FR2465340A1 - FAST SWITCHING SYSTEM - Google Patents

Abstract

THE PRESENT INVENTION RELATES TO A RAPID SWITCHING SYSTEM FOR CUTTING OFF ELECTRIC CURRENTS OF HIGH INTENSITY IN A CURRENT TRANSMISSION CIRCUIT PLACED BETWEEN A SOURCE OF ENERGY AND A CHARGING CIRCUIT AND INCLUDES A DETECTION MEANS 84, A SWITCHING MEANS A SEMICONDUCTOR 76, A QUICK SWITCHING MEANS 80, AN EXCITATION 78 MEANS AND A CIRCUIT SWITCH MEANS RESPONDING TO OVERCURRENT 70, 72, 74. ON DETECTION OF A FAULT CURRENT BY THE MEANS FROM DETECTION GREATER THAN A PREDETERMINED VALUE, THE SWITCHING MEANS ACTIVATE THE EXCITATION MEANS SO AS TO OPEN THE NORMALLY CLOSED CONTACTS OF THE SWITCHING MEANS, AND ALLOWS THE INTERRUPTION OF THE CURRENT TRANSMISSION CIRCUIT THROUGH THE SWITCHING MEANS.

Description

1.

The present invention relates to pro-

protection against overloads or faults and, more particularly

  in particular, an advanced rapid switching system enabling the cutting of high intensity electric currents in the event of overload. In U.S. Patent No. 3,215,896 to D.P. Shattuck et al of November 2

  1965 describes an overload protection circuit

fast response which includes a silicon thyristor which is made conductive in response to an error signal, which causes the actuation of a fuse placed in series with

load.

  In U.S. Patent No. 3,493,815 to R. L. Hurtle of February 3, 1970, an electrical protection system is described comprising a fuse which is actuated by a silicon thyristor in response to

a fault current.

  In patent of the United States of America n ° 3.525.019 in the name of J. Lansch of August 18, 1970, a power protection circuit is described which includes a relay responding to an error voltage detection means for

  cut triacs and open the load lines.

  In the patent of the United States of America no. 3.868.552 of February 25, 1975 in the name of A. Wickson, there is described 2. an electrical circuit interrupter o an error signal

triggers a silicon thyristor, which causes circulation

  tion of a larger current in the secondary of a trans-

trainer and in fuses, which has the effect of reducing

  re the time required to open a circuit in re-

  response to electrical disturbances.

In the patent: of the United States of America No. 3,957,329 in the name of L. D. McConnell of May 18, 1976, a fault current limiter is described which comprises a fuse connected in parallel with the normally open contact.

of a vacuum switch.

  In the patent of the United States of America No. 3,987,340 in the name of FW Kussy of October 19, 1976, a motor controller is described consisting of overload relay heating elements, electromagnetic contactors, circuit breakers, and fusible elements in parallel

with resistances.

In industry there is an increasing interest in the use of inverters to vary the speed of induction motors. However, a significant problem arises

  found raised when using these inverters when

that some of the semiconductor switching devices

  the inverters do not switch

  tion or to a cut. This causes the application of a short

  circuit at the motor terminals, with the production of a short-circuit current and a negative torque, or braking effect,

important. In machines such as turbochargers

  centrifugal sors o coupling between engine and train

  drive is maintained by a positive torque on an ar-

short threaded, the braking effect can cause damage as a result of detachment by unscrewing between motor

and drive train. Thus, it is desirable to have

  install a switching system to interrupt

currents very quickly so as to disconnect the mo-

  inverter before a negative torque is developed

developed having sufficient value to cause the unscrewing

  ge. 3. The object of the present invention is to provide an improved rapid switching system allowing the disconnection of high intensity electric currents from a

charge in response to an overload.

  Another object of the present invention is to provide a rapid switching system which includes a vacuum interrupter having a plurality of contacts carrying the full load current and a plurality

  fuses connected in parallel to the contacts to avoid

carry that fault current.

Another object of the present invention is to provide a fast switching system which comprises a plurality of low caliber fuses responding to a

overload to very quickly interrupt a load applied

quée to a polyphase line.

  Another object of the present invention is to

  provide a rapid switching system which includes a

  fault detector, semiconductor, repellant coil

, a vacuum interrupter and blown fuses, all connected so as to very quickly disconnect a

charge of an energy source.

  Another object of the present invention is to pre-

  see a quick build switching system rela-

  tively simple and easy to manufacture.

