0.6
AMZ11-08P39RH270 39 ohm 105mA 70mA 210mA 270V 0.8A 120C 9.5 5.0 0.6
AMZ11-08P45RH265 45 ohm 105mA 80mA 200mA 265V 0.8A 120C 9.5 5.0 0.6
AMZ11-08P55RH265 55 ohm 90mA 70mA 180mA 265V 0.8A 120C 9.5 5.0 0.6
AMZ11-08P70RH265 70 ohm 75mA 60mA 150mA 265V 0.8A 120C 9.5 5.0 0.6
AMZ11-07P82RH265 82 ohm 70mA 50mA 140mA 265V 0.6A 120C 8.5 5.0 0.6
AMZ11-07P56RH265 56 ohm 90mA 60mA 175mA 265V 0.6A 120C 8.5 5.0 0.6
AMZ11-06P33RH250 33 ohm 110mA 85mA 200mA 250V 0.4A 120C 7.5 4.5 0.6
AMZ11-05P70RH265 70 ohm 65mA 50mA 130mA 265V 0.3A 120C 6.5 5.0 0.6
AMZ11-05P85RH265 85 ohm 60mA 45mA 120mA 265V 0.3A 120C 6.5 5.0 0.6
AMZ11-05P121H265 120 ohm 45mA 35mA 90mA 265V 0.3A 120C 6.5 5.0 0.6
AMZ11-05P181H265 180 ohm 40mA 30mA 80mA 265V 0.3A 120C 6.5 5.0 0.6
AMZ11-04P70RH250 70 ohm 50mA 40mA 100mA 250V 0.2A 120C 5.5 5.0 0.6
AMZ11-04P121H265 120 ohm 40mA 30mA 80mA 265V 0.2A 120C 5.5 5.0 0.6
AMZ11-03P151H250 150 ohm 40mA 30mA 75mA 250V 0.2A 120C 4.5 5.0 0.5
AMZ11-03P221H265 220 ohm 30mA 24mA 60mA 265V 0.2A 120C 4.5 5.0 0.5
AMZ11-12N12RH265 12 ohm 200mA 140mA 400mA 265V 1.8A 100C 14.0 5.0 0.6
AMZ11-12N10RH265 10 ohm 220mA 180mA 440mA 265V 1.8A 100C 14.0 5.0 0.6
AMZ11-12N8RH265 8 ohm 250mA 200mA 500mA 265V 1.8A 100C 14.0 5.0 0.6
AMZ11-10N12RH250 12 ohm 180mA 130mA 350mA 250V 1.2A 100C 11.5 5.0 0.6
AMZ11-10N12RH265 12 ohm 210mA 160mA 420mA 265V 1.2A 100C 12.0 5.0 0.6
AMZ11-10N15RH265 15 ohm 175mA 120mA 320mA 265V 1.2A 100C 11.5 5.0 0.6
AMZ11-10N18RH265 18 ohm 145mA 110mA 320mA 265V 1.2A 100C 11.5 5.0 0.6
AMZ11-10N22RH265 22 ohm 140mA 100mA 260mA 265V 1.2A 100C 11.5 5.0 0.6
AMZ11-10N27RH265 27 ohm 120mA 90mA 240mA 265V 1.2A 100C 11.5 5.0 0.6
AMZ11-08N25RH265 25 ohm 110mA 80mA 230mA 265V 1.0A 100C 9.5 5.0 0.6
AMZ11-08N35RH265 35 ohm 95mA 70mA 190mA 265V 1.0A 100C 9.5 5.0 0.6
AMZ11-08N45RH265 45 ohm 85mA 55mA 170mA 265V 1.0A 100C 9.5 5.0 0.6
AMZ11-07N22RH250 22 ohm 120mA 80mA 210mA 250V 0.5A 100C 8.5 5.0 0.6
AMZ11-07N35RH265 35 ohm 95mA 70mA 190mA 265V 0.5A 100C 8.5 5.0 0.6
AMZ11-07N50RH265 50 ohm 85mA 60mA 170mA 265V 0.5A 100C 8.5 5.0 0.6
AMZ11-07N60RH265 60 ohm 80mA 50mA 160mA 265V 0.5A 100C 8.5 5.0 0.6
AMZ11-05N82RH265 82 ohm 55mA 40mA 105mA 265V 0.3A 100C 6.5 5.0 0.6
AMZ11-05N101H265 100 ohm 50mA 35mA 100mA 265V 0.3A 100C 6.5 5.0 0.6
AMZ11-05N121H265 120 ohm 45mA 32mA 90mA 265V 0.3A 100C 6.5 5.0 0.6
AMZ11-05N151H265 150 ohm 38mA 30mA 80mA 265V 0.3A 100C 6.5 5.0 0.6
AMZ11-05N201H265 200 ohm 30mA 25mA 65mA 265V 0.3A 100C 6.5 5.0 0.6
AMZ11-05N301H265 300 ohm 27mA 20mA 55mA 265V 0.3A 100C 6.5 5.0 0.6
AMZ11-05N601H265 600 ohm 20mA 12mA 40mA 265V 0.2A 100C 6.5 5.0 0.6
AMZ11-04N151H265 150 ohm 36mA 28mA 80mA 265V 0.3A 100C 5.5 5.0 0.6
AMZ11-03N151H265 150 ohm 33mA 25mA 65mA 265V 0.2A 100C 4.5 5.0 0.5
AMZ11-03N101H250 100 ohm 40mA 30mA 80mA 250V 0.2A 100C 4.5 5.0 0.5
AMZ11-03N70RH250 70 ohm 45mA 35mA 90mA 250V 0.1A 100C 4.5 5.0 0.5
AMZ11-08M25RH265 25 ohm 90mA 50mA 180mA 265V 0.8A 80C 9.5 5.0 0.6
AMZ11-08M35RH265 35 ohm 80mA 45mA 160mA 265V 0.8A 80C 9.5 5.0 0.6
AMZ11-08M40RH265 40 ohm 75mA 40mA 150mA 265V 0.8A 80C 9.5 5.0 0.6
AMZ11-08M50RH265 50 ohm 60mA 35mA 120mA 265V 0.8A 80C 9.5 5.0 0.6
AMZ11-07M101H265 100 ohm 40mA 25mA 80mA 265V 0.6A 80C 8.5 5.0 0.6
AMZ11-05M70RH250 70 ohm 50mA 30mA 100mA 250V 0.3A 80C 6.5 5.0 0.6
AMZ11-05M121H265 120 ohm 30mA 20mA 60mA 265V 0.3A 80C 6.5 5.0 0.6
AMZ11-03M101H250 100 ohm 25mA 18mA 55mA 250V 0.2A 80C 4.5 5.0 0.5
AMZ11-03M151H265 150 ohm 22mA 15mA 45mA 265V 0.2A 80C 4.5 5.0 0.5
Note: If not specified, Resistance @25C (R25) tolerance shall be +/-25%.

