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3 phase DC relay

Discussion in 'Power Electronics' started by magtec, Mar 17, 2021.

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  1. magtec

    magtec

    11
    0
    Jul 29, 2020
    Driving three phase motor without the relay produces 569rpm, power supply 30V 6.3A 190W and using the relay produces 392rpm, power supply 30V ~5.5A ~172W, where are my losses across the relay?, what am I missing?
     

    Attached Files:

  2. bertus

    bertus Moderator

    1,611
    638
    Nov 8, 2019
    Hello,

    There is a voltage drop accross the mosfets, as they are likely not full in conduction.
    You might notice that the mosfets get warm when activated.

    Bertus
     
  3. WHONOES

    WHONOES

    1,113
    310
    May 20, 2017
    If your incoming 30V is positive (you gave no indication) then your FET's are upside down. Their sources should be connected to 30V. They way you have got the Opto Isolated trigger circuit oriented is also wrong. As shown on your diagram, you are turning the devices off rather than on. Your 6K8 resistors should be connected between gate and source with the "Opto" output connected between Gate and Drain. Is there any particular reason for having it this way round as the normal way to execute this sort of circuit would use N Channel FET's with source connected to ground making the turning on and off much simpler and probably doing away with the "Opto" bits. Do your drives need to be floating?
     
  4. magtec

    magtec

    11
    0
    Jul 29, 2020
     
  5. magtec

    magtec

    11
    0
    Jul 29, 2020
    I suspected as much, any suggestion as to full conduction solution? ground relocation? Thanks
     
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