FR2634578A1 - LIQUID RHEOSTAT WITH ELECTROLYTE CIRCULATION - Google Patents

Abstract

The electrolyte 13 contained in a tank 10 is discharged by a turbine 18 via a distributor 14 and supply columns such as 31C in sets of electrodes each comprising an upper electrode 31A immersed in a lower electrode. 31B in the form of a channel which extends from an upstream end disposed opposite the supply column 31C, to a downstream end equipped with a weir valve 31D of adjustable height by means of a control 54. On thus constitutes a rheostat with electrolyte circulation easily adaptable to the most diverse applications.

Description

"Liquid electrolyte rheostat" The present invention

  generally relates to liquid resistance rheostats, in particular for the controlled start-up of electric motors. It relates more particularly to rheostats of the so-called electrolyte circulatiuon type where electrodes define between them a circulation volume for the electrolyte under the effect of an electrolyte.

means of drive.

  Such rheostats have in particular been described by the Applicant in EU-A171 317 where the electrodes themselves were adapted to form between them a holding capacity for the electrolyte in combination with means of evacuation suitable for ensuring in a controlled manner the

drain.

  The subject of the present invention is an improvement of the liquid resistance rheostats thus designed tending to improve the conditions of circulation of the electrolyte between the electrodes, in particular in the case of polyphase embodiments where it is important to achieve as complete a balancing as possible. operating conditions of a plurality of electrode sets

  respectively assigned to the various phases.

  Another object is to control with all the desirable flexibility the law of variation as a function of time of the resistance actually inserted by the rheostat into

the circuit served.

  To this end, the invention proposes, in a liquid-resistance rheostat of the kind considered with electrodes defining between them a circulation volume for the electrolyte under the effect of a pulse means, a substantially characterized arrangement for each game. of electrodes, by a circulation volume in the form of a channel delimited by an electrode, said by simple lower convenience, between an upstream end arranged facing a supply column and an equipped downstream end.

  a weir valve with adjustable height.

  Thanks to such an arrangement, the retention and circulation conditions of the electrolyte can be easily controlled in each set of electrodes by a positive and coordinated control valves correspondingdévoirsoirs, while the drain automatically results from the simple stop operation of the means impulse upstream of the

each channel.

  A rheostat thus developed offers the advantage of being easy to apply and adapted to start asynchronous motors with rotor start as that of stator driven motors thanks to the complete flexibility of determination of the law of variation as a function of time, conditions for filling circulation volumes

arranged between electrodes.

  The characteristics and advantages of the invention

  will emerge from the description which follows,

  By way of example, with reference to the accompanying drawings, FIG. 1 is a diagrammatic perspective view with various detachments of a liquid rheostat according to the invention; FIG. 2 is a sectional view along the broken plane

II-II of Figure 1.

  According to the embodiment chosen and shown, the invention is considered in its most common application when starting a three-phase asynchronous electric motor M from a three-phase power supply sector L1, L2, L3. These are connected to the three terminals M1, M2, M3 of the motor, on the one hand, via the starting rheostat whose assembly is designated by the reference 10, and, on the other hand, directly by a contactor

  11 which is adapted to close at the end of the start-up period.

  The rheostat 10 comprises a tank 12 of insulating material containing an electrolyte bath 13 in which is immersed a dispenser 14 of elongated parallelepipedal general shape also made of electrically insulating material and extending horizontally along most of the length of the tank . It has an end portion 15 of reduced height o the distributor has a suction pipe 16 equipped with a turbine 18 coupled to an electric motor 20 installed on the upper wall or ceiling of said end portion 15. In view of the inlet of the suction pipe 16 is disposed, moreover, a flap 21 hinged to an axis 22, free to oscillate between two abutments 23, 24 implanted on a rod 25 passing through the ceiling of the tank and resulting in a

control panel 26.

  Beyond its end portion 15, the tank 10 comprises a main portion 30 delimiting above the bath 13 an area occupied by the actual rheostat here comprising three sets of electrodes generally designated in Figure 1

by references 31, 32 and 33.

  These three sets of electrodes having a similar structure, it will suffice to consider in more detail one of them, for example the game 31 which appears in section at the

figure 2.

  In each set of electrodes, such as 31, there is thus a so-called upper electrode, 31A, plunging into a so-called lower, channel-shaped electrode 31B which extends from an upstream end connected to a supply column 31C, to a downstream end equipped with a spillway valve 31D forming a spillway. The electrodes are fixed to the insulating ceiling 35 of the elevated portion 30 of the tank by means of metal rods such as 41, 42 for the upper electrode and 43, 44 for the lower electrode,

  these rods terminating at appropriate connection terminals.

