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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

I suppose the only place where you may need an inrush current limit is between the battery and the reservoir capacitor of 1000uF. Depending on the internal resistance of the capacitor there may be overcurrents at startup. In normal use I would think the idea of a NTC resistor in the power supply line is neither good not necessary. If you (...)

## HV Contractor coil inrush limiting.

Basically the "inrush" current (I think, the term isn't really appropriate in this case) is required to overcome the strong spring force. All electromagnets have weaker force with open magnetic circuit. Once the magnetic circuit is closed, the current can be considerably reduced. But the initial current has to be dimensioned (...)

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

Hi.......... I gone through the topics discussed on three phase rectifier.I am facing some problem with three phase diode rectifier.i am not that much of expertise in that just learning how to design power input is 415VAC.Can u please tell me the details how to calculate the proper value of filtering electrolytic capacitor???here m not u

## Solution for large inrush currents

Hi there, I have a power supply with a filter, diode bridge and a large cap to hold the voltage close to DC. A NTC is mounted to minimise inrush but this is not enough due to its lose (Thinking Green :-) ) When powering up large inrush currents are seen. Is there a cheap and easy way to elimnate this problem. Using Relays acroos (...)

## 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.