Smallest motor that C2000 can support

Randhir,

InstaSPIN-FOC doesn't have a hard lower boundary regarding motor size. The bounds that are set for usage are more related to the electrical frequency and back-EMF for the motor you're looking to control.

USER_IQ_FULL_SCALE_FREQ_Hz must be < 4 * USER_VOLTAGE_FILTER_POLE_Hz is a design spec we require, with USER_IQ_FULL_SCALE_FREQ_Hz = (target rpm * number of poles)/120. Take for example:

• 6 pole motor
• 20k RPM target speed

USER_IQ_FULL_SCALE_FREQ_Hz = (20,000 * 4)/120 = 1000 Hz leading to USER_VOLTAGE_FILTER_POLE_Hz > 250 Hz, with USER_VOLTAGE_FILTER_POLE_Hz being set by hardware. There is no voltage pole upper bound except that higher poles are more sensitive to drift, etc. Most of our kits are designed in the 300-400Hz range, but can be changed if the user makes hardware modifications according to their system needs.

An issue we do see often is this: smaller motors that are used to run at high speeds often have low inductance, which leads to a small back-EMF signal which in turn creates difficulty reconstructing the phase currents. The situation I describe is dependent on your motor and HW design as much as InstaSPIN software.

That said, I think it's reasonable to test the motor using the MotorWare software suite and an inexpensive HW setup like the F28069 Launchpad (LAUNCHXL-F28069M) and DRV8301 Booster pack (BOOSTXL-DRV8301). This will be the quickest way to determine whether sensorless FOC will be a good control algorithm for the end system.

Sean