Questions tagged [fault]
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0answers
38 views
Calculate ground fault current leak on human contact
I am sure this is very very simple and probably realy dumb but I've been banging my head for hours and can't figure this out. Or find an answer on google/books for that matter.
Even with the diagram ...
1
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1answer
54 views
Can a ground fault be caused by something outside the home?
Yesterday afternoon, I had a GFCI switch trip. It would not reset. I figured I had a ground fault.
I left the home for a few hours and after I returned I was able to successfully reset the GFCI.
The ...
2
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2answers
82 views
If neutral line touches the live wire, how to protect the devices connected due to neutral fault?
If the neutral line accidental touched the live wire, then due to momentary surge the home appliances connected gets damaged, what are the ways to protect the devices. Would RCCB be helpful to protect ...
1
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1answer
57 views
Substation grounding
I am trying to understand a grounding system for substations, fault current is something I am not getting. For example, for a small substation with some transformers, if there is a fault in the system ...
0
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2answers
87 views
X2 capacitor. Test if failed open
I am looking at a small board in a paper shredder (it does not work). If I apply AC power and measure AC voltage across the X2 capacitor (I think it acts as a voltage dropper for the low voltage ...
0
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1answer
64 views
How to build (from scratch) a GFCI Circuit? [closed]
I am looking to understand what is the circuit inside a Ground Fault Current Indicator (GFCi). What does the circuit look like?
Simple google search is not yielding good results about the guts of it.
0
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1answer
62 views
Best way to locate a 4k stray resistance between 2 bus lines in a PCB?
I have a faulty PCB which is showing an unexpectedly low resistance between certain pairs of bus address lines. I'm measuring a little over 4k ohms between these bus lines, but according to the ...
0
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1answer
119 views
Linear voltage regulator failure?
I've been building USB powered audio DAC circuit which is using multiple LDO voltage regulators.
I discovered one of the regulators, namely TPS79333, which is responsible for supplying 3.3V to ...
0
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1answer
37 views
Purpose of using per unit when calculating faults?
I read a book about power system faults - they all use per unit. They show examples of generators supplying motors through a transmission lines. They convert real voltages, powers and resistances into ...
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2answers
99 views
RS485 Multidrop Issues
I have an application where we use RS485 to communicate messages to a series of LED Displays on the bus. Our first version of the board seemed to work fine with no problems, however we have made a new ...
1
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3answers
123 views
Not understanding why in overcurrent protection only a certain section will isolate (why not the whole system)
I'm having an issue understanding a simple concept for faults. I understand the principles of how the relays cause the circuit breaker to open etc when a larger current goes through them to provide ...
0
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1answer
34 views
Voltage fault injection possible on switch output?
I am required to check that the software in a system correctly handles a fault condition from a high side power switch. The switch has a current sense pin which sends a voltage back to a ...
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1answer
27 views
Fault modelling stuck at fault for combinational circuit
A circuit has n inputs and n outputs. It is implemented only using AND, OR and NOT gates. Further, there are no fan-out branches. What is the number of s-a faults that remain after fault collapsing?
...
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1answer
75 views
Why does one of my HiFi speakers only start working after several minutes? [closed]
not sure if this is an EE question, it's the closest SE site I could see?
I have a Sony separates mini-system (HCD-SD1) I was given; it's quite old now but good. Except that for a while now, when I ...
1
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1answer
264 views
HDMI triggering the Ground Fault Circuit Interrupters via Projector
Overview: A colleague of mine took her HP laptop from Canada (19.5 V, 1.4 A DC rated) to work in Brazil and experienced ground fault trips on the outlets when she connected an HDMI to a projector ...
0
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2answers
326 views
Single-Phase-to-Ground Fault doubts
I'm studying Fault Analysis Using Symmetrical Components and I have doubt over the single Phase to Ground Fault.
On the book is written that generally Is and It are equal to 0 during a single-phase ...
1
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2answers
325 views
Ordinary Differential Relay Problem
The answer given in my workbook to the above problem is A.
