In addition, the magnet wheel can be located at any load.

The polarity sign alone indicates whether the sensor is approaching or moving away from the magnet wheel.

The invention relates to a synchronous machine which comprises a magnet wheel and a stator winding which are necessary for an excitation device.

The pole pin, surrounded by a winding, connects to a permanent magnet whose magnetic effect extends to the pole wheel.

Electric energy is transferred to the magnet field coils of a rotor of an electric machine.

These motors are normally equipped with a pole wheel, which is sensed by a speed sensor.

The sensor apparatus 2 has a rod-shaped sensor carrier 4 and a sensor 6 which is introduced into the sensor carrier 4 and, in order to detect the wheel speed, senses the rotation of a rotor rotating together with the wheel.

The neutral zone of the permanent magnet is slightly displaced when the distance of the movement sensor to the magnet wheel is changed.

The magnet field coils are made of a super-conductive material, such that the rotor is located in a shielded manner in a low temperature range.

In order to manufacture magnet wheels, a mould (9) is used that consists of two dies (10, 11) and may be inserted into a press.

When the mould is closed, the inner contour of the dies (10, 11) corresponds exactly to the final form of the magnet wheel (1).

It is also necessary to transfer energy to a magnet wheel inductivity, preferably, energy to a super-conductive coil, by means of an excitation device.

According to the invention, therefore, screening (8) is provided, preferably disposed between the toothed magnet wheel (2) and the element (4) which is sensitive to magnetic fields.

The technical problem is to design the magnetic pole wheel so that a rotationally fixed connection with the shaft continues to be guaranteed even at high operating temperatures.

The sensor device 1 has a sensor carrier 2 with a sensor 18 integrated into the sensor carrier 2, in order to sense the rotation of a pole wheel that rotates along with the wheel for the purposes of the speed measurement.