how to check igbt or mosfet ?

Discussion in 'Power Electronics' started by kittoo, Jul 27, 2016.

  1. kittoo

    Thread Starter New Member

    Jul 11, 2016
    25
    1
    how to check a igbt or mosfet devices.when they are connected to the inverter stack (or) any other driver circuit. without disturbing the circuit?
     
  2. BR-549

    Well-Known Member

    Sep 22, 2013
    1,981
    388
    Use an octopus.



    You can passively look at all the junctions.
     
  3. kittoo

    Thread Starter New Member

    Jul 11, 2016
    25
    1
    hai sir
    thanks for your reply
    The components which he is testing are not connected to any circuit.
    My question : let us take any example like 3phase full bridge converter,in that circuit you will have six igbt\mosfet's .
    without removing the igbt ,how to check the igbt is working?
     
  4. BR-549

    Well-Known Member

    Sep 22, 2013
    1,981
    388
    I am perplexed by your post.

    Is the device isolated and out of circuit?

    Is the devise mounted in a circuit?

    Does the device have power applied?

    Does the device power a motor?

    Pick one.
     
  5. ian field

    Distinguished Member

    Oct 27, 2012
    4,413
    782
    I would advise against relying on in circuit testing.

    You can test by isolating 2 of the 3 pins, usually most convenient with bolted on power devices.

    From drain to source - any leakage whatsoever is a fail, but make sure the gate capacitance is discharged. In fact a slight revision to the procedure - isolate only the drain first and check for leakage, either its leaky or the gate drive circuit is faulty.

    Isolate the gate and charge the gate capacitance with a continuity tester - the MOSFET should turn on and stay on until you discharge the gate - if it leaks away; that's another fault mode.

    Regular power MOSFETs need about 8V to turn on, the maximum rating can be as low as 15V, so a tester with 12V internal source is usually safe. Some special types like RF can be only a few volts - so don't wade into those without checking the datasheets.
     
  6. kittoo

    Thread Starter New Member

    Jul 11, 2016
    25
    1
    The device is non-isolated and fixed inside the circuit
     
  7. ian field

    Distinguished Member

    Oct 27, 2012
    4,413
    782
    In that case - switch it on and see if it goes bang.
     
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