AMWEI PTC Thermistor for Circuit Overload Over-current Protection 140V Series

Part Number Resistance
@ 25C
R25
OHM
Non-trip
current
IntmA
Trip
current
@25C
It
mA
Max.
operating
voltage
Vmax
(V)
Max.
current
Imax
(A)

Reference
temperature
Tref
(Centigrade)

Dimension
mm
@25C @60C Dmax Tmax d
AMZ12-20P1R5H140 1.5 ohm 850mA 680mA 1700mA 140V 4.3A 120C 22.0 5.0 0.6
AMZ12-20P2R6H140 2.6 ohm 650mA 500mA 1300mA 140V 4.3A 120C 22.0 5.0 0.6
AMZ12-16P4R7H140 4.7 ohm 425mA 330mA 850mA 140V 3.1A 120C 17.5 5.0 0.6
AMZ12-16P5R6H140 5.6 ohm 400mA 310mA 800mA 140V 3.1A 120C 17.5 5.0 0.6
AMZ12-13P6R8H140 6.8 ohm 325mA 250mA 650mA 140V 1.8A 120C 14.0 5.0 0.6
AMZ12-12P5R6H140 5.6 ohm 325mA 250mA 650mA 140V 1.8A 120C 13.5 5.0 0.6
AMZ12-12P6R8H140 6.8 ohm 300mA 230mA 600mA 140V 1.8A 120C 13.5 5.0 0.6
AMZ12-10P10RH140 10 ohm 225mA 170mA 450mA 140V 1.2A 120C 11.5 5.0 0.6
AMZ12-10P6R8H140 6.8 ohm 275mA 200mA 550mA 140V 1.2A 120C 11.5 5.0 0.6
AMZ12-08P22RH140 22 ohm 135mA 110mA 270mA 140V 0.8A 120C 9.5 5.0 0.6
AMZ12-06P25RH140 25 ohm 125mA 90mA 250mA 140V 0.5A 120C 7.0 5.0 0.6
AMZ12-16R2RIH140 2.1 ohm 710mA 570mA 1420mA 140V 3.1A 140C 17.5 5.0 0.6
AMZ12-13R3R8H140 3.8 ohm 500mA 400mA 1000mA 140V 1.8A 140C 14.5 5.0 0.6
AMZ12-10R15RH140 15 ohm 210mA 170mA 420mA 140V 1.2A 140C 11.5 5.0 0.6
AMZ12-10R6R7H140 6.7 ohm 300mA 230mA 600mA 140V 1.2A 140C 11.5 5.0 0.6
AMZ12-10R10RH140 10 ohm 250mA 200mA 500mA 140V 1.2A 140C 11.5 5.0 0.6
AMZ12-08R12RH140 12 ohm 200mA 160mA 400mA 140V 0.6A 140C 9.5 5.0 0.6
Note: If not specified, Resistance @25C (R25) tolerance shall be +/-25%.

