The control principles of permanent magnet synchronous motor (PMSM) drives differ fundamentally from those of standard asynchronous motor inverters. Asynchronous motors use V/F or vector control, whereas PMSMs require FOC algorithms based on rotor position feedback. Accurate parameter tuning directly determines system performance, efficiency, and reliability, making it the core task of on-site commissioning.
Flux-weakening parameters are among the most critical settings for permanent magnet drives. When the motor must operate above rated speed, the drive injects negative d-axis current to weaken the air-gap magnetic field, enabling constant-power speed extension. The three key parameters—flux-weakening start point, flux-weakening depth, and d-axis current limit—must be tuned in coordination. Improper settings can cause excessive torque drop in the high-speed region or trigger overvoltage protection. It is recommended to gradually approach the optimal values by referencing the manufacturer-provided flux-weakening curves.
Tuning the torque limit parameters defines the system's safety boundaries. A permanent magnet motor's maximum torque is constrained by inverter current capacity and demagnetization risk. Continuous torque limits should be set based on the motor's nameplate ratings and actual cooling conditions, while peak torque limits must account for short-term overload requirements and the safe operating area of the magnets. During site commissioning, verify the reasonableness of torque limits through incremental load testing to prevent irreversible magnet demagnetization caused by excessive settings.
Tuning of the speed and current loop PI parameters follows an inside-out approach. First, tune the current loop to achieve a fast response and strong disturbance rejection. Then, based on this, tune the speed loop. For loads with high inertia, avoid setting the speed loop proportional gain too high, as this may cause low-frequency oscillations. Use the drive's built-in inertia identification feature to obtain an accurate load inertia ratio, which serves as the basis for calculating the PI parameters.
After completing on-site setting, perform comprehensive performance verification. This includes tests for smooth no-load start-up, steady-state speed accuracy at rated load, dynamic response to sudden load addition/removal, stability at maximum speed, and temperature rise during extended full-load operation. All test results must be recorded and archived as baseline data for future maintenance and fault diagnosis. The system shall only be officially commissioned for production once all parameters meet process requirements.