JPH11178260A - Cylindrical rotor of electrically rotating machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optimize the thickness of a damper bar, so that the eddy-current loss of a rotor is not increased when a thyristor is stated. SOLUTION: When a wedge 5 is shorter than the axial length of an electrically rotating machine and a plurality of the wedges 5 are placed in one slot 2, a damper bar 4 of copper or copper alloy is installed at the lower part of the wedges 5 over the overall length of the slots 2. Both the ends of the damper bar 4 placed in each slot 2 are connected with a short-circuit ring 8 of copper alloy, and the thickness A of the damper bar 4 in the radial direction is controlled within a range of not less than 1.1 mm but not more than 2.3 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylindrical rotor of a rotary electric machine, and more particularly to a cylindrical rotor of a rotary electric machine in which a shaft, a field pole and an iron core are made of a single piece of forged steel like a turbine generator. About.

[0002]

2. Description of the Related Art A turbine for driving a generator is more efficient and smaller at a higher speed, and a turbine generator for thermal power is generally a two pole machine. Therefore, since the centrifugal force of the rotor increases, the rotor of the turbine generator produces the shaft, the field poles, and the iron core from a block of forged steel. Therefore, since the rotor of the turbine generator is electrically conductive, the generation of an asynchronous magnetic field induces an eddy current on the rotor surface.

[0003] When the generator is in the power generating operation, when the load state of the three-phase armature winding is unbalanced in each phase, an anti-phase rotating magnetic field is generated in the rotor due to imbalance of the armature current. This anti-phase rotating magnetic field has an angular frequency ω of the output voltage.
And an asynchronous magnetic field component having an angular frequency 2ω which is twice as large as the above.
When such a reversed-phase rotating magnetic field is generated, an eddy current is induced in each conductor portion of the rotor, and the temperature of each portion of the rotor rises beyond an allowable range.

Therefore, in order to solve such a problem, as described in Japanese Patent Publication No. 60-34340,
A method has been proposed in which a current flowing in the axial direction of a massive iron core is guided to a damper bar via a conductive wedge to thermally balance each part of the rotor.

[0005]

In the above prior art, during power generation operation, eddy currents due to an asynchronous rotating magnetic field are led to a damper bar via a conductive wedge to balance the thermal balance of each part of the rotor. The thickness of the damper bar is set to be greater than 3.0 mm from the viewpoint of reverse phase resistance. on the other hand,
The turbine generator used in the combined cycle power generation system is a machine of 400 MVA class or less.
Since the capacity is not large, it is common that the rotor body is not provided with a damper bar. However, when the thyristor is started, it is different from the time of the power generation operation. Therefore, it is necessary to provide a damper bar to suppress a rise in the temperature of the rotor. This is for the following reason.

[0006] The combined cycle power generation system comprises a gas turbine, a steam turbine using the residual heat of the exhaust gas of the gas turbine as a boiler heat source, and a turbine generator.
The gas turbine, steam turbine and turbine generator are arranged on the same axis. Since the turbine generator used for combined cycle power generation is 400 MVA class or less,
Unlike a large capacity machine of 00 MVA class or higher, the temperature rise of the rotor due to the eddy current during the power generation operation is small, and generally no damper bar is provided on the rotor body.

In the thyristor starting method, a turbine generator is started as a variable-speed synchronous motor using a thyristor power supply. The load imposed on the turbine generator is sufficiently small as compared with a normal power generation operation. Therefore, the current flowing through the armature winding of the turbine generator at the time of starting the thyristor is 10% or less of the rated current. However, in a low-speed region, the cooling effect of the rotor is small, and the temperature rise of the rotor becomes a problem.

Generally, when the capacity is increased and the shaft length of the generator is increased, various phenomena due to thermal expansion are alleviated. In order to reduce the rotor wedge, a so-called short wedge which is sufficiently short with respect to the shaft length is used. In this way, when the short wedges are arranged in the axial direction to hold the field winding in the slot, the gap between the short wedges is usually smaller than 1 mm, but the eddy current circuit is incomplete, and the eddy currents are reduced between the wedges. Can not flow through the breaks. Therefore, in order to prevent the eddy current flowing in the wedge at the cut of the wedge from sneaking into the rotor teeth, it is necessary to install a damper bar so that the eddy current loss does not increase.