AMWEI PTC Thermistor for Circuit Overload Over-current Protection 60V Series

Part Number Resistance
@ 25C
R25
Non-trip
current
IntmA
Trip
current
@25C
It
mA
Max.
operating
voltage
Vmax
(V)
Max.
current
Imax
(A)
Reference
temperature
Tref
(Centigrade)
Dimension
mm
@25C @60C Dmax Tmax d
AMZ13-16P2R3H60 2.3 ohm 550mA 450mA 1100mA 60V 8.0A 120C 17.5 4.0 0.6
AMZ13-12P3R7H60 3.7 ohm 380mA 320mA 750mA 60V 5.5 13.5 4.0 0.6
AMZ13-10P5R6H60 5.6 ohm 300mA 250mA 600mA 60V 4.3A 11.0 4.0 0.6
AMZ13-08P9R4H60 9.4 ohm 180mA 150mA 360mA 60V 3.0A 9.0 4.0 0.6
AMZ13-05P25RH60 25 ohm 100mA 85mA 200mA 60V 1.0A 6.5 4.0 0.6
AMZ13-03P55RH60 55 ohm 60mA 50mA 120mA 60V 0.7A 4.5 4.0 0.5
AMZ13-08M4R7H60 4.7 ohm 180mA 120mA 360mA 60V 3.0A 80C 9.0 4.0 0.6
Note: If not specified, Resistance @25C (R25) tolerance shall be +/-25%.

AMWEI PTC Thermistor Current Limiting Devices for Transformer Over-current Overload Protection 265V, 100C
(For application of PTC thermistor protector installation inside transformer windings coil)

Part number Resistance
@25C
R25
(OHM)
Non-trip
current
Int (mA)
Trip
current
@25C
It
(mA)
Max.
operating
voltage
Vmax
(V)
Max.
current
Imax
(A)
Reference
temperature
Tref
(Centigrade)
Dimension
(mm)
@25C @80C Dmax Tmax d
AMZ11-05N121H265 120 ohm 45mA 25mA 90mA 265V 0.4A 100C 6.5 5.0 0.6
AMZ11-05N151H265 150 ohm 38mA 20mA 80mA 265V 0.4A 6.5 5.0 0.6
AMZ11-07N22RH265 22 ohm 110mA 60mA 220mA 265V 0.7A 8.0 4.5 0.6
AMZ11-07N32RH265 32 ohm 95mA 50mA 190mA 265V 0.7A 8.0 4.5 0.6
AMZ11-07N55RH265 55 ohm 70mA 40mA 140mA 265V 0.7A 8.0 5.0 0.6
AMZ11-08N30RH265 30 ohm 100mA 55mA 200mA 265V 1.0A 9.0 5.0 0.6
AMZ11-08N35RH265 35 ohm 90mA 50mA 180mA 265V 1.0A 9.0 5.0 0.6
AMZ11-08N40RH265 40 ohm 85mA 45mA 170mA 265V 1.0A 9.0 5.0 0.6
AMZ11-08N39RH265 39 ohm 95mA 50mA 180mA 265V 1.2A 9.5 5.0 0.6
AMZ11-08N25RH265 25 ohm 110mA 60mA 220mA 265V 1.2A 9.5 5.0 0.6
AMZ11-10N22RH265 22 ohm 125mA 70mA 250mA 265V 1.5A 11.0 5.0 0.6
AMZ11-10N18RH265 18 ohm 145mA 80mA 290mA 265V 1.5A 11.0 5.0 0.6
AMZ11-10N12RH265 12 ohm 170mA 95mA 340mA 265V 1.5A 11.0 5.0 0.6
AMZ11-12N18RH265 18 ohm 180mA 100mA 360mA 265V 2.0A 13.5 5.0 0.6
AMZ11-12N12RH265 12 ohm 210mA 120mA 420mA 265V 2.0A 13.5 5.0 0.6
Note: If not specified, Resistance @25C (R25) tolerance shall be +/-25%.

