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 15-19 shows the current waveform under these conditions. Notice how the current changes phase indicating a change in direction.
The flux estimation can be seen to have a transient when it changes direction, although it stabilizes after a few seconds. A constantly growing flux can be noticed from the plot shown in Figure 15-20. This can indicate a slight mismatch between the motor model represented in software compared to the real system. The error in flux might be due to inaccuracies of the modeled motor compared to the actual motor, possibly due to overheating or current and voltage sensing tolerances. In cases where the flux is constantly growing, this might indicate that the stator resistance is converging into a new value due to the motor load causing the motor to warm up. It is recommended to try the Rs Online feature of InstaSPIN in such a case. For an example on how to run Rs Online feature, see Section 16.
In Figure 15-21, we can see the flux angle changing phases when it is going through zero speed.
If we zoom-in when the motor is changing direction (Figure 15-22), we can see more clearly how this transition is done. We can actually see that it changes direction twice. This is because at near zero, the algorithm tries to find the direction in which the angle is rotating.
The estimated speed of the motor also shows how the speed when it crosses zero can have some error in sign (Figure 15-23). This is when it is within ±10 RPM, which translates to ±0.66 Hz.
The torque signal coming from FAST can be seen continuously growing from -1.9 Nm to +1.9 Nm (Figure 15-24), with a small overshoot on the positive side. That overshoot might have been the accumulation of current in the hysteresis dynamometer while going through zero speed, which is an expected behavior of these types of dynamometers.
The quadrature current, Iq, is displayed in Figure 15-25. It can be seen how this follows a very similar waveform compared to the estimated torque waveform. Not too much noticeable in this plot, but we can see that the current is flatter than the torque. This is due to a flux estimation converging to a new value after some time driving full load.