MXPA01007514A - Synchronisation system - Google Patents

Abstract

Synchronisation systems have existed in diverse forms for a long time. Synchronisation systems of this type generate very high short-circuit torque, both during generator operation and motor operation in the case of a short circuit, e.g. a short circuit in connecting terminals, or also within the stator winding. The peaks of said very high short-circuit torque can reach values of between six and eight times the nominal torque of the synchronisation system. The short circuit which occurs very rarely and the related appearance of a very high short-circuit torque must therefore be taken into account in the mechanical construction of the synchronisation system. The invention aims to simplify the construction of the synchronisation system and to avoid the aforementioned disadvantages. The invention also relates to a synchronisation system which comprises a rotor and a stator, whereby the stator has at least two independent alternating current (three-phase) windings which are insulated electrically and/or spatially from each other.

Description

Synchronous machine FIELD OF THE INVENTION Synchronous machines have been known for a long time in many different forms. In operation as a generator and also in operation as a motor, in the situation of a short circuit, for example a short circuit in connection terminals or also within a stator winding, those synchronous machines produce very high short-circuit torque moments. In that respect, those crests so high at the moment of short circuit can reach values of up to six to eight times the speed of the synchronous machine speed. Therefore, one must also consider the very rare situation of the short circuit and the concomitant occurrence of a torsional moment of very high short circuit, in relation to the mechanical construction of the synchronous machine. BACKGROUND OF THE INVENTION Synchronous machines of the aforementioned kind have been used for a long time in wind energy installations of the Enercon company. In these types of wind power installations, the synchronous machines are in the form of ring generators, where the rotor of the generator rotates inside the generator stator and the rotor of the generator is installed by means of a REF: 128537 flange assembly directly to the rotor of the wind power installation. In the case of a generator rotor directly installed by a flange assembly to a drive machine, very high short-circuit torques occur in a short-circuit situation and the constructions are related to very high cost levels and a very high level maintenance, in order to avoid major damage. Therefore, in a synchronous machine such as the one used for example in the Enercon type E-40 wind power installation, a mechanical safety device was developed and used in the form of a coupling with a pin security. In this case, the part known as a star or stator carrier spider (holding part) carrying the stator (stationary element of the generator) is connected by means of safety pins to the stub shaft or stub axle which is also stationary. In the event of a short circuit in the generator, the pins slide and allow the stator to also rotate around the axle journal. In this way the moment of crsi transmitted is limited to a maximum of four times the moment of the regime and the safety of the drive train is guaranteed in a short-circuit situation of a generator. DE 197 29 034 discloses a wind power installation with a synchronous generator having a generator stator with a stator winding and a generator rotor that is movable relative to the stator. In one embodiment, the stator has a stator winding of 6 stages. The 6 stages of the synchronous generator are connected to a common rectifier circuit. WO 88/07782 discloses a wind power installation with an electric generator having a rotor and a stator. The stator has a plurality of turns that can be connected together in different ways by means of a suitable interconnection element in order to produce a convenient output signal. DE 40 32 492 discloses an electric machine for power converter operation comprising a switchable polyphase stator winding, which can also be used in a wind power installation. The stator winding in that case is subdivided into similar winding subsystems respectively with type phase m that are galvanically separated and fixedly connected in a star or polygon configuration. Special switching elements are provided for interconnection during winding. The object of the invention is to simplify the synchronous machine in terms of its structure and to avoid the aforementioned disadvantages. According to the invention, that objective is obtained by means of a synchronous machine having the characteristic stipulated in claim 1. Useful trends are described in the other claims. The invention is based on the understanding that particular safety elements such as a safety pin coupling are not necessary if the maximum torque of short circuit is limited to a fraction of what is usual to date. Preferably, in the synchronous machine according to the invention, the torsional short-circuit moment is always less than twice the torsional moment. To limit the torsional short-circuit moment, the rotor has at least two independent three-phase windings that are electrically and / or spatially separated from one another. This causes the generator power to be divided into two different three-phase systems. With two independent three-phase systems, each system includes only 50% of the rated power. These systems move through an angle of 30 °. This means that both three-phase systems are electrically and / or mechanically (spatially) separated. However, in this way the reactance X_ is also approximately doubled and thus the short-circuit current is split in half. This provides the particular advantage that, in the event of a short circuit in a system, only half of the short-circuit power can occur. It is thus possible to have a reduction in the maximum short-circuit moment (short of two phases, for example Ul and VI) of 50% in relation to the configuration of the simple system usual to date. Another measure to reduce the short-circuit torsional moment is to eliminate a shock absorber shell, especially when the X_ "and Xd 'reactances determine the dynamic short-circuit current configuration.The maximum short-circuit torque can be reduced by approximately 30% under of the omission of the shock absorber shell, i.e. by virtue of the use of a pole-and-protrusion machine without a shock-absorbing winding As another measure to reduce the torsional moment involved, it is proposed that the polar heads of the rotor have an approximate configuration of an arrow. In the case of a short circuit in one of the two three-phase systems, the magnetic induction flux in the exciter pole can then quickly deviate in the direction of rotation, which provides smooth dynamic decoupling of the exciter flow with the flow of the stator within a slot. According to the width of the pole, the short-circuit current flows then lamente in two of a total of six slots. This dynamic decoupling of the exciter flow further reduces the torque of the short circuit.

