4.4 Control of Permanent Magnet Synchronous Machine
Permanent magnet synchronous motors (PMSM) have received increased attention in industry due to their mature material and design technology. Their high torque to inertia ratio, power density, and high efficiency make them an attractive alternative to industry's workhorse IM for many applications (Table 4.1).
Table 4.1 Advantages and disadvantages of PMSM comparing with induction motor.
- Higher torque for the same dimension. For the same power, the dimension is lower by almost 25%;
- Lower weight for the same power, around 25%;
- Lower rotor losses, which results in higher efficiency of up to 3%;
- Decreased motor noise by 3dB, which causes that the rotor to run smoother. This helps in reducing the harmonics that result from an irregularity of the air gap;
- Higher inductance inside the magnetic path, around 1.2[T].
- In the case of inverter faults, it is not possible to reduce the magnetic field by reducing the torque surge, which forces a use of switch between the motor and the inverter;
- It is possible to connect only one motor to the inverter; therefore group motor work is not possible;
- The use of permanent magnet forces using enclosed motor housing complicates the cooling process;
- Importance of using high switching frequency of the power transistors, which increases the switching losses and also the inverter structure, should be changed, e.g. trapezoidal inverter;
- An increase of ...