CN108447748A - A Vacuum Interrupter Using an Externally Applied Rotating Magnetic Field and Its Direct Current Breaking Method - Google Patents

Abstract

The invention discloses a vacuum interrupter using an externally applied rotating magnetic field and a method for breaking a direct current, belonging to the field of electric system circuit breakers; the vacuum interrupter using a rotating magnetic field includes a vacuum interrupter and a plurality of external coil units; Breaking method: 1) When a fault occurs, the contacts of the vacuum interrupter are opened to generate an arc; 2) A current with a phase difference is passed through several pairs of coils arranged outside the vacuum interrupter to generate a rotating magnetic field; 3) The arc is rotating Moving under the action of a magnetic field, the arc voltage rises to the system voltage, and the arc is extinguished, thereby realizing breaking.

Description

A Vacuum Interrupter Using an Externally Applied Rotating Magnetic Field and Its Direct Current Breaking Method

technical field

The invention relates to the technical field of power system circuit breakers, in particular to a vacuum interrupter using an externally applied rotating magnetic field and a method for breaking a direct current.

Background technique

1. The low-voltage DC power system is more and more widely used in the field of ship power system, telecommunication equipment power distribution system, subway and other rail transit traction power distribution systems and DC micro-grids composed of renewable energy. Low-voltage DC circuit breakers are key equipment for the safe operation and protection of low-voltage DC power grids, and their performance is critical to the formulation of system protection strategies and engineering realization. However, since the DC current does not have a natural zero-crossing point, the arc extinguishing during the breaking process mainly depends on increasing the arc voltage to limit the current. At present, the relatively mature current limiting technology in low-voltage DC circuit breakers includes 1) using the near-cathode voltage drop of the arc, and using metal grids to divide the arc into series short arcs to increase the arc voltage; 2) using a magnetic field to elongate the arc horizontally; 3) Increase the pressure of the gas medium in the arc extinguishing chamber or blow the arc. At present, air circuit breakers are mainly used for breaking low-voltage DC, which are larger in size and longer in breaking time.

2. Vacuum circuit breakers have the advantages of small size, simple maintenance, high reliability, and little impact on the external environment, and have been widely used in the field of medium-voltage AC. However, the arc voltage of the vacuum circuit breaker is small when the arc is extinguished, which limits its application in the field of low-voltage DC breaking.

It can be seen from the above that, on the one hand, the field of low-voltage DC breaking has higher requirements on the performance of circuit breakers; on the other hand, vacuum circuit breakers have a series of excellent performances. However, if you want to apply vacuum circuit breakers to low-voltage DC breaking, you need to use effective technical means to increase the vacuum arc voltage and force the current to cross zero.

Contents of the invention

In order to overcome the above-mentioned problems in the prior art, the object of the present invention is to provide a vacuum interrupter using an externally applied rotating magnetic field and a method for breaking DC, which can apply the vacuum interrupter to low-voltage DC interrupting and improve vacuum Arc voltage, limit current, achieve fast and reliable breaking, and ensure safe operation of the system.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A vacuum interrupter using an externally applied rotating magnetic field, consisting of a vacuum interrupter 1 and an external rotating magnetic field generating device, the rotating magnetic field generating device mainly consists of several pairs of coils symmetrically arranged around the vacuum interrupter Each pair of coil units 2 passes currents i ₁ , i ₂ . . . i _n with a certain phase difference.

Further, the direction of the rotating magnetic field generated by the external rotating magnetic field generating device is not parallel to the direction of the arc column axis of the arc during arcing, and the rotating magnetic field has a component perpendicular to the axis of the arc column.

Further, each pair of coil units 2 is formed by connecting two opposite coils in series, and each coil is formed by multi-layer winding of a good conductor such as copper wire covered with insulating varnish.

Further, the currents passing through each pair of coil units are respectively i ₁ , i _{2 .} . . i _n , and the amplitudes of i ₁ , i ₂ . _. .

Further, the frequencies f ₁ , f _{2 . . . f n of} the currents i ₁ , i ₂ .

Further, the initial phases θ ₁ , θ _{2 .} . . _{θ n} of the currents i ₁ , i ₂ .

Further, the vacuum interrupter using an externally applied rotating magnetic field can be used as a low-voltage DC circuit breaker in conjunction with the operating mechanism, which is divided into three steps for breaking: when a low-voltage DC system fault occurs, the operating mechanism moves, and the vacuum interrupter The contacts in the chamber 1 are opened to generate an arc; the coil units 2 arranged around the vacuum interrupter 1 respectively pass currents i ₁ , i ₂ ...i _n with a certain phase difference to generate a transverse rotating magnetic field inside the vacuum interrupter 1 ; The arc moves under the action of the rotating magnetic field, and the arc voltage rises to realize breaking.

