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UCC28070: 10kW 230V single phase AC variable power controller with minimal harmonic distortion

Glen Johnston
Prodigy 10 points
Part Number: UCC28070

Tool/software:

I am looking to design a 10kW power controller for use with kilns fitted with silicon carbide heating elements. 

SiC has the uncomfortable characteristic of changing its resistance with temperature, with the elements going from 2.7 Ohm to 3.6 Ohm over temperatures of 600C to 1300C, with corresponding applied voltages of 164V to 190V, respectively.

A simple triac phase control power regulator creates massive harmonics, of course, and is unusable in a typical industrial/commercial setting.

I had been wondering if some sort of power control could be used with a UCC28070 PFC, in order to manage the harmonics, but I'm not finding documentation that would show how this could be used to create variable power control as well.

I'd be very appreciative of any advice or pointers as to what might be the most likely solution to this problem.

Regards...

  • 0
    TI__Genius 12795 points

    Can you please share the current schematic (or block diagram) of your design?

    It is not clear to me how you'd use UCC28070.

    Thanks,

  • 0 in reply to Ning Tan
    Prodigy 10 points

    The overall concept is fairly simple.  The following block diagram illustrates what I am hoping to:

    Essentially control 1-10kW of power to a resistive load of 2.7-3.6 Ohm from a 230V single phase source, with a PFC element between the power controller and the source in order to minimise harmonic distortion going back to the supply.

    Is this PFC function something the UCC28070 would be used for, or would you suggest another solution?

    Thanks for your thoughts.

  • 0 in reply to Glen Johnston
    TI__Genius 12795 points

    Glen,

    Yes, PFC would help reduce the harmonics going back to the supply. 

    I don't know how fast your power control will change. Please keep in mind that PFC bandwidth is not fast, typically less than 100Hz. You may need a big cap bank to provide the transient power. 

    You also need to design your power stage properly to support 10kW. 

    Overall, UCC28070 can support the highest power among all the analog PFC controllers we have.

  • 0 in reply to Ning Tan
    Prodigy 10 points

    Thanks for that advice, Ning.

    I'm wondering if a UCC28070 PFC design can be altered to incorporate power control as well as its PFC function?

    It strikes me that there is PWM functionality in the UCC28070 circuit operation, and I wonder if this can be a vector for power control as well?

    Further to your comments, the rate of power change is very slow, in the order of adjustments required very 30-60 minutes.  So this should not be a problem.

    When you say that the power stage needs to be designed properly in order to support 10kW, I am wondering what this proper design will include?

    I have been looking at TI application notes and example circuits, and note a discussion some time ago (https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/646262/ucc28070-ucc28070-design-for-10kw) for a 10kW PFC design, which notes that a 10kW reference design is not available, but there is one for a 5 kW design, but when I click on the link, it doesn't seem to end up at that design.

    I've also read about an Excel spreadsheet design assist tool for the UCC28070, but I can't seem to find a link that takes me to that tool.

    Could you please advise how to access current reference designs and the spreadsheet tool?

    Many thanks...

  • 0 in reply to Glen Johnston
    TI__Genius 12795 points

    You can download the calculator here:

    https://www.ti.com/tool/download/SLUC114

    We don't have a 10kW ref design available. You will need to scale it from the 5kW one. By proper design, I mean size the FET and transformer for your power requirement. 

    I don't know how your power control algorithm works so I cannot comment how to incorporate this by UCC28070.