According to the present invention, a system is provided.

fast switching me for disconnecting cables

  rants of high intensity in a circuit if-

killed between an energy source and a load circuit comprising a detection means, a semiconductor switching means, a rapid switching device, an excitation means, and a circuit switch means

in response to an overcurrent. The detection means is

connected to an energy source for the detection of an over-

  charge and provide a trigger signal. Way to

  semiconductor switching includes a control terminal

of which is coupled to the detection means to trigger this

  it in response to the trigger signal. Normally closed contacts of the fast switching device are

  connected in series with the current transport circuit.

The excitation means is connected in series with the means

  semiconductor switch to activate the device

switching. The switch means is coupled in parallel with the switching means to interrupt the

current flow in the transmission circuit

  rant so as to disconnect the load from the power source

  when an overload is detected by the means of

  tection. During the production of a fault current by the detection means, exceeding a predetermined value, the switching means actuates the excitation means so as to cause the opening of the contacts normally

  closed by the switching means and allow by means of inter-

switch to cut the current transport circuit.

  The present invention will be well understood during

the following description made in conjunction with the drawing

single attached in which the figure represents a diagram

  functional of a fast switching system according to the pre-

invention.

  The figure shows a functional diagram

fast switching system 10 according to the pre-

invention which is connected between a three-phase energy source, such as an inverter 12 and a charging circuit comprising a three-phase motor 14. The output terminals 18,

and 22 of the inverter 12 are connected to polypha- lines

  respective inputs 24, 26 and 28. The input terminals 30, 32 and 34 of the motor 14 are connected to polyphase lines

respectively 36, 38 and 40.

  The rapid switching system 10 includes a

  circuit switch means 42, responding to a surin-

current, and a switching circuit 44. The means of inter-

breaker 42 comprises a plurality of fuse terminals 46,

  48; 50.52; and 54, 56 which are disposed to a certain

  both of them. Conductors 58, 60 and 62 are connected respectively between terminals 46, 50, 54 and the polyphase lines 28, 26, 24. Conductors 64, 5. 66 and 68 are connected respectively between terminals 48, 52, 56 and the polyphase lines 40, 38, 36. Cut-off conductors, or fuses 70, 72 and 74 are fixed and coupled

between terminals 46, 48; 50, 52; and 54, 56, respectively.

  The switching circuit 44 includes a means of

  semiconductor switching 76 such as a thyristor at

  silicon, excitation means 78, switching means

  pide 80 and an energy supply means 82. We also have

  Means provided for detection such as a

fault 84 which is connected to the inverter 12 by conduc-

86 and 88 for the measurement of the current absorbed by the motor

  tor 14 or an excessive current flowing in the inverter 12. The thyristor 76 is arranged so as to be triggered

  by the output of detector 84 coupled to the terminals of the

  chette and cathode 90, 92 of the thyristor through-

diary of conductors 94, 96.

  The energy supply means 82 comprises

  an alternating voltage source 98, connected to the winding-

  primary 100 of a transformer 102. The voltage al-

  ternative to the secondary winding 104 of the transformer 102 is rectified by half-vibrations by a diode 106 and a resistor 108, to charge a capacitor 110 at a desired DC voltage level. This continuous tension of

capacitor 110 is applied to one side of the excitation means

tion 78 having the form of a repulsion coil. A diode 112 is connected to the terminals of the capacitor 110 so as to avoid its reverse polarization. The other side of the coil 78 is connected to the anode of the thyristor 76. The coil is used to create a magnetic field intended to cause the operation of the switching device 80, which

  is in practice a class vacuum switch-switch

sic comprising a plurality of contacts a, b and c. Each contact a, b and generally closed, is located in the current transmission lines. Note that the respective contacts

  a, b and c are arranged in parallel with the respective fuses

tifs 70, 72, 74.

The fault detector 84 is preferably a

  6. non-contact direct current and alternating current detector of a type manufactured and sold by the company known as F. W. Bell Inc. under the brand IF-5000M. We will find a

  detailed description of the operating theory and

characteristics of the repulsion coil 78 in the article entitled "Analysis of a Fast Acting Circuit Breaker Mechanism" by S. Basu and K.D. Srivastava, presented at the IEEE Summer Meeting and at the International Symposium on

high power testing, Portland, Oregon, July 18-23

  let, 1971. The vacuum interrupter may be of a fa-

  bricked by the company known as ITT Jennings and designated under the

no RP 157-1 with a typical response time of 0.3 mil-

second. The fuses 70, 72 and 74 can be of a type that is found on the market, the specific nominal current 1S of the fuses being selected so as to be

  adapted to the desired application.

