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Thread: Leviton GFCI nuisance tripping and circuit analysis

  1. #21
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    I made a series of tests.

    I inserted a 240v surge protection between the waterpik shade pole motor and Leviton chipped GFCI. It only trips rarely, like once in 20 switchings!



    Here I inserted a 1:1 medical grade isolation transformer (with dielectric shielding between primary & secondary) between the waterpik shaded pole motor and GFCI.




    It doesn't trip at all. But is it not transients still pass through an isolated transformer and only the common mode surges were suppressed? But noticed there is no ground, the surface is glass, so could the 240v 1:1 isolation transformer filtering some line to line transients too? The model of it is: http://catalog.triadmagnetics.com/Asset/VPM240-2080.pdf

    I bought the 240v 1:1 isolation transformer supposedly to put it on the refrigerator which I tested to trip last year on the GFCI outlet. I thought it trips on all GFCIs. But when I tested the Siemens GFCI breaker lately, the refrigerator no longer trips!

    The meter at the left side is a flux meter. I'm studying the flux properties of the shaded pole motors. Note the behavior is the same whether the rotor is put in the stator or not. The flux meter is also to verify if the motor is turned on or off. The needle jumps above 100mG when it is turned on.

    Here the shaded pole motor is connected directly to the GFCI. The tripping is 80-90% of the time.



    Do you have any flux mapping or plot of a shaded pole motor? Why does it produce more inductive kick than other motors. I noticed the magnetic flux is very strong, more than a 500va isolation transformer or autotransformer. Does motor with very large magnetic flux have more inductive kick?



    Btw.. there is no other 240v GFCI receptacle with 5mA tripping in the entire world. Only one brand carries it. It doesn't have the auto-monitoring self test in UL 2015. So all using 240v are stuck with it and have to deal with shaded pole motors (in refrigerator, etc.) that can trip it.

  2. #22
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    Quote Originally Posted by tersh View Post
    I made a series of tests.

    I inserted a 240v surge protection between the waterpik shade pole motor and Leviton chipped GFCI. It only trips rarely, like once in 20 switchings!



    Here I inserted a 1:1 medical grade isolation transformer (with dielectric shielding between primary & secondary) between the waterpik shaded pole motor and GFCI.




    It doesn't trip at all. But is it not transients still pass through an isolated transformer and only the common mode surges were suppressed? But noticed there is no ground, the surface is glass, so could the 240v 1:1 isolation transformer filtering some line to line transients too? The model of it is: http://catalog.triadmagnetics.com/Asset/VPM240-2080.pdf

    I bought the 240v 1:1 isolation transformer supposedly to put it on the refrigerator which I tested to trip last year on the GFCI outlet. I thought it trips on all GFCIs. But when I tested the Siemens GFCI breaker lately, the refrigerator no longer trips!

    The meter at the left side is a flux meter. I'm studying the flux properties of the shaded pole motors. Note the behavior is the same whether the rotor is put in the stator or not. The flux meter is also to verify if the motor is turned on or off. The needle jumps above 100mG when it is turned on.

    Here the shaded pole motor is connected directly to the GFCI. The tripping is 80-90% of the time.



    Do you have any flux mapping or plot of a shaded pole motor? Why does it produce more inductive kick than other motors. I noticed the magnetic flux is very strong, more than a 500va isolation transformer or autotransformer. Does motor with very large magnetic flux have more inductive kick?



    Btw.. there is no other 240v GFCI receptacle with 5mA tripping in the entire world. Only one brand carries it. It doesn't have the auto-monitoring self test in UL 2015. So all using 240v are stuck with it and have to deal with shaded pole motors (in refrigerator, etc.) that can trip it.
    This is inside the CD-R king surge protector:



    It's from file photo I took about 6 months ago. Notice the 3 MOVs (Metal Oxide Varistors). It's only line to line only (made in china) so they are all connected line to line. Our electricity is equivalent to the 240v red and black hot lines in the US so we don't have any line to neutral, or neutral to ground. So there is no protection modes for them unlike in US manufactured surge protectors.

    Now my question about it. Inductive kicks are not surges, are they?! Why did the surge protection strip eliminate the tripping to almost 5% only? It trips once in every 20 switchings. Without the surge protection strip, the shaded pole motor trips 4 out of 5 switchings in the Leviton based GFCIs (never in the Siemens GFCI which perhaps contain more MOVs)?

  3. #23
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    Inductive kicks are not surges, are they?!

    Yest they are.

    The MOVs with clip the top off the inductive voltage kicks, by providing a low impedance path. Same type peak voltge limiting as the capacitor across the device as mentioned in an earlier EU appliance comment.

  4. #24
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    Quote Originally Posted by junkhound View Post
    Inductive kicks are not surges, are they?!

    Yest they are.

