Protective Earth, Chassis Ground, Analog Ground

Discussion in 'General Electronics Chat' started by usernumber10, Jul 18, 2013.

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  1. usernumber10

    Thread Starter New Member

    Jul 18, 2013
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    Hi,

    Please see the grounding scheme below. I would like to prevent electric shock. In the picture everything is referenced to the chassis. The AC inlet has the earth ground connected to chassis. However, the Analog ground (after AC-DC conversion) has it's ground connected to chassis too.

    The chassis is then not protective earth but a functional ground, correct?

    Is the transformer still isolating?

    What is the proper way to ground this type of system? Should only the earth ground be connected to the chassis?

    Thanks for any helpful advice!
     
  2. #12

    Expert

    Nov 30, 2010
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    That should work. Just be sure to use the "star" method for your ground wires so you don't have load current running through the chassis to get back to its power supply.

    I just got done considering an old, vacuum tube guitar amplifier. In those, all the signal input jacks and power output jacks were electrically connected to the chassis. A bad design would have ground loops that were impossible to fix.
     
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
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    The transformer still isolates, make sure the secondary of the transformer is galvanically isolated from earth ground, and then you can Earth ground the common of the DC supply.
    This is often the way it is done in control systems.
    http://www.automation.siemens.com/doconweb/pdf/840C_1101_E/emv_r.pdf?p=1
    Is there a reason you would not want to earth ground the DC common?
    Max.
     
  4. #12

    Expert

    Nov 30, 2010
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    Naw. He's just uncertain. A little bit short of being completely sure this is the right way.
     
  5. atferrari

    AAC Fanatic!

    Jan 6, 2004
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    Hola #12,

    Coukld you rephrase that for me?
     
  6. #12

    Expert

    Nov 30, 2010
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    Are you playing at being a troll right now?:confused:
    incierto is not that far from "uncertain"
    I did rephrase my first answer...by using 2 sentences.
    I think you are trying to play a joke on me.:rolleyes:
     
  7. vk6zgo

    Active Member

    Jul 21, 2012
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    If you like,you can have both sides of the DC supply "floating" w.r.t ground/chassis.

    Many power supplies are ,in fact built like this,so you can have either'the negative or positive side of the DC supply returned to ground/chassis,or neither,as dictated by the external equipment being supplied with power.
     
  8. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    While it does NOT provide shielding against RF type noises. using a magnetic material as a shield around a power wire pair WILL provide a low impedance path for the magnetic flux created around the power wires and act a noise reducing agent for signal carrying(very low amperage) wires in close proximity
     
  9. telefunkinu476

    New Member

    Sep 10, 2014
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    just a shot in dark .but neutral and ground go to the same bar in your panel you can bond them together on one side for appliances for pops an surges an leave the other bar un bonded for your 15 amp breakers so they go directly to ground.this seemed to reduce a lot of pops in my audio stuff .no fires ether
     
  10. MaxHeadRoom

    Expert

    Jul 18, 2013
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    That is a no-no, the neutral should never be connected to any place but at the service entry, as I have posted before, there is an exception and that is where you are providing 120vac control voltage from an isolation transformer, in this case a local neutral can be created by connecting one side of the transformer secondary to earth ground at the transformer terminal, essentially re-referencing the neutral to earth ground, which otherwise would be isolated.
    Max.
     
  11. #12

    Expert

    Nov 30, 2010
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    It's a necropost, Max. Reported to mods.
    #12
     
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