In operation, when an over-

load, a fault current of a value greater than one

  predetermined value will be detected by the detector of

  84 is required and this will produce a trigger output signal

This will be applied to the decraxnde 90 terminal of the thym ristor 76. Such a signal will trigger the

  silicon thyristor, which will make it go to the con-

  conductor. In this state, the current will pass through the anode of the thyristor, and will excite the repulsion coil 78. The activation

  coil work will create a ma-

  which will cause the opening of normal contacts

  closed a, b and c of the vacuum interrupter 80 and the

  main load current from the inverter

their in fuses 70, 72 and 74. The charging current will continue to flow to motor 14 for a relatively short period necessary for the fuses to blown and

  at the opening of the circuit, which will have the effect of

  connect the load 14 from the source 12.

  In a particular case of application of this

  invention, the maximum fault current measured at the terminals

, 32 and 34 of motor 14 was equal to 4,000 or 2,828 amp -

7.

  res effective. In normal operation, the full current

  the motor load is typically 450 amps. It has also been determined by tests that the cut-off time (total of the melting time and the arc extinction time) of the switching system used should be less than 2

  milliseconds to avoid unscrewing or uncoupling

  of the drive train motor shaft. A fusi-

  ble of 500 amps would have a melting time just less than a second for operation in 60 periods. Thus, any attempt to normal blow with a 500 amp fuse would not provide adequate protection against unscrewing, since the opening of the circuit is too slow and therefore too high current is absorbed by

engine.

  However, a much shorter duration for

  connecting the power source 12 of the load 14 is obtained in the present invention thanks to the fact that the full load current of 450 amps passes through the contacts a, b and

  c of the vacuum interrupter 80 under standard conditions

  them and does not pass through fuses 70, 72 and 74. In addition

  very terms, the fuses are shunted by the contacts in

normal operating conditions and are not used

only for the passage of high overload intensities.

  As a result, much smaller fuses or fuses

sables at relatively low nominal current can be chosen to be mounted in the circuit and give a much shorter breaking time. If a 20 amp fuse with a breaking capacity of 200,000 amps is used, the breaking time in the event that the fault current is 4,000 amps would be approximately

  0.89 millisecond, after opening the contacts of the inter-

switch 80.

  From the above, it can be seen that the pre-

The present invention provides an improved rapid switching device which includes low-current fuses for disconnecting the motor from the inverter within a lapse of time.

relatively short time. In addition, the communication system

  8.Quick tation includes a silicon thyristor, a repulsion coil and a vacuum interrupter to deflect the

  fault current to the fuses.

  The present invention is not limited to the examples

  ples of realization which have just been described, it is on the contrary susceptible of variants and modifications which

will appear to those skilled in the art.

9.

Claims (5)

IONS CLAIMS   1 - Rapid switching system for cutting off high intensity electric currents in a current transport circuit between an energy source and a load circuit, characterized in that it comprises: - a detection means (84 ) connected to a source   energy to detect overload and pro-   draw a trigger signal; - a semiconductor switching means (76)   having a control terminal. coupled by means of detection tion for triggering the switching means in response to at the trigger signal;   - a fast switching device (80) comprising   carrying normally closed contacts which are connected in series with the current transport circuit; - an excitation means (78) connected in series with the semiconductor switching means for actuating the switching device; and - circuit switch means responding to an overcurrent (70, 72, 74) connected in parallel with the switching device to interrupt the flow of current in the current transport circuit so as to disconnect the load circuit from the energy source when an overload is detected by the detection means, the switching means actuating the excitation means   when the fault current from the detection means   tion exceeds a predetermined value, to cause the of the normally closed contacts of the switching means   tion and allow the switch to interrupt the current transport circuit. 2 - Rapid switching system according to resale   dication 1, characterized in that the detection means comprises   takes a fault detector (84). 3 - Rapid switching system according to resale   dication 1, characterized in that the switching means   semiconductor includes a silicon thyristor (76).   4 - Quick switching system according to the claim   10. cation 1, characterized in that the switching device   includes a vacuum interrupter (80).   - Fast switching system according to the res-   dication 1, characterized in that the excitation means takes a repulsion coil (78).   6 - Rapid switching system according to resale dication 1, characterized in that the switch means comprises a plurality of low current fuses (70, 72, 74) which are fixed to terminals distant from each other very.