In the following, the invention will be described in greater detail by means of an embodiment illustrated in the drawings, wherein: Figure 1 is a cross-sectional view through a wind energy installation capsule according to the invention, with a synchronous generator according to the invention. Figure 2 is a cross-sectional view through a known wind energy installation capsule with a known synchronous generator. Figure 3a is a part view of a synchronous generator according to the invention, Figure 3b is a diagrammatic view of the distribution of the phase conductor, Figure 3c shows a part view of a known synchronous generator, Figure 4a is a perspective view of an arrow-shaped polar head, Figure 4b is a plan view of an arrow-shaped polar head, Figure 5 shows a magnetic induction flow configuration without short circuit, Figure 6 is a configuration of magnetic induction flow without short circuit and Figures 7 and 8 show measurement records in a short-circuit situation with partial load or total load. Figure 1 shows a part of a wind energy installation capsule with a rotor that is supported on a stub axle or axle stub axle. The rotor is connected without a transmission directly to a generator rotor of a synchronous generator. The rotor generator is placed inside a generator stator which is installed by means of a flange assembly directly on the axle journal. The axle stump, like all the drive train installed in it, in addition to the generator, is transported by the carrier of the machine. A rotor head 5 and a bearing 6 are also shown. Figure 2 shows a wind energy installation capsule with a known synchronous generator, wherein the generator stator is transported by a carrier star or stator spider and this in its moment is placed on the axle stump and fastened by means of a coupling with safety pin. In the case of a short circuit, for example at the connection terminals or also within the stator winding (not shown), very high torsional moments of short circuit are produced in the synchronous generator. These torsional moment crests, which are so high that they can reach values of up to six or eight times (or more) the torque of the regime, have to be considered by means of the participating mechanical structure. In the case of the Enercon type E-40 wind power installation shown in Figure 2, this mechanical structure is represented by a mechanical safety device in the form of a safety pin coupling. In the case of a generator short circuit, the pins slide and allow the stator to also rotate around the axle journal. This means that the torsional moment transmitted is limited to a maximum of four times the torque of the speed. Therefore, in the event of a generator short circuit, the protection of the drive train is guaranteed. Figure 3a is a cross-sectional view of a part of a synchronous machine (synchronous generator) according to the invention. In this case the rotor rotates inside the stator and the pole machine protruding from the rotor does not have a shock absorber shell (shock absorber winding) or a short-circuit ring. In addition, two independent three-phase windings Ul, VI, Wl and U2, V2, W2 are placed in the stator. In this way, the generator power is divided for the two three-phase windings (three-phase systems) so that each three-phase system has to deal with only 50% of the rated power. The two three-phase systems move through an electric angle of 30% and thus separate electrically and mechanically (spatially) from one another. However, this means that the Xd reactance also approximately doubles and the short-circuit current is halved. This has the advantage that, in the event of a short circuit in a three-phase system, only half of the short-circuit power occurs. This allows a reduction in the maximum moment of the short circuit (short circuit of two phases, for example Ul and VI), of 50% in relation to a configuration of the system (new technology). Figure 3b is a better perspective showing the configuration of the individual phases of two different three-phase systems in a larger region of the stator. Figure 3c is a cross-sectional view of part of a known synchronous generator (synchronous machine in the form of a full pole machine with shock absorber shell) (type E-40) wherein the generator rotor is equipped with a shock absorber shell and the generator power is only compensated by a three-phase system U, V, W. It is shown: magnetic core 9, short circuit ring 10, shock absorber bars 11, stator plate 12. The polar parts or polar heads that are transported in The magnetic cores of the rotor, as shown in Figure 3a, have an arrow-shaped configuration, as shown in Figure 4a. In this case, the polar head, see Figure 4b, in a plan view on the surface that is in the direction of the air gap, has the shape of an arrow. The edge, which is the leading edge in the direction of movement of the rotor, identified by an arrow in Figure 3a, has two edge portions that are arranged in an inclined relation to each other and that are joined together to form a tip and that are arranged in inclination with respect to the direction of movement of the rotor and thus to the polar heads. The edge portions are arranged at an angle of approximately 150 ° with respect to the direction of rotor movement. The edge of a polar head, which is the trailing edge in the direction of rotor movement, also has edge portions placed in inclination with respect to the direction of rotor movement. Figure 5 shows a view of the magnetic induction flux in the generator according to the invention (rotor - ^ stator) without short circuit. In this case the magnetic induction flux passes directly from the polar head to the stator evenly between the slots. In the case of a short circuit, Figure 6, in a slot, identified here by U2, the magnetic field lines (magnetic induction flux F) must deviate. The arrow shape of the polar heads allows deflection into the pole to the right and to the left so that the magnetic induction flux can be distributed to other adjacent slot surfaces. The deviation of the magnetic induction flux at the exciter pole in the direction of rotation provides smooth dynamic decoupling of the exciter flow with the stator flux within a slot. According to the width of the pole, the short circuit current flows only in two of a total of six slots. This dynamic decoupling of the exciter flow further reduces the short circuit torsional moment. Figures 7 and 8 show series of time measurements as an example with respect to rotor torque, power and rotation speed of a 1.5 MW synchronous generator (type E-66 from Enercon) under partial load (1200 kW ) and total load (1500 kW) and with a generator short circuit artificially produced. The measurements show that the maximum torque that occurs in all operating stages due to a short-circuit of the two-phase generator is much less than twice the rated torque. As described in the combination of several measures, at least two independent three-phase systems, without shock absorber shell, polar heads with arrow shape, provide drastic reduction at the time of the short circuit, which is a great advantage particularly in the case of a generator for use in wind power installations. Along with the reduction of the short-circuit moment, it is also possible to achieve a simplified design for the machine because the general structure of the stator carrier, Figure 1, can be simplified considerably compared to the configurations of previous designs, Figure 2 It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (10)