AMWEI PTC Thermistor Current Limiting Devices for Transformer Over-current Overload Protection 265V 120C
(For application of PTC thermistor protector installation outside transformer windings coil)

Part number Resistance
@25C
R25
OHM
Non-trip
current
IntmA
Trip
current
@25C
It
mA
Max.
operating
voltage
Vmax
(V)
Max.
current
Imax
(A)
Reference
temperature
Tref
(Centigrade)
Dimension
mm
@25C @60C Dmax Tmax d
AMZ11-16P6R0H265 6.0 ohm 390mA 300mA 780mA 265V 3.1A 120C 17.5 5.0 0.6
AMZ11-13P10RH265 10 ohm 260mA 200mA 520mA 265V 1.8A 14.0 5.0 0.6
AMZ11-12P10RH265 10 ohm 250mA 200mA 500mA 265V 1.8A 13.5 5.0 0.6
AMZ11-10P15RH265 15 ohm 180mA 140mA 350mA 265V 1.2A 11.0 5.0 0.6
AMZ11-08P25RH265 25 ohm 130mA 100mA 250mA 265V 0.8A 9.0 5.0 0.6
AMZ11-08P35RH265 35 ohm 115mA 90mA 225mA 265V 0.8A 9.0 5.0 0.6
AMZ11-08P45RH265 45 ohm 105mA 80mA 200mA 265V 0.8A 9.0 5.0 0.6
AMZ11-08P55RH265 55 ohm 90mA 70mA 180mA 265V 0.8A 9.0 5.0 0.6
AMZ11-05P70RH265 70 ohm 65mA 50mA 130mA 265V 0.3A 6.5 5.0 0.6
AMZ11-03P151H250 150 ohm 40mA 30mA 75mA 250V 0.2A 4.5 5.0 0.5
Note: If not specified, Resistance @25C (R25) tolerance shall be +/-25%.

PTC Thermistor for Measuring Instrumentation Meter Overload and Short Circuit Protection

The input circuitry of digital multimeters and other instrumentation requires overcurrent protection against the unintentional fault conditions which can occur. PTC thermistors offer reliable, convenient and cost-effective protection. Solid state construction allows resettable operation, eliminating the inconvenience of fuse replacement.

Modern multimeters, with wide-ranging functions, are particularly at risk. The inadvertent application of a voltage source to an instrument in resistance mode will cause excessive currents within the input circuitry. Multi-channel instruments, such as oscilloscopes, are also susceptible if the ground terminals are raised to high potential. These high currents, if unchecked, would destroy the input circuitry.

The PTC thermistor is connected directly in series with the input terminals. It is chosen so that over the expected range of working conditions (current, voltage, ambient temperature) the device remains in a low resistance state, offering as little series resistance as possible to ensure accurate measurement.

When a fault condition occurs, the abnormally high current causes sufficient I2R heating in the thermistor to switch it from low to high resistance, reducing the circuit current and preventing damage.

After removal of the fault condition, the thermistor reverts to low resistance to reestablish normal operation. Devices can be chosen to achieve automatic reset (fault condition must be removed) or manual reset (power source disconnected).

AMWEI PTC Thermistor current limiting devices for measuring instrumentation and meter circuit overload and short circuit protection, Voltage 265V/420V/550V, Reference Temperature 80C, 100C, 120C

