MOTOR-DRIVE-FET-LOSS-CALC_Rev1a

Vignesh d

Other Parts Discussed in Thread: MOTOR-DRIVE-FET-LOSS-CALC

Hello Ti,

I found this MOTOR-DRIVE-FET-LOSS-CALC tool from Ti web site which is very useful.

for a low side MOSFET switching loss only considered for the electrical frequency of the motor and neglected for switching frequency. Could some one explain this?

I'm very much expecting these kind of tool for FOC based control algorithm for MOSFET and IGBT based tool for trapezoidal and FOC as well.

Thanks for the support

over 1 year ago

0 Ryan Kehr over 1 year ago

TI__Guru 54675 points

Vignesh,

I am moving this into the BLDC forum for a response.

Regards,

Ryan

0 Aaron Barrera over 1 year ago in reply to Ryan Kehr

TI__Mastermind 26046 points

Hi Vignesh,

This seems like a typo. We are double checking.

We have FOC and trap calculators for integrated MOSFET devices here: https://e2e.ti.com/support/motor-drivers-group/motor-drivers/f/motor-drivers-forum/1078268/faq-bldc-integrated-mosfet-thermal-calculator?tisearch=e2e-sitesearch&keymatch=faq%3Atrue

Thanks,
Aaron

0 Vignesh d over 1 year ago in reply to Aaron Barrera

Prodigy 110 points

Hello Aaron

Thanks for the reply.

We are looking for a tool MOTOR-DRIVE-FET-LOSS-CALC for FOC . We have product which is running on DRV8353RS with trapezoidal control and currently planning to chnage to FOC. So we are trying to evaluate our current MOSFET since FOC increase the switching loss of the MOSFET.

Do you have exact tool like MOTOR-DRIVE-FET-LOSS-CALC but for FOC?

Thanks.

0 Aaron Barrera over 1 year ago in reply to Vignesh d

TI__Mastermind 26046 points

Hi Vignesh,

I got feedback and the equation below I have an explanation for:

Vignesh d said:
for a low side MOSFET switching loss only considered for the electrical frequency of the motor and neglected for switching frequency. Could some one explain this?

This is for unipolar switching, low side FET is soft switched.

We do not have a tool like MOTOR-DRIVE-FET-LOSS-CALC for FOC.

What losses are you trying to calculate specifically, switching/conduction/diode losses in FOC? We can help the calculation if you share the MOSFETs used.

Thanks,
Aaron

0 Vignesh d over 1 year ago in reply to Aaron Barrera

Prodigy 110 points

Hello Aaron,

Thanks for the reply.

For unipolar switching also low side MOSFET will be operated at switching frequency as well. Please refer the below image

0 Aaron Barrera over 1 year ago in reply to Vignesh d

TI__Mastermind 26046 points

Hi Vignesh,

I'll get you a reply on Monday about this.

Thanks,
Aaron

0 Aaron Barrera over 1 year ago in reply to Aaron Barrera

TI__Mastermind 26046 points

Hi Vignesh,

The unipolar diagram does not seems to be correct. The diagram shows 60 degree switching and 60 degree clamp for both positive and negative current polarity.

Our assumption of uniploar switching is in the 120 degree period of positive current, both high side and low side switches are complimentary. In the 120 degree period of negative current, the low side switch is completely on. See below.

This is referred to as "high side modulation" in the datasheet.

We will have the same total loss in low side modulation and mixed modulation. In low side modulation, the high side switch will be soft-switched. The entire switching loss will be part of the low side. In mixed modulation, the switching loss will split between the HS and LS switches. This is referred as synchronous modulation. See below.

Thanks,
Aaron

0 Vignesh d over 1 year ago in reply to Aaron Barrera

Prodigy 110 points

Thanks for giving clarity on unipolar switching.

As mentioned in the table, low side mosfet also operating at complementary PWM but switching loss only considered for motor electrical frequency not for pwm.

I assume this is because current already circulating through body diode of the mosfet so switching loss for low side mosfet not applicable.

My understanding was right?

0 Aaron Barrera over 1 year ago in reply to Vignesh d

TI__Mastermind 26046 points

Yes Vignesh, your understanding is correct.

Thanks,
Aaron

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