1. Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
    Dismiss Notice

AC output wave distorted

Discussion in 'General Electronics Chat' started by Pravin Gosavi, Aug 18, 2017.

  1. Pravin Gosavi

    Pravin Gosavi Member

    Joined:
    Nov 30, 2014
    Messages:
    130
    Likes:
    0
    Location:
    Nashik, Maharashtra
    Hello. I am working on a 3 phase inverter. I have generated 6 SPWM. But output waves don't always seem like sinewave. I have connected three transformers ( delta ) to three IGBT modules. Output is taken with neutral common ( star connection ) and filtered using 10 MFD ( big! ) caps.
     
  2. Pravin Gosavi

    Pravin Gosavi Member

    Joined:
    Nov 30, 2014
    Messages:
    130
    Likes:
    0
    Location:
    Nashik, Maharashtra
    With capacitors attached and without load-
     

    Attached Files:

  3. Pravin Gosavi

    Pravin Gosavi Member

    Joined:
    Nov 30, 2014
    Messages:
    130
    Likes:
    0
    Location:
    Nashik, Maharashtra
    With capacitors attached and with 200W bulb load-
     

    Attached Files:

  4. dave

    Dave New Member

    Joined:
    Jan 12, 1997
    Messages:
    -
    Likes:
    0


     
  5. Pravin Gosavi

    Pravin Gosavi Member

    Joined:
    Nov 30, 2014
    Messages:
    130
    Likes:
    0
    Location:
    Nashik, Maharashtra

    With load and two of the capacitors removed-
     

    Attached Files:

  6. Diver300

    Diver300 Well-Known Member

    Joined:
    Oct 19, 2007
    Messages:
    3,062
    Likes:
    101
    Location:
    England
    Can you post a circuit?

    If you are creating a sinewave with PWM, you need to have some sort of filter.
     
  7. Pravin Gosavi

    Pravin Gosavi Member

    Joined:
    Nov 30, 2014
    Messages:
    130
    Likes:
    0
    Location:
    Nashik, Maharashtra
    Capacitors are the only filter.
     
  8. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

    Joined:
    Apr 17, 2007
    Messages:
    7,252
    Likes:
    961
    Location:
    Loveland, CO USA
    "Something is wrong but I will not post my circuit, please tell me what is wrong"

    My guess is that R5 is the wrong value. lol
    If you want help you need to help us understand what you are doing.
     
    • Funny Funny x 1
    • Agree Agree x 1
  9. Pravin Gosavi

    Pravin Gosavi Member

    Joined:
    Nov 30, 2014
    Messages:
    130
    Likes:
    0
    Location:
    Nashik, Maharashtra
    I don't have simulator but this rough diagram could help. Boxes near the IGBTs represent isolated gate drivers. The numbers near them represent their switching sequence. SPWM signals are taken from a microcontroller. And the transformer windings are connected to IGBTs ( delta connection). The output is taken as a star connection with common neutral. And the caps connected between each phase and neutral. Tell me if I'm missing something else!
     
  10. Pravin Gosavi

    Pravin Gosavi Member

    Joined:
    Nov 30, 2014
    Messages:
    130
    Likes:
    0
    Location:
    Nashik, Maharashtra
    Diagram-
     

    Attached Files:

  11. Pravin Gosavi

    Pravin Gosavi Member

    Joined:
    Nov 30, 2014
    Messages:
    130
    Likes:
    0
    Location:
    Nashik, Maharashtra
  12. alec_t

    alec_t Well-Known Member Most Helpful Member

    Joined:
    Jul 10, 2011
    Messages:
    9,246
    Likes:
    1,218
    Location:
    Cardiff, Wales
    ..... and we're still waiting for further details. Block diagrams aren't enough for dignosing your 'problem'. A full schematic (even hand sketched) clearly showing component values would be helpful.
     
  13. Pravin Gosavi

    Pravin Gosavi Member

    Joined:
    Nov 30, 2014
    Messages:
    130
    Likes:
    0
    Location:
    Nashik, Maharashtra
    There's nearly nothing between the IGBTs and the PIC microcontroller except the ISOLATED GATE DRIVERS- which are completely fine. If they would have problems why I would get sinewaves as shown in the pics above?
     
  14. alec_t

    alec_t Well-Known Member Most Helpful Member

    Joined:
    Jul 10, 2011
    Messages:
    9,246
    Likes:
    1,218
    Location:
    Cardiff, Wales
    Perhaps the windings of your transformers (properties unknown) are saturating at parts of the sine cycle when you draw significant load current.
     
  15. Pravin Gosavi

    Pravin Gosavi Member

    Joined:
    Nov 30, 2014
    Messages:
    130
    Likes:
    0
    Location:
    Nashik, Maharashtra
    The transformers and IGBTs are taken from a 6 KVA old inverter. I also want to load it with 6 KVA. For now the load given is 200 W X 3 bulbs.
     

Share This Page