DE1765125C - Circuit arrangement for switching an inductive consumer - Google Patents

Description

1. Circuit arrangement for switching an inductive load via a mechanical switch in DC circuits, in which the mechanical switch has a series circuit consisting of a protective resistor and a quenching capacitor and a diode in parallel with the inductive load, characterized in that it is known per se Way with the mechanical switch (S) and the inductive consumer (//) a thyristor (Γ) has happened in a row, deseen control electrode with (Z) or which is acted upon if the failure (S) has been closed beforehand, and that the The thyristor (T) is deleted by opening the scolding (S).

2. Circuit arrangement according to claim 1, characterized in that the inductive consumer, the excitation winding of the lifting magnet is used for the Ppiersere a formulant printing, from ZtHKftmrnth (Z) a form end signal obtained from a data processing system (A) is used and the mechanical switch (X) van der Paper scissors receive an opening order as soon as the penis lever is completely open.

eTereWeevJP ■ e ^ Pnev «M ^ lvvllllllVI | IVfl

Claims (1)

The invention relates to a circuit arrangement for switching an inductive load via a mechanical switch in direct current circuits, in the case of the spark quenching the mechanical switch one of a protective resistor and one Quenching capacitor existing series circuit and the inductive consumer a diode is in parallel. Are connected to an inductive load, such as the lifting magnet for the paper scissors a form printer, large currents switched, so the switch is at its contacts by contact bouncing, Sparking and erosion are subject to severe wear and tear, which affects its service life shortened. In order to counteract this and thus to extend the service life of the switch, it is all- »5 Commonly known, the switch one from a quenching capacitor and a protective resistor existing series circuit and the inductive consumer a To connect diode in parallel. The polarity of the diode is such that the ao that occurs when the switch is opened Countercurrent is short-circuited directly at the inductive consumer. In principle, it is possible to use an electronic switch instead of mechanical switches without their disadvantages Switches made of semiconductor diodes, transistors as or other semiconductor elements such as thyristors, to use. The forward voltage is, however, not nearly as low as with a mechanical one Switch and, in turn, the storage resistance considerably lower than the insulation resistance of the isolating distance of the mechanical switch. For this it is from the German patent specification 1 114 225 and similar Form also known from the German Auslegeschrift 1 238 541, mechanical and electronic To combine switching elements, especially in that the electronic switching elements be bridged in the on state by a parallel connected mechanical switch and in the blocked State relieved of voltage by a mechanical switch connected in series with them are. In addition, a device for disconnecting a load from a direct current network is known from Swiss patent specification 391 053, which device consists of a thyristor and an isolating contactor as a mechanical switch. The isolating contactor should only be operated when the thyristor is not drawing any current. Since the mechanical switch only switches in the de-energized state, no precautions are then necessary to prevent excessive wear and tear on the mechanical switch due to the formation of sparks and erosion. For this, however, complex ignition and extinguishing devices are required, because the thyristor independently gnSndet tew regardless of the state of the isolating protection. deleted M are irbB. The disadvantage of this arises because of the good protection of the esc scolding advantageous ventilation, therefore, in the switching effort. It is therefore the task of the fire protection system to achieve an inductive de * sum switching an In the case of a circuit arrangement for switching inductive loads, your task becomes a mechanical *! Switch Hi DC circuits, hw Λ-r rare FunkenMhchuM the mechanical switch utM on a protective wideniand and a L4hrbkondensatar existing series circuit and the inductive consumer a diode in parallel, solved according to the invention that in a known manner with the mechanical »switch and the inductive consumer a thyristor is connected in series, the control electrode of which, however, is only acted upon by ignition pulses if the switch has previously been closed and the thyristor is cleared by opening the switch. An embodiment of the invention with an electromagnet as an inductive consumer is shown in the drawing. The electromagnet is labeled H and serves as a lifting magnet for the paper scissors of a form printer. Its excitation winding is in series with a switch S, which means that it receives an opening command from the paper scissors as soon as the paper web has been completely cut. The countercurrent caused by the excitation winding of the lifting magnet H when the switch S is opened is short-circuited in a diode D directly on the excitation winding. In addition, a series circuit consisting of a protective resistor R and a quenching capacitor C is connected in parallel to the switch S for spark quenching. The thyristor T lying in series with the excitation winding of the lifting magnet H and the switch S is de-energized after opening the Schaker 5 as soon as the quenching capacitor C is charged. In this way, when you open the Sc !. ^: ters 5 made sure that contact bruises do not lead to sparking and erosion on the contacts. In order also to protect the contacts in the same way during closing of the switch S, the switch S is already closed before the thyristor T receives a ZündimpulsZ at its control electrode, the "cn an originating from a data processing system Λ form end signal is derived. The advantages achieved by the invention are in particular that no further switching element such. B. another thyristor or, for example, a light barrier, is required to delete the thyristor T in series with the switch S again. _patent claims: