RU2398301C1 - Three-phase current-limiting reactor for motor smooth-starter - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: three-phase current-limiting motor smoother starter comprises face and side structural elements that form housing. Phase windings are arranged vertically with spacers between wire rows to form vent channels. Bearing elements comprise plates and cross pieces with dampers arranged between insulation face elements and phase windings. Tightening elements represent plates with studs. Every isolating cylinder accommodates multi-face phase winding locked in face zones by tightening elements via dampers. Four-beam bearing and face elements are connected crosswise and locked between lateral structural elements. Phase winding wire cross section is selected subject to tolerable wire heating on starting the motor. Distance between phase windings is selected subject to mutual inductance required to ensure reactor inductance that allows providing necessary insulation for corresponding voltage class.

EFFECT: lower labor input and reduced consumption of major materials, higher reliability and reparability.

8 cl, 2 dwg

Description

The invention relates to the field of electrical engineering, in particular to three-phase current-limiting reactors, and can be used to protect the soft starter (SCP) of the electric motor.

Known three-phase current-limiting reactor type RTST-6-100-2,2 (see the product catalog of RosEnergoTrans, Yekaterinburg, 2007), containing vertically mounted phase windings made of a special reactor cable in silicone insulation, wound on insulating cylinder in rows parallel to its axis. Between the rows of wires installed gaskets made of fiberglass in the form of rails to create ventilation ducts. Each winding is pressed with end elements in the form of an upper and lower crosspiece made of massive fiberglass beams, pulled together at the edges with non-magnetic metal studs. The basis for the installation of phase windings are supporting insulators attached to the cross pieces, connecting the phase windings in a single design. The findings of the windings are led to the edges of the crosses, where they are welded to the contact plates for external connections. The specified reactor is used in soft starters (UPP) of the UBPVD-S series of powerful synchronous electric motors with a voltage of 6-10 kV.

The disadvantages of the analogue are the large overall dimensions, high consumption of the reactor cable and insulating materials, causing a high cost of both the reactor itself and the reactor cabinet used to protect maintenance personnel; the use of a special expensive multi-core reactor cable with silicone insulation, which significantly increases the cost of the reactor.

Closest to the claimed invention is a three-phase current-limiting reactor of the type RTST-10-250-0.87 (Product catalog: "Transformers, autotransformers, electric reactors, switches, disconnectors", OJSC "Electrozavod", Moscow, 2000), adopted for the prototype, containing the Central, end and side structural elements that form the frame, vertically arranged phase windings with spacers between the rows of wires forming the vertical ventilation ducts, supporting elements, crimping elements.

The specified reactor is also widely used in soft starters of the UBPVD-S series.

The disadvantages of the prototype reactor are the high consumption of basic materials, the complexity of the design of the reactor, the complexity of the manufacturing and assembly of the reactor, insufficient reliability and low maintainability.

When the reactor is part of the soft starter, the winding wire of the phase windings of the prototype reactor does not have time to heat up significantly, which indicates the redundancy of its cross section. The turns of the phase winding wire are wound around the circumference and pressed to the ventilation gaskets in a limited number of places (12 places around the circumference). As a result, the chord distance between adjacent gaskets is 15-18 cm, due to which the arrow of the wire sag can reach 1 cm. In emergency mode, the electrodynamic forces in the phase winding tend to compress the outer rows of turns and stretch the inner rows. As a result of this, the wire in the outer rows tends to bend towards the center of the phase winding, violating its strength and the degree of crimping the phase winding through the support rings. If the bending arrow is too large, the wire can bend up to the next row, which does not exclude the breakdown of the wire insulation and the formation of a short-circuited coil in the phase winding. This leads to insufficient reactor reliability.

The central structural element is made in the form of a pipe with structural grooves into which the supporting elements are inserted and with which the phase windings are crimped. The presence of grooves in the central element of the frame leads to a weakening of the entire reactor structure and, for its strengthening, requires thick-walled construction, and since the central element is made of high-strength fiberglass, this leads to an increase in the consumption of insulating material, increasing the cost of the reactor. The same drawback (the implementation of the Central grooves on both sides of the support elements) leads to the implementation of bulky support elements in the form of plates of high-strength fiberglass. The implementation of the Central grooves on both sides of the support elements and grooves on the Central structural element of the frame increases the complexity of manufacturing these elements of the reactor. The implementation of the end elements of non-magnetic stainless steel 6-beam and welded also increases the consumption of materials and the complexity of manufacturing.

The manufacture of phase windings from copper wire with glass insulation impregnated with organosilicon varnish, winding the entire three-phase set of phase windings with the simultaneous installation of: support rings and their fixation to the outer wires, gaskets between rows of wires, support elements and their fixation in the central structural element is carried out from one installation on a special machine and, therefore, requires additional special equipment for assembling and disassembling the reactor. This disadvantage also leads to an increase in the complexity and costs of its manufacture. When repairing, for example, the middle winding, complete disassembly and assembly of the entire reactor is required using special tools for dismantling and mounting the windings. This characterizes the prototype in terms of design imperfections and low maintainability.

