Adjustable rotating magnetic field vacuum arc-extinguishing chamber
Technical Field
The invention relates to a vacuum arc-extinguishing chamber, in particular to a vacuum arc-extinguishing chamber with an adjustable rotating magnetic field.
Background
With the continuous expansion of the grid capacity and the continuous increase of the voltage class, the switchgear for control and protection of the power system is faced with more severe working conditions and more severe requirements. The vacuum switch uses high vacuum as an arc extinguishing and insulating medium, and the contact and arc extinguishing system is simple, has the advantages of high insulation grade, easy maintenance, long electric service life, suitability for frequent operation, small volume, light weight and the like, and is dominant in the medium-voltage field.
While vacuum interrupters have four common contact configurations. The contact comprises a disc-shaped flat plate butt-joint contact, a spiral transverse magnetic contact, a coil-shaped longitudinal magnetic contact and a cup-shaped longitudinal magnetic field contact.
The disc-shaped flat plate butt-joint type contact is the simplest structure in a vacuum arc-extinguishing chamber and is only suitable for low diffusion type arc current, and the current is generally lower than 5 kA. The high-voltage switch is widely applied to vacuum arc-extinguishing chambers for load current breaking and vacuum arc-extinguishing chambers for contactors, and the maximum breaking current is 4 kA. When the on-off current is large, the anode can generate spots, the vacuum arc can generate a strong contraction phenomenon, and the metal vapor arc can be changed from a diffusion type to a contraction type, so that the on-off failure is caused.
And the spiral transverse magnetic field contact is suitable for switching on and off a large-current arc. The contact uses the electrodynamic force generated by a transverse magnetic field to enable a large-current arc to rotate at a high speed on the contact; at the beginning, the molten metal bridge is broken between the contacts to generate electric arc, and the electric arc is maintained for a certain time; then the contact instantaneously rotates at a high speed along the periphery of the contact, the surface of the contact generates uniform and slight ablation, and heat is dispersed around the contact area; the diffusion type arc is forced to cut off the current when the current crosses zero because the arc is added with the continuous high-speed movement of the arc under the condition that the self-generated heat of the contact is insufficient.
The longitudinal magnetic field contact is also suitable for breaking high-current electric arcs. It is mainly characterized by that it utilizes longitudinal magnetic field to control vacuum electric arc so as to obtain uniform distribution of electric arc and reduce electric arc voltage, so that its breaking capacity can be raised. The longitudinal magnetic field is an axial magnetic field which is generated by that the breaking current flows through the contact and is along the arc column direction, so that the magnetic field is used for stabilizing the arc, the aggregation of the large-current vacuum arc on the surface of the anode can be fundamentally prevented, and the breaking capacity is greatly improved. At present, the contact form of the longitudinal magnetic field structure becomes the dominant structure of the contact of the high-current vacuum arc-extinguishing chamber.
As can be seen from the above, when using a disc-shaped flat plate butt-type contact, the anode may be spotted due to the absence of the transverse and longitudinal magnetic fields, and the arc may cause uneven ablation of the contact, reducing the electrical life of the vacuum circuit breaker. This therefore poses a major limitation on the use of disc-shaped flat plate butt-type contacts.
Disclosure of Invention
Therefore, in order to overcome the defect that the service life of the vacuum circuit breaker is reduced due to the uneven ablation of the electric arc to the contact, the invention provides an adjustable rotating magnetic field vacuum arc-extinguishing chamber, which comprises: the device comprises a pair of conducting rods, a shielding cover, a pair of disc-shaped contacts, an insulating shell, a rotating magnetic field generating device and an amplitude-frequency adjusting device;
the insulating shell is arranged outside the shielding case;
the rotating magnetic field generating device is fixed outside the insulating shell and is coaxially arranged with the disc-shaped contact;
the amplitude-frequency adjusting device is connected with the rotating magnetic field generating device and is used for adjusting the magnetic field generated by the rotating magnetic field generating device;
the conductive rod is connected with the disc-shaped contact;
the pair of disc-shaped contacts are coaxially and oppositely arranged in the shielding case.
The rotating magnetic field generating device is in a cylindrical shape formed by laminating soft magnetic sheets.
And a winding chute is formed in the inner side of the rotating magnetic field generating device.
And a coil winding is arranged in the winding chute and is connected with the amplitude-frequency adjusting device.
The amplitude-frequency adjusting device is communicated with three-phase power frequency alternating current.
The amplitude-frequency adjusting device adjusts the voltage and frequency output to the coil winding according to the magnitude of the switching current, and controls the strength of a longitudinal magnetic field and the strength and speed of a transverse rotating magnetic field generated by the rotating magnetic field generating device;
the longitudinal magnetic field and the transverse rotating magnetic field are combined into an oblique rotating magnetic field.
The number of the winding chutes is 6.
