Let's say one accidentally touch a live wire with the feet on ground, and the source is 3A. When the sense coil detects 5mA leakage, it triggers the IC to open the relay. But before the relay open. Can't it pass more than 5mA? Maybe 100mA? But 100mA is lethal dose already. So could china made GFCI be slower to respond. How do they test what mA of current are actually passed before the relay open say the trigger ampere is really 5mA?
Leviton GFCI nuisance tripping and circuit analysis
- Thread starter tersh
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Let's say one accidentally touch a live wire with the feet on ground, and the source is 3A. When the sense coil detects 5mA leakage, it triggers the IC to open the relay. But before the relay open. Can't it pass more than 5mA? Maybe 100mA? But 100mA is lethal dose already. So could china made GFCI be slower to respond. How do they test what mA of current are actually passed before the relay open say the trigger ampere is really 5mA?
ptonsparky
Tom
- Occupation
- EC - retired
Explain the source is 3A. I would be more concerned with the voltage of the source.
If you do not have any testing labs, such as UL, you are taking the word of the manufacturer that their equipment works as they claim. How they test is up to them. They may test it on 100 __________, and if 95% of them live it's good enough. They may not test at all.
junkhound
Senior Member
- Location
- Renton, WA
- Occupation
- EE, power electronics specialty
Here is a 70 Year old chart from Dalziel, data from zapping a few thousand pigs and sheep in lieu of people.
40 years later it was also established that 'chance' plays a role for short duration shocks, as the shock has to occur during the T-wave (per EKG) fro fibrillation to occur.
Note that these levels are fatal to 'only' 1/2 of 1% of the sheep and pigs tht got zapped at that level.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
190111-1147 EST
tersh:
See:
https://www.csemag.com/articles/uls-new-gfci-classes/
https://electrical-engineering-portal.com/ground-fault-circuit-interrupter-gfci
for some curves.
.
tersh:
See:
https://www.csemag.com/articles/uls-new-gfci-classes/
https://electrical-engineering-portal.com/ground-fault-circuit-interrupter-gfci
for some curves.
.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
190111-1330 EST
tersh:
RF (Radio Frequency) dating back to probably before 1900, possibly not by that name.
See https://en.wikipedia.org/wiki/Guglielmo_Marconi
Radio frequencies are reasonably from about 50 kHz to very high frequencies. However, there are radio transmissions around 70 Hz to communicate with underwater submarines. Rightfully these are radio frequency frequencies, just not common. Radio frequencies can be transmitted thru the ether or by a conductor.
Generally radio frequencies are considered to be above the audio spectrum.
A 1 microsecond pulse every 1/10,000 sec is in the radio frequency spectrum, but not usually described as RF, but may cause RFI (radio frequency interference), either by radiation or conduction.
.
tersh:
RF (Radio Frequency) dating back to probably before 1900, possibly not by that name.
See https://en.wikipedia.org/wiki/Guglielmo_Marconi
Radio frequencies are reasonably from about 50 kHz to very high frequencies. However, there are radio transmissions around 70 Hz to communicate with underwater submarines. Rightfully these are radio frequency frequencies, just not common. Radio frequencies can be transmitted thru the ether or by a conductor.
Generally radio frequencies are considered to be above the audio spectrum.
A 1 microsecond pulse every 1/10,000 sec is in the radio frequency spectrum, but not usually described as RF, but may cause RFI (radio frequency interference), either by radiation or conduction.
.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Here is something disturbing for 240v users especially since the only GFCI receptacle model in the world was assembled by an unknown company. Meiji is just one OEM customer of this unknown company that assembled the cloned Fairchild chip. The first url above mentioned:
"
At voltages greater than 150 V, the resistance of the human body decreases dramatically and the fault current flowing through the body increases to unsafe levels requiring impossibly fast trip time. The purpose of the grounding conductor is to prevent the case or cabinet of a piece of equipment from exceeding 150 V if an energized conductor faults to it. The resulting current through the grounding conductor will also trip the GFCI to eliminate the danger of fibrillation."
The same url gave this formula
T = (20/I)^1.43
The same url gave this formula
T = (20/I)^1.43
where T is in sec and
I is in mA, and shown in Figure 3. Note that at currents greater than 300 mA, the delay is fixed at 20 msec.
For 120v. What is the resistance of the human body and if the fault current is 1A. How much current can pass between your two hands passing through the heart? What about at 240v?
Assuming the fault current of 1A can pass through your body. Then computing for T given I = 1000mA
T=(20/1000)^1.43 = 0.0037 second or 3.7millisecond
In the second url is this graph:
For 120v. What is the resistance of the human body and if the fault current is 1A. How much current can pass between your two hands passing through the heart? What about at 240v?
