In an electric power system, a fault or fault current is any abnormal electric current. For example, a short circuit is a fault in which current bypasses the normal load. An open-circuit fault occurs if a circuit is interrupted by some failure. In three-phase systems, a fault may involve one or more phases and ground, or may occur only between phases. In a "ground fault" or "earth fault", current flows into the earth.
Questions tagged [fault]
148 questions
33
votes
6 answers
How did smacking electron tube TVs help?
In old movies (or new movies playing in these times), I often see people smacking the top of electron tube TVs or screens. Somehow it seems to help to stabilize/sharpen the picture. But why?
Are there any reasons an electronic circuit could go from…
OddDev
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12
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3 answers
What can cause a Drain-Source short in a FET?
Background:
I am using a Si7456CDP N-channel MOSFET in a switching power supply. The power supply and load are housed in a plastic enclosure. Yesterday, the power supply and load were working perfectly. This morning, when I came to power it on,…
Rocketmagnet
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votes
5 answers
Fault modeling for embedded systems
I have a wireless sensor circuit with a microcontroller and a 2.4 GHz transceiver module, some integrated sensors with I²C interface, a UART port and the necessary discrete components.
This board is designed for scavenging power from a solar (PV)…
clabacchio
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8
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What is the science behind percussive maintenance?
On electronic devices in the '80's, electronic malfunctions could sometimes be temporarily fixed by physically "hitting" the device.
For example, I once had a colour TV - "ECTV" (from Electronics Corporation of India ECIL) which would lose image. It…
Pranab
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7
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4 answers
Troubleshooting a new PCB
I designed and got a PCB manufactured for the first time, and have soldered the component and powered it up. However it is not behaving as expected. I think I may learn something by everyone here for advice instead of ripping it apart and trying it…
David777
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votes
5 answers
Is it possible to make an MCU hang by messing with its power?
We have a bunch of ARM microcontrollers on test at the moment. The test runs for 360 hours and mostly completes without a hitch, but very occasionally, one of the microcontrollers will hang. We have seen this problem occur twice so far.
Looking at…
Rocketmagnet
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5
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Diode stops conducting. Conducts again after applying higher voltage. What happened there?
I have the following circuit for providing regulated 5V from a 12V power supply:
I have several hundreds of PCB with this circuit, and they work fine. However recently I have had a few of these PCBs stop functioning. I have tracked the problem to…
Endika
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5
votes
1 answer
Operating Temperature Range question for Inrush Current Limiting Thermistors
I have a friend who has brought me a circuit board from her flat screen TV. She assumed it was bad because the TV no longer turns on and there was off-white stuff leaking out of some of the components. When I got the board, the off-white stuff…
Spencer Renosis
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votes
1 answer
How can I identify the fault on an Arduino Uno board that's had the smoke let out?
I recently purchased an Arduino Uno. I've been having a ton of fun fiddling with it -- that is until I pushed +12V to the Vin without any kind of voltage step-down. The smoke was violently released from the Atmega chip and the chip socket itself…
Peter Grace
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How can a Live-Neutral transformer fault cause 2000 Ampere to flow?
In this critique of an ELV PSU design, it is suggested that a "Live-Neutral" fault could result in a fault current of thousands of amps.
It says:
Fire – (d) the plastic had a UL94-HB rating ( which limited its use to a decorative enclosure); (e)…
Jodes
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What is air contamination fault?
I read the following in the datasheet of ULN2803
Utmost care is necessary in the design
of the output line, COMMON and GND
line since IC may be destroyed due to
short−circuit between outputs, air
contamination fault, or fault by
improper…
csadam
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4
votes
2 answers
Information leakage due to fault propagation in XOR gates
From the paper Fault Template Attacks on Block Ciphers Exploiting Fault Propagation, in the concept of Automatic Test Pattern Generation (ATPG), two events are required to perform in sequence: Fault Activation and Fault Propagation.
In the case of…
4
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0 answers
Can chips be sensitive to mechanical stress after an electrical incident?
Is it possible to electrically damage a microcontroller (or any chip) in such a way that it becomes very sensitive to mechanical stress?
Some background:
We are developing a board with 7 identical microcontrollers, each running the same motor…
Rocketmagnet
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4
votes
1 answer
Difference in current transformers conection for ground fault detection
I have seen that for detecting ground faults on a 3-phase system powered by a secondary wye connected transformer, current transformers (CTs) can be connected in several ways:
On the ground connection of a grounded system
Can be installed in a…
VMMF
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4
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1 answer
Why symmetrical component analysis is necessary for fault calculation?
If a 3 phase fault occurs the direct axis sub-transient reactance is sufficient to calculate the fault current. But in case of an unbalanced fault it is not.
Taking the example of Line to Ground fault, where generator neutral is ground and a fault…
spaul
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