SU922955A1 - Electric machine stator winding - Google Patents

Description

The invention relates to electrical engineering, in particular to the design of the stator winding of an electric machine with direct liquid cooling.

The stator winding of an electric machine with direct liquid cooling of rods containing transported in the slot part is known ^; hollow and hollow conductors, with the hollow conductors being uniformly distributed over the cross section of the rod [13 "· ¹

Also known is the electric stator winding. Direct liquid cooling machine, the rods of which contain hollow and solid conductors, ₁₅ transported in a groove part, in which the cross section of the rod is symmetrical about the axis and consists of an integer number of identical groups of conductors, in each of which several solid ones are formed per hollow _χ . Each conductor has its own insulation. The design assumes that losses from solid conductors are diverted to near -

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Zhaytsie hollow through the appropriate insulating gaps. It is usually assumed that the difference in temperature between colder hollow and more heated solid conductors should not exceed 20 ^d C. In fact, this value is a function of the current density in the winding, as well as the number and thermal conductivity of the insulating gaps to more distant from the conductor losses of solid conductors.

Since all channels in hollow conductors are supplied with the same amount of cooling agent, all groups of conductor ©, regardless of their position relative to the axis or the ends of the rod, are cooled equally.

It would be good if the losses were also distributed evenly over the cross section of the rods and along the groups of conductors.

However, it is known that. because of the circulation currents between the elementary conductors, the losses in them are sharply3

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chatsya These points, as shown by numerous studies, are the result of tangential magnetic fields in the end zones of the stators. The density of these fields increases with an increase in the electromagnetic use of electric machines, which is precisely the purpose of the application of fixed cooling systems. Therefore, it is in the windings with direct cooling that the effect of circulating currents © is more pronounced. It manifests itself in an increase in the resulting currents (the sum of the main and circulation currents in the conductors lying in the frontal parts 15 at the narrow face of the rods on the rotor side, and, conversely, the decrease in the resulting currents in the conductors located in the frontal parts in the middle height of the rods zone. The greatest losses 20 take place in the outermost and nearest conductors located in the frontal parts on the side of the rotor [2].

A disadvantage of the known design of rods with direct cooling is that the cooling agent is distributed evenly across the groups of conductors at th time, as the losses that it must divert are far from even. As a result, in Canada are individual crystals of hollow conductors ₃₀ and the refrigerant is heated much higher than the average for the rod. There are significant unevenness in the heating of the end parts of the conductors in substantially gre- ₃₅ upward scheduled between the hollow and solid, additional heat deformation, leading to disruption of pre-baked monolithic rods disbonding most HA ₄₀ Greta outer conductor ©, the appearance of dangerous vibrations of the conductors leading over time, either to their fatigue failure, or to damage by them of the winding case insulation. ₄₅

The increased heating of water in the channels of hollow conductors on the rotor side also leads to a significantly more intensive thermochemical processes in them with the deposition of oxides and salts on the walls — ^{50 of} these channels. As a result, a narrowing of the channel section occurs, and, consequently, a decrease in the consumption of the cooling agent and an increase in its heating. This process priob- ⁵⁵ PETA avalanche, leading to complete blockage kanale® in the conductors in the narrow side front parts of the rods. The result is high local temperatures leading to machine breakdown. In the process of manufacturing rods, especially during pressure testing, sometimes full or partial overpressures of the channels of hollow outer conductors occur, which cannot be identified at the factory. The narrowing of the channels for technological reasons leads to their accelerated blockage.

In addition, a known construction is characterized by a small working resource in case of channel blockages that are possible in the course of production and operation. The latter concerns only the channels of rods closest to the narrow face from the side of the rotor, since blockage, for example, in the middle part of the cross section of the frontal parts does not lead to such disastrous consequences.

There are two ways to improve the design. The first is associated with the use of transposition of elementary conductors not on 360, but on 540 e.grad. It has found wide application in turbogenerators, but does not provide a complete solution to the problem.

For example, in relation to hydrogenerators, this method of transportation allows reducing the losses in the conductors extreme to the rotor by an average of 15%, but they remain several times higher than the average over the cross section of the rods.

