SPRUHJ1 User guide

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

14.4.2.1 From Standstill to 4 Hz with Full Load

Figure 15-34 shows the current waveform under these conditions. Notice how the current grows from 0 A all the way to 6 A, which is set as the maximum output of the speed controller, or maximum Iq current controller reference (see max current in Section 6). It can also be seen that within one cycle of forced angle, the motor current goes back to 4 A, which is the rated current to produce full torque. Keep in mind that in this case the maximum current of the motor is 6 A, while the rated current to produce rated torque is 4 A.

Figure 14-34 Standstill to 4 Hz with Full Load Plot

Figure 14-35 Speed Controller Cycle

Figure 15-36 is the flux plot, where we can see how it has a transient, and then it stabilizes.

Figure 14-36 Flux Plot

As far as the angle goes, it can be seen that at the beginning, a forced angle is done for less than one cycle (Figure 15-37).

Figure 14-37 Angle Plot

In fact if we zoom-in we are able to tell how many cycles, or actually what percentage of one cycle, the angle was forced. In this example only half of one electrical cycle was used for forced angle.

Typically, less than 1 electrical cycle required to lock on angle.

This can be calculated from Figure 15-38, where a slope of 1 electrical cycle per second is generated, since the angle increased from 0 to 0.5 in 0.5 seconds.

Figure 14-38 Zoom-in on Angle Plot

If other frequencies of forced angle are required, user can change the frequency by modifying the following value in user.h file:

//! \brief Defines the forced angle frequency, Hz
#define USER_FORCE_ANGLE_FREQ_Hz (1.0)

This frequency might need to be changed due to startup time requirements, by providing a faster forced angle. However, having a faster forced angle requires a faster speed in open loop, which might not be slow enough to rotate the load in open loop.

The estimated speed tells a lot in this example (Figure 15-39). First, it can be seen that there was no initial alignment of the motor compared to the forced angle, that's why the speed goes negative for a period of time. Also, it can be seen that by the time the motor is aligned, there is more current than needed to speed up the motor to the commanded speed. That is why the speed overshoots so much. Typically, a maximum of one electrical cycle is needed for the estimator to catch up with the rotor's flux angle. So a typical maximum of one electrical cycle would be driven in the reverse direction.

Figure 14-39 Speed Plot

The estimated torque overshoots due to the transient present in the estimated flux, as shown in Figure 15-40. Although as soon as the estimated angle aligns with the motor angle, this transient is reduced and the estimated torque stabilizes and matches what the dynamometer controller displays.

Figure 14-40 Torque Plot

The last plot we will show in this example is the current in Iq (Figure 15-41). Recall we have a limitation of the Iq reference of 6 A, which is the maximum safe current for this motor. It can be seen how this maximum is reached when starting up, then when there is angle alignment the current goes back to the rated current of 4 A.

Figure 14-41 Iq Current Plot