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saw triggering breaker

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  • #31
    Another possibility might be some appliance that uses a single wave rectifier, which causes some DC to flow through the circuit. At some point this may cause saturation of the differential transformer and a shifted or distorted waveform. This should cancel out if the same DC flows in both windings, but it may have some effect. Also, a DC component might cause magnetization of the motor. This can also happen if current flow is abruptly stopped at a peak value, and then very high current can flow when re-energized, due to remanent magnetism. This also occurs in transformers.
    http://pauleschoen.com/pix/PM08_P76_P54.png
    Paul , P S Technology, Inc. and MrTibbs
    USA Maryland 21030

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    • #32
      The markings tend to indicate the RCD is OK with half wave current, but how far that goes is not clear.

      However the fault seems to be associated with the saw jamming. I am not sure how that affects the current balance, other than causing a much higher current and possibly causing a trip per my item 3 suggestion.

      The fact that the RCD is rated to 40A indicates that it has to operate correctly up to at least 40A. But it may not necessarily operate correctly above 40A, and the existing load plus the stalled motor current probably goes over 40A. It is rated to open the contacts up to a considerably higher current, but that does not mean the RCD part operates right at over 40A.

      Originally posted by MattiJ View Post
      4. part of the return current on neutral wire goes to somewhere it shouldn't. (some fool connecting ground and neutral)
      In other words, an actual ground fault......per item 1. But why only when the saw jams?
      CNC machines only go through the motions.

      Ideas expressed may be mine, or from anyone else in the universe.
      Not responsible for clerical errors. Or those made by lay people either.
      Number formats and units may be chosen at random depending on what day it is.
      I reserve the right to use a number system with any integer base without prior notice.
      Generalizations are understood to be "often" true, but not true in every case.

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      • #33
        yes, its my understanding this has no overcurrent function. there are three 40 amp breakers outside of the house. i run several vfds with no problems. also the high frequency start from the welder (closer to the box than the saw) is no problem. the rcd tripps about every second time the saw stalls. at that time of the day there is usually little load connected. lights, heater, toasters, watter kettle and hairdryiers are off, as well as the heat pump.

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        • #34
          Originally posted by dian View Post
          yes, its my understanding this has no overcurrent function. there are three 40 amp breakers outside of the house. i run several vfds with no problems. also the high frequency start from the welder (closer to the box than the saw) is no problem. the rcd tripps about every second time the saw stalls. at that time of the day there is usually little load connected. lights, heater, toasters, watter kettle and hairdryiers are off, as well as the heat pump.
          Have you tried another plug from another breaker?
          Helder Ferreira
          Setubal, Portugal

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          • #35
            you mean to plug it in somewhere else? no, all wall sockets in that area go to the same breaker and rcd. i could wire it to a ceiling light. that would be another breaker but still the same rcd. what is your idea?

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            • #36
              Originally posted by dian View Post
              you mean to plug it in somewhere else? no, all wall sockets in that area go to the same breaker and rcd. i could wire it to a ceiling light. that would be another breaker but still the same rcd. what is your idea?
              You have the F20 and F30 rcd circuits. You could get an extension cord to try the other circuit temporarily.
              Helder Ferreira
              Setubal, Portugal

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              • #37
                you mean i dive into that breaker box. never! so you mean to check if the rcd is defective? very unlikely, they are high quality components about 10 years old.

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                • #38
                  Originally posted by dian View Post
                  you mean i dive into that breaker box. never! so you mean to check if the rcd is defective? very unlikely, they are high quality components about 10 years old.
                  No. I didn't mean any hard wiring. I meant that you find an outlet serviced by the other RCD just to make sure. 10 years or 1 year, even on high quality equipment does't mean a thing. Components simply fail.
                  Helder Ferreira
                  Setubal, Portugal

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