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How to calculate DC BUS capacitor at HVMotorctrl+PFC-TL

Joseph Lee90700
Prodigy 140 points

Dear All,

Could you guide how to calculatre DC Bus Capacitors(C6, C7, C8, C19, C20) at circuit schematic of "High Voltage Motor Control and PFC Developers Kit(TMDSHVMTRFCKIT)?

At this schematic Diagram, C6==C7==C8==C19==C20 == 330uH.

The key feature of this EVM is as follows.

• High voltage PFC and single axis motor control board
• 1.5KW, 350V, 20A three phase motor driver stage
• 750W 110-220 Vac PFC stage
• Can control most common motor types
• ACI, PMAC, and BLDC
• Motors available directly from TI
• Isolated CAN and UART interfaces
 
I hope you reply as soon as possible.

sincerely,

Joseph

  • 0
    TI__Guru** 119500 points

    per the BOM and schematic they are each 220 uF

  • 0 in reply to ChrisClearman
    Prodigy 140 points

    Could you provide how this value(220uF) was decided ?

    I just estimated this value using 1/2*C*V*V = P(the power of motor drive)*T.

    However I want to know the correct method about this.

     

    One more question.

    Could we recommend High Voltage EVM kit to customer if we consider the followed specification ?

    　 Value
    Voltage Range 250V ~ 310V
    Current Range ~17A
    RPM in no load 18,000 ~ 19,000 RPM
    Max Load(Torque) 12Nm/12Arms
    Noraml Operation 15,500RPM
    0.3Nm
    3.8A

    (The Motor is BLDC motor.)

  • 0 in reply to Joseph Lee90700
    TI__Guru** 119500 points

    Joseph,

    Current Range ~17A

    This requirement makes the HVKit not the right fit.  You will find very few "kits" in the chip industry that will support this sort of voltage and current range.  It will be very expensive and somewhat dangerous.

    It's possible that this kit could be used for their normal and very lightly loaded operation but using a BLDC technique there will probably be a very large in-rush current spike that could/will blow the fuse (ships with 4A, I've used 10A).  If you try it I'd use a 10A fuse, make sure the IPM is attached well to the heat sink, and provide as much thermal cooling as possible.

    Often times what is done is development on a lower voltage/current platform to work out the sampling, control techniques, and fault capability before moving to a custom HW implementation to support the current needs.

  • 0 in reply to Joseph Lee90700
    TI__Intellectual 930 points

    Joseph

    The way you are calculating the cap size is correct, you can use that formula.

    HVDMC kit cap size purposely kept high to cover as many apps as possible, it is not optimized for a particular application.

    Regards

    Bill