It is more efficient to perform the transposition of elementary conductors in the frontal parts, but with a short length of the latter (in multi-pole machines), it is often impossible to perform because of the inability to bend the entire mass of conductors in a small section along the length.

Since it is practically impossible to obtain a more or less uniform distribution of losses over conductors, it is naturally necessary to set the task to provide approximately such a distribution of cooling agent (water) over the cross section of the rod, which would possibly take into account the distribution of losses and provide a sufficiently effective cooling for the highlander rod in the frontal part, even in the case of complete or partial blockage of the end hollow conductor.

The purpose of the invention is to increase operational reliability by reducing heating.

This goal is achieved by the fact that in the stator winding of an electric machine with liquid cooling, made in the form of rods with a rectangular cross section, facing one

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from their smaller sides to the rotor, each of which has hollow and solid conductors transported, in the groove part, the hollow conductors in the frontal winding parts are unevenly distributed over the cross section of the 5th rod and are located more often in the zone of the smaller sides of the terminals than in the remaining hours—

'yah sections of rods, for example, in a row, and this zone is 0.2 - ¹⁰

0.3 larger side of the cross section of the rod.

FIG. 1 is a graph of the distribution of losses in the elementary conductors of the frontal part of the rod; SchA FIG. 2 section of the rod; in FIG. 3 - slot and ¹⁵ frontal winding parts; in fig. 4 - part of the winding facing the rotor.

The rod contains hollow 1 and solid 2 conductors transported in the slot part 3 and non-transported ²⁰ in the frontal part 4 of the rod. Conductors 1 and 2 have their own insulation 5 and case insulation 6. Hollow conductors 1 are unevenly distributed over the cross section of the rod, i.e. for narrow beams ²⁵ and 7 facing the rotor 8, at a depth of up to 0.2-0.3 of the rod height, hollow conductors 1 are placed more often, for example, in a row, and less often alternating with ³⁰ solid conductors on the rest of the middle section of the rod section. 2. With such an arrangement, even in the case of blocking of the end hollow conductor, its losses will be retracted by the refrigerant circulating through the channel of the adjacent hollow conductor.

FIG. 1 shows an example of loss distribution in the elementary conductors of the frontal part of the mop / nosgyu hydrogenerator core 500 MW. The core ⁴⁰ has transpositions only in the slot part on 360 el. hail.

A significant increase in losses occurs at approximately 0.25 of the total height of the rod (Fig. I). ⁴³ Approximately the same data was obtained when testing a number of other machines, and they are in good agreement with the results of calculations.

In relative units, in the section 50 from O (the boundary of the copper rod at a smaller diameter in the frontal part, on the side of the rotor) to 0.25 of the rod height, the specific losses change almost linearly from about 4 to 1 relative 55 units, i.e. about 4 times. On the remaining conductors, which make up 75% of its height, the average specific losses amount to an average of 0.56 relative units, and the total amount of losses in this volume is about thirty-five pips of all rod losses.

Thus, on 1/4 of the most heated conductors, the average density of losses is on average six times higher than on 3/4 parts of the remaining conductors.

The present invention allows to increase the durability of the winding due to the uneven distribution of hollow conductors in the cross section of the rod, i.e. ensuring distribution of refrigerant taking into account the distribution of losses from circulating currents, more uniform heating of the distillate in all channels parallel to the water and reducing the maximum local heating of the conductors.

The invention is proposed to use in the vertical hydrogenerator type CB —-- 64 for the Krasnoyarsk hydroelectric station.

Claims (1)

Claim The stator winding of an electric machine with liquid cooling, made in the form of rods with a rectangular cross section, facing one of its smaller sides to the rotor, each of which has hollow and solid conductors transported in a groove part, characterized in that, in order to increase operational reliability by reducing heat, the hollow conductors in the frontal winding parts are unevenly distributed over the cross section of the rod and are located more often in the zone of the mentioned smaller sides of the cross sections than in other parts terzhney, e.g., successively, wherein said zone is 0.2-0.3 of the larger side section of the rod.