The coil winding is a three-phase single-layer winding, and the windings are symmetrically arranged.
Compared with the closest prior art, the technical scheme provided by the invention has the following beneficial effects:
according to the technical scheme provided by the invention, the rotating magnetic field generating device is completely arranged outside the insulating shell of the arc extinguish chamber, so that the possibility of gas generation is avoided, and the generated transverse magnetic field is more concentrated between the contacts, namely the electric arc part, so that the contacts can be more favorably switched on and off;
according to the technical scheme provided by the invention, the vacuum arc-extinguishing chamber is provided with an amplitude-frequency adjusting device, after three-phase alternating current is switched on, the frequency and the voltage of a power supply output to a winding coil are manually adjusted according to the magnitude of switching-off current, so that the rotating magnetic field generating device finally generates a corresponding transverse rotating magnetic field with constant amplitude and constant rotating speed and a longitudinal magnetic field with constant amplitude corresponding to the switching-off current value, and the transverse rotating magnetic field and the longitudinal magnetic field are synthesized to form an oblique rotating magnetic field inclined at a certain angle. Under the action of the transverse rotating magnetic field and the longitudinal magnetic field, the electric arc rotates on the surface of the contact at a high speed, so that the ablation of the surface of the contact is more uniform, the ablation and melting degree of the surface of the contact by the electric arc is reduced, the recovery speed of a medium after the arc is increased, the breaking capacity of the vacuum circuit breaker is improved, and the electric service life of the contact is prolonged;
according to the technical scheme provided by the invention, both the transverse rotating magnetic field and the longitudinal magnetic field are provided with the rotating magnetic field generating device;
according to the technical scheme provided by the invention, the rotating magnetic field generating device is in a cylindrical shape formed by laminating soft magnetic sheets, so that the eddy current effect is reduced;
according to the technical scheme provided by the invention, the winding chute is formed in the inner side of the rotating magnetic field generating device, so that a rotating transverse magnetic field and a rotating longitudinal magnetic field can be generated simultaneously.
Drawings
Fig. 1 is a schematic view of the overall structure of the vacuum interrupter according to the present invention.
Fig. 2 is a schematic view of a rotating magnetic field generating device of the vacuum arc-extinguishing chamber of the present invention.
Fig. 3 is an overall schematic view of a slot of the rotating magnetic field generating device of the vacuum arc-extinguishing chamber of the invention.
Fig. 4 is a front sectional view of a slot of the rotating magnetic field generating device of the vacuum arc-extinguishing chamber of the invention.
Fig. 5 is a schematic diagram of a three-phase winding of the vacuum interrupter according to the present invention.
Fig. 6 is a schematic diagram of the variation process of the rotating transverse magnetic field of the vacuum arc-extinguishing chamber according to the present invention.
Fig. 7 is a schematic diagram of a synthetic oblique magnetic field of the vacuum arc-extinguishing chamber according to the present invention.
Reference numerals: 1. a conductive rod; 2. a shield case; 3. a disc-shaped contact; 4. an insulating housing; 5. a rotating magnetic field generating device; 6. an amplitude-frequency adjusting device; 7. laminating into cylindrical soft magnetic sheets; 8. and (4) winding the coil.
Detailed Description
The adjustable rotating magnetic field vacuum arc-extinguishing chamber of the invention is described in detail with reference to the accompanying drawings and embodiments.
Fig. 1 is a schematic view of the overall structure of the vacuum interrupter according to the present invention. The invention comprises a conducting rod 1, a shielding case 2, a disc-shaped contact 3, an insulating shell 4, a rotating magnetic field generating device 5 and an amplitude-frequency adjusting device 6; the magnetic field generating device is fixed outside the arc extinguish chamber insulating shell and is arranged in the direction coaxial with the arc extinguish chamber. A winding chute is formed in the rotating magnetic field generating device; a coil winding is arranged in the chute; the coil winding is connected with the amplitude-frequency adjusting device.
The amplitude-frequency adjusting device is electrified with three-phase power frequency alternating current, and the output end of the amplitude-frequency adjusting device is correspondingly connected with the wiring end of the coil winding through a wire. The amplitude-frequency adjusting device rectifies three-phase power frequency alternating current into direct current, a controller of the amplitude-frequency adjusting device inverts the direct current into alternating current with corresponding voltage and frequency according to the magnitude of short-circuit current and outputs the alternating current to a winding coil, and the current flowing through the winding coil is increased along with the increase of the voltage output to the winding coil, so that the strength of a generated longitudinal magnetic field and the strength and the speed of a transverse rotating magnetic field are controlled, and the arc can be uniformly ablated on the surface of a contact under different breaking current levels.