Assuming the fault current of 1A can pass through your body. Then computing for T given I = 1000mA
T=(20/1000)^1.43 = 0.0037 second or 3.7millisecond
In the second url is this graph:
Before the above graph is this statement:
"What a Ground Fault Current Interrupter does not:
2.
It
does not limit the magnitude of ground fault current. It does limit the length of time that a ground fault will flow. In other words, you will still receive a severe shock during the time it takes the GFCI device to trip “off.” See Figure 3"
If the current passing through the human body is 1A. The tripping time must be 0.0037 second which is not possible for GFCI.
For 240v. What is the resistance and maximum current that can really pass through the body so we can accurately compute for T and decide if the 240v cloned GFCI outlet sold worldwide is useless for utmost safety.
Here is something disturbing for 240v users especially since the only GFCI receptacle model in the world was assembled by an unknown company. Meiji is just one OEM customer of this unknown company that assembled the cloned Fairchild chip. The first url above mentioned:
"At voltages greater than 150 V, the resistance of the human body decreases dramatically and the fault current flowing through the body increases to unsafe levels requiring impossibly fast trip time. The purpose of the grounding conductor is to prevent the case or cabinet of a piece of equipment from exceeding 150 V if an energized conductor faults to it. The resulting current through the grounding conductor will also trip the GFCI to eliminate the danger of fibrillation."
The same url gave this formula
T = (20/I)^1.43
where T is in sec and Iis in mA, and shown in Figure 3. Note that at currents greater than 300 mA, the delay is fixed at 20 msec.
For 120v. What is the resistance of the human body and if the fault current is 1A. How much current can pass between your two hands passing through the heart? What about at 240v?
Assuming the fault current of 1A can pass through your body. Then computing for T given I = 1000mA
T=(20/1000)^1.43 = 0.0037 second or 3.7millisecond
In the second url is this graph:
Before the above graph is this statement:
"What a Ground Fault Current Interrupter does not:
2.It does notlimit the magnitude of ground fault current. It does limit the length of time that a ground fault will flow. In other words, you will still receive a severe shock during the time it takes the GFCI device to trip “off.” See Figure 3"
If the current passing through the human body is 1A. The tripping time must be 0.0037 second which is not possible for GFCI.
For 240v. What is the resistance and maximum current that can really pass through the body so we can accurately compute for T and decide if the 240v cloned GFCI outlet sold worldwide is useless for utmost safety.
I was thinking if using isolation transformer for fridge for 240v users is safer than a 240v GFCI from an unknown manufacturer and especially with the information above.
Say. What would happen when you connect an GFCI to an isolation transformer. Would it trip if there is leak from one live wire to ground? Since the ground is isolation, it shouldn't trip, should it?
But connecting the shaded pole motor to the Meiji GFCI outlet and to a medical isolation transformer.
The shaded pole motor still trips 4 out of 5 switchings (sometimes 100% trip 5 out of 5). The isolation transformer totally isolate the ground from source. It is a high quality medical isolation transformer with datasheet at http://catalog.triadmagnetics.com/Asset/VPM240-2080.pdf I got precisely to make sure the isolation is top notch. It even has dieelectric shielding between primary and secondary of the toroid which is difficult to manufacturer that is why it costs a lot.
If you connect GFCI to a true isolation transformer, what instance can the GFCI still trip when the ground is supposed to be separated already?
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Theoretically speaking, on a genuinely isolated, ungrounded electrical supply, a GFCI cannot detect when there is a connection between a supply conductor and earth. GFCI's serve no purpose on ungrounded systems.
In your experiments, there has been nothing to even suggest that the GFCI was tripping due to an unintentional leakage current to earth.
So what is the relationship between inductive kick and LC filter? What part of inductive kick can LC filter able to filter?
mopowr steve
Senior Member
- Location
- NW Ohio
- Occupation
- Electrical contractor
Probably doesn’t take make of any thing to help quench the peak of the kickback spike
such as a capacitor, LC filter, etc
such as a capacitor, LC filter, etc
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
190111-2032 EST
Larry Fine:
In post #65 I was trying to point out what frequencies are typically called RF. Not whether those frequencies were radiated or conducted. I did say there were in use frequencies around 70 Hz that are probably used as radiated signals.
Relative to sound and radio radiated waves. Both are radiated. Energy set in motion flows away from the source. In radio wave it is an electro-magnetic field. In an acoustic signal it is a pressure wave.
tersh:
If you have a pure LC low pass filter, and pulse it with a pulse much shorter in duration than the filter bandwidth, then the input energy is not lost going thru the filter, it is just modified. The output rate of rise is much slower than was the input. The peak output voltage is thus reduced, and the duration of the output pulse us greatly increased. The energy in the output pulse is the same as the input energy. I am describing total energy of the input pulse equals total energy of the output pulse.. That is the integral of instantaneous power input over the total time period of the input pulse is equal to the integral of the instantaneous power of the output pulse over the period of the output pulse. If the input pulse is rectangular, then the output pulse becomes rounded.
