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Original question:

CCS/TIDA-00364: Vbus from 48VDC to 86VDC

CCS/TIDA-00364: 10KW to 15KW Motor design

Rajesh Gopisetty
Prodigy 60 points
Part Number: TIDA-00364


Tool/software: Code Composer Studio

Hello Pawan,

I would like to adapt your design for 10KW to 15KW motor with 48V.

Is it a good Idea to paralleling more MOSFET Boards?

I am planing to give a common Input signal for each Boad, as Shown in Below image.
Will this concept Works ? I will take care about the PWM signals with Buffers

Please suggest the best option to achieve this requirement.

Thanks in advance
Regards

Rajesh

  • 0
    TI__Expert 3825 points
    Hello Rajesh,

    Driving a 15kW motor with a 48V battery means a motor phase current of more than 300Arms. Thermal design will be critical here.

    It is important to drive all the FET's in a phase with a single gate driver so that all of them switch at the same time and the motor phase current is distributed equally between all the FET's. The distance of all the FETs from the gate driver should be as symmetrical and equidistant as possible.

    Are you trying to give a single PWM input signal to all the 3 gate drivers on a single PCB? The tolerance of the discretes used in each gate driver circuit might put some asymmetry in the switching of the phases. It is better to use single gate driver circuit and redesign the board for symmetry.

    Regards,
    Pawan
  • 0 in reply to Pawan Nayak
    Prodigy 60 points

    Dear Pawan,

    Thank you very much for your quick response.

    I would like to do this project in 2phases.

    Stage 1. (Demo)

    • I wanted to use only TI reference design board without modification, as shown on previous picture.
    • Only common PWM signals will be given to each board,using buffers / Isolators
    • Means each board will work as hole single phase.

     

    Phase 2 (Product design)

    • Planning to use new PCB with one or two drivers per phase.
    • targeted to maintain, same parameters for each gate signal like track length, track capacitance, impedance etc
    • Also planning to implement diagnostics & current measurement.

     

    Cooling

    • Regarding the cooling, we are planning to use forced air cooling
    • We are planning to fix the power PCB on 1.5 Inch Thick aluminium plate

     

    Metal Clad PCB

    • I have checked with local PCB suppliers in Bangalore, most of the suppliers are using only 1oz copper, where as 2oz is required for our board.
    • Could you please help me on this issue, Is it a good idea to go with 1Oz?
    • If possible could you please suggest any of suppliers in India who can support 2Oz copper  

    Could you please suggest us what are the additional parameters we need consider for designing the new PCB

    Thanks & Regards

    Rajesh.G

    +91-7204000011 

  • 0 in reply to Rajesh Gopisetty
    TI__Expert 3825 points
    Hello Rajesh,

    Using 1oz copper will increase your (I^2)R losses which is significant for the currents you will be designing for. You can use any online calculator tool to find the resistance of the PCB tracks and get an estimate of the losses. The best and accurate way to check for thermals in such a design is to model the PCB in an electronic thermal analysis software.

    As this is a special kind of PCB, vendors will support 2oz copper on IMS PCB only if they have it in stock or there will be some lead time. The other option will be to get it fabricated outside.

    Regards,
    Pawan
  • 0 in reply to Pawan Nayak
    Prodigy 60 points

    Hello Pawan

    Thank you very much for your quick support,
    We have noted all your points & will try implement for our next design.

    I would like to know one more point, can we use the same circuit for BLDC 3KW?

    Thanks & Regards

    Rajesh

  • 0 in reply to Rajesh Gopisetty
    TI__Expert 3825 points
    Yes it is possible to use it for a 3 kW design. You might only require 2 or 3 FETs in parallel.

    Regards,
    Pawan