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Motor start-up jitter or failure to start

user4708725
Expert 1030 points

Evaluation board:  drv8301-hc-evm revd

Lab 10a Overmodulation

Nominal voltage V                                                               24
No load speed rpm                                                              60800
No load current mA                                                             282        
Nominal speed rpm                                                             57500
Nominal torque (max. continuous torque) mNm     23.6
Nominal current (max. continuous current) A            6.45
Stall torque mNm                                                                 561
Stall current A                                                                        149
Max. efciency %                                                                      91.6
Terminal resistance W                                                         0.161
Terminal inductance mH                                                    0.0171
Torque constant mNm/A                                                   3.76
Speed constant rpm/V                                                        2540
Speed/torque gradient rpm/mNm                                 109
Mechanical time constant ms                                           2.04
Rotor inertia gcm                                                                  1.79

when 400rpm,the motor output torque is  70mNm。

I set the maximum current limit of the motor to 60mNm, which confirms that the motor can output 70mNm of torque,

but I use 50mNm of load to jam the motor shaft, the motor occasionally can not start, according to the theory,

the motor 60mNm of torque can completely overcome the 50mNm of load, but in the instant of starting,

the motor stopped without a moment of force, it should be. How to solve the occasional failure of startup in this situation?

The working speed of the motor is 400 rpm

  • 0
    TI__Guru** 116920 points

    You might have look at chapter 14 of instaSPIN user's guide. A motor is not easy to startup with the full load if the parameters of the motor are not exact, and you may enable force angle for a startup also.

    Btw, what board are you using? A customized board, or drv8301-hc-evm? You need to design a board with the appropriate scaling current and voltage based on the specification of the motor.

  • 0 in reply to Yanming Luo
    Expert 1030 points

    1.How to make sure the motor parameters are correct? The motor parameters I set can ensure the motor torque output of 70mNm。

    2.Based on drv8301-hc-evm, I drew my own hardware-like motherboard,How to design a board with the appropriate scaling current and voltage based on the  the motor?

    Nominal voltage V                                                               24
    No load speed rpm                                                              60800
    No load current mA                                                             282        
    Nominal speed rpm                                                             57500
    Nominal torque (max. continuous torque) mNm     23.6
    Nominal current (max. continuous current) A            6.45
    Stall torque mNm                                                                 561
    Stall current A                                                                        149
    Max. efciency %                                                                      91.6
    Terminal resistance W                                                         0.161
    Terminal inductance mH                                                    0.0171
    Torque constant mNm/A                                                   3.76
    Speed constant rpm/V                                                        2540
    Speed/torque gradient rpm/mNm                                 109
    Mechanical time constant ms                                           2.04
    Rotor inertia gcm                                                                  1.79

  • 0 in reply to user4708725
    TI__Guru** 116920 points

    1. Identify the motor parameters based on the motor bundled the board, not use the same parameters for all motors and boards if you want to get higher performance.

    2. Don't reserve too much margin for the maximum sampling value of the current and voltage for the h/w board, the scaling value should be based on the maximum current&voltage of the motor. Please refer to chapter 5.2 of the instaSPIN user's guide (SPRUHJ1G).