DE1085601B - Overcurrent release with temperature-dependent components - Google Patents

Description

LIBRARY

OF THE GERMAN

PATENT OFFICE

The invention relates to circuit arrangements for overcurrent releases. Such overcurrent releases are used in conjunction with magnetic switches or contactors to control the connected consumers to protect against excessive current consumption. If the current consumption is too high, the overcurrent release speaks and switches off the contactor by interrupting the pull-coil circuit, whereby the main contacts of the Contactor disconnect the consumer from the mains. It is important here that protection against long-term, only slightly above the nominal load overload is guaranteed, as this z. B. occur in engines can. In this case, the motor would increasingly exceed its permissible continuous temperature heat out, and its insulation would be damaged.

It is known to build such overcurrent releases in the form of bimetal releases. Here is a Bimetal strips heat up and bend directly or indirectly from the current to be monitored by. With a correspondingly strong curvature, a contact is actuated, which the pull coil circuit of the Contactor interrupts and causes the same to fall. The disadvantage is that such bimetallic release especially with the mostly common three-phase design, a large number of mechanically moved Have parts whose manufacture is very difficult in view of the required high accuracy. Furthermore, an additional adjustment is required after assembly to ensure that all in Switch off the bimetal release lying in the individual phases when the currents are approximately the same. Is disadvantageous furthermore that in the event of strong vibrations there is a risk of tripping if the current values are too low.

The invention relates to solutions in which such overcurrent release without the use of mechanically interacting parts can be built. Almost all of them come static, electronic components for use; only the pull coil circuit is disconnected when If the fault occurs, it is advisable to use a simple auxiliary relay.

By eliminating the previously required mechanically moving parts of high precision, the Manufacture and adjustment of overcurrent releases according to the invention significantly simplified and cheaper. Such triggers are insensitive to vibrations during operation.

According to the invention these advantages are achieved in that with overcurrent releases for single or multi-phase magnetic switches and contactors with resistors switched on in the circuits provided for monitoring with these resistors temperature-dependent electrical components heat over it stromauslö s he
with temperature dependent]! Components

Applicant:

Copper asbestos co. Gustav Bach,

Heilbronn / Neckar-Sontheirn,

Kreuzäckerstr. 6th

Richard Heinrich, Heilbronn / Neckar,

and Hermann Sturm, Horkheim via Heilbronn / Neckar,

have been named as inventors

are moderately coupled in such a way that with increasing current a heating of this temperature-dependent Components takes place, the temperature-dependent components together with non-temperature-dependent Resistors are preferably connected to one another in the form of a bridge circuit, and that transistors are connected to the bridge output, which immediately when the bridge is detuned or indirectly cause the circuit or circuits to be monitored to be switched off, the feed current for the transistors via the bridge resistor. The transistors will possibly with the interposition of a further-for Amplification serving transistor, an auxiliary relay controlled, whose contact when a Overload interrupts the pull coil circuit.

According to a further embodiment of the invention, it is also possible to control the transistors Use components that emit a thermal voltage when heated. When used of such thermocouples, it is useful to bring the so-called cold solder joint to a temperature level that corresponds to the ambient temperature of the overcurrent release. This can be done in a simple way a compensation of the influence of a changing ambient temperature on the trigger values is achieved will.

In order to ensure that the monitoring device responds suddenly in the event of a slow overload To achieve, it is provided according to the invention, the supply current for the transistors to lead across the bridge resistance. At the beginning of the triggering process, the change results from The supply current flowing through the bridge resistance causes a potential shift at the base-emitter path of the transistor in the sense that the tripping process is accelerated.

