DE1665064C - Overvoltage protection device for an AC switch - Google Patents

Description

1666 064

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The invention relates to an overvoltage protection generated by means of the Transformatorsim ^ far f ¹

Device for an alternating current switch with a step-up that the FJnJwhlohtd ode

Half- a rapidly rising ^K J ^em ™ fW " ⁿ . ^u " f. ^{Orhä |} t

conductor arrangement whose behavior in the case of positive and This is sufficient for the ignition * r Wn ^ iobtdiode,

negative half-waves of the alternating current is equal. a before a stable light *

It is known to have designed to suppress the opening arc. In this way_ is always one;

and locking spark when switching on and off a faultless timely ignition of the five-shift

AC circuit the switching contacts a half diode and thus an arc suppression

Connect the conductor arrangement in parallel, which is possible from two.

Semiconductor diodes polarized against each other. The 10 parallel to the switching contacts can still be a

This arrangement works as follows: Capacitor to suppress overvoltage

In each half-wave there is at least one diode connected, although this is not absolutely necessary.

not in the direction of current flow, so it is manoeuvrable after opening. _ ...

of the switch contact is claimed in the blocking direction, the resonant circuit can depending on the desired

until the reverse voltage is exceeded and there is 15 input resistance as a parallel resonant circuit or

the operating point can be formed in the area of the limit voltage series resonant circuit. Also can

shifts. The inherent resistance becomes very small and the load at different points in the oscillating circuit

bridges the opening switches without inertia.

contacts. The other diode is during operation. Some embodiments of the invention will be implemented

sought half-wave in the direction of current flow and has ao described below with reference to the drawing,

thus no influence on the current curve. Thereby is therein

a light- Fig. 1 a typical characteristic of a five-layer-

arc-free disconnection of inductive alternating diodes,

Circuits can be reached. F i g. 2 a basic circuit of the invention

Instead of the mutually connected half-as-appropriate switching device for the arc lower conductor diodes a five-layer diode can be used for pressing and

will. Such symmetrical five-layer F i g. 3 to 9 modifications of the circuit according to

arrangements are known. Thus, for the name Fig. 2.

In the drawings, SSS denotes a five-semiconductor component with five layers, known as a 30-layer diode, SW a switch, L the load, and C ₁ , which shows symmetrical behavior. Leaves C ₂ capacitors and T a transformer with this component, the control electrodes of the primary and secondary windings L ₁ and L ₂ .
away, the element can be used as a five-layer diode. First, the voltage behavior of one can be used that shows symmetrical behavior. known five-layer diode with reference to FIG. 1

It has been found, however, that such 35 is briefly explained.

Up to the normal diodes for arc suppression switching voltage V ₀₁ given by the construction of the diode, the semiconductor element is not sufficient in all cases. At very high, very high resistance. Reaches the external voltage current intensities it can namely occur that the value V _BI), the resistance suddenly breaks zuAnsprechzeit the five-layer diode greater than the 40 together, the diode wirrt d ^"r chlässig and shows nut time is that the formation of a rod ' ¹ "; τ ϊ · - ».. _jc h a voltage drop '.on *. · .ν r. O 8 to 1.2 Voit. bogens between the Sch.iltkontnlijcn? * - <; _t one Dc. Lci '.-. Igs / ustanu stop so i.-igc, ims the holding arc voltage ·: · ::: ' - y? _: s * J Ycii is sufficient. Current intensity Λ, is undershot. This happens with Π ... j ....... the switching contacts are interrupted by an alternating current towards the end of the relevant one

standing overvoltage already leads to a stable 45 current half-wave. At that moment the diode will Arc is conducted before the breakdown voltage is blocked again and assumes its high resistance. the five-layer diode is reached, the terminal drops in contrast to the normal diodes with only voltage of the five-layer diode to the light, a barrier layer and also to the four-layer diodes arc voltage from about 10 to 13 volts, so that the characteristic of the five-layer diode is symmetrical The diode can no longer ignite. 50 trisch, d. i.e., in the next half cycle of the change task of the invention is to switch a switching device, the process described above takes place in FIG processing of the type described with arcing under exactly the same way.