Fig. 2 is a schematic view of a rotating magnetic field generating device of the vacuum arc-extinguishing chamber of the present invention. The rotating magnetic field generating device comprises a soft magnetic sheet 7 and a coil winding 8 which are laminated into a cylindrical shape. In a preferred embodiment, the cylinder is provided with a chute at 60 ° intervals, and the number of chutes is 6.
The soft magnetic sheet 7 may be made of an iron-cobalt alloy sheet.
Fig. 3 and 4 are an overall schematic view and a front sectional view of a slot of the rotating magnetic field generating device of the vacuum arc-extinguishing chamber according to the present invention. The rotating magnetic field generating device adopts soft magnetic sheets, and the soft magnetic sheets are laminated into a cylinder shape so as to reduce the influence of eddy current. The magnetic field generating device is internally provided with a chute so as to generate a transverse rotating magnetic field and a longitudinal magnetic field at the same time. Preferably, the soft magnetic sheet is made of iron-cobalt alloy sheet, and the chute angle beta of the chute is 7 degrees 37'.
Fig. 5 is a schematic diagram of a three-phase winding of the vacuum interrupter according to the present invention. The coil winding adopts a three-phase single-layer winding, and the windings are symmetrically arranged. Two straight line parts of the coil winding are inclined at an angle according to the requirement of the inclined groove. The winding coil is a mica flat copper wire, the turn-to-turn insulation is a mica powder tape flat package, and a polyterephalimide film is additionally wrapped at the interval turns at the two nose ends of the coil during winding so as to make up for turn-to-turn insulation damage caused in the forming process.
Fig. 6 is a schematic diagram of the variation process of the rotating transverse magnetic field of the vacuum arc-extinguishing chamber according to the present invention. When the amplitude-frequency adjusting device is electrified with three-phase power frequency electricity, the three-phase power frequency electricity supplies power for the coil winding through the amplitude-frequency adjusting device, and at the moment, the rotating magnetic field generating device can be equal to a stator of the motor. When the voltage and the frequency output by the amplitude-frequency adjusting device are fixed values, a longitudinal magnetic field with fixed size and a transverse magnetic field with fixed size and rotating speed are simultaneously applied to the magnetic field generating device in the direction parallel to the surface of the contact in the arc extinguish chamber. The amplitude locus of the transverse rotating magnetic field is a circle. The transverse rotating magnetic field rotates as the phase of the current in the coil windings changes. When the current in the coil winding changes by one sixth of a cycle, the transverse rotating magnetic field has rotated 60 ° clockwise.
After the three-phase alternating current is conducted, the amplitude-frequency adjusting device can manually adjust the power frequency and the voltage output to the winding coil according to the magnitude of the cut-off current, so that the rotating magnetic field generating device finally generates a corresponding transverse rotating magnetic field with constant amplitude and constant rotating speed and a longitudinal magnetic field with constant amplitude corresponding to the cut-off current value. Under the action of the transverse rotating magnetic field and the longitudinal magnetic field, the electric arc can not only rotate along the tangential direction of the contact, but also move outwards along the radial direction of the contact. Thus, the arc ablates the contact surface more uniformly, extending the electrical life of the contact. Meanwhile, due to the high-speed rotation motion of the electric arc, the diffusion of the energy of the electric arc is accelerated, the medium recovery speed after the electric arc is increased, and the breaking capacity of the vacuum circuit breaker is improved.
Fig. 7 is a schematic diagram of a synthetic oblique magnetic field of the vacuum arc-extinguishing chamber according to the present invention. The magnetic field generating device can simultaneously generate a longitudinal magnetic field with fixed size and a transverse magnetic field with fixed size and fixed rotating speed, and the longitudinal magnetic field and the transverse magnetic field are combined to form an oblique rotating magnetic field inclined at a certain angle, as shown in the figure

As shown. In the figure, the X-Y plane coincides with the surface of the contact, the origin of coordinates O coincides with the center of the circle of the surface of the contact, and the Z axis is perpendicular to the surface of the contact. An oblique rotating magnetic field synthesized by the longitudinal magnetic field and the transverse rotating magnetic field generated by the magnetic field generating device keeps a certain angle theta with an X-Y plane and rotates around a Z axis. The rotating angular speed omega is 2 pi times of the frequency of the current flowing in the winding coil, and the amplitude of the synthetic magnetic field is in direct proportion to the amplitude of the current flowing in the winding coil. When the on-off current value changes, the amplitude-frequency adjusting device can change the voltage and frequency output to the winding coil according to the magnitude of the on-off current required and the actual requirement of the magnetic field generating device, and further adjust the magnitude and the speed of the generated magnetic field, so that the magnetic field generated by the magnetic field generating device can enable the arc to uniformly ablate the surface of the contact under the condition of corresponding different on-off currents, and the on-off capacity is improved.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the scope of protection thereof, and although the present application is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: numerous variations, modifications, and equivalents will occur to those skilled in the art upon reading the present application and are within the scope of the claims appended hereto.