DE2613818C3 - Circuit arrangement with overvoltage protection for controlling and operating an induction motor - Google Patents

Description

The invention relates to a circuit arrangement according to the preamble of the patent claim.

DE-OS 20 05 657 discloses a protective switching arrangement for a controlled semiconductor switching element known, in the case of the switching element two /? C elements are connected in parallel. The AC members have accordingly the possible overvoltage. · η different Time constants. Despite the use of special /? C-terms, however, it is only larger in the case of Vc Capacitors, which are mostly uneconomical and cannot be used for reasons of space, are possible too prevent very rapid overvoltages from damaging the switching element.

From DE-AS 11 96 786 a protective circuit is known in the individual, series-connected semiconductor elements to control the effect non-linear resistances of inertia effects, d. H. Varistors, are connected in parallel.

The invention is based on the object of providing the circuit arrangement of the type mentioned at the beginning to be trained in such a way that the triac against damage by interference voltages, switching overvoltages or excessive inrush currents is effectively protected

This object is achieved according to the invention by what is stated in the characterizing part of the patent claim specified combination of features. This training ensures that the operating voltage contained overvoltages can be eliminated by the blocking capacitor. Surges that can act on the triac from the motor

ίο derived via the ÄC element If these voltages however, are very steep, the FLC element no longer reacts sufficiently fast. In this case, the varistor comes into play. When overvoltages in conjunction with If a relatively large current occurs, the power consumed by the varistor would destroy it. this however, resistors connected upstream of the motor windings are prevented

The invention is explained below with reference to the drawing, for example, which shows a circuit arrangement

voltage with overvoltage protection for controlling and operating an induction motor with two windings and shows a sliding capacitor

As the drawing shows, the phase "R" is transferred to the mains voltage via a fuse el to a blocking capacitor C4, which is between the phase R and a neutral conductor MP of the capacitor C4 on the mains voltage to the anode A 1 is a triac 7Ί and a Triacs T2, which control and operate the two windings of a single-phase induction motor, transmit. Parallel to the triacs there are ÄC elements el, r3 or c2, r5 as well as varistors r9 and r 10. Since when one of the limit switches Ei and El of the motor is switched off, very high voltage peaks on the triac that has just been blocked

up to 1.2 kV and above can occur, which an ÄC element with a conventional capacitor cannot divert, the varistor r 9 or r 10 'is connected in parallel to each nC-Güed, which keeps the voltage peaks below 6OC V at the moment of switch-off limited From the connections A 2 of the triacs 7 * 1 and Ti, the phase R is fed to the motor windings via resistors r 1 and r 2, which limit the charge currents of the sliding capacitor C of the motor, via the limit switches E 1 and E 2 located in the motor other ends of the motor windings are brought together and are connected to the center conductor MP via a thermal protection contact d.

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1 sheet of drawings

Claims (1)

Claim: Circuit arrangement with high voltage protection for the control and operation of an induction motor with two windings and a sliding capacitor, to which the supply voltage taken from the mains is fed via at least one triac, with two different protective circuit arrangements, parallel to the triac for suppressing switching overvoltages, of which at least one is an ÄC -Guide contains, and with a bias circuit for controlling the triac, which draws the voltage and current required to switch the triac from the network, characterized by the combination of a varistor for 9, r 10) in the further protective circuit arrangement, a blocking capacitor (c 4) for interference suppression of the voltage supply line and resistors (r 1, r2), which are connected upstream of the motor windings to limit the charging current of the sliding capacitor.