However, when the damper bar is installed, the rotor slot becomes deeper by that amount, and the magnetic saturation increases. Therefore, the thickness of the damper bar should be reduced as much as possible. Therefore, as a result of examining the optimum thickness of the damper bar at the time of starting the thyristor, it was found that even if the thickness of the damper bar was made thinner than the current thickness, the loss of the damper bar hardly changed, and it was unnecessary to make the damper bar more than 3.0 mm. .

It is an object of the present invention to reduce the thickness of the damper bar so that the temperature rise of the rotor due to eddy current is not as high as possible, to make the rotor slot shallower by that amount, and to provide a cylindrical rotor for a rotating electric machine having a small magnetic saturation. Is to provide.

[0011]

To achieve the above object, the present invention provides a cylindrical rotor core and a field winding housed in a slot cut on the outer peripheral side of the rotor core. A wedge for holding the field winding in the slot, wherein the wedge is shorter than the axial length of the rotating electric machine, and a plurality of the wedges are housed in one slot in a cylindrical rotor of the rotating electric machine. A copper or copper alloy damper bar is provided under the wedge over the entire length of the slot, and both ends of the damper bar housed in each slot are connected to a copper alloy short-circuit ring, respectively, so that the radial thickness of the damper bar is 1.1 m.
It is characterized by being within the range of not less than m and not more than 2.3 mm.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a cross section of a cylindrical rotor of a rotary electric machine showing an embodiment of the present invention, FIG. 2 shows a cylindrical rotor of the rotary electric machine according to the present invention, and FIG. 3 shows a flow through a damper bar according to the present invention. FIG. 4 shows the flow of the eddy current according to the present invention.

The rotating electric machine includes a stator (not shown) and a rotor 1.
The cylindrical rotor 1 is used for a turbine generator driven by a steam turbine or a gas turbine because of its high mechanical strength and small windage loss.

The cylindrical rotor 1 of the turbine generator has a main shaft,
The most common method is to make the whole of the field poles and the iron core with a lump of forged steel, and a high-tensile alloy steel of a magnetic material is used.
Slots 2 are cut radially in the core portion of the cylindrical rotor 1, and a field winding 3 is held inside the slot 2, and is fixed with a wedge 5 so that the field winding 3 does not protrude. . In order to hold down the end of the field winding 3, a holding ring 9 is provided.
Is provided.

The turbine that drives the generator is higher in efficiency and smaller in size at higher speeds. Generally, a turbine generator for thermal power is a two pole machine. Therefore, the rotation speed is 36 for 60 Hz.
Since the rotation speed is 3000 rpm for 00 rpm and 50 Hz, and the peripheral speed increases, the rotor diameter is limited to about 1100 mm, and the structure becomes long in the axial direction. When the shaft length is increased, so-called short wedges, which are sufficiently short with respect to the shaft length, are used for the rotor wedge 5 in order to reduce various phenomena due to thermal elongation.

Generally, the material of the wedge 5 is steel or an aluminum alloy, and the damper bar 4 is copper or a copper alloy. The eddy current 10 is generated by the harmonic magnetic flux. When the change of the magnetic flux becomes faster, the frequency of the eddy current 10 becomes higher and concentrates on the surface of the rotor 1. That is, as shown in FIG. 4, the eddy current flowing through the wedge 5 and the damper bar 4
Eddy currents flowing through the eddy currents 10A and 10B, respectively.
Then, although the damper bar 4 has higher conductivity than the wedge 5, the higher the frequency, the higher the eddy current 10
A is larger than the eddy current 10B.

As described above, when the short wedges 5 are arranged in the axial direction to hold the field windings 3 in the slots, an asynchronous magnetic field is generated in the generator, and the eddy current 10 is generated on the rotor surface.
Flows, the eddy current 10A flowing through the wedge 5 at the break of the short wedge 5 mainly flows around the damper bar 4 and concentrates on a specific location. That is, as shown in FIG. 4, the eddy current 10A flows, and the eddy current 10A flowing around the rotor teeth 6 having lower conductivity than the damper bar 4 is slight. That is, since the eddy current 10 concentrates on the rotor surface, it mainly flows to the wedge 5, but when the eddy current 10 wraps around like a cut of the wedge 5, it concentrates on the damper bar 4 having a small resistance.

