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
Compressors often cannot have the load torque completely eliminated. This causes the motor to require a large amount of Iq reference to begin spinning. For these applications it is important to increase the PosOut parameter. This parameter is located in the configuration structure of the SpinTAC Velocity Identify global structure. The PosOut value represents the amount of Iq reference, in PU, that will be applied as part of the inertia identification process. Increasing this value will apply more current to the motor during the process. It might also be important to decrease the RampTime_sec parameter. This will increase the rate at which the Iq reference is applied to the system.
Figure 8-10 is the speed feedback during the inertia identification process for a compressor. You should notice that the speed does not accelerate up to the goal speed very quickly. It takes a long time for it to build up to the goal speed. This indicates that the motor needs additional torque in order to reach the goal speed. The configuration parameter that needs to be adjusted is PosOut. This parameter should be increased in order to supply more torque to the motor during the inertia identification process. The inertia identification process will only use as much torque as is required to reach the goal speed. It is better to have the PosOut parameter be larger than what is required.
Many compressors cannot run in the negative direction. The inertia identification process applies negative Iq reference to the system in order to decelerate the motor. Even though negative Iq reference is being applied, the motor still does not end up rotating in the negative direction due to the inertia identification process ending before the motor would spin in the negative direction.