Modern motor and control technology divides permanent magnet brushless DC motors into two categories based on different current drive modes: square wave drive motors, namely brushless DC motors (BLDC); sine wave drive motors, namely permanent magnet synchronous motors (PMSM)
The basic structure of the two motors is the same. They are both composed of a rotor made of permanent magnets, a stator with multi-phase AC windings, and the interaction of the AC currents between the permanent magnet rotor and the stator generates the torque of the motor. The stator current in the winding must be synchronized with the rotor position feedback. The rotor position feedback signal can be obtained from the rotor position sensor, or in some sensorless control methods, by detecting the back electromotive force of the motor phase winding.
Although the basic structure of the two motors is the same, the driving methods are different. PMSM adopts sine wave drive and has sine wave back electromotive force and sine wave stator current; while BLDC adopts square wave drive and has trapezoidal wave back electromotive force and rectangular wave stator current. This difference in driving methods leads to differences in their design and control details.
The stator winding distribution is different: PMSM uses short-pitch distributed windings, and sometimes fractional slots or sinusoidal windings are used to further reduce ripple torque; while BLDC uses full-pitch concentrated windings.
Permanent magnet shape and operation mode: PMSM's permanent magnet shape is parabolic, and the magnetic density generated in the air gap is as sinusoidal as possible; BLDC's permanent magnet shape is tile-shaped, and the magnetic density generated in the air gap is trapezoidal. Wave distribution. PMSM uses three phases to work at the same time, and the current of each phase differs by 120° electrical angle, requiring a position sensor; while BLDC uses two windings to conduct, each phase conducts
Modern motor and control technology divides permanent magnet brushless DC motors into two categories based on different current drive modes: square wave drive motors, namely brushless DC motors (BLDC); sine wave drive motors, namely permanent magnet synchronous motors (PMSM)
The basic structure of the two motors is the same. They are both composed of a rotor made of permanent magnets, a stator with multi-phase AC windings, and the interaction of the AC currents between the permanent magnet rotor and the stator generates the torque of the motor. The stator current in the winding must be synchronized with the rotor position feedback. The rotor position feedback signal can be obtained from the rotor position sensor, or in some sensorless control methods, by detecting the back electromotive force of the motor phase winding.
Although the basic structure of the two motors is the same, the driving methods are different. PMSM adopts sine wave drive and has sine wave back electromotive force and sine wave stator current; while BLDC adopts square wave drive and has trapezoidal wave back electromotive force and rectangular wave stator current. This difference in driving methods leads to differences in their design and control details.
The stator winding distribution is different: PMSM uses short-pitch distributed windings, and sometimes fractional slots or sinusoidal windings are used to further reduce ripple torque; while BLDC uses full-pitch concentrated windings.
Permanent magnet shape and operation mode: PMSM's permanent magnet shape is parabolic, and the magnetic density generated in the air gap is as sinusoidal as possible; BLDC's permanent magnet shape is tile-shaped, and the magnetic density generated in the air gap is trapezoidal. Wave distribution. PMSM uses three phases to work at the same time, and the current of each phase differs by 120°electrical angle, requiring a position sensor; while BLDC uses two windings to conduct, each phase conducts 120°electrical angle, and the phase changes every 60° electrical angle, and only needs to change Phase point position detection. electrical angle, and the phase changes every 60°electrical angle, and only needs to change Phase point position detection.