Inrush Current Limiting B 57234 S 234 Applications @ Inrush current limiting in peripheral communication equipment, monitors, PCs, etc. @ Soft-start motors, e.g. in vacuum cleaners @ Circuit applications requiring high continuous currents @ Useable in series connection up to 245 Vime Features @ Coated thermistor disk @ Kinked leads of tinned, nickel-plated copper wire @ Wide resistance range @ Available on tape Options Resistance tolerance < 20 % available Tmax 4 3_-w|_ 22 max $0,8 peta + N j -Y TNT0035 Dimensions in mm Approx. weight 2.0 g Lower/upper category temperature 55/+ 170 C Max. power at 25 C Pos 3.2 Ww Resistance tolerance AA/Ry | 420% Rated temperature Ty 25 C B value tolerance AB/B |43% Dissipation factor (in air) Sth approx. 17 mW/K Thermal cooling time constant (in air) Te approx. 90 s Heat capacity Crh approx. 1530 mdJ/K Type Ros | Imax No. of Bosiyo9 | Cy" | Parameters Ordering code (T= 25C) | A/T char- for A(l) Q A acteristic | K uF k n S 234/1.0/M 1.0 | 11.5 1201 2600 | 700 0.622 |-1.27 | B57234-S109-M 234/2.2/M 2.2 | 9.0 1202 2800 | 700 0.806 | 1.30 | B57234-S229-M S 234/2.5/M 2.5) 84 1202 2800 | 500 0.843 |- 1.30 | B57234-S259-M S 234/4.7/M 47| 66 1203 2900 | 700 1.03 |-1.32 | B57234-S479-M S 234/5.0/M 5.0) 6.4 1203 2900 | 700 1.05 |-1.32 | B57234-S509-M S 234/7.0/M 7.0 | 6.0 1302 3000 | 700 1.16 |-1.33 | B57234-S709-M S 234/10/M | 10 5.0 1308 3060 {700 1.29 |-1.34 | B57234-S100-M S 234/15/M | 15 4.0 1302 3000 | 700 1.49 |~1.33 | B57234-S150-M S 234/22/M | 22 4.0 1304 3300 | 700 1.57 |-1.37 | B57234-S220-M S 234/33/M | 33 3.3 1304 3300 | 900 1.78 |-1.37 | B57234-S330-M S 234/40/M | 40 3.4 1306 3450 |}400 (1.82 |-1.38 | B57234-S400-M S 234/60/M 60 4.0 , 1103 4000 | 400 ! 1.77. |-1.44 | B57234-S600-M S 234/220/M 220 2.0 i 1013 3900 500 (222 |-1.43 | B57234-S221-M \ For details on the canacitance Cr as well as on the parameters kK and n refer to pages 189 - 191. 4.2.4 Load derating The power handling capability of an NTC thermistor cannot be fully utilized over the entire temper- ature range. For circuit dimensioning the derating curve given below provides information on the extent to which the current must be reduced at a certain ambient temperature. Wycnax Ot I ! | | | | | | | | | | | | | | j | -25 0 25 65 C 170 _ Th TNT0195 -O Figure 12 Derating curve The /.,,, values specified in the data sheets (T, = 25 C) denote the maximum permissible con- tinuous current (dc or rms values for sine-shaped ac). 4.2.5 Restart When the load has been switched off the thermistor slowly cools down. Its resistance increases steadily, but the full resistance value is only reached after 1 to 2 minutes (depending on ambient ' temperature and type). It: may therefore be useful in some applications to bypass the thermistor during restart. Operation can thus be faster resumed and system performance will not be affected by the thermistor. 4.2.6 Dependence of NTC resistance on current The resistance effective in the usual operating current range can be approximated as follows: Ayre =k.[" 0.3 - bax <4 S max Auto Resistance value to be determined at current / [ Q ] k,n Fit parameter, see individual data sheets ! Current flowing through the NTC (insert numerical value in A) The calculated values only serve as an estimate for operation in still air at an ambient temperature of 25C. Note: With the equation above sufficiently accurate results are only obtained for the limited current range stated above. 4.2.7 Pulse strength The currents during turn-on are much higher than the rated currents during continuous operation. To test the effects of these current surges S+M uses the following standard procedure: Thyristor switch 0 THe |" te, a, | TNTO209-M Figure 13 Test circuit for evaluating the pulse strength of an NTC thermistor Ve Load voltage [ V ] Cr Test capacitance [ uF J Rg Series resistance [ Rg = 1 22 } Vytc Voltage drop across the NTC under test [ V } In the pulse test the capacitor C; is discharged via the series resistor Rg and the NTC thermistor. The load voltage is chosen such that the voltage applied to the thermistor at the start of discharge is Vuro = 345 V (corresponds to (230 V + AV) x V2). 400 TNT0220-X 120 \ , 300 50 | Se < 200 \ MN 100 SS 30 a 0 0 0.0 0.8 1.6 2.4 3.2 ms 4.0 - } Figure 14 Pulse strength test : typical curves The maximum capacitances that can be switched depend on the individual thermistor type and are given in the data sheets. 4.2.8 Applications Inrush current limiters are primarily used in industrial electronics and equipment engineering. Appli- cation examples are: Inrush current limiting in fluorescent, projector and halogen lamps, rotational speed limiting in kitchen machines, soft start of motors and switch-mode power supplies etc. S4M thermistors are available in a variety of sizes and rated resistances to optimally match your application. The product line ranges from the small-size $153 with a maximum power of 1.4 W through to the at present largest S464 with a maximum power of 6.7 W. Maximum continuous ac currents of 20 A are reached. Inrush current limiters are presented on pages 250 to 255.