This filtering is why your outlet strip labeled "Voltage Surge Protector" reduced the false trips of the GFCI. The fact that the false trips were reduced indicates that false triggering occurred from conducted noise energy, and not from radiated RF energy.
.
Larry Fine:
In post #65 I was trying to point out what frequencies are typically called RF. Not whether those frequencies were radiated or conducted. I did say there were in use frequencies around 70 Hz that are probably used as radiated signals.
Relative to sound and radio radiated waves. Both are radiated. Energy set in motion flows away from the source. In radio wave it is an electro-magnetic field. In an acoustic signal it is a pressure wave.
tersh:
If you have a pure LC low pass filter, and pulse it with a pulse much shorter in duration than the filter bandwidth, then the input energy is not lost going thru the filter, it is just modified. The output rate of rise is much slower than was the input. The peak output voltage is thus reduced, and the duration of the output pulse us greatly increased. The energy in the output pulse is the same as the input energy. I am describing total energy of the input pulse equals total energy of the output pulse.. That is the integral of instantaneous power input over the total time period of the input pulse is equal to the integral of the instantaneous power of the output pulse over the period of the output pulse. If the input pulse is rectangular, then the output pulse becomes rounded.
This filtering is why your outlet strip labeled "Voltage Surge Protector" reduced the false trips of the GFCI. The fact that the false trips were reduced indicates that false triggering occurred from conducted noise energy, and not from radiated RF energy.
.
Last edited:
ptonsparky
Tom
- Occupation
- EC - retired
Mine were inexpensive, considering I bought them from an AB wholesaler.
I put the LC filter strip between the Meiji GFCI and the Refrigerator to see if the ref would still trip and frequency. Before it tripped twice a day probably due to the shaded pole motor used in the fan in the ref. Do all ref use shaded pole motor based fan? (notice the refrigerator has no EGC and use 2 prong plug, it is brand new refrigerator).
I can't find the spectrum of inductive kick. What are the frequencies involved? Is it also the source of all surges inside the building or house? The SPD people say surges come from outside and inside the building. What does it differ to RF noises and what creates RF noises?
Do you know a reference that explains all of them at once? I only see unrelated reference and couldn't seem to combine all the concepts together. Thanks.
I was thinking if using isolation transformer for fridge for 240v users is safer than a 240v GFCI from an unknown manufacturer and especially with the information above.
Say. What would happen when you connect an GFCI to an isolation transformer. Would it trip if there is leak from one live wire to ground? Since the ground is isolation, it shouldn't trip, should it?
But connecting the shaded pole motor to the Meiji GFCI outlet and to a medical isolation transformer.
The shaded pole motor still trips 4 out of 5 switchings (sometimes 100% trip 5 out of 5). The isolation transformer totally isolate the ground from source. It is a high quality medical isolation transformer with datasheet at http://catalog.triadmagnetics.com/Asset/VPM240-2080.pdf I got precisely to make sure the isolation is top notch. It even has dieelectric shielding between primary and secondary of the toroid which is difficult to manufacturer that is why it costs a lot.
If you connect GFCI to a true isolation transformer, what instance can the GFCI still trip when the ground is supposed to be separated already?
The url below mentioned the resistance of the human body was about 1500 ohms arm to arm, but there is something I'd like to ask clarification about. First in one of gar's 2 urls is this paragraph.
"At voltages greater than 150 V, the resistance of the human body decreases dramatically and the fault current flowing through the body increases to unsafe levels requiring impossibly fast trip time. The purpose of the grounding conductor is to prevent the case or cabinet of a piece of equipment from exceeding 150 V if an energized conductor faults to it. The resulting current through the grounding conductor will also trip the GFCI to eliminate the danger of fibrillation."
Look at this url:
http://electronicstechnician.tpub.com/14086/css/Amount-Of-Body-Resistance-34.htm
resistance of the body arm to arm is said to be 1500 ohms. So if voltage is 240v.
I=V/R = 240/1500 = 0.16A or 160mA
Is this the context that as voltage increase, the current increases? (here the resistance stays constant).
Or can the 1500 ohms go even lower that can further as voltage is increased?
But isn't it the formula I=V/R already take into account the increased voltage?
Or does it mean if the resistance gets lowered to say 1000 ohm. Then current is I =V/R = 240/1000 = 0.24A or 240mA?
