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Ground Fault Interrupter Circuit




I am trying to simulate the ground fault interrupter circuit on multism by using the attached document of FAN4147 ic, i didnt find this ic built in in multism so i have tried to made it myself but after preparing the complete circuit in multism i came to know that it is not working as a GFCI Circuit, i am attaching my multism circuit for reference. Can someone help me in this regard.


I just need tips on how to simulate the GFCI circuit on multism.




Hammad Zaman



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Message 1 of 13

Hi Hammand,



I was able to make your circuit simulation by doing the following:


1.  Reset all simulation back to default

2.  From Simulate>>Interactive Simulation settings.>Analysis Options>>Customize, change Reltol to 0.01


I ran this circuit for about 8 sec in simulation time and randomly switched S2 without simulation error.


Tien P.

National Instruments
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Message 2 of 13

Hello Tien,


Thank you for your prompt response, i really appreciate it.


The problem of error is resolved now and as you have mentioned the circuit is simulating even after the closing of switch S2 but as i have mentioned earlier my primary purpose for developing this circuit is to simulate Ground Fault Interrupter Circuit. I am observing that even after the closing of switch (short between hot and neutral) the load (100ohms and 1mH) is not disconnected from circuit which means that the circuit is not tripping.


Your valuable comments are required for this scenario.




Hammad Zaman

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Message 3 of 13

Hi Hammad,


It looks like the circuit you created was from the datasheet functional block diagram and to honest; I don't think this will work since manufacturers don’t show the complete schematic.  I know a few people who created a component from the datasheet diagram, they had to design each section and then put everything together and this is a lot of work.


Another way to simulate like this is use parts such as voltage control voltage source, voltage control switch and the analog behavioural model (ABM) source etc... to model this component at a high level.  Have to look at this tutorial to learn how to use the ABM source:

Tien P.

National Instruments
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Message 4 of 13
Hello Tien,

Its really so nice of u to help me out in this.

Actually I have to simulate gfci circuit on multism as a part of my project work in graduate studies, while searching for gfci I have found that functional diagram on net so I tried it.

Its not necessary that I have to stick on that functional diagram, can u tell me another ways of developing gfci circuit on multism?

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Message 5 of 13

Hammad Zamman,


In any simulation the approach depends on the goal.  What characteristic or aspect of the GFCI circuit are you trying to study? That is the part for which the simulation must be most realistic.  If you do not care about second order effects in the amplifiers, you can use a voltage controlled voltage source.  But if you are studying the effects of input bias current and input offset voltage of the amplifiers on the performance of the GFCI, then you need a model which accurately represents the devices used in the circuit.



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Message 6 of 13

Hello Lynn,


Actually i am working on the gfci circuit to calculate the effects of radio frequencies of smart meters on the gfci outlets installed in homes.


To accomplish this task i have to simulate the gfci circuit on multism or any equivalent software first for which i have been trying since so many days but unfortunately i didn't succeed yet, right now i am seraching for the problem due to which my gfci circuit is not tripping under fault conditions.



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Message 7 of 13



Radio frequency (rf) interference to devices which are not intended to operate at radio frequencies is typically due to rectification of the rf signal which then produces a voltage or current with a DC component. That DC or low frequency interfering signal causes the malfunction of the device.


To simulate this behavior you need to know the details of the input or output circuits which are connected to any conductors which cold serve as antennas.  Any non-linearities in those input or ourput circuits can become the rectifiers.  You also need to know the frequencies and amplitudes of the interfering signals and the modulating waveforms, if the signal is modulated. You need to model the coupling between the rf device and the branch circuit wiring connected to the GFCI devices.


Since you have not been able to get good schematics for the GFCI IC, you will have much difficulty trying to produce a model good enough to create a meaningful radio frequency interference simulation.  Most standard op amp SPICE models probably do a very poor job of simulating the rf response (although I have never tried to simulate that).


I do not know what frequencies or power levels your smart meters use, but I suspect that those signals are likely on the low amplitude range of the kinds of signals which might produce rf interference.  Most rf interference cases occur with transmitters producing tens to thousands of watts, depending on the coupling.  Are the smart meters using radiated or conducted signals to communicate with the grid operator?


If I were working on a problem like that, I would start with some controlled measurements rather than simulation.  I understand that simuation can (sometimes) be much less expensive, but spending a lot of time to get a bad simulation is foolish.



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Message 8 of 13

Hi Lynn,


Actually it is a part of my assignment to first simulate the gfci circuit and then check the rf effects on it that's why i am doing this.


Smart meter transmitter usually operates on less watts and it communicate with the grid through radiation.


Doing RF Analysis is the secondary part, my primary focus is to get the gfci circuit work properly on multism.


As you can see in the attached data sheet of GFCI (in my first post) the model number of Sense Amplifiers, window comparators and SCR Driver are not present i guess tthis is the basic issue for improper working of my circuit on multism.



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Message 9 of 13

I understand that it is part of your assignment.  I just wanted to point out that getting the simulation to work at power line frequencies does not mean that it will be a good simulation at radio frequencies.


I think that some circuits were published a number of years ago when GFCI devices first were being developed.  I do not have ready access to that literature at the moment, but searching that may give you an actual circuit with real device part numbers which could be used for your model. It might not include the latest ICs, but it would give you a working model.



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Message 10 of 13