    The MOVs with clip the top off the inductive voltage kicks, by providing a low impedance path. Same type peak voltge limiting as the capacitor across the device as mentioned in an earlier EU appliance comment.
    Ok.

    Here is a big washing machine with big motor that can run for half a day without tripping the same GFCI once.



    But a tiny shaded pole motor can trip it so repetitively.




    What's in a shaded pole motor that can repetitively cause inductive kick? any clue anyone?

  5. #25
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    Quote Originally Posted by tersh View Post
    Ok.

    Here is a big washing machine with big motor that can run for half a day without tripping the same GFCI once.



    But a tiny shaded pole motor can trip it so repetitively.




    What's in a shaded pole motor that can repetitively cause inductive kick? any clue anyone?
    The coil.
    Tom
    TBLO

  6. #26
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    Quote Originally Posted by ptonsparky View Post
    The coil.
    An electric fan also has coil but no matter how many times it is turned on and off.. it doesn't trip the Leviton based GFCI, why?

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    Different inductances.

    BTW, the "Levitoncircuit' in yoaur original post is simly a copy of the Fairchild spec typical circuit.

    Have you actually traced out the real circuit in the Leviton gfci? Differences are likely.

    You (or Gar) could hook up a scope to pin1 of the Fairchild chip with different motors and see the different responses.

    Also, in your photos, do not see a switch except on the outlet strip. I'm not clear on where the switch is, where is it in the circuit ?

  8. #28
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    Quote Originally Posted by junkhound View Post
    Different inductances.

    BTW, the "Levitoncircuit' in yoaur original post is simly a copy of the Fairchild spec typical circuit.

    Have you actually traced out the real circuit in the Leviton gfci? Differences are likely.

    You (or Gar) could hook up a scope to pin1 of the Fairchild chip with different motors and see the different responses.

    Also, in your photos, do not see a switch except on the outlet strip. I'm not clear on where the switch is, where is it in the circuit ?
    Here is the switch.




    Note the GFCI is not made by Leviton. It just used the same chipset used by Leviton. It's not even the same chipset. That is. A china company copied the Fairchild chipset 100%. It has even same wordings in the manual. I don't know if it's under license or illegally. The Fairchild chipset copied is the N4141A (diagram and manual in the original post) produced about 2008. The Leviton video bellow detailed it.

    It's made by this company in year 2007: Shanghai Fudan Microelectronics Group Co. Ltd

    http://www.chip-memory.com/4-1-2-int...d-circuit.html

    It's the only 240v GFCI with 5mA tripping model in the whole world. Distributed here OEM to many companies.

    http://www.internationalconfig.com/i...tem=74900-RCDS

    The 100% copied chipset is called FM2141 with diagram here:



    Noticed it is 100% identical to the Fairchild N4141A:



    In this Leviton video. You can see the above R4141A chipset exactly mentioned and even the second coil explained in detail.



    The Shanghai company never copied other models. So all 240v GFCI receptacle users worldwide were stuck with their 2007 model.

    In current Leviton GFCIs, it no longer trips on inductive kick right? They have fixed all the problems and it is only the old stock at homes which experienced it?

  9. #29
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    Quote Originally Posted by tersh View Post
    What's in a shaded pole motor that can repetitively cause inductive kick? any clue anyone?
    Quote Originally Posted by ptonsparky View Post
    The coil.
    Exactly. The coil.

    Examine the wire gauge and number of windings in the different types of motors your are raising in you question. You will find that the tiny shaded pole fractional horsepower motor that you have in your photos has a coil that has a large number of turns (windings) of very fine gauge wire.

    That right there is what sets your little motor apart from the rest.

    When the supply to the motor is switched off at an instant of maximum magnetic field density in the laminated core, the field will collapse. The collapsing magnetic field, moving by the coil windings, induces the "kick". Strength and speed of the collapsing magnetic field and the turns ratio of the windings in the coil do the rest.
    Another Al in Minnesota

  10. #30
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    Quote Originally Posted by al hildenbrand View Post
    Exactly. The coil.

    Examine the wire gauge and number of windings in the different types of motors your are raising in you question. You will find that the tiny shaded pole fractional horsepower motor that you have in your photos has a coil that has a large number of turns (windings) of very fine gauge wire.

    That right there is what sets your little motor apart from the rest.

    When the supply to the motor is switched off at an instant of maximum magnetic field density in the laminated core, the field will collapse. The collapsing magnetic field, moving by the coil windings, induces the "kick". Strength and speed of the collapsing magnetic field and the turns ratio of the windings in the coil do the rest.
    You have a point. The shaded pole motor has very strong magnetic field even a meter away, more than a 500va transformer. My EMF meter range is only up to 100mG. Does anyone know of the best quality EMF/flux meter that has range up to say 10 Gauss and accurate. I'd like to measure the leaking flux half inch away from the coil and compare it to other transformers.

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