monitoring system of transformer fail

Discussion in 'The Projects Forum' started by afiqaris, Mar 22, 2013.

  1. afiqaris

    Thread Starter New Member

    Mar 17, 2013
    18
    0
    analog board requires 0-5V for input to scada system.

    as i tested,each output of my circuit gives values of 3.2VDC(voltage sensing) at 240+-VAC,

    Current sensor gives output of 2.3VDC at nominal load to the transformer,

    and at LM35 varies from 0.3-0.67VDC as body of transformer heats up with extra load.(mounted on core body of transformer)

    hence, as i link my output to the analog board WTADC-M,upon switching on my circuit,the ic of the analog board explodes.

    twice explode, 1st by inserting all 3 analog inputs to port 1,2,3 with my command ground to the COM port,

    2nd test,only my command ground linked to the COM input port of the analog board.

    "how can it explode when i only link my command ground to the COM input port."

    the analog board was fed 25V power supply from an external component.a RTU power supply.

    what am i doing wrong? cud it be my grounding connections wrong??

    i cant afford a 3rd explosion.

    i hope this is clear to understand.

    pls help..
     
  2. crutschow

    Expert

    Mar 14, 2008
    13,003
    3,232
    You appear to have the 220V connected to your circuit directly to your circuit ground through the bridge rectifiers B2. That is a big no-no. You are putting high voltage on the ground so it's no surprise that something blows. You need an isolation transformer for the 220V.
     
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  3. afiqaris

    Thread Starter New Member

    Mar 17, 2013
    18
    0
    Ic,
    So i need to isolation transformer,

    Where should it be connectted?

    What ratings of transformer should i purchase?

    And,do i need to change my circuit design?
    Is there anyway to apply a plug n play to my circuit design?

    Any hints or tips to do so?

    Really urgent.

    I appreciate the feedback.so much.thx a million for the help.
     
    Last edited: Mar 22, 2013
  4. crutschow

    Expert

    Mar 14, 2008
    13,003
    3,232
    You connect the isolation transformer output to the 220V inputs for the bridge rectifier. The transformer just has to be capable of providing whatever current you draw from the 220V. What is the 220V used for?
     
  5. afiqaris

    Thread Starter New Member

    Mar 17, 2013
    18
    0
    220V used for to supply to a stepdown 230-12v ac transformer. At X2-1 and and X2-2

    To simulate a distribution power station.

    So,as i apply isolation transformer, at X1-1 and X1-2??

    Izit a matter of plug and play?

    May circuit be tested on the analog board once isolation applied?

    Tq so much again.
     
  6. crutschow

    Expert

    Mar 14, 2008
    13,003
    3,232
    Yes, you apply the isolation transformer output to X1.

    You should be able to buy a 220V to 220V isolation transformer off the shelf.

    Still don't understand why you are monitoring the 220V. Can't you just monitor the output of the 230V-12V transformer instead?
     
  7. absf

    Senior Member

    Dec 29, 2010
    1,492
    372
    I think what crutschow was asking is what is the purpose of pin 5 of connector SL1. Are you sampling or powering something?

    Allen
     
    Last edited: Mar 22, 2013
  8. afiqaris

    Thread Starter New Member

    Mar 17, 2013
    18
    0
    Pin 5 is intended for input Vac monitoring.
    The voltage drop output would be obtain to know whats the input voltage to the primary side of step down transformer.

    Substation parameter monitoring.
    Allen,Crutschow

    Isit possible to do so?

    Do i need to edit my circuit since i would apply this isolation transformer?

    My three parameters are,

    Temperature of body transformer,input voltage Vac to a step down transformer and load monitoring through current transducer.
     
    Last edited: Mar 22, 2013
  9. crutschow

    Expert

    Mar 14, 2008
    13,003
    3,232
    Yes you need to use an isolation transformer and add it to your circuit. It could be a step-down transformer such 220V to 12V if you like. You would just need to calibrate the input voltage versus the output voltage with a good digital meter since that has a fairly wide tolerance for a standard transformer.
     