Compared with the prior art, the present invention has the advantages of:

A new method is proposed to effectively increase the vacuum arc voltage, and the vacuum interrupter is applied to low-voltage DC breaking, which has the advantages of simple maintenance, good insulation performance, high reliability and short breaking time.

Description of drawings

Fig. 1 is a structure diagram of a vacuum interrupter using an externally applied rotating magnetic field provided by the present invention.

Fig. 2 is a typical waveform diagram of vacuum arc voltage and current after applying the present invention.

Among them: 1 is the waveform diagram of the arc voltage, and 2 is the waveform diagram of the current. At t ₀ , the contacts of the vacuum interrupter are opened to start arcing; at t ₁ , the transverse rotating magnetic field is put into operation.

Detailed ways

Below in conjunction with accompanying drawing, the present invention is described in further detail:

A structure diagram of a vacuum interrupter using an externally applied rotating magnetic field provided by the present invention is shown in FIG. 1 , which mainly includes: a vacuum interrupter 1 and an external rotating magnetic field generating device. The external rotating magnetic field generating device is composed of n pairs of coil units 2, and each pair of coil units 2 is composed of two opposite coils connected in series. N pairs of coil units 2 are symmetrically arranged outside the vacuum interrupter 1, and each pair of coil units 2 has currents i ₁ , i ₂ ...i _n passing through them, with arbitrary amplitude and frequency, and initial phases θ ₁ , θ ₂ ... Theta ₃ can differ by any number of degrees.

The vacuum interrupter using an externally applied rotating magnetic field _can be used as a low-voltage DC circuit breaker in conjunction with the operating mechanism. 1 The contact opens to generate an arc, and the arc voltage is stable at about 20V; at time t ₁ , currents i _{1 , i 2 ...i n with a certain phase difference pass through the external n pair of coil units 2, and a current i 1} , i ₂ ...i _n with a certain phase difference is generated inside the vacuum interrupter 1 Horizontal rotating magnetic field; the arc moves under the action of the horizontal rotating magnetic field, and the arc voltage jumps from about 20V to 70-80V, exceeding the system voltage, forcing the loop current to cross zero, and the arc is extinguished.

Claims (7)

1. a kind of using the vacuum interrupter for applying rotating excitation field outside, it is characterised in that：By vacuum interrupter (1) and external rotary magnetic Field generating means composition, the external generation device of rotating magnetic field is mainly by n to being spatially symmetrically arranged in vacuum interrupter (1) Coil unit (2) composition of surrounding；Pass through the electric current i with certain phase difference in each pair of coil unit (2)₁、i₂…i_n。

2. according to claim 1 using the vacuum interrupter for applying rotating excitation field outside, it is characterised in that：The external rotation The arc column axis direction of electric arc is not parallel when the direction for the rotating excitation field that field generator for magnetic generates and arcing, and rotating excitation field has vertical Directly in the component of arc column axis.

3. according to claim 1 using the vacuum interrupter for applying rotating excitation field outside, it is characterised in that：Each pair of coil unit (2) it is connected in series by two opposite coils, each coil is formed by the conductor sandwich wound of outsourcing insulation coat of paint.

4. according to claim 1 using the vacuum interrupter for applying rotating excitation field outside, it is characterised in that：Vacuum interrupter (1) around arrange each pair of coil unit (2) in by electric current be respectively i₁、i₂…i_n, the amplitude of electric current is arbitrary, it is equal or Differ.

5. according to claim 4 using the vacuum interrupter for applying rotating excitation field outside, it is characterised in that：Each pair of coil unit (2) in respectively by the arbitrary electric current i of amplitude₁、i₂…i_n, power frequency f₁、f₂…f_nArbitrarily, equal or different.

6. according to claim 4 using the vacuum interrupter for applying rotating excitation field outside, it is characterised in that：Each pair of coil unit (2) in respectively by amplitude is arbitrary, the arbitrary electric current i of frequency₁、i₂…i_n, initial phase θ₁、θ₂…θ_nDiffer arbitrary degree Number.

7. claim 1 to 6 any one of them is using the direct methods that cut-off for the vacuum interrupter for applying rotating excitation field outside, special Sign is：The vacuum interrupter coordinates operating mechanism, can be used as low-voltage direct breaker；Low-voltage direct-current system failure When generation, operating mechanism action, vacuum interrupter (1) contact is opened, and electric arc is generated；It is arranged around vacuum interrupter (1) Respectively by the electric current with certain phase difference in coil unit (2), coil unit (2) will produce inside vacuum interrupter (1) Raw transverse rotating magnetic field；Electric arc will move under transverse rotating magnetic field effect, and arc voltage rises, when more than system voltage, Current over-zero, arc extinction, to realize that direct current is cut-off.