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BLDC inverter output measurement

Ajay P
Intellectual 310 points

HI all,

While I was testing BLDC motor driver controller, while measuring phase to phase voltage, from the output of the motor driver IC, which is the inverter output, we were getting phase to phase voltage amplitude as 310V. Input given is 310V DC. But while checking with multimeter, we are getting 42.41V for same phase to phase voltage. Why is that? The motor controller is working. Please help with suitable reference document and formula.

  • 0
    TI__Mastermind 18981 points

    Hi Ajay,

    Can you help share the name of the TI DRV IC you are using?

    We may also need a schematic diagram to be able to evaluate the system being discussed, and some waveforms would be very helpful as well (preferably showing individual phase-gnd voltage measurements).

    From an initial glance, we speculate that this might be an issue with the measurement itself - 

    For your first set of measurements showing 310V, what instrument were you using to measure the voltage?

    For the second set of measurements, is the multimeter instrument rated to be able to measure the voltage expected? And how well does it handle AC vs DC measurements? If you are measuring DC via multimeter, then I suspect that would be the root cause of the measurement inaccuracy.

    If the motor is commutating, then i think an oscilloscope would be better for analyzing the waveforms individually (phase-Gnd) instead of phase-phase.

    Also, if you are concerned about high voltages, then we may be able to step down the voltage using a resistor divider network or changing the attenuation on the scope probe

    Hope the above info helps

    Best regards,

    Andrew

  • 0
    TI__Mastermind 18981 points

    Hi Ajay, 

    Just following up on this topic - do you still require any assistance? 

    Best Regards,  
    Andrew 

  • 0
    TI__Mastermind 18981 points

    Hi Ajay, 

    Closing the thread for now - but feel free to open another e2e thread for follow-up questions.

    Best Regards, 
    Andrew