| 摘要 |
<p>A device for overload and short-circuit protection in low-voltage plants includes a circuit breaker (1, 2, 3) which is connected in series with a current limiter (4, 5) which comprises two parallel-connected current branches. One of the branches comprises a thermistor (4) with a positive temperature coefficient, whereas the other branch comprises an impedance (5) for current and voltage relief of the thermistor. The thermistor (4) comprises at least one body (10), provided with two parallel surfaces, of an electrically conductive polymer composition and two electrodes. At least one of the parallel surfaces on the body or one of the bodies of polymer composition is adapted to make free contact with an electrode (11) or with a parallel surface on another body of electrically conductive polymer composition. A pressure device is adapted to exert on the electrodes a pressure directed perpendicular to the parallel surfaces on the body, or the bodies, of polymer composition. The pressure device is preferably provided with pressure-exerting devices (15, 16, 17, 17a, 17b) with the ability to be resilient. After changing from a low resistance to a high resistance state, the thermistor returns to the initial resistance and is reusable after having been subjected to short-circuit currents.</p> |