Although a damper bar 4 is provided below the wedge 5 in a turbine generator of 700 MVA class or higher, a damper bar 4 is generally not provided in a 400 MVA class turbine generator used for combined cycle power generation equipment. This is because if the capacity is small, the asynchronous magnetic field component flowing into the generator is also small, and the rise in temperature of the rotor does not pose a relatively problem.

However, when the thyristor is started, unlike the normal power generation operation, the operation is a variable speed operation, so that the cooling effect is small in a low speed range, and a rise in the temperature of the rotor becomes a problem. Therefore, by providing the damper bar 4, it is necessary to prevent the eddy current 10 from flowing around the teeth 6 at the cut of the wedge 5, and to suppress the loss due to the eddy current 10.

At the time of starting the thyristor, the cooling effect in the low speed range is small, so that the temperature rise of the rotor becomes a problem.
Since the value of 0 is sufficiently smaller than the value during the power generation operation, 7
It is considered that the optimum value is different from the thickness of the damper bar used for a machine of 00 MVA class or higher.

FIG. 3 shows the eddy current 10 flowing through the damper bar 4 when the thickness A of the damper bar is changed, calculated and actually measured at the cut of the wedge 5 (point B in FIG. 4). These results are obtained when an armature current and a field current that match the operating conditions at the time of starting the thyristor are input. The results are based on the value of the eddy current 10 when the thickness of the damper bar is 3.0 mm. , Relative values are displayed.

As can be seen, even if the thickness A of the damper bar 4 is greater than 2.3 mm, the eddy current 10 flowing through the damper bar 4 is substantially constant. The reason is that the eddy current 10
When A goes around the minute gap C smaller than 1.0 mm between the wedges 5, the path of the eddy current 10A flows so as to be shorter. Therefore, the damper bar 4 is closer to the wedge 5 (outer diameter side of the rotor 1). It is considered that the current density is high and the current density on the inner diameter side of the rotor 1 is low. That is, even if the thickness A of the damper bar 4 is greater than 2.3 mm,
The eddy current is almost 10 A on the inner diameter side of the rotor of the damper bar 4.
Found that it did not flow.

Further, when the damper bar 4 becomes thinner than 1.1 mm, the eddy current 10 flowing through the damper bar 4 sharply decreases. That is, if the damper bar 4 is made thinner than 1.1 mm, the eddy current 10A does not satisfy the damper bar thickness A necessary to go around the cut of the wedge 5, so that the amount of bypassing to the teeth 6 increases.

Therefore, the thickness A of the damper bar 4 of the turbine generator driven by the thyristor starting method is set to 1.
It has been found that it is better to make it 1mm or more and 2.3mm or less. If the thickness A of the damper bar 4 is 1.1 mm or more and 2.3 mm or less, the temperature rise of the rotor due to the eddy current 10 is equivalent to the case where the thickness of the normally used damper bar is 3.0 mm or more. As a result, the rotor slot 2 can be made shallower, so that the iron core of the rotor 1 becomes larger and magnetic saturation can be reduced. Furthermore, the weight of the damper bar is reduced by the thinner the damper bar 4, and the wedge 5
Therefore, the radial thickness of the wedge 5 can be reduced.

As described above, the wedge 5 is generally formed of an aluminum alloy or steel. If copper having higher conductivity than the aluminum alloy and steel is used, the eddy current loss of the wedge 5 can be reduced. . However, since the wedge 5 must hold the field winding 3 in the slot 2 in a high rotation region, a high strength is required. Since copper has a problem in mechanical strength, it is necessary to add some material to copper to increase the strength.

When Cr is added, fine particles of metallic Cr are precipitated by aging treatment at 400 ° C. to 600 ° C., thereby increasing the strength of the alloy. If Cr is less than 0.4%, precipitation is small and strength is insufficient, and if it exceeds 1.0%, strength is saturated. The addition of Cr decreases the conductivity of the copper alloy,
The amount of Cr added is preferably in the range of 0.4 to 1.0% by weight.

