JPH0783638B2 - Wire wound induction machine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a wire wound induction machine that performs speed control by changing a secondary excitation frequency by a frequency conversion device, and particularly to a wire wound induction machine suitable for a variable speed generator. Regarding the machine.

[Conventional technology]

Generally, in a generator, operation at the point of maximum efficiency is desired, and for that purpose, controlling the rotation speed of the generator is the most effective means. For this rotation speed control, a frequency converter using a thyristor is used for the wire wound induction machine.

FIG. 2 is a system diagram of a conventional wound-rotor induction generator. In the figure, reference numeral 1 denotes a wound-rotor induction generator, and a primary winding 2, a secondary winding 3, and a collector ring 4U, 4V connected to each phase (U, V, W) of the secondary winding 3. , With 4W. Reference numeral 5 is a frequency converter connected to each of the collector rings 4U, 4V, 4W, and usually a thyristor is used. Reference numeral 6 denotes a power transmission line connected to the primary winding 2.
The operation of speed control using the frequency conversion device 5 in such a system is well known, and therefore its description is omitted.

[Problems to be Solved by the Invention]

By the way, when a variable frequency AC secondary current is supplied by the frequency conversion device 5 using a thyristor as described above, an undesirable phenomenon occurs. This is shown in FIG.
This will be described with reference to the waveform chart shown in (b).

FIG. 3 (a) is a general waveform diagram of the three-phase secondary current, and FIG. 3 (b) is a detailed waveform diagram of a part thereof. In each figure, the horizontal axis represents time and the vertical axis represents secondary current. The secondary current supplied from the frequency converter 5 to the secondary winding 3 via the current collector rings 4U, 4V, 4W generally has the waveform shown in FIG. 3 (a).
However, for example, the portion A in the vicinity where the U-phase current becomes 0
The waveform of the U-phase current is not smooth when viewed in detail. A waveform diagram of this portion A is shown in FIG. 3 (b). That is, when the U-phase current switches from positive to negative,
There is no current for a certain period t. This is an unavoidable phenomenon in view of the performance of the thyristor used in the frequency conversion device 5.

It can be considered that the U phase is in an open state during the currentless period t, and during this time, in the V phase and the W phase, the current is V phase → O point (secondary winding neutral point) → W. Flow with Ai. Therefore, the sum of the instantaneous currents becomes 0 in the period t. Therefore, one of the V-phase and W-phase current waveforms must be distorted. For example, when the gain of the V-phase thyristor in the frequency conversion device 5 is high, the W-phase current waveform is as shown in FIG. It will be distorted as indicated by the alternate long and short dash line.
Such distortion of the current waveform distorts the magnetic flux waveform in the air gap of the wound-rotor induction generator 1, and eventually distorts the current waveform generated in the primary winding 2 and adversely affects the power transmission system. It had a flaw.

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a wire-wound induction machine capable of preventing distortion of the current waveform of another phase during a no-current period that occurs during switching of one phase thyristor in a frequency conversion device. There is.

[Means for Solving the Problems]

In order to achieve the above-mentioned object, the present invention provides a winding type induction machine having a primary winding and a secondary winding, wherein the secondary winding has an alternating current through a frequency conversion device having an excitation output adjusting means. It is characterized in that the neutral point of the secondary winding is connected to the frequency conversion device while being excited next, and the frequency conversion device can be independently controlled for each phase.

[Action]

For example, in a three-phase alternating current of U-phase, V-phase, and W-phase, even if a no-current period occurs in one of the phases, for example, the U-phase, the excitation output adjusting means for the V-phase and W-phase in the frequency converter is A current can flow through each of the neutral points, and as a result, a sinusoidal alternating current without distortion can flow.

〔Example〕

 Hereinafter, the present invention will be described based on the illustrated embodiments.

FIG. 1 is a system diagram of a wire-wound induction generator according to an embodiment of the present invention. In the figure, the same parts as those shown in FIG. Reference numeral 1'indicates a wire wound induction generator of this embodiment. The winding-type induction generator 1'is different from the winding-type induction generator 1 shown in FIG.
Is provided. That is, the collector ring 4N is connected to the neutral point O of each phase secondary winding 3 of the wound-rotor induction generator 1'and to the frequency converter 5 '. Unlike the frequency converter 5 shown in FIG. 2, the frequency converter 5'includes a thyristor for controlling the N-phase current passing through the neutral point O and the collector ring 4N.

In such a configuration, the current between the U-phase and the N-phase, the current between the V-phase and the N-phase, and the current between the W-phase and the N-phase can be independently controlled. Therefore, for example, in the currentless period in which the positive or negative of the U-phase current is switched, the V-phase-N-phase and W-phase-N-phase currents are independently controlled and flow through the neutral point O and the collector ring 4N. As a result, it is possible to prevent the occurrence of distortion of the V-phase or W-phase current as shown in FIG. 3 (b).

〔The invention's effect〕

As described above, in the present invention, since the current collecting ring connected to the neutral point of the winding type induction machine is provided and the current collecting ring and the frequency conversion device are connected, the winding type induction machine The alternating secondary current of the secondary winding can be controlled for each phase, so that the secondary current can supply a sinusoidal current without distortion, and thus the primary winding current also becomes a sinusoidal wave without distortion, The influence of harmonic components on the system can be reduced.

[Brief description of drawings]

1 is a system diagram of a wire wound induction generator according to an embodiment of the present invention, FIG. 2 is a system diagram of a conventional wire wound induction generator, and FIGS. 3 (a) and 3 (b) are secondary currents. It is a waveform diagram. 1 '... Winding type induction generator, 2 ... Primary winding, 3 ... Secondary winding, 4U, 4V, 4W, 4N ... Current collecting ring, 5' ... Frequency conversion device, O ... Medium Sex point.

Claims (1)

[Claims] 1. A winding-type induction machine having a primary winding and a secondary winding, wherein the secondary winding is AC-secondarily excited through a frequency converter having an excitation output adjusting means, and A winding-type induction machine characterized in that a neutral point of a secondary winding is connected to the frequency conversion device, and the frequency conversion device is configured to be independently controllable for each phase.