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

Single Phase Controlled Rectifier Problem

Discussion in 'Homework Help' started by Luis Eduardo, Nov 16, 2017.

  1. Luis Eduardo

    Luis Eduardo New Member

    Joined:
    Nov 16, 2017
    Messages:
    1
    Likes:
    0
    Question
    Consider a heating system with strongly inductive characteristic and with an electronic control of temperature performed by varying the firing angle of a single-phase controlled bridge.
    a) Determine the value of resistance to to ensure a maximum power of 7500W if this system is powered with 220V (effective).
    b) Determine the fire angle to a power of 3000W.

    My attempt of solution:
    a)
    If the system is strongly inductive so the current is constant, then we should use average voltage. So, maximum power is when the average voltage is maximum and this is possible when fire angle = 0 degree. Then:
    [​IMG]
    And the resistance is:
    [​IMG]
    b) Using the same idea:
    [​IMG]

    The problem is:

    Many friends (and maybe the professor) solved this problem on a exam using 220 V as voltage to find the resistance when maximum power, but I don't think this is totally correct because the problem tells us that the system is strongly inductive, so Irms = Iaverage = I constant, then, to find the voltage we should use average voltage and not effective as many other did. So, What do you think ? If I'm incorrect, why ? I'm a bit upset because I studied a lot for this exam and I was confident that the correct was average voltage when constant current.
     
  2. cowboybob

    cowboybob Well-Known Member Most Helpful Member

    Joined:
    Oct 22, 2011
    Messages:
    3,052
    Likes:
    479
    Location:
    James Island, SC
    Welcome to ETO, Luis Eduardo!

    I googled "heating system with strongly inductive characteristic with single-phase controlled bridge" and found this paper using this circuit:
    upload_2017-11-16_17-43-49.png
    The transformer output voltage is irrelevant, in this case, for the solution to your question.

    May, or may not be of any use to you.
     

Share This Page