When Zr is added, Cu ₃ Zr fine particles are precipitated by aging treatment at 300 ° C. to 600 ° C., and as a result, the strength of the alloy is increased. If Zr is less than 0.01%, the precipitation is small and the strength is insufficient, and if it exceeds 0.3%, the strength is saturated. When Zr is added, the conductivity of the copper alloy decreases, so the amount of Zr added is 0.01 to
A range of 0.3% is good.

Therefore, if a CuCr alloy, a CuZr alloy and a CuCrZr alloy are used as the wedge material and the thickness A of the damper bar 4 is set to 1.1 mm or more and 2.3 mm or less, the eddy current loss in the damper bar 4 becomes 3 mm. The eddy current loss in the wedge 5 is smaller than that in the case of aluminum alloy and steel wedge. Further, since the rotor slot 2 can be made shallower by the thickness of the damper bar 4, the iron core of the rotor 1 becomes large, and magnetic saturation can be reduced. Furthermore, the weight of the damper bar is reduced by the amount of the thinner damper bar 4 and the centrifugal force applied to the wedge 5 is reduced, so that the radial thickness of the wedge 5 can be reduced.

In a large-sized machine, the centrifugal force is increased, and at the same time, the shaft length is increased, and the thermal expansion and contraction are increased. Therefore, instead of copper, silver-containing copper having good creep characteristics is used for the damper bar 4 and the end ring 8. Use will increase reliability.

[0031]

As described above, according to the present invention, the damper bar can be made thinner without increasing the eddy current loss in the damper bar, so that the temperature rise of the rotor can be suppressed and the rotor can be prevented from rising. Slots can be made shallower. As a result, the iron core of the rotor becomes large, so that the magnetic saturation of the rotor can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a cylindrical rotor of a rotating electric machine according to an embodiment of the present invention.

FIG. 2 is a schematic view of a cylindrical rotor of the rotating electric machine according to the present invention.

FIG. 3 is a characteristic diagram showing a relationship between a thickness of a damper bar and an eddy current according to the present invention.

FIG. 4 is a schematic diagram of an eddy current flow according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Rotor, 2 ... Rotor slot, 3 ... Field winding, 4 ...
Damper bar, 5 ... rotor wedge, 6 ... teeth, 7 ...
Field pole, 8: end ring, 9: holding ring, 10: eddy current.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshinobu Mori 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside the Hitachi Research Laboratory, Hitachi, Ltd. Hitachi 1-1, Hitachi Works, Ltd. (72) Inventor Yasuomi Yagi 3-1-1, Sakaimachi, Hitachi City, Ibaraki Prefecture, Hitachi, Ltd.

Claims (3)

[Claims] A cylindrical rotor core, a field winding housed in a slot cut on the outer peripheral side of the rotor core, and a wedge for holding the field winding in the slot. A cylindrical rotor of a rotating electrical machine in which the wedges are shorter than the axial length of the rotating electrical machine and the plurality of wedges are accommodated in one slot, wherein a copper or copper alloy damper bar is provided under the wedge over the entire length of the slot. The ends of the damper bar accommodated in each slot are connected to a short-circuit ring made of a copper alloy, and the radial thickness of the damper bar is set to 1.1 mm.
A cylindrical rotor for a rotating electric machine, wherein the diameter is within the range of not more than 2.3 mm. 2. A rotor having a cylindrical rotor core, a field winding housed in a slot cut on the outer peripheral side of the rotor core, and a wedge for holding the field winding in the slot. The wedge is shorter than the shaft length of the rotating electric machine, and in a cylindrical rotor of the rotating electric machine in which a plurality of the wedges are accommodated in one slot, the wedge is formed of a copper alloy, and the wedge is formed over the entire length of the slot. A damper bar made of copper or a copper alloy is provided at the lower part of the damper bar, and both ends of the damper bar housed in the respective slots are connected to short-circuit rings of the copper alloy, respectively. A cylindrical rotor for a rotating electric machine, wherein the cylindrical rotor is disposed inside. 3. A cylindrical rotor for a rotating electric machine according to claim 1, wherein said damper bar is made of silver-containing copper.