009 567/25 +

3 4

In the case of multi-phase overcurrent releases, motor 1 and mains terminal 5. With resistor 7 According to the invention, a simplification and the temperature-dependent one is thermally coupled Achieve approval by the fact that for all phases only resistor 16, which together with the reins common transistor part with auxiliary relay boards 17, 18 and 19 forms a bridge circuit, hand is. The resistance 16 elements are used by the temperature-sensitive components depending on the resistor 18 to be monitored and resistor 17-resistor 19 Voltages supplied to currents reach a supply voltage, which in the present case common to the control circuit of a transistor; they trap by means of rectification and sieving are, however, mutually decoupled by diodes, so rectifier 15 and capacitor 35 are one of the second only the highest voltage in each case a development 14 of the contactor coil 3 removed change control of the transistor causes. tension is gained. The connection point

In a simple manner according to the invention at resistor 16-resistor 17 is connected to the base multi-phase overcurrent release and a protective connection of the transistor 8, the connection against uneven load can be achieved, such as connection point resistor 18-resistor 19 is with the such z. B. in single-phase operation of motors on 15 emitter connections of the transistors 8 and 10 can represent. By arranging the temperature-bound. A balancing of the bridge and thus a sensitive component in the differential circuit setting of the tripping current can be achieved by means of which can be made with such a non-equal resistance 18,
If the overcurrent release is operated, the overcurrent release is heated to currents below the rated current. 20 next to the current to be monitored

The power supply of the monitoring part of a flowed resistor 7 the temperature-dependent

Such an overcurrent release can according to the invention resistor 16, which with increasing heating

be done in a simple manner that on the changed its resistance value, z. B. in advance

Contactor coil a second winding is attached, whose lying case is reduced. Leveling the bridge

AC voltage is rectified and screened. 25 is now expediently done so that when flowing

Often it is desirable to have overcurrent release of the rated current the bridge is balanced. Increases

in their tripping characteristics to the requirements of the current to be monitored over this value, see above

of the connected consumers. Resistance 16 becomes lower and out of tune

there is such a requirement in the case of motor - thereby the bridge, i. H. steps at the bridge exit

driven. 30 a voltage whose polarity is such that the

According to the invention, this can be done both through the negative pole at the base terminal of the transistor 8. Measures in the electronic part as well as in this way the emitter-collector path of the Tranthermischen Perform part. So z. B. by sistors 8 from the blocking state to the conductive state adjustable setting resistors offset a slight setting and, as a result, the base connection of the the required tripping current. Next- 35 transistor 10 placed on emitter potential. In order to Delay elements in the control circuit can block the emitter-collector path the transistors, consisting z. B. causes the transistor 10 adjustable, whereby auxiliary relay 11 Series resistance and shunt capacitor, one setting drops and with its contact 12 the circuit cause a bare response delay. It is also interrupted by the pull coil 3; the contactor drops out. the possible, the thermal circuit, formed from the in 40 leadership of the positive pole of the rectifier 15 flow Monitoring circuit lying resistance ßenden supply current for the transistor 10 via the and the thermally coupled temperature bridge resistor 19 has the advantage of sensitive components, by mechanical adjustment that when initiating the release process and the daglieder, z. B. with regard to its heating time with associated current decrease in the emitter collector constant, to change. 45 gate circuit of transistor 10 is the emitter terminal of the

Some embodiments of overcurrent off transistor 8 have an increasingly positive potential Solvers according to the invention are obtained in the drawing in opposite to its base connection, d. H. Tran shape reproduced by circuit diagrams and after-transistor 8 is thus more strongly in the conductive state explained in more detail below. offsets and offsets transistor 10 in turn

Fig. 1 shows a single-phase overcurrent release, 50 more and more in the blocking state. This causes in in which the modulation of an auxiliary relay advantageously results in a sudden expiry of the modulation Transistors by means of a dissolving process.

Bridge circuit lying temperature-dependent. In the exemplary embodiment according to FIG. 2, one is used

Resistance is caused; Thermocouple arrangement heated by resistor 7

Fig. 2 shows a single-phase overcurrent release, 55 36 for controlling the transistor 8. The thermal

in which a modulation of the transistors element arrangement is expediently made

takes place by thermocouples, which in a number of individual elements connected in series

Bridge circuit lie; which one side of the soldering points with heat

Fig. 3 shows a three-phase overcurrent release resistor 7 is connected, whereas the other

with a central control part, 60 side of the soldering points at the ambient temperature

4 a three-phase overcurrent release is held with the overcurrent release. The one with the central control unit and differential release. warming through. -, the resistance 7 occurring

Fig. 1 shows an overcurrent release in connection with thermal voltage of the thermocouples causes a

with a contactor for monitoring a detuning of the bridge from the network and leads when exceeded

powered motor 1. Here, 2 is the contactor contact, 65 of the set nominal current to respond to the

3 is the pull coil of the contactor. In a known manner monitoring device and thus for triggering

the contactor is activated by pressing the ON button 4.