To provide pressure for AC circuits, one switches such a five-layer diode

even with high currents and relatively switches in an alternating current circuit in parallel, so can

slow rise of the terminal voltage after opening the switch due to inductive

responds freely. Behavior of the alternating current circuit

Dics is achieved according to the invention in that the voltage only grows until the switching

has reached the half-voltage of the five-layer diode lying parallel to the switching contacts. Immediately

conductor arrangement consists of a five-layer diode, the diode begins to conduct independently

which is in series with the secondary winding of a trans- 60 of the polarity of the half-wave in which the output

formator is, whose primary winding was made with a circuit. Is the response time

Capacitor a high-frequency resonant circuit of the diode so short that up to this point no

forms in which the switching contacts included arc has arisen, the voltage drops

are. the switch contacts now because of the low

When the switching resistance of the five-layer diode is opened, this resonant circuit is

contacts through the briefly in the primary winding and is no longer sufficient to form a

of the transformer flowing switching current on - arc off. It then just continues to flow in

bumped so that he has a high frequency voltage conduction current through the diode until the amperage

1 663

at the end of the half-wool in question falls below the Wen I _n . At this moment the diode blocks. with which the shutdown process is ended.

If the switch is closed again, so are before Pay particular attention to the bouncing phenomena that can generate short sparks. Oh this become immediately with a sufficiently short response time of the diode connected in parallel to the switching contacts deleted, while after complete closure of the contacts, the contact voltage is less than the holding voltage of the diode, so that the diode returns to the blocked state and the load current flows solely through the contacts. This also avoids the contact damage caused by bruises.

However, especially at very high currents, it can happen, as I said, that the rate of rise of the overvoltage occurring in the AC circuit is not sufficient to cause the Switching contacts parallel-connected diode to safely tip into the conductive state. Here she creates Invention remedy.

In the basic circuit of FIG. 2, when the switch SW is opened, a charging current flows through the primary winding L _{1 of} the transformer Γ to the capacitor C ₁ , whereby a high-frequency oscillation is generated in the resonant circuit C ₁ -L ₁ -SW. This oscillation is transmitted from the primary winding L ₁ to the secondary winding L ₂ , so that a strong high-frequency voltage occurs at the terminals of the secondary winding L ₂ . This high-frequency oscillating voltage opens the diode SSS, whereby the arc between the contacts SW is short-circuited and suppressed. If later the current in the diode falls below the holding current.;!, «Si oi; Interruption of the circuit completed. _{A capacitor C 2} is also used to protect the diode SSS against overvoltages. If a considerable part of such overvoltage is already _{absorbed by capacitor C 1} , the condor can. wiLi »- '" if necessary also give away throw »» · λ Oi "".

F i g. 3 shows a circuit for the case that the impedance of the electrical voltage source is small compared to that of the high-frequency oscillating circuit. If the switch SW is opened, the high-frequency resonant circuit C _x -L ₁ -SW is triggered, which in this case represents a series resonant circuit. the

10 high frequency current is transmitted to the secondary winding L ₁ , at the terminals of which a strong oscillation voltage develops, through which the diode SSS is opened. Otherwise, the mode of operation corresponds to that of the circuit according to FIG. 2.

The circuit according to FIG. 4 differs from that according to FIG. 3 again by the omission of the capacitor C _s for the suppression of the overvoltages.

F1 g. 5 shows a circuit in which the primary winding L _{1 is} not in the load circuit as in FIGS. The high-frequency oscillation voltage is not attenuated by the load L here.

F i g. 6 differs from FIG. 5 again by the omission of the overvoltage capacitor C _n .

F i g. 7 is based on the same principle as FIG. 5,

however, the parallel resonant circuit is similar to that in

Fig. 3 replaced by a series resonant circuit. this

is recommended if the terminal resistance is low

ao voltage source c.

FIG. 8 again differs from FIG. 7 only in that the capacitor C _{2 is} omitted.

Claims (1)

Patent claims: 1. Overvoltage protection device for an AC switch with a semiconductor arrangement connected in parallel to the switching contacts, the behavior of which is the same for positive and negative half-waves of the alternating current, characterized in that the semiconductor arrangement consists of a five-layer diode (SSS) which is in series with the secondary winding (L ₂ ) a transformer (T) is located, the primary winding (L ₁ ) of which forms a high-frequency resonant circuit with a capacitor (C ₁ ) in which the Schahkoruci * · {Sw ') si.'uk.2 <'; _v <.; i «inri. 2. Device n. * - jn Arspnn '· 1. dadunh gekennzeici. ·.? * Jaß it / u the switching contacts (SW) em ΚοΛ ^ ε-jsiu. jf (*. _ .. is switched. ^. Orientation according to Ai-p-uch 1 odti 2. ua-Hnnzeicta-? ·. that ciüv: fv.Vr'ipp. dv. load <> us ■ · <> us ?. j. mark that a. (L) between inductance (L ₁ ) and capacitance (C ₁ ) of the resonant circuit is connected. 4. Device according to claim 1 or 2, characterized in that a terminal of the load (L) is connected between the primary winding (L ₁ ) and the secondary winding (L ₂ ) of the transformer (T). 1 sheet of drawings