Overview
Small high-speed BLDC motors have a very low inductance, which is different from conventional BLDC motors. When PWM control is applied to the phases of a small high-speed BLDC motor, the current follows the rectangular PWM voltage shape. This change of current magnetizes and demagnetizes the motor iron at a frequency equal to the PWM frequency, which can cause the motor to become hot enough to be damaged. To prevent this, special techniques are required to control this type of motor. The method used in this reference design consists of a DC/DC inverter that generates the desired voltage for the motor. The motor then uses a conventional 3-phase inverter for commutation.
Features
- Voltage control of a BLDC motor using Hall sensors
- Targeted at the MC56F8013 Controller Board
- Running on "3-Phase Power Stage with DC/DC Inverter Lite"
- Control technique incorporating:
- BLDC motor closed-loop voltage control using a DC/DC inverter
- BLDC motor closed-loop speed control
- Both directions of rotation (however, because an impeller fan is used in the application, the FreeMASTER page is locked to one direction only)
- Both motor mode and generator mode
- Starting from any motor position without rotor alignment
- Minimum speed - 300 RPM
- Maximum speed - 38000 RPM
- FreeMASTER software control interface (motor start/stop, speed setup)
- FreeMASTER software monitor
- FreeMASTER software graphical control page (required speed, actual motor speed, start/stop status, DC bus voltage level, motor current, system status)
- FreeMASTER software speed scope (observes actual and desired speeds)
- FreeMASTER software Hall sensors scope (observes actual state of the Hall sensors)
- DC bus over- and under-voltage, over-current, and Hall sensor cable error fault protection
