| 摘要 |
The invention relates to an electrical safety device controlled by mutually independently generated pulse trains (ia1, ib1) for providing alternating current (iL1) through a winding (L1) only as long as the pulses in the pulse trains occur alternatingly and the components in the safety device are not faulty. The safety device in accordance with the invention includes at least one pair of switching devices (T1, T2) provided with control electrodes (a1, b1) each adapted for receiving a pulse train for alternatingly making the switching devices (T1, T2) conductive and non-conductive. The switching devices (T1, T2) are either connected in series between both poles of a DC voltage source, one end of the windings (L1) being connected to the connection point between said switching devices (T1, T2) while the other end of the winding (L1) is connected either to the center tap of the DC source, or to a potentially stable point via a capacitor (C1) or to the connection point between a further pair of like switching devices provided with control electrodes, each of which is also adapted for receiving a pulse train for making said further pair of switching devices alternatingly conductive and nonconductive, or they are connected with one of their poles to the one pole of the DC voltage source, while the other poles of the switching devices are connected to either end of the winding, which has a center tap connected to the other pole of the DC source. |