1. CLAIMS Having described the invention as above, it is claimed as property contained in the following claims: 1. A wind power installation with a synchronous machine with a rotor and a stator, characterized in that the stator has at least two independent three-phase systems that they are electrically separated from each other, where the synchronous machine has elements that always limit the torsional short-circuit moment that occurs in the event of a short-circuit in the stator winding to a maximum of four times the torsional moment of the regime, preferably at double the torque of regime.
2. 2. A wind power installation according to claim 1 characterized in that the rotor does not have a shock absorber shell or damping windings.
3. 3. A wind power installation according to one of the preceding claims, characterized in that the short-circuit torque is always less than twice the rated torsional moment.
4. 4. A wind power installation according to one of the preceding claims, characterized in that the rotor has pole pieces of a substantially arrow-shaped configuration.
5. 5. A wind power installation with a synchronous machine, according to in particular one of the preceding claims characterized in that the rotor and the stator are transported by a common axle journal and the stator is installed by a flange assembly directly to the axle journal.
6. A wind power installation according to one of the preceding claims, characterized in that the stator is supported by a carrier, that the rotor of the synchronous machine and the carrier are transported by a stationary axle journal and that the carrier and the axle stump have the shape of a structural unit.
7. A wind power installation according to one of the preceding claims, characterized in that the synchronous machine is a synchronous generator and / or the stator carrier and the axle journal are in the form of an integral component fused in steel.
8. A wind power installation according to one of the preceding claims, characterized in that no mechanical safety element is provided between the stator and the axle journal that releases the stator in the event of a short circuit.
9. 9. A wind power installation according to one of the preceding claims, characterized in that the first three-phase system is moved through an angle (electric) of approximately 30 ° in relation to the second three-phase system.
10. 10. A wind power installation according to one of the preceding claims with a power of at least 100 kW, preferably a power of 500 kW to 10 MW.