TMS320F28069F: Determined motor parameters differ depending on the set PWM frequency

Thanks. Actually, the motor parameters are independent from PWM frequency, should only have a little error using different PWM frequency. We need to take some time to check the problems you reported, even though we didn't meet these problems before.

EngineTestStand.pdfMotor_3GAA071312-ASE.pdf25643.user.hmotorware_selecting_user_variables_v2p0_T_Motor.xlsx

Detailed information about my problems.

Thanks for the reply! 

Let us know if you need more information.

Best, Miriam

For the issue with the speed decreasing as torque increases, can you try increasing your USER_MOTOR_MAX_CURRENT value in user.h? The value may be too low, limiting the output of the PI controller during increasing torque conditions

Sean

I bought a new HVKit (TMDSHVMTRINSPIN) and repeated the measurements. Here are the new results:

#elif (USER_MOTOR == T_Motor)                                                            // Name must match the motor #define
    #define USER_MOTOR_TYPE                                 MOTOR_Type_Induction // Motor_Typ
    #define USER_MOTOR_NUM_POLE_PAIRS       (1)                           // PAIRS, not total poles. Used to calculate user RPM from rotor Hz only
    #define USER_MOTOR_Rr                                      (3.5962502)          // Identified phase to neutral in a Y equivalent circuit (Ohms, float)
    #define USER_MOTOR_Rs                                     (4.1712555)          // Identified phase to neutral in a Y equivalent circuit (Ohms, float)
    #define USER_MOTOR_Ls_d                                 (0.017856076)      // For Induction, Identified average stator inductance  (Henry, float)
    #define USER_MOTOR_Ls_q                                 USER_MOTOR_Ls_d      // For Induction, Identified average stator inductance  (Henry, float)
    #define USER_MOTOR_RATED_FLUX                         (0.8165*230.0/50.0)  // sqrt(2/3)* Rated V (line-line) / Rated Freq (Hz)
    #define USER_MOTOR_MAGNETIZING_CURRENT  (2.1128540)   // Identified magnetizing current for induction motors, else NULL
    #define USER_MOTOR_RES_EST_CURRENT           (1.0)                // During Motor ID, maximum current used for Rs estimation, 10-20% rated current
    #define USER_MOTOR_IND_EST_CURRENT            (NULL)           // not used for induction
    #define USER_MOTOR_MAX_CURRENT                      (5.0)                // CRITICAL: Used during ID and run-time, sets a limit on the maximum current
    #define USER_MOTOR_FLUX_EST_FREQ_Hz            (5.0)                // During Motor ID, maximum commanded speed (Hz, float). Should always use 5 Hz for Induction.

• The determined motor parameters (Lab02b) differ depending on the set PWM frequency.

	TI-High-Voltage-Motor-Control-Kit with ACIM-Motor (2polig, 0.55W) InstaSPIN_F2806xM_UNIVERSAL (proj_lab02b)
PWM-Frequenz	USER_MOTOR_ Rr (Ω)	USER_MOTOR_ Rs (Ω)	USER_MOTOR_ Ls_d (H)	USER_MOTOR_ MAGNETIZING_CURRENT (A)
12kHz	3.7603125	4.0875058	0.0096661774	2.0907561
16kHz	3.4968752	4.1300058	0.012127553	2.0863764
18kHz	3.5962502	4.1712555	0.017856076	2.1128540
20kHz	3.6728124	4.1806306	0.017301019	2.1240024
24kHz	3.3259379	4.2081308	0.019840614	2.1279840

• If the PowerWarp (EPL) is deactivated, the speed is not reached (Lab05b).

• With the example project (Lab11a / 18kHz), the speed drops at a load of more than 0.3kW.

	Invertek-P2-Frequency-Converter Optidrive P2 ODP-2-22220-1KF42-SN (Vectorcontrol/16kHz)				TI-High-Voltage-Motor-Control-Kit InstaSPIN_F2806xM_UNIVERSAL (proj_lab11a/18kHz)
Braking load	Motor power	Motor current	Intermediate circuit voltage	Rotor speed	Torque	Motor current	Intermediate circuit voltage	Rotor speed
0 (0V)	0.04kW	1.4A	310V	2797rpm	0.08Nm	0.44A	305V	2801rpm
1 (10V)	0.16kW	1.4A	298V	2787rpm	0.55Nm	1.00A	286V	2798rpm
2 (12V)	0.24kW	1.4A	292V	2778rpm	0.80Nm	1.26A	275V	2799rpm
3 (14V)	0.33kW	1.5A	285V	2761rpm	1.19Nm	1.52A	269V	2570rpm
4 (16V)	0.45kW	1.7A	276V	2738rpm	Motor stops!
5 (18V)	0.58kW	2.1A	267V	2705rpm
6 (20V)	0.72kW	2.5A	258V	2650rpm

 

 

Thanks for your help and kind regards,

Roberto

For lab05b, the behavior you are seeing is as expected. Powerwarp is causing a decrease in Id, which leads to an increase in the speed as bemf is decreased. This will also decrease the torque, so it is a trade-off in a system to use this function. To reach your target speed without Powerwarp (field weakening), you will need to increase your DC bus. Perhaps you can try lab10a - in this lab, it will be better to limit your modulation index to 0.57 to limit the system to ignoring only 1 shunt (i.e. always 2-phase read with reconstruction).

We are still investigating the motor ID changes with respect to PWM frequency change on our end. Initial test show some change in Ls, but it does not follow the pattern that you report, certainly not a doubling of the value as you are seeing. On our end, we are experiencing less than 20% variation over PWM frequency (15kHz - 25kHz).

Sean

It also seems that these values: USER_MOTOR_RES_EST_CURRENT & USER_MOTOR_MAX_CURRENT are too low. You can try increasing USER_MOTOR_RES_EST_CURRENT to 1.0 and USER_MOTOR_MAX_CURRENT to 5.0. We are assuming that your motor is actually 0.55kW, not the 0.55W that has been mentioned in the above posts

Sean

As I mentioned above, the current values are as follows:

USER_MOTOR_RES_EST_CURRENT = 1.0

USER_MOTOR_MAX_CURRENT = 5.0

 

AC induction motor 3-phase 2-pole (ABB 3GAA071312-ASE)

Frequency: 50Hz

Voltage: 230VAC

Power: 0.55kW

Speed: 2790rpm

Current: 2.20A

Power Factor: 0.78

Efficiency: 78.4%

Torque: 1.88Nm

 

I tried the example 10a and set the modulation to 0.65.
With this setting, the speed is achieved in the unloaded state, but it breaks down under load.

See my measurements: