IGBTs and the Standard Induction motor

This topic contains 8 replies, has 3 voices, and was last updated by John C John C 9 months, 1 week ago.

  • Author
    Posts
  • #8411

    Pablo Tejada
    Participant

    So like I read that you can damage dee motor with these IGBT devises
    What dos do to them


  • #8412
    John C
    John C
    Galco Representative

    Hello Pablo, thanks for asking Galco today.
    Well hopefully the application was setup correctly and nothing will happen.
    But if the drive manufacturer recommendations for maximum motor lead length was neglected then these reflected waves can develop and damage the motors insulation and even cause premature failure. Generally speaking, if you have more than 75 feet of motor lead length out there, you better test for reflected waves at the motor junction box connections. Keep in mind you will not see them at the drive terminals, you have to go to the motor end of the cable to see them. If they are found present, (usually using an O-scope) then an output filter can easily be installed to remedy the problem, ok?


  • #8413

    Pablo Tejada
    Participant

    I herd it will cus bearing prolems you didt mention this, is tru


  • #8414
    John C
    John C
    Galco Representative

    Yes that is another problem you can have and is actually more common. The Bearings can become pitted due to unwanted bearing currents caused by the “Stray Capacitance” that can cause “Common Mode Currents”. Usually the motor has to have insulated bearings to prevent this from happening. Inverter Duty rated motors have everything to tolerate or reject PWM generated issues. ok?


  • #8415

    Pablo Tejada
    Participant

    Ok yes thank you John


  • #8416

    Renita Johansen
    Participant

    Hi I wanted to know what other things are possible to prevent these “Common Mode Currents”?


  • #8417
    John C
    John C
    Galco Representative

    Hi Renita, be happy to help you with this 1.
    For new installations it is probably best to spec out an Inverter Duty motor.
    If not in the budget or retrofitting an existing application you can use an output filter and/or Shielded motor cable. Both of these items help reduce reflective waves on the motor leads. Keep in mind the shielded motor cable should be grounded at both ends. Most VFD manufacturers have specifications listed in their manuals for this type of cable.


  • #8418

    Renita Johansen
    Participant

    And this will help diminish the bearing currents?


  • #8419
    John C
    John C
    Galco Representative

    Yes it will help, however if your using an older motor that has had bearing failure, you might make sure the repair shop is aware that you need insulated bearings for an Inverter duty application.


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