JPH11178261A - Rotor of rotating electric machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To press wedges down and to absorb impulses, and to prevent electrolytic corrosion between a wedge and a damper by fitting the dampers only to the Joints of the wedges, and causing the dampers to perform spring action. SOLUTION: A damper 7 is buried in a creepage block 8 only to the Joint between wedges 3 and the next. As the result of this, it becomes possible to cause dampers 7 to perform spring action, and to keep the wedges 3 and dampers 7 in good contact even at the time of low-speed rotation. Besides, it becomes possible to improve electrolytic corrosion keeping the spring action, by burying the dampers 7 directly in the wedges 3. Accordingly, it is possible to concentrate overcurrents induced in the rotor of a generator on the wedges 3 and the dampers 7. Consequently, it becomes possible to suppress the temperature rise of the rotor surface, and to enhance the endurability and reliability of the generator against higher harmonic currents.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rotor for a rotating electric machine.

[0002]

2. Description of the Related Art Generally, a damper for passing an eddy current generated at a wedge for holding a field winding of a rotor of a generator used in a power generation equipment driven by a gas turbine or a steam turbine to an end thereof is generally a wedge. It is installed below and connects the end damper ring at the end of the rotor.

[0003]

In recent years, large-capacity power generation facilities have been constructed in response to an increase in power demand. Along with this, a large-capacity starting device for starting a gas turbine or a combined cycle power generation facility has been required, and thyristor starting methods have attracted attention. This is a method in which a synchronous generator in the power generation equipment is operated as a variable speed motor when starting up the power generation equipment, and the gas turbine is accelerated to a speed at which the gas turbine can be accelerated by the torque obtained from the motor.

[0004] The rotational speed of the synchronous motor depends on the frequency of the AC power supply applied to the armature winding. Therefore, in order to operate the synchronous generator at a variable speed, an AC power source having a variable frequency is required, and its frequency must be controllable according to the rotation speed of the variable speed motor. In order to obtain the power supply, a frequency converter using a semiconductor element such as a thyristor is used.

The frequency converter comprises a forward converter for converting AC to DC and an inverse converter for converting DC to AC. When starting up the power generation equipment using this frequency converter, a square wave current is passed through the armature winding of the generator. The square wave current includes a harmonic current, and the current can be represented by the following equation.

The frequency of the harmonic fi = (6i ± 1) f0 The magnitude of the harmonic Ai = A0 / (6i ± 1) where i = 1, 2, 3,... F0 = the frequency of the fundamental wave A0 = the fundamental wave The harmonic current flowing through the armature winding induces an eddy current on the surface of the rotor. FIG. 1 shows the rotor structure of the generator and the flow of the eddy current induced by the harmonic current on the surface of the rotor. Eddy current 1 flowing in rotor wedge 3
Flows to the teeth 2 at the seam between the wedges and flows.

The eddy current flows from the end wedge 3a to the retaining ring 6 and the end damper ring 4 and flows in the circumferential direction of the rotor. Further, in the magnetic pole portion, current flows intensively at the end of the cross slot near the cross slot 5. These eddy currents flowing on the rotor surface cause losses, and as a result, the temperature of the rotor surface increases. On the other hand, the cooling performance of the rotor depends on the number of revolutions, and there is no sufficient cooling performance at the time of low-speed rotation at the time of starting.

In addition, since the power system contains harmonic currents generated by various electric devices, the generator is in a state where harmonic currents are always flowing.

In order to prevent the eddy current from flowing on the surface of the rotor, it is conceivable to concentrate the eddy current on a wedge and a damper which hold down a field winding of the rotor of the generator.

FIG. 2 is a sectional view of the rotor end portion in FIG. 1 cut along the axial direction. When the eddy current is concentrated on the wedges as described above, the eddy current 1 flowing through the wedges 3 and the teeth 2 flows into the end damper ring 4 and the retaining ring 6 from the wedge 3a at the end of the rotor. become. Electric erosion occurs at wedges, dampers, and the like due to sparks in the gaps in the rotor that occur during low-speed rotation. (During low-speed rotation, the centrifugal force is insufficient.
The wedge, damper, etc. move in the coil slot as shown in FIG. )

[0011]

According to the present invention, to solve the above-mentioned problems, a damper is attached only to the joint of the wedge, and the damper is provided with a spring action to hold down the wedge and absorb the impact. This can prevent electrolytic corrosion between the wedge and the damper.

