| 摘要 |
<p>Sodium sulphur cells are commonly connected in parallel. It is a problem with such arrangements that if one cell sustains a short circuit failure, the parallel connected cells discharge through it. In an embodiment disclosed, a switch (12), series connected to a cell (10) or series of cells, goes open circuit should current in excess of a predetermined value and consequently associated with the failure of a cell (10), flow through the switch (12). The switch (12) comprises a conducting rod separated into two portions (17, 18) and placed within a beta alumina tube (14) containing sodium (22): the level of the sodium (22) determines whether an electrical circuit is completed between the portions (17,18) rendering the switch 'on'. Sodium, containing within an outer conducting tube (21), also surrounds the inner beta alumina tube (14), there being an electrical connection from the outer tube, via a resistor (25), to one portion of the rod (18). Should a current flow in a direction (17/18) through the switch corresponding to discharge through a failed series connected cell, the arrangement is such that sodium (22) within the inner tube (14) is at a higher potential than sodium outside the inner tube (14). Accordingly, sodium cations flow out of the inner tube (14) resulting in the lowering of the sodium level until the switch (12) turns off, thus preventing further discharge through the failed cell (10).</p> |