The technical result of the claimed invention is a significant reduction in the complexity of manufacturing and consumption of basic materials, overall dimensions and improving reliability and maintainability, reducing the cost of the reactor.

The technical result is achieved by the fact that in a three-phase current-limiting reactor for a soft starter of the electric motor, containing end and side structural elements forming a frame, vertically arranged phase windings with spacers between the rows of wires, forming ventilation ducts, supporting elements, crimping elements, tightening elements are introduced, shock absorbers, insulating cylinders, on each of which there is a corresponding phase winding, made at least in the form of a polygon nnika, fixed in the end zones through the shock absorbers by the tightening elements, and the supporting and end elements made of at least 4-beam are connected crosswise and fixed between the side structural elements. The tightening elements are made in the form of strips with fixing elements. Supporting elements additionally contain crosses with shock absorbers. Between the end elements and the phase windings are crosses with shock absorbers. End elements are made of at least insulating material. The cross section of the phase winding wire is selected from the condition of its allowable heating during the start of the electric motor. The distance between the phase windings is selected taking into account their mutual inductance from the conditions of the required reactor inductance, providing the necessary insulation level for the corresponding voltage class. The fixing elements are made in the form of studs.

Figure 1 presents a front view of the reactor, figure 2 is a top view where the following notation is taken:

end elements - 1, 2;

lateral structural element - 3;

phase winding - 4;

gaskets - 5;

supporting elements - 6, 7;

crimping elements - 8;

insulating cylinder - 9;

tightening elements - 10, 11;

shock absorbers - 12.

The reactor contains end 1, 2 and side 3 structural elements, vertically arranged phase windings 4 with spacers 5 between the rows of wires, forming ventilation ducts, supporting elements 6, 7, crimping elements 8, insulating cylinders 9, tightening elements 10, 11, shock absorbers 12 .

Shock absorbers 12 are made in the form of rectangular plates, at least of silicone rubber.

Each phase winding 4 is wound on a corresponding insulating cylinder 9 and is made in the form of a polyhedron. Between the rows of wires of the phase windings 4, gaskets 5 of insulating material are formed, forming ventilation ducts. The winding wire of the phase winding 4 between 2 adjacent spacers 5, wound in a straight line, forms the side of the polyhedron. The shape of the polyhedron of the phase winding 4 provides a strong tension of the winding wire. In this case, the wire only works for breaking and is able to withstand high electrodynamic forces, which eliminates its sag in the direction of the adjacent row. Each phase winding 4 is fixed in the end zones through shock absorbers 12 by means of tightening elements 10 and 11, made in the form of strips (10), and fixing elements in the form of studs (11) installed on the outer and inner surfaces of the phase winding 4. Phase winding 4 is located on the supporting elements 6 and 7. The supporting elements 6 and 7 in the form of plates (6) and crosses (7) with shock absorbers 12 are connected crosswise and made at least 4-beam. The ends of the supporting elements 6, 7 are fixed between the lateral structural elements 3, made in the form of rails. The distance between the phase windings 4 is calculated from the conditions of the required reactor inductance, taking into account the mutual inductance of the phase windings and provides the necessary insulation level between the phase windings for the corresponding voltage class.

End elements 1 and 2 are made of insulating material, at least 4-beam. Between the end elements 1 and 2 and the phase windings 4 there are crosses 7 with shock absorbers 12 of the supporting elements.

The upper end element 1 is equipped with crimping elements 8. The end elements 1 and 2 are located above and below the three-phase reactor structure, their ends are fixed between the side structural elements 3, forming a vertical three-phase reactor structure.

The reactor is included in the input circuit of the soft starter device and is designed to protect the thyristors of the device in emergency mode. The total operating time of the soft starter device usually does not exceed 60 s with two pauses of 5 minutes.

The cross section of the phase winding wire is selected from the condition of obtaining the required reactor inductance, taking into account the mutual inductance of the phase windings, but not less than the permissible value of the insulating level for the corresponding voltage class. The cross section of the phase winding wire depends on many factors:

- heating of the wire during start-up and cooling during pauses;

- heating the wire with the emergency current of the device;

- changes in the resistivity of the wire due to its heating;

- on the properties of the material of the wire, on the shape of the winding and on the number of gaskets between the rows, reducing the sag;

- the magnitude of the electrodynamic forces and the time of their action.

Electrodynamic forces depend on the size of the phase windings and on the distance between them. The duration of maximum electrodynamic forces depends on the magnitude of the active resistance of the phase winding. The dimensions of the phase winding, in turn, depend on the cross section of the wire.

Considering the multi-criteria nature of the problem being solved, the choice of the dimensions of the reactor construction elements and the optimal section of the phase winding wire was carried out using computer simulation of thermal, electromagnetic and electrodynamic processes using the Elcut 5.5 program.

With a decrease in the cross section of the wire, the active resistance of the phase winding increases, which leads to a significant decrease in the decay time constant of the transient process of the short circuit current. The current drops much faster from the shock value to the steady state (a difference of 2.54 times). The design of the reactor and the phase winding wire are experiencing maximum effort for less time, which simplifies the design of the reactor.