The things I was able to point out
secondary c-phase current = 300A and other secondary phase currents = 0A since the entire current ...
0
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3answers
1k views
What causes a faulty Linear Voltage regulator to output wrong voltage [closed]
I made a circuit where I needed DC 8v supply. I was using a KA7808 to regulate the voltage. While testing the voltage regulator unit, I identified that the Regulator IC might be faulty because I was ...
1
vote
1answer
75 views
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 ...
0
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0answers
55 views
Unbalanced Fault Problem
I have attached the image of a theoretical question with its explanation given in my book. can anyone please explain this ?
I am not able to start from anywhere so I can't show my work. I am posting ...
0
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2answers
397 views
How do solar panels affect the short circuit fault currents of a network? [closed]
As title suggests, I'm trying to find out how adding PV, both residential and solar farms, have an effect on the short circuit fault current of a network.
I wasn't given much info to go off, so I am ...
2
votes
5answers
215 views
How can I protect a 12VDC power source from high-resistance shorts? [closed]
I have a pickup truck with a 3kw AIMS inverter-charger. It is wired with 4/0 welding cable (for both positive and dedicated neutral back to the alternator), and I installed a block with a 300A fuse in ...
0
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1answer
58 views
Historical Addressing Modes/Conditions that Complicate Page Fault Handling
I was reading this linked question and the following paragraphs stood out to me:
For example x86 and 68000 had instructions which access memory two or more times. Each memory access could cause a ...
2
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0answers
103 views
Why won't LED light? [closed]
So I'm attempting to diagnose what's wrong with my daughters light up fidget spinner after she dropped it on the floor (and if possible fix). But I seem to be having a failing at electronics 101 and ...
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1answer
60 views
how decreasing ground fault resistance decrease the touched voltage?
Fault current = supply voltage / fault path R.
Assume live conductor of 230v touches the equipment metal frame.
1) assume R path through grounding electrode 25 ohm
I= 230/25=9.2A
2) R=3 ohm
I=76....
3
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1answer
882 views
Ground fault protection for fault on delta side of a wye-delta step down.
I have a distribution circuit with a primary 4-wire 21 kV and secondary 3-wire 12 kV circuit. The two winding transformer is a (grounded) Wye-(closed) Delta transformer. I know that if I have a ground ...
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1answer
100 views
Repairing Television in Protect-Mode [closed]
My 5-year-old television (Philips 32pfl5405h/12) stopped working two weeks ago. It seems to be in protect mode as its standby LED keeps blinking three times.
I pulled the plug and left it for a week -...
1
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0answers
377 views
When are positive-sequence and negative-sequence equivalent impedance the same?
One of the topics we covered in an introduction to power systems class was using zero/positive/negative sequence networks to analyze faults in networks. For many problems, this requires setting up ...
0
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0answers
58 views
Shock From HDMI Plugged Into TV [duplicate]
I recently bought a new TV and I noticed that when I touch the end of the HDMI cable I get a shock even when the TV is off (this also happens with the VGA -> Mini DP cable). I can only feel the shock ...
0
votes
2answers
1k views
advantages and disadvantages of using a microcontroller vs dedicated switching controller for a switching power supply?
Trying to build a constant current power supply for a laser diode here. I don't think I can use an off the shelf one because of the large 10A max current and because the current has to be controlled ...
3
votes
3answers
633 views
Class A amplifier asymmetric distortion mystery
I have an amplifier that went bad on the left channel a couple of days ago. I'm kinda intrigued by the failure and symptoms, which is also why I'm posting here and not just counting my losses.
I was ...
0
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1answer
62 views
Simple method to find open fault in three wire power cable?
I have a three wire power cable - live, neutral and ground. My multimeter shows no fault with the neutral and ground wires, but there is an open fault on the live wire. Nothing suspicious upon visual ...
1
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1answer
114 views
What's the use of the ground socket of an ungrounded GFCI receptacle?