Part number Resistance
@25C
R25
(OHM)
Non-trip
current
IntmA
Trip current
@25C It
mA
Max. operating
voltage
Vmax
(V)
Max. current
Imax
(A)
Reference
temperature
Tref
(Centigrade)
Dimension
mm
@25C @60C Dmax Tmax d
AMZ11-03M151N265 150 ohm 20mA 15mA 50mA 265V 0.2A 80C 4.5 5.0 0.5
AMZ11-03M102N265 1000 ohm 10mA 7mA 20mA 265V 0.1A 4.5 5.0 0.5
AMZ11-03M152N265 1500 ohm 7mA 5mA 15mA 265V 0.1A 4.5 5.0 0.5
AMZ11-04M45RN265 45 ohm 40mA 30mA 80mA 265V 0.3A 5.5 5.0 0.6
AMZ11-05M601N420 600 ohm 20mA 16mA 40mA 420V 0.2A 6.5 5.0 0.6
AMZ11-05M232N420 2300 ohm 8mA 6mA 17mA 420V 0.1A 6.5 5.0 0.6
AMZ11-05M312N420 3100 ohm 5mA 4mA 13mA 420V 0.1A 6.5 5.0 0.6
AMZ11-07M251N265 250 ohm 25mA 20mA 50mA 265V 0.5A 8.0 5.0 0.6
AMZ11-07M112M550 1100 ohm 15mA 10mA 30mA 550V 0.5A 8.0 7.0 0.6
AMZ11-08M12RN265 12 ohm 120mA 70mA 220mA 265V 0.8A 9.0 5.0 0.6
AMZ11-03N151N265 150 ohm 30mA 25mA 60mA 265V 0.2A 100C 4.5 5.0 0.5
AMZ11-03N401N265 400 ohm 25mA 20mA 45mA 265V 0.2A 4.5 5.0 0.5
AMZ11-05N751N420 750 ohm 25mA 20mA 45mA 420V 0.2A 6.5 5.0 0.6
AMZ11-05P39RN265 39 ohm 85mA 70mA 170mA 265V 0.4A 120C 6.5 5.0 0.6
AMZ11-05P65RN265 65 ohm 70mA 60mA 140mA 265V 0.4A 6.5 5.0 0.6
AMZ11-05P601N420 600 ohm 20mA 16mA 39mA 420V 0.2A 6.5 5.0 0.6
AMZ11-05P122N550 1200 ohm 15mA 10mA 30mA 550V 0.1A 6.5 5.0 0.6
AMZ11-05P152N550 1500 ohm 12mA 9mA 24mA 550V 0.1A 6.5 5.0 0.6
AMZ11A-08P70RN420 70 ohm 64mA 50mA 127mA 420V 1.4A 8.5 7.0 0.6
AMZ11A-08P121N420 120 ohm 49mA 40mA 97mA 420V 1.4A 8.5 7.0 0.6
AMZ11A-08P151N420 150 ohm 43mA 35mA 86mA 420V 1.4A 8.5 7.0 0.6
AMZ11A-08P501N550 500 ohm 24mA 19mA 48mA 550V 1.0A 8.5 7.0 0.6
Note: If not specified, Resistance @25C (R25) tolerance shall be +/-30%.

AMWEI PTC Thermistor Circuit Protector Reliability Data

Test Standard Test conditions |R25/R25|
Switching test at room temperature IEC 60738-1 Imax, Vmax, 50 cycles. <25%
Rapid change of temperature in air IEC600628-2-14,
Test Na
T=TLCT, T=TUCT 5 cycles,
30minutes.
<10%
Endurance at max. operating temperature
and max. operating voltage
IEC 60738-1 Ambient temperature: +60,
Maximum Operating Voltage,
Current limited to Imax.
Time: 24 hours
<25%
Storage in damp heat IEC 600628-2-3 Temperature of air: 40,
Relative humidity of air: 93%,
Duration: 56 days
<10%
Lead wire tensile GB2423.29 Test Ua: pull strength 10N, 10 seconds,
Test Ub: bending 90, pull strength 5N,
successively twice.
Test Uc: revolving 180,
successively twice.
20%

AMWEI PTC Thermistor current protector code

How to select PTC thermistor circuit protector for overcurrent and overload protection?

Following 5 factors should be taken into consideration in selecting PTC thermistor circuit protector for overcurrent and overload protection.
1) Maximum operating voltage
PTC Thermistor over-current protection device is connected in series in the circuit , In normal operating state, only a small portion voltage is on PTC thermistor protector. When PTC thermistor current limiting devices is in high resistance state, it must bear almost all the power voltage. Therefore in PTC thermistor protector model selection, it must have sufficient high operating voltage, and also power voltage fluctuation must be taken into consideration.

