SPRUHJ1I January 2013 – October 2021 TMS320F2802-Q1 , TMS320F28026-Q1 , TMS320F28026F , TMS320F28027-Q1 , TMS320F28027F , TMS320F28027F-Q1 , TMS320F28052-Q1 , TMS320F28052F , TMS320F28052F-Q1 , TMS320F28052M , TMS320F28052M-Q1 , TMS320F28054-Q1 , TMS320F28054F , TMS320F28054F-Q1 , TMS320F28054M , TMS320F28054M-Q1 , TMS320F2806-Q1 , TMS320F28062-Q1 , TMS320F28062F , TMS320F28062F-Q1 , TMS320F28068F , TMS320F28068M , TMS320F28069-Q1 , TMS320F28069F , TMS320F28069F-Q1 , TMS320F28069M , TMS320F28069M-Q1
Figure 15-49 represents one of the phase currents when doing a fast acceleration with no alignment. As can be seen, the current goes up to the maximum limit for less than one cycle, then it speeds up to the commanded speed reference of 200 RPM.
The flux also has a transient which happens while the estimated angle is not aligned with the actual motor angle (Figure 15-50), and then after the transient, it stabilizes to a fairly constant value.
The angle can be seen to be forced for the first cycle (Figure 15-51), and then the frequency is rapidly changed since it is already in closed loop using the estimated angle instead of the forced angle.
Zooming in to the angle (Figure 15-52) it can be seen that the forced angle lasts less than once electrical cycle to ramp up to the commanded speed of 200 RPM.
Due to the initial misalignment, it can be seen that the speed goes negative for a short period of time (Figure 15-53), and once the estimated angle is aligned with the motor angle, the speed accelerates very rapidly up to the commanded speed of 200 RPM. In fact, there is an overshoot due to the excess of current accumulated on the integral portion of the speed controller while the angle was forced.
We can see the effect of the flux angle error in the torque signal (Figure 15-54), as well as the excess in current due to the forced angle. After this transient in the flux, the torque signal is accurate and can be seen constant once the speed has stabilized.
The current Iq has an overshoot of about 0.5 A due to the step command on the speed, as shown in Figure 15-55. That overshoot can be seen as a small impulse at the beginning, and then it goes down to the limit of 6 A that we configured in user.h as the motor maximum current. The current goes down to the rated current value of 4 A to produced full torque after the motor has sped up to the commanded speed and the estimated flux has stabilized.
As a conclusion of this example we can say that the fastest acceleration we can achieve will depend on the initial difference between the initial estimated angle and the real value of the motor. This is because the forced angle feature will be enabled while those angles are aligned, taking a maximum of one electrical cycle. The electrical cycle of the forced angle provided in user.h has a default frequency of 1 Hz, so worst case it takes 1 second to speed up from standstill. However, depending on the type of load present in the motor shaft, this frequency of the forced angle can be changed to a higher frequency, providing a fastest acceleration from standstill.