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RTI Electronics

RTI Electronics Parts First launched in 1972, RTI Electronics brand products include passive electronic components including film capacitors, magnetic transformers and inductors, and audio power conditioning units. The line spans value-added and application specific components as well as custom design to meet a variety of unique customer requirements.

SURGE-GARD Thermistors RTI Electronics / Ketema Thermistor , Now part of API Technologies, RTI Electronics brand products include passive electronic components including thermistors, film capacitors, magnetic transformers

RTI SURGE-GARD

RTI Surge-Gards Thermistors
Inrush Current Limiters

RTI Electronics manufactures SURGE-GUARD™ Inrush current limiting devices (thermistors) using specially formulated metal oxide ceramic materials. These devices are capable of suppressing high inrush current surges. They are especially useful in power supplies where the low impedance of the charging capacitor exposes the diode bridge rectifier to an excessively high current surge at turn-on.

NTC Thermistors
Negative Temperature Coefficient (NTC) thermistors are thermally sensitive semiconductor resistors which exhibit a decrease in resistance as absolute temperature increases. Change in the resistance of the NTC thermistor can be brought about either by a change in the ambient temperature or internally by self-heating resulting from current flowing through the device. Most of the practical applications of NTC thermistors are based on these material characteristics.

Negative Temperature Coefficient (NTC) thermistors are thermally sensitive semiconductor resistors which exhibit a decrease in resistance as absolute temperature increases. Change in the resistance of the NTC thermistor can be brought about either by a change in the ambient temperature or internally by self-heating resulting from current flowing through the device. Most of the practical applications of NTC thermistors are based on these material characteristics.Thermistor Terminology for Inrush Current Limiting DevicesRTI’s SURGE-GARDs ™ are used in many applications today that require limiting inrush current when power is applied to a system. The most popular application is the inrush protection of the AC current in switching power supplies (SPS). The primary reason for having surge current suppression in a SPS is to protect the diode bridge rectifier as the input or charging capacitor is initially charged. This capacitor draws significant current during the first half AC cycle and can subject the components in line with the capacitor to excessive current. The inherent equivalent series resistance (ESR) of the capacitor provides very little protection for the diode bridge rectifier. Use of the proper SURGE-GARD™ will provide maximum current protection when the power supply is turned on and allow the design engineer to select lower peak current rated diode bridge rectifiers for use in their SPS.

SG Series Thermistors If the resistance of one SURGE-GARD does not provide sufficient inrush current limiting for an existing application, two or more may be used in series or in separate legs of the power supply circuit. SURGE-GARDs™ should not be used in parallel since one unit will tend to conduct nearly all the current available. SURGE-GARDs™ may be used in the AC input side or in the circuit on the DC line between the charging capacitors and the diode bridge rectifier circuit.

The term thermistor originated from the descriptor THERMally Sensitive ResISTOR. The two basic types of thermistors are the Negative Temperature Coefficient (NTC) and Positive Temperature Coefficient (PTC). The NTC thermistor is best suited for precision temperature measurement. The PTC is best suited for switching applications. The NTC thermistor is used in three different modes of operation which services a variety of applications. One of the modes exploits the resistance-versus-temperature characteristics of the thermistor. The other two modes take advantage of the voltage-versus-current and current-over-time characteristics of the thermistor.

IBS Electronics is an authorized distributor. We offer a broad range of thermistors from RTI. You'll find NTC inrush current limiters, surge limiters, probes, and over-current protection PTC thermistors. For all your protection needs (switching power supplies, AC motors, UPS systems, frequency generators).

Part Number Max. D Max. T Lead Dia. Surge  
(Inches) (Inches) (Inches) Rating Description
Style A Style B Style C       (Joules)  
SG260 SG326   1.25 0.2 0.04 31* Thermistor 0.5 Ohms Tolerance: Tolerance (AMPS) Amps 
SG415 SG327   0.77 0.2 0.04 45 Thermistor 0.7 Ohms Tolerance: (±%)  Amps 
SG100 SG301   0.9 0.3 0.04 48* Thermistor 1 Ohms Tolerance: 20 30 Amps 
SG405 SG328   1.25 0.25 0.04 157 Thermistor 1 Ohms Tolerance: 25 12 Amps 
SG416 SG329   0.55 0.2 0.04 40 Thermistor 1.3 Ohms Tolerance: 15 20 Amps 
SG110 SG302   0.9 0.35 0.04 80 Thermistor 2 Ohms Tolerance: 25 30 Amps 
SG420 SG355   1.25 0.3 0.04 250 Thermistor 2 Ohms Tolerance: 25 8 Amps 
SG120   SG303 0.6 0.25 0.032 27 Thermistor 2.5 Ohms Tolerance: 15 18 Amps 
SG130   SG304 0.6 0.25 0.032 27 Thermistor 2.5 Ohms Tolerance: 25 23 Amps 
SG140   SG305 0.6 0.25 0.032 27 Thermistor 2.5 Ohms Tolerance: 15 3 Amps 
SG150 SG306   0.9 0.3 0.04 87 Thermistor 2.5 Ohms Tolerance: 15 7 Amps 
SG160 SG307   0.9 0.3 0.04 87 Thermistor 2.5 Ohms Tolerance: 15 9 Amps 
SG170 SG308   0.6 0.25 0.04 27 Thermistor 4 Ohms Tolerance: 15 10 Amps 
SG32 SG330   0.9 0.35 0.04 100 Thermistor 4 Ohms Tolerance: 15 15 Amps 
SG180   SG309 0.6 0.25 0.032 36 Thermistor 5 Ohms Tolerance: 15 8 Amps 
SG413     0.53 0.2 0.025 23 Thermistor 5 Ohms Tolerance: 20 14 Amps 
SG190   SG310 0.6 0.25 0.032 36 Thermistor 5 Ohms Tolerance: 15 2 Amps 
SG450   SG373 0.6 0.25 0.032 30 Thermistor 5 Ohms Tolerance: 25 2.8 Amps 
SG200   SG311 0.6 0.25 0.032 40 Thermistor 5 Ohms Tolerance: 15 4 Amps 
SG44 SG332   0.6 0.25 0.04 40 Thermistor 5 Ohms Tolerance: 15 6 Amps 
SG26 SG333   0.9 0.275 0.04 100 Thermistor 5 Ohms Tolerance: 15 7 Amps 
SG418   SG334 0.6 0.27 0.032 40 Thermistor 6 Ohms Tolerance: 20 8 Amps 
SG210 SG312   0.6 0.3 0.04 50 Thermistor 7 Ohms Tolerance: 15 12 Amps 
SG85 SG335   0.6 0.3 0.04 45 Thermistor 7 Ohms Tolerance: 15 5 Amps 
SG64 SG336   0.95 0.275 0.04 100 Thermistor 7 Ohms Tolerance: 15 4 Amps 
SG13   SG337 0.5 0.25 0.032 17 Thermistor 10 Ohms Tolerance: 25 5 Amps 
SG220   SG313 0.45 0.3 0.032 17 Thermistor 10 Ohms Tolerance: 15 10 Amps 
SG42 SG338   0.6 0.35 0.04 44 Thermistor 10 Ohms Tolerance: 15 2 Amps 
SG27 SG314   0.5 0.35 0.04 40 Thermistor 10 Ohms Tolerance: 15 3 Amps 
SG40 SG72   0.9 0.35 0.04 50 Thermistor 10 Ohms Tolerance: 15 5 Amps 
SG451 SG374   0.5 0.35 0.04 40 Thermistor 12 Ohms Tolerance: 15 6 Amps 
SG452   SG375 0.55 0.3 0.032 40 Thermistor 15 Ohms Tolerance: 20 8 Amps 
SG86     0.53 0.3 0.025 45 Thermistor 16 Ohms Tolerance: 15 4 Amps 
SG414     0.53 0.3 0.025 45 Thermistor 16 Ohms Tolerance: 15 2.5 Amps 
SG63 SG320   0.75 0.25 0.04 50 Thermistor 16 Ohms Tolerance: 25 1.7 Amps 
SG230   SG315 0.5 0.3 0.032 31 Thermistor 20 Ohms Tolerance: 25 2.7 Amps 
SG411   SG341 0.5 0.3 0.032 30 Thermistor 25 Ohms Tolerance: 25 4 Amps 
SG412   SG342 0.5 0.3 0.032 30 Thermistor 25 Ohms Tolerance: 15 1.75 Amps 
SG38 SG343   0.6 0.25 0.04 25 Thermistor 30 Ohms Tolerance: 25 1.7 Amps 
SG240   SG316 0.625 0.25 0.032 20 Thermistor 40 Ohms Tolerance: 25 2.4 Amps 
SG52 SG344   0.77 0.24 0.04 55 Thermistor 47 Ohms Tolerance: 15 3 Amps 
SG453   SG376 0.6 0.25 0.032 50 Thermistor 60 Ohms Tolerance: 15 2 Amps 
SG250 SG317   0.925 0.25 0.04 36 Thermistor 120 Ohms Tolerance: 25 3 Amps 
SG31 SG346   0.6 0.3 0.04 25 Thermistor 220 Ohms Tolerance: 15 1.5 Amps