AC Neutral and DC ground "internally" connected

Discussion in 'Power Electronics' started by Saiful Bahri, Aug 7, 2016.

  1. Saiful Bahri

    Thread Starter New Member

    Feb 16, 2016
    4
    0
    Hi All , I am looking for the solution for my project .I just bought the evaluation power monitoring board from ST its name was EVALSTPM34 and I having the problem on the DC power for the microprocessor on AC line .The 1st picture is my basic connection and the 2nd picture is the schematic for EVALSTPM34 board.

    Problem = turn on the AC and DC Isolated power supply ,the isolated DC supply explode while the EVALSTPM34 did not working the bulb remain OFF
    Schematic[Metrology Circuit]= I wondering why the neutral and DC ground is connected (refer connector J8 , i measured the resistance neutral-ground is <0.7ohm)

    Step taken=
    1.testing putting different value of resistor(1M,2.2M,1.5K,600ohm) between Neutral-Ground ,DC part seems working while the AC remain OFF
    2.did contact with ST support but they did not answer my question.

    Hope You guys can help me to find the best solution for my project thank you
    EvalSTPM34 basic connection.jpg evalstpm34 schematic.jpg
     
  2. tcmtech

    Well-Known Member

    Nov 4, 2013
    2,039
    1,667
    Incomplete post.
     
    Last edited: Aug 7, 2016
  3. tcmtech

    Well-Known Member

    Nov 4, 2013
    2,039
    1,667
  4. Saiful Bahri

    Thread Starter New Member

    Feb 16, 2016
    4
    0
    yeah i agree with you tcmtech , but how about the board connection neutral is directly connected with DC ground ? even in schematic they said 1.5kohm between Neutral-Ground but I could n`t find any existing of this thing.
     
  5. tcmtech

    Well-Known Member

    Nov 4, 2013
    2,039
    1,667
    Unfortunately, it has to have the two common lines connected so that the two circuits can work together inside the IC.

    If the power supplies are blowing up something is wired wrong or they do not have true isolation from their AC power input side to the three DC power output side and the AC line power is feeding through them into a shorted circuit being their DC common is sharing a connection with the AC common.

    Does the circuit work on battery power?
     
  6. Saiful Bahri

    Thread Starter New Member

    Feb 16, 2016
    4
    0
    UM1748 board connection.JPG
    basically the board connection that I make almost the same like User Manual UM1748 [ http://www.st.com/resource/en/user_manual/dm00113794.pdf ]

    wait ...I think my bulb is currently in series connection between L1 and AC source ...but I don't think it can solve the problem.
    Ok I going to test with the battery supply ..but what if the battery supply also explode ?
     
  7. tcmtech

    Well-Known Member

    Nov 4, 2013
    2,039
    1,667
    The battery supply is a totally isolated non AC line connected power source. If it explodes you have a whole lot of other problems to deal with.
     
  8. Saiful Bahri

    Thread Starter New Member

    Feb 16, 2016
    4
    0
    I just found the solution I just re-check and identified my wire connection is not really correct, so I follow the connection from the previous posted diagram and re-connect all of the wire and walllllaah is working

    thanks a lot tcmtech for your guide :)
     
Loading...