“Optimization of electric motors for cost-effective production in high volumes”
Synchronous machines with permanent excitation (PMSM) have permanent magnets in the rotor. Depending on the type of magnet material, demagnetisation of the magnets can sometimes occur at too high temperatures. The electric motor then no longer has its full torque. If neodymium-iron-boron is used as the magnet material, it contributes significantly to the cost of the motor. If the magnets are arranged favourably in the rotor, a reluctance torque can be utilised and thus the magnet material used can be reduced. We help you to reduce the amount of magnet material without reducing the motor performance.
Due to their higher power density and better efficiency, AC motors are primarily used for electric vehicles. The battery of electric vehicles supplies a DC voltage, so an inverter is still needed for AC motors.
As reluctance motors do not require permanent magnets, they are inexpensive to manufacture. However, a higher phase current is usually required, making the inverter more expensive than a motor with magnets. A differentiation is made between switched reluctance motors (SR motor) and synchronous reluctance motors, which have a smaller torque ripple and a higher efficiency. The air gap has a great influence on the efficiency of reluctance motors and should not be greater than 0.8 mm.
The process of designing electric motors starts with defining the requirements. It is very important to compare the advantages and disadvantages of different types of electric motors.
Externally excited synchronous motors (SESM) do not have permanent magnets in the rotor, but copper windings which generate the rotor field. The magnetic field of the rotor can therefore be adjusted by the level of the current. A disadvantage is the additional electronics required for the rotor current as well as the brush system to connect the rotor with the electronics. We help you to increase the maximum speed of externally excited machines in order to improve their power density.
In an asynchronous motor, the rotor runs slower than the rotating field of the stator. In other words, the rotor runs asynchrone to the magnetic field of the stator. The speed difference induces a voltage in the short circuit cage, which leads to a magnetic field of the rotor. This is why the asynchronous motor is often called an induction motor. With the right control strategy, induction motors today can achieve similarly high efficiencies as motors with permanent magnets. They are very robust against high temperatures and cost-effective in production.