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TMS320F28062F-Q1: Motor speed

user6346729
Prodigy 160 points
Part Number: TMS320F28062F-Q1

We use TMS320F28062F-Q1 control board to control a new delta connected permanent magnet synchronous motor. The motor parameters are ：

Stator Resistance（phase to phase）：5.6mΩ；Stator Inductance (phase to phase）20uH

Maxspeed：70000rpm；Number of Pole Pairs：1；Rated current：260A；The open circuit back EMF@70000rpm：11.625V， DC Bus Voltage：24V；

USER_ADC_FULL_SCALE_VOLTAGE_V：27.3V，

 USER_VOLTAGE_FILTER_POLE_Hz： (1167)

PWM FREQ：25kHz

The problem now is that when the motor starts with load, the actual speed of the motor is 0, but the speed estimated by FAST is 4000rpm (the given reference speed is 4000rpm),

the motor phase current frequency is 43Hz.
Why does this happen?
What is the estimation principle of motor speed?
What adjustments should I make/
  • 0
    Prodigy 160 points

    SORRY:The open circuit back EMF@30000rpm：11.625V

  • 0 in reply to user6346729
    TI__Guru** 109740 points
    user6346729 said:
    The problem now is that when the motor starts with load,

    What do you mean this? What load is adding on the motor when startup? Is the motor stalled when you try to run it?

    If the motor didn't startup and was stalled, the estimation speed will be not correct. So please take a look at chapter 14 "Managing Full Load at Startup, Low-Speed and Speed Reversal" in InstaSPIN-FOC and InstaSPIN-MOTION User's Guide.

    Having an incorrect Rs value (especially a value higher than the actual Rs) will make the start-up behave poorly. so you may try the following methods.

    1. Enable stator Rs recalibration before startup
    2. Enable forced angle
    3. Make sure that the current ADC offset is calibrated.
  • 0 in reply to Yanming Luo
    Prodigy 160 points

    The load on the motor at startup is about 1.1Nm， Run the motor at no-load to 40000 rpm without stalling。Motor identification has been run twice, once RS is 2.898m Ω. The other is 2.876m Ω，The actual measured relative phase resistance of the motor is 5.6m Ω, and 2.898m Ω includes part of the line resistance and contact resistance on the line。

    We have enable forced angle， “USER_FORCE_ANGLE_FREQ_Hz ”is 10Hz，Maybe we need to set "USER _ FORCE_ ANGLE_ FREQ_ Hz" set to 100 Hz,because the speed estimated by FAST is 4000rpm .

    And，we want to  know why the motor didn't startup and was stalled, the estimation speed will be not correct？

     We  will try the following methods.

    1. Enable stator Rs recalibration before startup
    2. Enable forced angle
    3. Make sure that the current ADC offset is calibrated
  • 0 in reply to user6346729
    TI__Guru** 109740 points

    The force angle frequency can't be set too high value, it should be far lower than the rated frequency like 1~10Hz.

    What's the rated output load of the motor?  As you know, the FAST is still a sensorless-FOC, it's difficult to generate the full torque and startup the motor at a heavy load.