Inrush Current Limiting Power Thermistors


Inrush Current Limiters
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U.S. Sensor’s inrush current limiters (power thermistors) are specially formulated and processed NTC thermistors suitable for suppressing high inrush currents in switching power supplies and other applications where the high initial starting currents are undesirable. Their unique design enables them to handle extremely high current and voltage levels. In a typical power supply application, the inrush current limiting power thermistor is used in series with the filter capacitors. Upon application of the initial voltage, the device, due to its relatively high resistance, limits the current flow to an acceptable level until the capacitors are charged. Thereafter, the device decreases in resistance substantially to a level where the voltage drop across it is negligible.

Maximum Steady State Inrush Current (Imax)

For inrush current limiters, the maximum continuous steady state current, either DC or RMS AC, which the device is capable of passing. The maximum steady state current for a U.S. Sensor inrush current limiter is determined assuming a maximum operating ambient temperature of 65°C. If a specific application requires ambient temperature operation above 65°C, custom designed devices are available.

Resistance At Maximum Inrush Current (RImax)

For inrush current limiters, the approximate resistance of the device under maximum steady state current conditions.

Thermistor Diagram
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IN-RUSH CURRENT LIMITERS (POWER THERMISTORS)
Part Number Ro Resistance @ 25°C ± 20% Ohms Imax Max. Steady State Current (Amps) RImax Resis. @ Max. Current Ohms Dim. "D"
(Max. Over Coating)
Dim. "T"
(Max. Over Coating)
Lead Dia. (Nom.) Download/view
ST1R020B 1.0 20 0.015 1.200 0.300 0.040 Drawing
ST1R030B 1.0 30 0.015 1.475 0.350 0.040 Drawing
ST2R018B 2.0 18 0.030 1.200 0.350 0.040 Drawing
ST2R503B 2.5 3 0.150 0.600 0.250 0.032 Drawing
ST2R507B 2.5 7 0.050 0.700 0.250 0.032 Drawing
ST2R509B 2.5 9 0.040 0.900 0.250 0.032 Drawing
ST2R510B 2.5 10 0.040 1.200 0.300 0.040 Drawing
ST2R515B 2.5 15 0.030 1.200 0.300 0.040 Drawing
ST5R002B 5.0 2 0.400 0.600 0.250 0.032 Drawing
ST5R005B 5.0 5 0.100 0.675 0.250 0.032 Drawing
ST5R007B 5.0 7 0.070 0.925 0.275 0.032 Drawing
ST7R004B 7.0 4 0.200 0.600 0.300 0.040 Drawing
ST10003B 10.0 3 0.200 0.575 0.300 0.032 Drawing
ST10005B 10.0 5 0.200 0.750 0.350 0.040 Drawing
ST10006B 10.0 6 0.150 1.175 0.350 0.040 Drawing
ST10010B 10.0 10 0.100 1.475 0.300 0.040 Drawing
ST20002B 20.0 1.75 0.600 0.500 0.300 0.032 Drawing

Note: All Dimensions are in Inches

The information contained herein is believed to be accurate. The user, however, should verify the suitability of a particular product for a specific application. U.S. Sensor Corp. does not warrant the accuracy of this information, and disclaims any liability with respect to its use.


You can fill out the Sensor Application Form with your requirements and send it to us.  
U.S. Sensor Corp.
(800) 777-6467
Contact U.S. Sensor 800-777-6467sales@ussensor.com