CS232411B1 - Wiring for shifting the moment of AC load switching - Google Patents

Abstract

The essence of the invention lies in the fact that a bridge rectifier is connected in series to the AC load, in the diagonal of which a thyristor with a parallel-connected timing circuit is inserted, the timing circuit consists of a delay capacitor and a charging resistor, between which the thyristor control electrode is connected. The thyristor control electrode can be separated from the timing circuit by a diac, and an auxiliary capacitor is also connected to it.

Description

BACKGROUND OF THE INVENTION The invention relates to a circuit for shifting the switching point of an alternating load.

In many machinery, it is a requirement to actuate several working devices by switching on a single switch, of which at least one device must only be moved after the other devices have already started or even stopped working. This is the case, for example, before starting the spraying of the shoe bottom, when after closing a single switch, the side mold parts are closed first and then the upper support can push the shoe with the hoof against the mold cavity. In general, it is therefore necessary to provide a delay in the performance of the function of one working device relative to the moment of the performance of the function of another working device. In practice, time relays are used almost exclusively for this purpose, in some cases powerful thermistors are used, time relays are either mechanical or electronic. Both types are relatively costly, with only a minimal amount of delay used for this purpose. In addition, especially in the case of mechanical construction, considerable installation space requirements are to be taken into account. The disadvantage of powerful thermistors is their considerable temperature dependence.

These disadvantages are eliminated by the circuit according to the invention, characterized in that a bridging rectifier is connected in series to the alternating load, in which a thyristor is connected in parallel with a timing circuit connected in parallel, the timing circuit consisting of a delay capacitor and a charging resistor. thyristor electrode. The thyristor control electrode can be separated from the timing circuit by a diac, and an auxiliary capacitor is connected to it.

The higher effect of the circuit is that the delay capacitor of the timing circuit is charged until the voltage thereon reaches the trigger voltage of the thyristor, which is then opened and only then switches on the controlled AC load via the bridge rectifier. The delay capacitor provides both a timer function and a function of keeping the thyristor in a conductive state. In the case of a less sensitive thyristor, its control electrode is separated from the time circuit by a diac, with the delay capacitor providing only the timer function while the holding function is performed by the auxiliary capacitor. The circuit according to the invention is very simple compared to the timing relays, which results in its very low production costs. Since the switching is non-contact, this connection is very reliable and durable. Another advantage is its very small size, which simplifies its installation in a controlled device.

1 shows a wiring diagram with a timing circuit connected directly to a thyristor control electrode, and FIG. 2 shows a wiring diagram with a timing circuit connected to a thyristor control electrode via a diac.

To the input branches γΐ. v2 (Fig. 1) of the alternating voltage Us, the individual loads Z1 to Zn are connected in parallel. to be actuated when the control switch S, which is upstream of these loads Z1 to Zn, is closed. The input branches know. vZ are equipped with terminals s1 s2. The AC load Zz is inserted in the input branch χΧ after the alternating loads Z1 to gn. to be activated with a certain delay from the moment the switch 8 is closed. A bridge rectifier M is connected in series to this alternating load Zz.

In the diagonal of the bridge rectifier M there is a thyristor Ty with a parallel timing circuit co. a timing circuit co consisting of a delay capacitor C1 and a charging resistor g between which a thyristor control electrode Tv is connected.

When using a less sensitive thyristor, its control electrode is separated from the tumbling circuit by a diac D (i.e., a semiconductor symmetric diode, Fig. 2) and additionally an auxiliary capacitor C2 is connected to it.

Wiring operation: By switching the control switch S (fig. 1), the alternating voltage Us appears on the loads Z1 to Zn, which immediately start to function. At the same time, the alternating voltage reaches the bridge rectifier g via the alternating load Zz, into the diagonal of which is then supplied in the form of a direct-current pulse voltage. This warming voltage is also on the thyristors Ty. which is now closed, the current does not pass through it. Only a very small current is passed through the alternating load Zz, which charges the delay capacitor C1 via the charging resistor R. The controlled alternating load Zz is therefore switched on and starts to perform its function with a safe delay with respect to the performance of the functions by the loads Z1 to, Zn. Thyristor Ty now flows through a current whose value is limited by the impedance of the controlled AC load Zz. For the following half-period rectified warming voltage, the delay capacitor G1 is no longer charged via the charging resistor R, since there is only a small voltage drop in the forward direction at the anode of the thyristors Tv. However, the delay capacitor C1 is now charged from the semiconductor structure of the thyristors Ty. wherein the passing current produces a voltage drop approximately equal to the trigger voltage. The current passing through the thyristor Ty drops between zero rectified pulse voltage to zero and the thyristor Tv would normally switch off. However, the delay capacitor C1 now supplies current to the thyristors Tv and thus keeps it in a conductive state.

'With less sensitive thyristors, the resistance of their control electrode is relatively low, and therefore the control electrode needs to be isolated from the timing circuit eo by using D (Fig. 2).

This timing circuit, which would otherwise be adversely affected by the low resistance of the control electrode, the delay capacitor C1 would have to have a disproportionately large capacity even for very small delays, of the order of tenths of a second, and in extreme cases the thyristor would not switch at all. In these cases, the function of the delay capacitor C1 from the circuit of FIG. 1 is divided so that the delay capacitor C1 only performs the function of the timer, while the function of keeping the thyristors Ty in the conductive state is taken over by the auxiliary capacitor C2.

For some applications of the circuit according to the invention, a variable resistor can be used instead of a stable charging resistor R, whereby the required delay time can be adjusted to a certain small extent.

The circuitry of the invention can be used in many different applications for short delays, eg instead of timing relays.

Claims (3)

OBJECTIVE OF THE INVENTION Wiring for shifting the switching time of the alternating load, characterized in that a bridge rectifier (M) is connected in series to the ₄ alternating load (Zz), in the diagonal of which a thyristor (Ty) is connected with a parallel connected timing circuit (co). « Wiring according to claim 1, characterized in that the timing circuit (co) consists of a delay capacitor (C1) and a charging resistor (R) between which the control electrode of the thyristors (Ty) is connected. Connection according to Claim 2, characterized in that the control electrode of the thyristors (Ty) is separated from the timing circuit (co) by a diac (D) and an auxiliary capacitor (C2) is connected thereto.