The reactor phase winding wire must withstand not only heating with a starting current for 60 s with pauses of 5 minutes, but also additional heating with a short-circuit current in the soft starter during the protection operation time installed at the input of the device. Typically, the response time of the protection does not exceed 0.5 s, and the magnitude of the emergency current is 8-12 times higher than the nominal value.

In addition, the cross section of the wire must have the necessary mechanical strength under the action of dynamic forces on it both inside the phase winding and between the phase windings. This circumstance is especially important for reactors with a reduced wire cross-section (it should be noted that in reactors operating in a continuous mode, the wire cross-section is several times higher than in the proposed reactor, therefore, checking the wire for dynamic stability of the phase winding under emergency currents is of an auxiliary character) .

Reducing the diameter of the phase winding increased the resistance of its wire to electrodynamic forces arising in the winding. In emergency mode, the electrodynamic forces in the phase winding tend to compress the outer rows of turns and stretch the inner ones. As a result, the wire in the outer rows tends to bend towards the center of the phase winding, violating its strength and the degree of crimping. With a large arrow, the wire can bend down to the next row. In this case, a breakdown of the insulation of the wire and the formation of a short-circuited coil in the winding are possible. The winding of the phase winding in the form of a polyhedron helps to ensure that the winding wire is tightly tensioned, when the reactor operates in the wire, there are tensile forces, the resistance to which is several times greater than the bending forces, which prevents the wire from sagging to the next row and, therefore, provides the strength of the phase winding.

It should be noted that the choice of aluminum as the material of the wire for the phase winding is not due to its cost, as in other reactors or transformers, but to its physical properties. If we compare the specific heat and the modulus of longitudinal elasticity (Young's modulus) of aluminum and copper, in aluminum they are higher. Since the time of smooth start-up of the electric motor and the mechanism does not usually exceed 60 s, during this period mainly only the heating of the wire occurs, its cooling is small. Therefore, the choice of wire material with high heat capacity, such as aluminum (with high heat storage properties), allows to further reduce the wire cross section.

The heating of the studs during the start-up of the electric motor is also negligible, and this fact allows the use of studs made of ferrous metal.

In the proposed reactor, the end elements can be made, for example, of fiberglass. Optimization of the cross section of the winding wire allowed to significantly reduce the wire consumption and the diameter of the phase windings, which significantly reduced the magnitude of the electrodynamic forces between the windings. The distance between the phase windings was reduced to a value determined by the test voltage between them. The material of the wire with high heat capacity - aluminum (with high heat storage properties) further reduced the wire cross section. The fixation of the supporting elements in the side structural elements made it possible to redistribute the forces between the phase windings on the reactor structure, make it strong with minimal consumption of fiberglass, and reduce the specific pressure on the phase winding wire.

The assembly of the reactor does not require special equipment and tools, and labor costs are minimal.

All of the above advantages of the proposed technical solution significantly reduced overall dimensions, material consumption and the complexity of manufacturing and assembling the reactor, and increased the reliability of the design during operation.

The tests of the prototype reactor also showed that the proposed design is simple and reliable in operation, has small overall dimensions and weight, low manufacturing complexity, and high maintainability.

The inventive reactor was successfully tested, and in the near future it is planned its serial production.

Claims (8)

1. Three-phase current-limiting reactor for a soft starter of an electric motor, containing end and side structural elements forming a frame, vertically arranged phase windings with gaskets between rows of wires, forming ventilation ducts, support elements, crimping elements, characterized in that tightening elements, shock absorbers are introduced , insulating cylinders, on each of which there is a corresponding phase winding, made at least in the form of a polyhedron, is fixed I in the end zones through the shock absorbers by the tightening elements, and the supporting and end elements made of at least four beams are connected crosswise and fixed between the side structural elements. 2. Three-phase current-limiting reactor for a soft starter of an electric motor according to claim 1, characterized in that the tightening elements are made in the form of strips with fixing elements. 3. A three-phase current-limiting reactor for a soft starter of an electric motor according to claim 1, characterized in that the support elements further comprise crosses with shock absorbers. 4. Three-phase current-limiting reactor for a soft starter of an electric motor according to claim 3, characterized in that crosses with shock absorbers are located between the end elements and the phase windings. 5. Three-phase current-limiting reactor for a soft starter of an electric motor according to claim 1, characterized in that the end elements are made of at least insulating material. 6. Three-phase current-limiting reactor for a soft starter motor according to claim 1, characterized in that the cross-section of the phase winding wire is selected from the condition of its allowable heating during the start of the electric motor. 7. A three-phase current-limiting reactor for a soft starter of an electric motor according to claim 1, characterized in that the distance between the phase windings is selected taking into account their mutual inductance from the conditions of the required reactor inductance, providing the necessary insulation level for the corresponding voltage class. 8. Three-phase current-limiting reactor for a soft starter of an electric motor according to claim 2, characterized in that the fixing elements are made in the form of studs.

Images