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
Similar to IQ Full-Scale Frequency, the IQ full-scale voltage value is used to normalize all the voltage terms inside of the library to a per unit value. For that reason, this define must be greater than any voltage provided to the motor windings, including voltages present inside the motor. These voltages inside the motor can be greater than the input voltage itself in cases where the motor is operated in field weakening, which is operating the motor beyond its rated speed.
Voltages inside the motor can be greater than the input voltage. Set IQ Full-Scale Frequency greater than any voltage inside the motor.
To illustrate, consider a PMSM motor with a rated speed of 4000 RPM. If the motor is driven with a 24V power supply, and no field weakening is used, all the voltages outside and inside the motor will be equal or less than 24V. However, if field weakening is used to double the speed of the motor to a maximum of 8000 RPM, then inside the motor, the back EMF voltage might be up to twice the input voltage of 24V, reaching up to 48V. In this scenario it is recommended to set the IQ full-scale voltage define to 48V as shown in the following code example:
//! \brief Defines the full-scale voltage for the IQ variable, V
#define USER_IQ_FULL_SCALE_VOLTAGE_V (48.0)
In the following flux calculation of , if any of these two values is equal to or greater than 2.0, a numerical overflow condition will occur, since this value is represented in a numeric format that has a maximum integer range of 2 (IQ30 actually has a maximum value very close to 2, which is (2 - 2-30), see the IQmath library for more details on this format).
In the previous example, both inductances are the same (Ls_d = Ls_q), hence the voltage must be greater than:
It is recommended to have 20-30% headroom on top of this minimum value. In the previous example, the motor can be operated up to 48 V, and since this voltage is greater than (with headroom) we can just simply set 48 V for our full-scale voltage:
//! \brief Defines the full-scale voltage for the IQ variable, V
#define USER_IQ_FULL_SCALE_VOLTAGE_V (48.0)
User must select parameters so that this overflow is prevented. If the inductance is unknown, a rough estimation must be used in the above calculation to know if there will be an overflow condition.
In addition to a minimum value set in USER_IQ_FULL_SCALE_VOLTAGE_V, there is a maximum value to be set here also. The maximum value relates to the minimum flux that can be identified by InstaSPIN. The minimum flux that can be identified is calculated as follows:
For example, if a motor has a flux of 0.001 V/Hz (this value is not unusual when working with hobby motors with extremely low flux values), and running the estimator at 20 kHz, then the maximum USER_IQ_FULL_SCALE_VOLTAGE_V that can be used to identify this motor is:
30% of headroom is recommended to allow a stable identification. So in the previous example, a USER_IQ_FULL_SCALE_VOLTAGE_V of 20.0V is recommended.