  Each lower electrode such as 31B, has a bottom wall 45 extending in a substantially horizontal plane between two vertical side walls 46, 47, the assembly forming a U-shaped channel connected on the upstream side to the column. feeding such as 31C. A number of plates, such as 48, electrically connected to the bottom 45, for example by welding, extend parallel to the side walls 46, 47: the number of these spacer plates 48 is two

in the example considered.

  Each upper electrode, such as 31A, comprises a horizontal plate 50 and, starting from the latter, vertical plates 51 in number corresponding to the number of gaps formed between plates of the lower electrode, this number being equal to three in each case. example and which can naturally vary according to the

power to dissipate.

  The electrodes consist of stainless steel plates or any other metal compatible with the nature of the electrolyte used. They are installed in such a way as to interlock by providing between them the spaces necessary for the circulation of the electrolyte and for the insulation

  required in the absence of electrolyte.

  Each slide valve such as 31D has its position in height determined by a pusher 53, these push rods made of insulating material being integral with a control shaft 54. Finally, each of the supply columns such as 31C which is made of a electrically insulating material is equipped with a shutter 55 with externally accessible control designed to create an adjustable pressure drop in order to equalize the discharged electrolyte flow rates in

  the various columns when the turbine is in action.

  The operation of the rheostat thus constituted can

to analyze as follows.

  At rest, the turbine 18 being stopped, all the electrolyte is in the tank, the flap 21 resting on its bottom stop 23. For starting, the turbine 18 driven by the motor 20 is actuated, it sucks the electrolyte at a rate adjustable by the position of the flap 21 which rises by suction in contact with the upper stop 24 whose position is determined by means of the flywheel 26. The flow rate in the dispenser 14 is divided between the

  columns 31C in equalized flows by adjusting the flaps 55.

  Each of these partial flows invades the channel formed by the corresponding lower electrode 31B and is retained in this channel at a level determined by the position of the control shaft 54; by acting on this position, it is therefore possible to modify the level of electrolyte in the electrodes and, consequently, the value of the resistance created between them. Any type of control may be used: manual, electromechanical, pneumatic or hydraulic, with any suitable law of variation, linear or nonlinear. The control can also be controlled by a microprocessor to the desired parameters: constant intensity - variable speed, intensity

  progressive- constant speed, etc ...

  Thus, in the case of a rotor start, it is possible to operate with a progressive rise of the overflow valves 31D, while for a statoric start, it is possible to set a

  predetermined level for obtaining a constant current.

  In any case, during the entire period of operation the electrolyte remains circulating in the

  electrodes and at the exit of these it returns to the tank.

  At the end of the start, the turbine is stopped, and this results in a rapid emptying of the electrodes, the shutter 21 being then

  dropped on the bottom stop 23.

  The invention is of course not limited to the details of the embodiment which has just been described for explanatory purposes. Thus, for example a simplification may consist in arranging the flaps 55 for distribution of the flow not in the columns with accessibility of their axes for an adjustment of the outside, but within the distributor itself

  for an adjustment of their positions once and for all.

Claims (4)

  1) Liquid resistance rheostat of the kind comprising, on the one hand, a vessel (10) containing electrolyte (13) and, on the other hand, at least two electrodes (31A, 31B) which, at a distance one of the other, are intended to be connected one to a power source, the other to an apparatus to be served, in particular an electric motor, said electrodes defining between them a circulation volume for the electrolyte under the effect of a pulse means (18), characterized by a channel-shaped capping volume delimited by a lower electrode (31B) between an upstream end disposed facing a supply column (31C) and a downstream end   equipped with an overflow valve (31D) of adjustable height.   2) rheostat according to claim 1, characterized in that the pulse means is constituted by a turbine (18) adapted to discharge the electrolyte in a distributor (14) which are connected to the supply columns (31C) electrodes.   3) Rheostat according to claim 2, characterized in that the flow of electrolyte directed towards the electrodes is adjusted by means of a flap (21) associated with the suction of the turbine (18), distribution flaps (55). ) being associated,   on the other hand, to the supply columns of the electrodes.   4) Rheostat according to any one of the claims   i to 3, characterized by means (54) for common control of the position of the overflow valves (31D) respectively   associated with a plurality of electrodes (31, 32, 33).