2) Rated current ( Non-trip current) and Switching current (Trip current)
The PTC thermistor over-current protection device should have sufficient high rated current (that current at which the PTC thermistor protector will under no circumstances turn off) within the suitable voltage class. Consider whether the overall layout of the circuit can handle the increased power for the short time until the PTC thermistor protector reduces it. Here a worst case estimate is necessary. Rated current ( Non-trip current) and Switching current (Trip current) depend on the ambient temperature. So, as the worst case for the rated current, the maximum permissible temperature for the application should be taken, and for the switching current the lowest possible ambient temperature. In order to get reliable switching function, tripping current should be at least twice of non-trip current.

3) Maximum current permissible in maximum operating voltage

When PTC Thermistor over-current protection device is required for protective function, it needs to check whether there is the case that the maximum permissible current, which has been listed in data sheet, has been exceeded. Overloading the PTC thermistor protector by too high a switching current must be avoided, it may lead to PTC thermistor protector destroyed, or early failure.

4)Selection of Reference temperature (also called Switch temperature or Curie temperature)

AMWEI offer PTC thermistors for over-current protection with reference temperature 80 , 100 , 120 , 140 . The rated current (non-trip current) depends on reference temperature and ceramic body diameter. In consideration of cutting down cost, high reference temperature and small dimension PTC Thermistor current limiting devices shall be more economical, but it may leads to higher PTC thermistor surface temperature, and need to check whether it will cause undesired unfavorable effects. Generally, reference temperature should be 20--40 higher than maximum operating ambient temperature.

5) Application environmental effects

If there is any contact with chemicals or use of potting or sealing compounds, all due care should be taken. The reduction of the titanate ceramic that can be caused by chemical effects on the surface of the thermistor and the resulting formation of low-resistance conducting paths. And the altered thermal relations in the sealant can lead to local overheating of the PTC thermistor protector and thus to failure.


An example selecting AMWEI PTC thermistor part for power transformer overload over-current protection

A transformer has primary voltage 220V, secondary voltage 16V, secondary current 1.5A , primary current 330mA in abnormal condition, it shall enter into protective state within 10 minutes. Operating ambient temperature: -10C--+40C , temperature may rise 15--20C in normal operating state. PTC Thermistor will be installed near transformer. Please select an appropriate PTC thermistor part for primary protection.

1) Determine maximum operating voltage
Operating voltage 220V, considering power fluctuation, maximum operating voltage should be
220V x (1+20% =264V
Maximum operating voltage shall be 265V.

2) Determine non-trip current

According to calculation and actual measurement, primary current is 125mA in transformer normal operation. In consideration the ambient temperature in installation position may reach to 60 , Non-trip current in 60 should be 130--140mA.

3) Determine trip current

As the ambient temperature in PTC thermistor protector installation position may reach -10 , non trip current in -10 should be 320-330mA, tripping time within 5 minutes.

4) Determine rated zero power resistance at 25 centigrade. R25

PTC thermistor is in series in the primary circuit, the voltage decreasing should be possibly small, the heating power of PTC Thermistor itself also maintain possibly small. Generally, the voltage decreasing should be less than total power voltage 1%. We can get R25 through calculation

220V X 1% 125mA=17.6

5) Determine maximum current

Trough practical measurement, primary current can reach 500mA in transformer secondary circuit in short circuit state. If considering that larger current may pass through PTC thermistor in the state of primary coil partial short circuit. The maximum current should be more than 1A .

6) Determine reference temperature and dimension of PTC thermistor over-current protection device

Maximum ambient temperature in PTC thermistor protector installation position may reach 60 , reference temperature should be 40 higher than that, then the reference temperature can be 100 . In considering cutting down cost, also PTC thermistor is not installed in the transformer windings coil, higher surface temperature won't have unfavorable effect to transformer, therefore reference temperature can also be 120 , and then the diameter of PTC Thermistor can be smaller.

7) Determine PTC thermistor over-current protection device AMWEI part number.

Based on the above technical requirement, in reference of our technical data, AMWEI part no. AMZ11-10P15RH265 shall be more appropriate.
Maximum operating voltage 265V, rated zero power resistance at 25C (R25) 15 20% , non-trip current 140mA , trip current 350 mA , maximum current 1.5A , reference temperature 120 , diameter 11mm .


MAIN  |  PRODUCTS  |  ABOUT US  |  CONTACT US     AMWEI Thermistor on FacebookAMWEI Thermistor on twitterLinkedin AMWEI ThermistorGoogle+ AMWEI Thermistor © 2017 Copyright by AMWEI Thermistor Sensor