SYSTEM FOR PROTECTING ELECTROLYTIC CELLS AGAINST SHORT CIRCUITS

• US 3,723,285 A
• Filed: 10/13/1970
• Issued: 03/27/1973
• Est. Priority Date: 10/16/1969
• Status: Expired due to Term

• Current Assignee: Giorgio Abbate Daga, Lino Cerrocchi, Pietro Fracassi
• Original Assignee: Giorgio Abbate Daga, Lino Cerrocchi, Pietro Fracassi
• Inventors: Fracassi, Pietro, Daga, Giorgio Abbate, Cerrocchi, Lino
• Primary Examiner(s): Mack, John H.
• Assistant Examiner(s): Valentine, D. R.
• Application Number:
  US05/080,433
• Time in Patent Office: 896 Days
• Field of Search: 204/99,219-220,225,228,250
• US Class Current: 204/229.2
• CPC Class Codes: C25B 15/06 Detection or inhibition of short circuits in the cell
• CPC Class Codes: H02H 7/00 Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions

Abstract

A device for protecting electrolytic cells against short circuits, having an operational amplifier for each of the ascent bars of said cells, said amplifiers having adjustable gain and being supplied through difference inputs with voltage falls picked up on said bars, circuits being included for compensating the effects due to temperature variations of the bars as well as circuits for the rejection of the common mode voltages due to anodic transversal voltages, the output voltages from said operational amplifiers supplying an averaging circuit for determining the average voltage and a discriminating circuit for determining the highest voltage, the outputs of said averaging and discriminating circuits terminating at a comparator circuit in its turn associated with an alarm and/or control unit.

Claims

1. A device for protection against short circuits in electrolytic cells, comprising:

a plurality of anodes operatively associated with said cells;

ascent bars connected to said anodes and carrying current therein;

at least one operational amplifier having adjustable gain operatively associated with each of said ascent bars;

difference input means supplying said amplifiers with voltage falls picked up on said bars, said difference input means including symmetrically connected means compensating the effects of temperature variations of said bars and means rejecting common mode voltages due to anodic transversal voltages;

means carrying output voltages from said operational amplifiers to averaging circuit means determining the average voltage and to discriminating circuit means determining the highest voltage obtained from said difference input means; and

means carrying the outputs of said averaging and discriminating circuit means to a comparator circuit operatively associated with control means.

2. A device according to claim 1, wherein each of said operational amplifiers includes an H-connected resistive network in negative feedback arrangement for gain control, said H-connected network including a potentiometer in its middle branch.

3. A device according to claim 2, wherein opposite branches of the remaining four branches of said H network comprise resistors of equal value.

4. A device according to claim 1, wherein said compensating means includes passive network means having a coefficient of temperature substantially equal to the a coefficient of temperature of the material of which said bars are constructed, said compensating means contacting said bars and being series connected to input connectors of said operational amplifiers.

5. A device according to claim 1, wherein said averaging circuit comprises a star network of resistors connected to the outputs of said operational amplifiers and the device further includes a potentiometer means controlling an alarm level, said averaging means being connected to the input of said potentiometer means, and said potentiometer means being calibrated in percent of average voltage.

6. A device according to claim 5, wherein said potentiometer means is connected to at least an input connector of an error amplifier, at least another input connector of which is supplied with said highest voltage, the error amplifier being triggered when the difference between these input voltages exceeds a value depending on the voltage supplied by said potentiometer means.

7. A device according to claim 1, wherein said discriminating circuit comprises a star network of diodes connected in series to the outputs of said operational amplifiers and the device further includes diode means for compensating temperature variations of the potential across said diodes in their conductive state.

8. A device according to claim 1, further comprising time-delay circuit means for adjusting delay time and for preventing transmission of transient irregularities connected between said comparator circuit and said control means, said time delay circuit including a potentiometer for regulating the delay time.

9. A device according to claim 1, further including a voltmeter having a plurality of operative positions, said voltmeter being connected at the outputs of said operational amplifiers and said averaging circuit, said voltmeter being operative in one state to read the currents of said bars and in a second operative state to read average current.

10. A device according to claim 2, wherein each of said operational amplifiers further includes a low-pass filter connected in negative feed-back arrangement.

11. A device according to claim 1, wherein said compensating means includes passive network means symmetrically connected at the inputs of said operational amplifiers.

12. A device according to claim 11, wherein said passive network means comprises thermoelectric elements, and wherein each of said bars is symmetrically provided with two of said thermoelectric elements.

13. A device according to claim 12, wherein said thermoelectric elements comprise resistors housed in caps screwed directly onto said bars, said resistors being series connected to input connectors of said operational amplifiers.

14. A method for protecting against overloads in electrolytic cells, comprising the steps of:

connecting a plurality of anodes with at least one cathode;

measuring voltage drops across predetermined portions of the connecting links between said anodes and said at least one cathode;

averaging said voltage drops;

discriminating said voltage drops to obtain the highest value voltage drop; and

obtaining a difference voltage between said highest value voltage drop and said average voltage drop.

15. A method according to claim 14, comprising the further step of amplifying said voltage drops;

and wherein said averaging step includes the further steps of obtaining a voltage proportional to the average value of said amplified voltage drops and adjusting said proportional voltage in a range from a value substantially equal to said average value to a value approximately 75 percent higher than saId average value.

16. A method according to claim 14 wherein said step of obtaining a difference voltage includes the further step of obtaining a signal of predetermined polarity when said highest value voltage drop exceeds said average voltage drop by a predetermined value which depends on said average voltage drop.

17. A method according to claim 14, wherein said measuring step includes the step of rejecting common mode voltages in said voltage drops.

18. A device for protecting electrolytic cells against short circuits, comprising:

a plurality of ascent bars connected to the anodes of said cells;

a plurality of operational amplifiers having adjustable gain;

difference input means connecting said operation amplifiers to respective ones of said ascent bars and supplying said amplifiers with voltage falls picked up on said bars, said difference input means including compensating means for compensating the effects of temperature variations of said bars and means rejecting common mode voltages due to anodic transversal voltages;

averaging circuit means connected to the outputs of said operational amplifiers for determining the average output voltage of said amplifiers;

discriminating circuit means connected to the outputs of said operational amplifiers for determining the highest voltage obtained from said difference input means;

comparator means connected to the outputs of said averaging means and discriminating means for comparing the outputs of the averaging and discriminating means; and

control means connected to the output of said comparator means, said control means being activated by the output of said comparator means.