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  10. afiqaris

    Thread Starter New Member

    Mar 17, 2013
    18
    0
    troubleshoot 1

    if i connect directly 240Vac to Transformer without going through the first circuit(voltage AC monitoring), would the outcome be the same??(analog board explode)

    desperate measures to not include one of the parameter monitoring which is the voltage VDC output.

    so ill be ending up with just 2 parameter sampling,temperature and load current.

    my concept of project is to prove overload to a transformer would lead to thermal heat on the body of the transformer.

    my transformer 240-12V step down with 1amp. so when i increase overload,LM35 does increase with time variation.

    so my question is,would the analog board be able to obtain my 2 parameters reading VDC without it to explode again.??

    please,tqvm.

    attached is my circuit display.
     
  11. crutschow

    Expert

    Mar 14, 2008
    13,003
    3,232
    The problem is the 220VAC connected to ground through the diode bridge. Remove that and you should have no problems.
     
  12. afiqaris

    Thread Starter New Member

    Mar 17, 2013
    18
    0
    once again crutschow,

    i dont want to be stupid forever.

    so,what you are suggesting is to remove the ground connection of my bridge from the VAC input supply?

    u mean to say leave it open?

    or remove to whole VAC supply?

    based on my attachments, schematics and actual display of circuit
    is it possible to just simply isolate my 1st circuit(supply voltage monitoring AC in)??

    and obtain VDC of my other 2 parameters, temp and current sensor?
    without having to destroy another analog board.

    forgive for my lack of knowledge

    pls help.tqvm
     
    Last edited: Mar 23, 2013
  13. afiqaris

    Thread Starter New Member

    Mar 17, 2013
    18
    0
    Gents,gurus.

    Can two AC 230/12V transformer share common ground?
    Base on my circuit design.

    My dc analog signal output varies as of now.
    Could that be the reason.
     
  14. afiqaris

    Thread Starter New Member

    Mar 17, 2013
    18
    0
    Hello sir

    Now ive used a step down 12vac into my bridge as u suggested,

    But my analog output signals varies.

    So now,TX 1(new addition) is stepdown,rectified and filtered to get analog signal out for VAC in.
    TX2 to power up LM35 and current transducer through voltage regulator 5Vcc and would give the vdc out for each sensing.

    However,in my HMI SCADA,the analog signals received arent stable. For all three.only temp LM35 varies at a small margin.

    Could it be due to TWO AC transformers sharing the same common ground.

    If so,can u suggest me a fix pls.

    I appreciate all ur inputs.
    Tqvm sir.
    Pls.
     
  15. crutschow

    Expert

    Mar 14, 2008
    13,003
    3,232
    Two transformers sharing the same output ground should not be a problem. What is the frequency and amount of the variation?
     
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  16. afiqaris

    Thread Starter New Member

    Mar 17, 2013
    18
    0
    Both transformer sharing same grounding through all four circuits.
    Voltage regulator
    Temperature
    Current transducer
    And newly improved voltage divider circuit.

    50hz

    And variation on GUI haywire.

    And sum how,checking AC VOUT, at the new TX1 drops significantly.

    What can be the cause,of all these instability?
     
  17. crutschow

    Expert

    Mar 14, 2008
    13,003
    3,232
    Show your compete circuit diagram with the new transformers.
     
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  18. afiqaris

    Thread Starter New Member

    Mar 17, 2013
    18
    0
    attached are
    1.initial schematic
    2.new schematic
    3.actual overview of developed new circuit

    tq.
     
  19. crutschow

    Expert

    Mar 14, 2008
    13,003
    3,232
    I don't see the transformers and their connections on the schematic.
     
  20. afiqaris

    Thread Starter New Member

    Mar 17, 2013
    18
    0
    x1-1,x1-2 are inputs of the new transformer 230/12V

    x4-1,x4-2 are inputs of another tranformers 230/12V to the VR and the bulb load.

    tq sir.
     
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