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# Inrush Current Limiting

17 Threads found on edaboard.com: Inrush Current Limiting

## power supply topology

Read the discussion thoroughly. It's assumed that the primary inrush current is caused by missing current limiting means in the secondary, inserting a secondary inductor would reduce both. It's however still unclear if the post #1 schematic is meaned as forward converter or a flyback with flawed polarity mark.

## AC relay contacts welded by inrush current to capacitors

I suppose there's already NTC thermistor for inrush current limiting in the supply. Your results are suggesting it's not. I've found this on internet, however i don't understand how it should help. It's not related to inrush current protection.

## Current Limiting Elements & MOV for SMPS

NTC is selected based on the energy to be charged i.e. bulk cap to be charged say 0.5*C*Vdc*Vdc. and the minimum resistance of the NTC can be decided as Vpeak/Ilimit. Here I limit is the inrush current expected in SMPS. Rminimum thus found is the resistance of the NTC at 25 deg C with calculated Joules. Based on the input energy of the leakage ind

## the comparison between the usage of PTC and Varasitors

In fact Epcos/TDK has a family of "PTC thermistors as inrush current limiters". They are used as current limiting resistors with built-in fuse function. E.g. to charge a capacitor with limited current. If the capacitor circuit is shorted by a fault, the PTC function protects the circuit. Means the PTC (...)

## fuse resistor calculation

Hello, The fuse resistors are rated by "fuse power". How to translate this in real world, protecting a PSU by limiting inrush current? So far, my assumption is (10uF) Rlim = Vpeak/Iinrush = 240*sqrt(2)/38A = 10R But how to compute required power of resistor?

My first guess, an inrush current limiting NTC.

## Unexplained over current HELP!

I think its the cyclic inrush current as the bridge rectifiers try and charge the 1000MF smoothing capacitor. This current has overheated the bridge and burnt a diode out. I think you need a current limiting resistor or inductor in series with the DC output of the bridge, or just disconnect one or both (...)

## Using Termistor as Inrush Current Bolcker

As I understand it, inrush current is an inherent property of motors, so trying to stop inrush current is self-defeating; maybe the motors will not start, or could be damaged. BTW a thermistor is a type of resistor whose resistance varies significantly with temperature

## inrush current limiting with the triacs helps needed

Dear all i am trying to design a inrush current limiting circuits with the help of triac (gate triggering will be after 100ms) Conditions: 1)the NTC will in parallel with the triacs terminals. 2)during turn on-ac current will be pass through the ntc which will limit currents for 100ms & after that (...)

## Soft Start/Inrush Limit for 0_30Vin design with PMOS/Transistor/OpAMP?

Hi Guys, Do you all have any idea to design a PMOS with either 1 of Transistor/Op Amp/any active element to have the soft-start or inrush current limits control? I tried some with a sense resistor series with the power line, and use a PNP to sense the voltage drop on that resistor and turn off the PMOS once it is over some current. (...)

## selecting proper NTC thermistor for limiting INRUSH CURRENT

Dear all, I need your help on selecting proper NTC THERMISTOR for our device to limit the inrush current. I have used 3.7v Li_ion Battery to power our device. I like to add NTC thermistor to limit the inrush current when the device is ON. I have tested using fixed 1.7 ohm resistor for limiting (...)

## HV Contractor coil inrush limiting.

Greetings I'm activating 4 x 500A contractors all at once whose coils draw a inrush current of 3.8A maximum each for maximum time of 130ms, totaling 15.2A. The contractors have coil economizers. This is powered by a 12V 15A SMPS which is already loaded by other components. Could someone recommend

## Problems on three phase rectifier design calculation.............

The size of your capacitor will be dependent on full or half wave bridge, worst case load and allowable ripple. As to limiting inrush current either a SCR bridge or diode bridge is used in conjunction to a current limiting resistor with a bypass, the bypass being energised when the voltage has stabilised to (...)

## Solution for large inrush currents

There's a nice application note from Motorola: Active inrush current limiting Using MOSFETs (AN1542) Unfortunately this document isn't available from ON anymore. Found it here:

## Inrush current limiting module for SMPS

hello, i am making an offline SMPS. When i switch on there will be inrush current so i want to limit it. -but not using an NTC as it has no protection when SMPS is repeatedly power cycled. However, the limiting circuitry will otherwise be a lot of components.....relay, relay driver, resistor, power supply for relay etc ...or if i (...)

## Current limiting for inrush current

Hi guys, it's been a while since i last posted. How's everyone? I currently have a problem which i hope you guys can comment. I have an application where i have a simple DC motor running at 24V (turned on for only 1 second). This motor switches a small load from A to B. According to specs i am to set my power supply at a current limit of 300mA.

## Resistor connection in a SMPS circuit

The resistors are probably just basic current limiting for inrush (thermistors would be more efficient or an active inrush limiting circuit), and the capacitor is used for high frequency bypass (low Z at the switching freq) AC mains rated x-type.