Burning BTS 240A

Discussion in 'General Electronics Chat' started by FroceMaster, Sep 13, 2015.

  1. FroceMaster

    Thread Starter Member

    Jan 28, 2012
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    Have this setup at my Brothers farm
    it's for a feeding machine, running on some beams in the ceeling.
    Works normaly ok, but here lately it keeps killing this BTS240A
    marked on pdf.
    can takes 2-3 weeks before it burns,
    any hints on what i can do to prevent it ?
    the supply is 2*12v battery, 24-28v total.
    The engine do takes up around 5-7 A while driving,
     
  2. Dr.killjoy

    Well-Known Member

    Apr 28, 2013
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    There is another problem here cause it to die cause it rated or 58amps and your not even coming close ..
     
  3. BR-549

    Well-Known Member

    Sep 22, 2013
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    How is the air flow around unit?
     
  4. Dr.killjoy

    Well-Known Member

    Apr 28, 2013
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    I was thinking about that too but my other guess was a part fail or the motor is stalling and pulling to much current ... When was the last time the feeder was cleaned and maintence..
     
  5. FroceMaster

    Thread Starter Member

    Jan 28, 2012
    400
    4
    BTS240A is mountet to a PCB and have a very big collingplate behind,
    Now we have moved it , and mounted wires from PCB to BTS240A cause it is not easy to get it fit propper to the cooling
    we will try Again and see how long it runs,

    As i can see it, it starts the motor at JP1 softly.
    when then BTS240 is burned it starts very hard, and will not stop Again,

    And yes, the motor gets cleaned regarly.
     
  6. Dr.killjoy

    Well-Known Member

    Apr 28, 2013
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    I am not just talking about the motor itself but the whole working..
     
  7. FroceMaster

    Thread Starter Member

    Jan 28, 2012
    400
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    All is been cleaned regarly.
    Motor transmission batteries ect.
     
  8. BR-549

    Well-Known Member

    Sep 22, 2013
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    I don’t know what your total setup is, but, I would look for an environmental change or a mechanical wear fault.

    By environmental....I would look for a stretched conveyor belt with morning cool temps, or condensation in product in blower causing increased current on start up. Some kind of temp or moisture change....it’s intermittent because it goes for two weeks.

    Mechanical could be a bearing or gearbox drawing current until it seats in its wear lines.

    You might want to isolate sections of the system for a few weeks.........to find area of fault.
     
  9. FroceMaster

    Thread Starter Member

    Jan 28, 2012
    400
    4
    Now it has been running for a while. But now it burns 2 times on one day
    The machine today start ok and run for 1 minut and stops as planed for filling up. That is controlled by timer on the PLC but when it was stop for atound half the time the machine just starts up with a burned BTS240A without change the direction as it should ( think its not the PLC that start it )

    Now we will change it again. Change the fuse from 30A to 15A and change 2 relays to try to do something

    Help would be great.
    Compagny that sold it is not anymore
     
  10. ian field

    Distinguished Member

    Oct 27, 2012
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    What are you replacing the MOSFET with?

    If the logic family of those gates can and does run on more than 5V, you should look elsewhere for the cause.

    If the gates are on 5V, you definitely need a logic level MOSFET - if the gates run from at least 12V, any regular MOSFET with adequate ratings should work.
     
  11. FroceMaster

    Thread Starter Member

    Jan 28, 2012
    400
    4
    Replace the mosfet with a new one. Same value
     
  12. FroceMaster

    Thread Starter Member

    Jan 28, 2012
    400
    4
    And it is controlled with a 74c14 so i think 5v will be the voltage to controll
     
  13. ian field

    Distinguished Member

    Oct 27, 2012
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    I lost track of what voltage which CMOS familiar use - the best thing to do is measure it.

    If its less than 10V - you need a logic level MOSFET, anything else will not turn fully on and dissipate energy that should be going to the load.

    The SMD version of TO220 MOSFETs on old PC motherboards have VGSthr in the right ball-park and typical Id ratings are about 70 - 80A - but the Vds rating is usually only 30V.
     
  14. crutschow

    Expert

    Mar 14, 2008
    13,003
    3,232
    That could be the problem.
    The BTS240A requires a Vgs of 10V to be fully on.
    I suggest you find a logic-level type N-MOSFET (fully turns on at Vgs of 5V as shown for Rds(on) in the data sheet) with voltage, current, and Rds(on) ratings equal or better than the BTS240A.

    Edit: Oops, Ian beat me to it. ;)
     
  15. FroceMaster

    Thread Starter Member

    Jan 28, 2012
    400
    4
    The circuit has been designed for many years ago by a compagny. They lust have know what component to use. So i think it should be the right one to use
     
  16. FroceMaster

    Thread Starter Member

    Jan 28, 2012
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    4
    The mosfet is only used when starting the machine and again when stopping for smoother start/stop. Used max 1 sec at a time
     
  17. alfacliff

    Well-Known Member

    Dec 13, 2013
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    have you checked the motor brushes? and commutator? arcing at the brushes can spike the mosfet and destroy it.
     
  18. FroceMaster

    Thread Starter Member

    Jan 28, 2012
    400
    4
    Have measured the input to mosfet
    But when the motor start i can not get anything but when motor is running i get 5.2v but as i can understand the circuit the mosfet is only used for soft start/stop
    The 5.2v is between gate and ground.

    Can i sagely change the mosfet and to what would you suggest
     
  19. crutschow

    Expert

    Mar 14, 2008
    13,003
    3,232
    I think you may have an unduly optimistic view of the expertise of the engineers who built the circuit. :rolleyes:
    It's a quite common mistake to misunderstand how to properly drive a MOSFET as a switch.

    Certainly if the device keeps failing then something was not designed properly.
    We are just suggesting what that may be.
     
  20. ian field

    Distinguished Member

    Oct 27, 2012
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    By all accounts - the MOSFET has been replaced on a number of previous occasions.

    Its entirely possible that the entirely random first failure involved a LL MOSFET, and subsequent replacements were not LL.
     
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