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CCS/LAUNCHXL-F28069M: question about instaSPIN application

ming chen3
Intellectual 775 points
Part Number: LAUNCHXL-F28069M
Other Parts Discussed in Thread: BOOSTXL-DRV8305EVM, TIDA-00774

Tool/software: Code Composer Studio

I uses the Launchpad-28069M and the BoostXL-DRV8305EVM to evaluate the InstaSPIN-FOC.

and now  I wants to use this solution to drive my  BLDC.but I have some questions about instaSPIN application.

Please give me a hand ,thanks.

1.BoostXL-DRV8305EVM parameters :

Supports 4.4- to 45-V voltage supply and up to 15-A RMS (20-A peak) drive current.

15A RMS and 20A peak motor winding current,  According to the sampling resistance of 0.007, the amp gain is 10 , so 1.65 / (0.007 * 10) = 23.57 A

 it is basically matches the 20A .

but, How much the bus current can be avaliable under 24V dc bus ?

the dc Bus current and winding RMS current, the winding  peak current have no  math relationship?

Is this related to Trapezoidal wave control and sine wave control?

2. The above problem is mainly due to my application of InstaSPIN . my motor parameters as shown below:

and I just know the max DC bus current ，max Power(W) and the rated voltage of my motor.

I do not know the RMS and Peak wind current .

So,I do not know how to slect the value of shunt resistance.

2.This  is a motor drive test parameter at TIdesign. Analyze the following parameters, the dc bus current is larger than the RMS winding current. Is this  true for all motors?


Now I just want to know how to design my current sampling circuit when I only know the motor power, voltage and bus current. and select the sampling resistance value?

Thanks.

  • 0
    TI__Guru** 115590 points
    1. The maximum current depends on MOSFET and h/w board, not related to input voltage. There is no formula between dc bus current and phase current, you can calculated the phase RMS current using the input power. You can select the shunt resistor based maximum power of motor, minimum input voltage. You need to select the power and resistance of shunt resistor according to both phase peak current and rms current.
    2. As talked above, to reserve some buffer, the peak current is about 3 times of maximum dc current to select the resistance of shunt resistance, the rms current is 1.5 times of maximum dc current to select the power of shunt resistor.
  • 0 in reply to Yanming Luo
    Intellectual 775 points

    thanks,yanming.

    1.you mean that  the EVM  maximum dc bus current depends on MOSFET  heat sink ,and it is not related to input voltage?

    You need to select the power and resistance of shunt resistor according to both phase peak current and rms current.

    the phase peak current  = 1.414* phase rms current ?

    I just need to  use 3 times of maximum dc current to select the resistance of shunt resistance?

    2.the test data is from  TIDA-00774.

    Plesse explain why select the resistance(0.5mΩ) of shunt resistance?

    I am confused that  the dc current and the RMS current  is not match the 1.5 times in the test data ?

    because of the  trapzoidal control or FOC control?

    I think it is different .

    please give me a hand .

    Thanks 

     

  • 0 in reply to ming chen3
    TI__Guru** 115590 points
    There is no directly relation between dc input current and phase rms current of motor, the dc current depends the dc inout voltage and motor power. You can caculate the dc input current or phase rms current based on the input power or motor power.