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Combining two ac sources rectifier

Discussion in 'General Electronics Discussion' started by Vindhyachal Takniki, Apr 29, 2015.

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  1. Vindhyachal Takniki

    Vindhyachal Takniki

    9
    0
    Apr 29, 2015
    1. I have two ac sources(from mains & generator) & have to run a circuit from it for which I need dc supply
    I had connected a bridge rectifier to each source. After that each output is shorted.
    2. Circuit is attached. It Actual circuit also has regulator & othe stuff, which i didn't show, I had only connected Rload & C.
    3. There may be three cases: Only main available, only generator available, or both are available.
    4. Is the circuit attached is safe.
    5. I think problem may arrive when both ac sources are available.
    Also it could be one may be at different angle then other. Like if first ac source have crest, other couls have trough or at some phase from each other.
     

    Attached Files:

    • ckt.pdf
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  2. Harald Kapp

    Harald Kapp Moderator Moderator

    10,323
    2,240
    Nov 17, 2011
    Welcome to electronicspoint.

    What kind of circuit requires 300V (DC) for operation and does not come with its own power supply?

    As shown in the PDF, the circuit is basically workable. However, if the primary sources (AC, 220 V) are grounded (which is typically the case for safety reasons), you will create a short circuit because the ground connection will bypass some of the diodes. This circuit will work only if at least one of the sources is floating with respect to the other.

    Since the peak voltage after the rectifier will be 220V * sqrt(2) = 312 V (375V allowing for 20% overvoltage), this circuit is very dangerous! Very careful construction is required as well as observation of applicable local standards and laws with respect to safety. I recommend that you check your circuit and the realization with a local expert.
     
  3. flippineck

    flippineck

    269
    9
    Sep 8, 2013
    I think you are trying to do what I was trying to do with grid power and inverter-based solar power as the sources.

    Somehow tie them in together in a seamless way such that the load would not 'notice' if one source ceased to provide supply whilst the other 'took up the slack' whilst, taking care of any random phase difference between the sources.

    If I am correct, no I never arrived at a practical solution, but would welcome any further discussion on this topic!
     
  4. ramussons

    ramussons

    365
    70
    Jun 10, 2014
    Use isolation transformers it should work fine. Careful with the high voltage though.
     
  5. flippineck

    flippineck

    269
    9
    Sep 8, 2013
    How would one reconcile any random phase and frequency difference between the supplies?
     
  6. mofy

    mofy

    46
    14
    Dec 19, 2014
    Just use an AC relay. Place the coil across the mains and ensure that the contacts connect the mains through when mains is available, else no mains then the alternator is connected.
     
  7. ramussons

    ramussons

    365
    70
    Jun 10, 2014
    Frequency and Phase is no issue. The setup behaves like 2 standalone power supplies

    Why the isolation? Is it an issue?
     
  8. Vindhyachal Takniki

    Vindhyachal Takniki

    9
    0
    Apr 29, 2015
    I don't need 300Vdc.
    There is SMPS in the circuit which I didn't shown. It makes 12V & then +5V dc from regulator.

    I have tested the circuit by connecting two 220V ac source from plug. basically its a short i.e phase1 of ckt is connected to phase 2 & similarly neutral.
    However in this circuit both phase & amplitude is same.

    But in real circuit, there will be different phase generator & main voltage. I don't know how this circuit will behave then.

    Also sometimes I have seen people, put connection across phase & earth to run the device.
    Will it create error?

    I have to simulate the circuit in multisim. Same circuit works fine. However there is no earth connection.
     
  9. ramussons

    ramussons

    365
    70
    Jun 10, 2014
    You better start a new thread.
    "Feeding a SMPS from 2 different power sources"
     
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