Magnetic gearboxes based on permanent magnets are becoming very popular and promising, since they have a number of advantages over mechanical ones. Magnetic gearboxes are capable of transmitting torque without mechanical contact, do not create additional noise, do not require lubrication, have high efficiency and reliability, are more durable, therefore they are very promising for use instead of mechanical gearboxes.
Magnetic gearboxes are currently used for a variety of applications, including electric vehicles. For an electric vehicle, in accordance with the driving cycle, the maximum wheel speed is 1000 rpm, the use of an electric motor without a gearbox at this speed is not advisable, since the dimensions of the electric motor will be very significant. Therefore, it is advisable to use electric motors with magnetic gearboxes for vehicles, including wheel motors, which are combined into one device with a magnetic gearbox and an electric motor based on rare earth permanent magnets.
For vehicles, including wheel motors, the shaft of the high-speed traction motor is connected to the shaft of the high-speed rotor of the magnetic gearbox, and the shaft of the low-speed rotor is connected to the shaft of the vehicle wheel. In this case, the traction motor and the magnetic gear must be designed in such a way that the electromagnetic moment of the traction motor is matched with the torque transmitted to the wheel of the vehicle, taking into account the reduction ratio of the magnetic gear and the driving cycle of the vehicle.
Another promising direction for the use of magnetic gearboxes is wind generators. Wind generators with a capacity of up to 5 kW, both with horizontal and vertical axis of rotation, have a low rotation frequency. With an average wind speed V = 5 ÷ 10 m / s, it is approximately n = 100 ÷ 300 rpm. A low-speed electric generator for a wind turbine with such a rotational speed with a direct connection of the shaft of the wind rotor and the electric generator has a large number of poles and rather large dimensions. Therefore, the use of an increasing magnetic gear (multiplexer) makes it possible to increase the rotational speed of the electric generator several times and, thereby, to reduce the mass of its active part.
The shaft of the wind rotor is connected to the shaft of the low-speed rotor of the magnetic gear, and the shaft of the high-speed rotor is connected to the shaft of the generator. The torque on the high-speed rotor of the magnetic reducer is less than on the low-speed one in proportion to the reduction ratio. Therefore, the generator must be designed in such a way that its torque is consistent with the torque on the high-speed rotor shaft for the entire range of the generator rotor speed.
Mathematical models have been developed that allow calculating the operating characteristics of magnetic gearboxes and the external characteristics of electric generators or electric motors and determining the optimal sizes of their magnetic systems. Comparison of the calculated characteristics with experimental ones obtained on physical samples of magnetic gearboxes, electric generators and electric motors confirms the adequacy of the developed mathematical models and the possibility of their usage for a wide range of power and rotational speed as a wind rotor, where a magnetic gearbox is used to increase the rotational speed of an electric generator, and for vehicles, where a magnetic gear is used to reduce the rotational speed of a high-speed traction motor. The know-how has been applied to the magnetic gearbox, electric generator and electric motor, allowing to reduce eddy current losses, as well as to simplify their manufacturing technology.
It should be noted that at the same power, an electric generator with a magnetic gear has approximately 2 times less mass of magnets and 1.7 times less mass of active materials in comparison with a multi-pole electric generator, the shaft of which is directly connected to the shaft of the wind rotor. Approximately the same ratios by the mass of magnets and active materials were obtained when using a magnetic gear for vehicles.