| 摘要 |
<p>A circuit for detecting excess load a.c. and various developed forms of it for motor starting circuits and the like, using the nonlinear magnetic characteristic of a core with hysteresis, is presented. The basic circuit consists of a current transformer with a primary winding (5) through which the alternating load current (9) flows, a secondary winding (6) through which a direct bias current (IB) flows, and a core (3) with a square loop hysteresis characteristic. The bias current in the secondary has such a magnitude that the core provides no effective coupling between the windings unless the load alternating current exceeds the required threshold. In this case pulses are produced in the secondary winding coincident with teh peak values of the load currents.</p> |
