First. My Siemens GFCI Breaker doesn't trip after 3 days with refrigerator on it. Good. While last year with the FM2141 chip GFCI outlet. It tripped twice a day or so hence I thought it was the fridge that was the problem.
Btw.. My course in college was electronic engineering. Spent 5 years in it. So I am supposed to be familiar with it. But that was long ago and changed interests to the medical field and then to physics now. Shaded pole motors and Leviton GFCIs are very common in the US. Can people with these try them on their oscilloscope? Also there is this person with electric fan that trips on his two Leviton GFCI. He has a theory how it occurs that it's because each of the two wire has actual inbalance current. Please comment on his theories and what could be wrong with it. He said in:
https://www.justanswer.com/electrical/2g0be-gfci-outlet-trips-even-when-clear.html
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It seems very unlikely that the problem is caused by a loose connection because the nuisance trips occur only when one opens a switch to the load, not at random as one would expect if the problem were caused by a loose connection.
After giving the problem a good deal of thought, I have concluded that it is due to a transient that occurs when the load is switched off. It does not occur when the load is purely resistive (e.g., an iron). It occurs when an inductive load , such as a
motorAfter giving the problem a good deal of thought, I have concluded that it is due to a transient that occurs when the load is switched off. It does not occur when the load is purely resistive (e.g., an iron). It occurs when an inductive load , such as a
is switched off. In the GFCI, the two wires that feed the load pass through a small current transformer that produces no output if the currents in the two wires are equal in magnitude and opposite in direction. In other words, the GFCI trips if the net current through the transformer is not zero.
When the load is purely resistive, the currnet in both wires falls to zero instantaneously when the switch is opened. Hence the GFCI does not trip.
Now suppose that the load is inductive (equivalent to a resistance in series with an inductance). When the switch is opened, one leg of the circuit consists of only a wire and hence the current in it falls instantaneously to zero when the switch is opened. In the leg of the circuit containing the load , what happens depends upon the currrent in the indictance at the moment when the switch opens. (Remember that the current in the inductance varies sinusoidally before the switch opens.) If the current is zero when the switch opens, nothing more happens and the GFCI does not trip because the currents passing through the transformer are equal and opposite at all times. If the current in the inductance is not zero when the switch opens. it does not fall to zero instantaneously when the switch opens because of the relationship E=L di/dt, which says that the voltage across the inductor would have to be infinite to cause the current to fall to zero instantaneously. Therefore, one concludes that the current in the wire to the load does not fall to zero instantaneously and hence for a brief time there is an imbalance in the currents in the two wires passing through the transformer and the GFCI trips.
This analysis indicates that the GFCI trips only some of the time when a motor load is switched off. "
When the load is purely resistive, the currnet in both wires falls to zero instantaneously when the switch is opened. Hence the GFCI does not trip.
Now suppose that the load is inductive (equivalent to a resistance in series with an inductance). When the switch is opened, one leg of the circuit consists of only a wire and hence the current in it falls instantaneously to zero when the switch is opened. In the leg of the circuit containing the load , what happens depends upon the currrent in the indictance at the moment when the switch opens. (Remember that the current in the inductance varies sinusoidally before the switch opens.) If the current is zero when the switch opens, nothing more happens and the GFCI does not trip because the currents passing through the transformer are equal and opposite at all times. If the current in the inductance is not zero when the switch opens. it does not fall to zero instantaneously when the switch opens because of the relationship E=L di/dt, which says that the voltage across the inductor would have to be infinite to cause the current to fall to zero instantaneously. Therefore, one concludes that the current in the wire to the load does not fall to zero instantaneously and hence for a brief time there is an imbalance in the currents in the two wires passing through the transformer and the GFCI trips.
This analysis indicates that the GFCI trips only some of the time when a motor load is switched off. "