Compare this to the US electricity of I=V/R = 120/1500 = 0.080 A or 80mA only.
What do you think?
junkhound
Senior Member
- Location
- Renton, WA
- Occupation
- EE, power electronics specialty
From a controlled experiment 15 years ago on myself at 60 YO:
with both my feet in 14% NaCl solution to 3" above the ankle at 20 mA 60 Hz measured 420 ohms.
btw, at the salt water level on one's legs at 20 mA there is an INTENSE burning sensation at the water line that goes away when current turned off
CAUTION - DO NOT TRY To REPEAT THESE TYPE EXPERIMENTS AT HOME.
If you can find a copy, a definitive treatise on impedance and shock and fibrillation is in Berglemiester's paper:
Dr B literally electrocuted himself with defilb equipment and medical doctors standing by.
Dr. G Biegelmeier, New knowledge on the impedance of the human body. (1985 PAPER)
https://ethw.org/Oral-History:Gottfried_Biegelmeier
https://www.sciencedirect.com/science/article/pii/B978008025399250014X
with both my feet in 14% NaCl solution to 3" above the ankle at 20 mA 60 Hz measured 420 ohms.
btw, at the salt water level on one's legs at 20 mA there is an INTENSE burning sensation at the water line that goes away when current turned off
CAUTION - DO NOT TRY To REPEAT THESE TYPE EXPERIMENTS AT HOME.
If you can find a copy, a definitive treatise on impedance and shock and fibrillation is in Berglemiester's paper:
Dr B literally electrocuted himself with defilb equipment and medical doctors standing by.
Dr. G Biegelmeier, New knowledge on the impedance of the human body. (1985 PAPER)
https://ethw.org/Oral-History:Gottfried_Biegelmeier
https://www.sciencedirect.com/science/article/pii/B978008025399250014X
When a person suffers fibrillation, why is death sudden? Does it immediately shut down the brain? In gunshot victims to critical body parts. they don't die suddenly, but those who were electrocuted died suddenly. If the heart stopped beating, does brain shut down immediately and death follows 2 seconds later??
for professional engineer eyes only
This is to remind even professionals that electrocution doesn't give you second chance.. so only let professional electrician connects anything electrical with fully body protection (like electrical gloves and googles).
This is also why I won't buy any oscilloscope and try to see the inductive surge spectrum of the shaded pole motor and what part of the GFCI circuit trips when exposed to these inductive kicks. Let professionals with full laboratory equipment trained handling it figure it out.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Maybe it was actually the energized water around the pole.
When a person suffers fibrillation, why is death sudden? Does it immediately shut down the brain? In gunshot victims to critical body parts. they don't die suddenly, but those who were electrocuted died suddenly. If the heart stopped beating, does brain shut down immediately and death follows 2 seconds later??
for professional engineer eyes only
This is to remind even professionals that electrocution doesn't give you second chance.. so only let professional electrician connects anything electrical with fully body protection (like electrical gloves and googles).
This is also why I won't buy any oscilloscope and try to see the inductive surge spectrum of the shaded pole motor and what part of the GFCI circuit trips when exposed to these inductive kicks. Let professionals with full laboratory equipment trained handling it figure it out.
I googled a lot about electrocution or fibrillation and loss of consciousness but not much direct hits. However. When I entered "cardiac arrest and loss of consciousness". There are many hits. So what happens in cardiac arrest is really lost of consciousness. In electrocution, one is inducing cardiac arrest.
https://www.everydayhealth.com/heart-health/is-it-cardiac-arrest-or-heart-attack.aspx
"
A heart attack and cardiac arrest, though both significant and dangerous, are two different cardiac events. Heart attacks happen when too little blood flow gets to the heart, but in cardiac arrest, the heart malfunctions and stops beating, at which point a person may suddenly lose consciousness."
If only consciousness wouldn't occur suddenly after one got fibrillation from electrocution, one could use defibrillator on oneself (by maybe bringing one in knapsack, no such emergency kit an electrician can bring, isn't it?).
junkhound
Senior Member
- Location
- Renton, WA
- Occupation
- EE, power electronics specialty
hmmm, profile lists 'engineer'? An engineer afraid to hook up a scope to simple 240 V 60 Hz? Untrained and an engineer? a locomotive or 'sanitary' engineer?
All you need to do to get your full data is to hook up a scope with a current probe (you don't even have to touch any 240 V wire with a clamp on probe) and look at the waveform. You will undoubtedly SEE a differential current at transitions.
Gar probably has already taken some waveforms and waiting to see if any others have
Using a small SP motor I see differential currents in the 10o's of mA at switch operations.
Another hint: the inductance of small sp motor is 500 mH, a 1/2 HP motor is only 2.6 mH - what does that tell you?
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