Synchronous machine excited by permanent magnets

The invention relates to a permanent magnet synchronous machine according to the preamble of claim 1.

Such a machine is known from the DE-U-88 16 122nd In this machine, the permanent magnets are arranged on the periphery of the rotor core. For secure mounting of the magnets, particularly at high speeds, an existing material of non-magnetic cylinder is pushed over the permanent magnets. This requires a considerable manufacturing expense, since these cylinders rotatably must be connected to the rotor. About the circumference of the rotor evenly distributed arrangement of the permanent magnets also does not lead to optimal utilization of the electric machine.

The invention has the object of developing a permanent magnet synchronous machine of the generic type such that it can be produced in spite of the design for high speeds with considerably lower production costs and has improved electrical properties.

The object set is achieved by the features specified in the characterizing part of claim 1. By introducing the permanent magnets in the receiving openings of the circumferentially closed rotor core, the permanent magnets against centrifugal stress at high speeds are protected. Through the appropriate spatial arrangement of the permanent magnets per pole of the machine a Flußsperre for the stator current excited armature transverse field and also from one pole to the other pole is reached on the pole gap across a bypass for a field-weakening stator flux.

The fact that the outer contour of the rotor core is designed so that the existing between the rotor and the stator air gap in the pole center is the smallest and increases to the pole gaps out an approximately sinusoidal course of the magnetic field is achieved at least. This results in uniform, symmetric Polkräften so that the electromagnetic force and vibrational excitations are minimized. In order for the machine as a whole is very stable vibration. Another essential aspect of to the pole gaps towards increasing air gap is impeding the armature transverse field and the reduction in the shunt inductance.

The appropriate design of the outer contour of the rotor core is achieved in a simple manner by a flattened profile between the pole centers. The air gap between the rotor and the stator is thus in the pole center is the smallest, so that here there is a high maximum air gap induction, which in turn results in a high torque / current ratio. Furthermore, can the outer contour of the rotor core in conjunction with the stator bore use as a flow channel for a possible natural ventilation.

Especially on machines with a number of pole pairs equal to or greater than 2, the described spatial arrangement of the permanent magnets in the rotor core enables the formation of the shaft of the rotor of a hollow shaft. A version with hollow shaft is especially favorable for the use of the machine in the field of machine tools, since through the hollow shaft through an access to the machine tool is.

On the basis of an electrical machine shown in the drawing in section, the invention will be described in more detail below.

1 with the stator of an electric synchronous machine is referred to, in the stator slots 2, a stator winding, not shown in the drawing is incorporated. In the stator bore 3 is excited by permanent magnets 4 rotor 5 is arranged, which is rotatably mounted in corresponding, mounted on the stator end plates by means of a hollow shaft. 6 On the hollow shaft 6 the rotor core 7 of the rotor 5 is applied.

In the rotor core 7, two slot-shaped accommodating openings 8 are provided for each pole are inserted in the permanent magnets 4th The spatial profile of the two receiving openings 8 of a pole is designed so that the receiving openings 8 come close to its one end to the pole center 9 towards close as possible to the outer circumference of the rotor core. 7 The other, located on the pole gap 10 towards extending the end of the receiving openings 8, on the other hand with respect to the entire course of receiving openings 8 at the greatest distance to the outer periphery of the rotor core. 7 In the pole gaps 10 of the machine, a scattering slit 11 is also provided in each case. In addition, the rotor core 7 on the outer periphery of a pole center 9 to the other pole center 9 a flattened curve 12. This results in the pole center 9 the smallest air gap width. From the pole center 9 to the pole gaps 10 through the air gap width increases and reaches in the pole gap 10 its greatest value.

Due to the described course of the receiving openings 8 in the region of one pole results in the pole center 9 with respect to the magnetic cross-section of the rotor laminations a constriction. The constriction acts as Flußsperre for excited by stator current armature transverse field. Thus the influence of the armature transverse field is weakened on the machine behavior. This leads to that, even with a wide power control range of the machine is still a largely linear relationship between current and torque remains. At the lying between two poles pole gap 10 toward the magnetic cross-section of the rotor laminations increases. This is between two pole centers 9 a bypass for an induced by the stator field weakening forth flow. This requires on the one hand allows a relatively low power requirements for a necessary to control the speed field weakening, on the other hand, a further speed range.

The different magnetic cross-sections in the pole centers 9 and the pole gaps 10 result in the reduction of the shunt inductance, which results in a corresponding increase of the breakdown torque of the engine. The machine therefore has a large overload capacity.