That is, in the present invention, by maintaining the contact state between the wedge and the damper, a harmonic component generated at the time of starting the thyristor and an eddy current induced in the rotor of the generator by the harmonic current flowing from the power system. Is concentrated on the rotor wedge and the damper.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

In order to concentrate the eddy current induced in the rotor of the generator on the wedge, it is necessary that the wedge and the damper have a higher conductivity than the rotor surface.

The eddy current IS induced in the rotor is proportional to the harmonic current I2 flowing through the armature winding, and the relationship between the temperature rise ΔT on the rotor surface and the eddy current IS can be expressed by the following equation.

ΔT∝R · IS2 (IS∝I2) where R is the resistance of the rotor surface. Accordingly, the temperature rise of the rotor surface is proportional to the magnitude of the resistance of the rotor surface through which the eddy current flows. That is, if the resistance of the portion of the rotor surface where the eddy current flows is reduced, the rise in the temperature of the rotor surface can be suppressed. At this time, the eddy current flows concentrated on the wedge. In particular, at the end, the air mainly flows to the end damper ring 4 via the end wedge 3a.

If the end damper ring 4 is omitted, it flows into the retaining ring 6 via the wedge and the damper in the slot. As shown in FIG. 2, the eddy current 1 flowing to the wedge flows into the end damper ring 4 and the retaining ring 6 from the rotor end wedge 3a. At the time of low rotation, the centrifugal force does not work sufficiently, so that electrolytic corrosion is a problem at this contact surface.

As shown in FIG. 4, the damper 7 is attached to the crimper block 8 only at the joint between the wedges. Thus, the damper 7 is provided with a spring action so that the damper 7 is kept in close contact even during low-speed rotation to prevent electrolytic corrosion. In addition, by embedding the damper 7 directly in the wedge 3 as shown in FIG. 5, the spring action is maintained and the electric conduction is further improved.

[0019]

As described above, when the wedge, the damper and the crimper block according to the present invention are employed, the damper absorbs the shock by the spring action and has a good contact state. When entering,
Eddy currents induced in the rotor of the generator can be concentrated on the wedges and dampers. Therefore, a rise in the temperature of the rotor surface can be suppressed, and the proof strength and reliability of the generator against harmonic currents can be improved. further,
A good contact state also prevents electrolytic corrosion.

[Brief description of the drawings]

FIG. 1 is a partial perspective view of a conventional rotor.

FIG. 2 is a partial cross-sectional view showing a cross section of a conventional rotor end portion in an axial direction.

FIG. 3 is a partial cross-sectional view showing a contact state of a conventional wedge.

FIG. 4 is a diagram illustrating a damper according to an embodiment of the present invention attached to a crimper block;

FIG. 5 is a diagram in which a damper is embedded in a wedge.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Eddy current, 2 ... Teeth, 3 ... Wedge, 3a ... End wedge, 4 ... End damper ring, 5 ... Cross slot, 6 ... Retaining ring, 7 ... Damper, 8 ... Cripage block.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Miyagawa Ieda 3-1-1 Sachimachi, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd. Hitachi Plant

Claims (4)

[Claims] In a rotor of a rotating electrical machine, a field winding of the rotor is held down by a wedge against centrifugal force, and each damper is electrically connected at an end of the rotor by end damper ring. A rotator characterized in that a damper is embedded in a crease page block only at a joint between the rotors. 2. A rotor of a rotary electric machine in which a field winding of the rotor is held down by a wedge against centrifugal force and each damper is electrically connected by end damper ring at an end of the rotor. A rotor characterized in that a damper is embedded only in a joint between the rotors. 3. The rotor according to claim 1, wherein each damper has a spring effect and presses the wedge even at a low rotation to absorb a shock. 4. A rotor of a rotary electric machine in which a field winding of the rotor is held down by a wedge against centrifugal force, and each damper is electrically connected by end damper ring at an end of the rotor. The gap in the radial direction is reduced only at the joint between wedges by increasing the thickness of the crease block.
The rotor described.