Is the ground socket of a GFCI receptacle that isn’t connected to ground useful? (I'm in the United States, if it matters.) If the connected appliance had current on its ground pin, where would this ...
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2answers
210 views
Setup for logging/displaying what command an OBD scan tool sends
I came across this video: youtube.com/watch?v=VtMvccqE8ks
Any idea/resources how to build this setup? I am not much interested in monitoring the CAN bus for commands (headers or CAN IDs) of power ...
0
votes
1answer
82 views
Fault finding (Basic) [closed]
I am currently trying to work out whether a particular PCB is faulty. The board consists of a low capacitance a.c filter in parallel across the line and neutral. The circuit also consists of ...
5
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1answer
131 views
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 ...
0
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0answers
88 views
The effect of series & parallel resistors/impedances on fault level
Can anyone explain or link to a source that explains this?
Simply put, what is the effect of having resistors/impedances in series/parallel on the fault level of a circuit? I haven't been able to ...
0
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0answers
101 views
Troubleshooting the pcb and understand the schematics
I’m writing because I want to understand the following diagram. I have a usb hub connected to 2 motors and 2 cameras. I will skip the motors for the time being because I have issue even when the ...
2
votes
1answer
74 views
What types of fault protection is recommended for low voltage power supplies?
I'm building an AC-DC 120/15 V isolated power supply using a transformer, buck regulator for constant voltage, and a diode bridge rectifier.
I'm not sure what type of fault protection to implement, ...
2
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3answers
2k views
Amplifier Repair - How can I find a replacement transformer? [closed]
So I'm trying to repair an old Marantz 1040M amplifier, which after being run at high volumes on New Year's(!!) no longer powers on :(
My electronics knowledge is fairly rudimentary, but I think I ...
0
votes
0answers
971 views
How to test darlington transistor in-circuit?
I'm trying to diagnose a faulty current limiting circuit in a piece of lab equipment from back in the 80s. The fault is too much current.
The tail end of the circuit is below. Q3 represents a ...
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votes
1answer
339 views
STM32F4 bugs in DMA, is there bug-free version?
Producer has confirmed that if there will be concurrent AHB and APB2 transfers using DMA2, then data corruption will occur (source). The bug discovery is from 2012, many years ago. Is the STM32F4 ...
1
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2answers
326 views
Power System Faults Problem
A sustained three-phase fault occurs in the power system shown in the figure (See Link). The current and voltage phasors during the fault (on a common reference), after the natural transients have ...
0
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1answer
349 views
Three phase short circuit and line to ground short circuit
Why is three phase short circuit calculated current higher than line to ground or (phase to ground) short circuit calculated current in most cases?
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2answers
50 views
Bad Headphone Connector Wiring Issues - What Could Be Wrong? [duplicate]
I am trying to repair a headphone cable with a splice. The audio sounds really bad after the repair. I can hear instruments, but not the vocals. Also, the playback is mono, same sound on both sides.
...
0
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1answer
56 views
Repeated dimmer switch fault following bulbs reaching end-of-life
I have a dual 1-way dimmer switch, 240V rated for 40W-400W, to which one of the dimmers has 5 x 60W dimmable bulbs (ceiling lights) and always works without any issue, and the other dimmer has 4 x 28W ...
31
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6answers
3k views
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 ...
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2answers
478 views
What is the difference between capacitive fault currents and resistive fault currents?
http://uk.megger.com/battery-ground-fault-tracer-bgft\
This website claims that it's product can differentiate between these two fault currents. But I don't know what the difference is.
0
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0answers
70 views
fault recovery processes for short circuit problem!
Are there any fault recovery processes to sustain a short circuit problem without changing the damaged element. Consider a smart grid distribution network, where it deals with normal household ...
0
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1answer
38 views
How do I determine expected harmonic frequencies and corresponding amplitudes in a case of synchronous machine?
1)find harmonic frequencies which source in synchronous machine in a) fault, and b) fault-free operation conditions, in steady state mode.
2) and find how harmonics are depended on power factor, load ...