The coil circuit is closed and the contactor is connected to the base line

drag brought. A current now flows from the network in conjunction with the adjustable series resistance

via mains terminal 6, contactor contact 2, resistor 7, 70 downstream shunt capacitor, the

speaking of the overcurrent release adjustable delayed will. The circuit according to FIG. 2 represents only one of the possible circuit examples. B. also be beneficial to insert thermocouples in the branch of a bridge to those with a bridge circuit related benefits.

In Fig. 1 and 2, for the sake of simplicity, only single-phase overcurrent releases are shown Monitoring shown. In principle, however, it is also possible to use such arrangements according to FIG. 1 and 2 to build overcurrent releases with multi-phase monitoring in each phase. With multi-phase However, it is also possible for overcurrent releases according to FIG. 3, a substantial simplification and to achieve cheaper by the fact that for all phases only one common control part, consisting of the transistors 8 and 10 and auxiliary relays 11 and resistors 9, 18, 19 and 27 is present. Here the resistors 18 and 19 represent one side of the bridge circuit, while the other side of the bridge the resistors 16 and 17, 20 and 21 as well as 22 and 23 assigned to the individual phases to serve.

At the connection points of the resistors assigned to the individual phases, there are connections to the base connection of the transistor 8 the diodes 24, 25 and 26. These diodes cause that mutual decoupling of the bridge sides assigned to the individual phases. In connection with the Cross resistor 27 brings the inclusion of such diodes with the advantage that as a result of The non-linear behavior of the diodes results in an increasingly rising voltage in the tripping area at the base terminal of the transistor 8 results.

In the circuit arrangement according to FIG. 4, compared to the arrangement according to FIG. 3 additional temperature-sensitive resistors 30, 31 and 32 in series with the resistors 23, 17 and 21 switched into the bridge branches.

The heating of the same takes place depending on the current of the respective neighboring phase. However, the bridge equilibrium that exists with a uniform phase load at nominal current becomes in the event of a phase failure, this is disturbed by the fact that one of the differential resistors 30, 31 or 32 is now colder and increases its resistance value. This brings and causes a bridge upset safe disconnection of the contactor, e.g. B. with single-phase running of a three-phase motor even with currents that are below the rated current.

Claims (7)

Patent claims: th resistors, characterized in that with these resistors (7) temperature-dependent electrical components (16) are thermally coupled such that when the current increases These temperature-dependent components are heated, with the temperature-dependent Components together with non-temperature-dependent resistors (17,18,19) are preferred are connected to one another in the form of a bridge circuit, and. that transistors (8, 10) are connected to the Bridge output are switched, which directly or indirectly if the bridge is detuned cause a shutdown of the circuit or circuits to be monitored, and that the feed current for the transistors (8, 10) via the bridge resistor (19). 2. Overcurrent release according to claim 1, characterized in that the temperature-dependent components find temperature-dependent resistors (16) use. 3. Overcurrent release according to claim 1, characterized in that the temperature-dependent components Find thermocouples (36) use. 4. Overcurrent release according to claims 1 and 2, characterized in that in contactors with multi-phase current monitoring by arranging the modulation of the transistors (8,10) causing temperature-dependent components (30,16 or 31, 20 or 32, 22) in a differential circuit in the event of uneven loading of the individual phases from each other, a shutdown occurs Current values is effected which are below the target trigger value (Fig. 4). 5. Overcurrent release according to claims 1 to 4, characterized in that the contactors with multi-phase current monitoring, a central transistor part (8, 10) is present, which is provided by each of the individual line branches is controlled independently of one another. 6. Overcurrent release according to claims 1 to 5, characterized in that the supply voltage taken from an additional winding (14) of the contactor coil (3) to operate the release device will. 7. Overcurrent release according to claims 1 to 6, characterized in that the characteristics of the thermal circuit and / or the characteristics of the electrical circuit through adjustable components can be changed so that different tripping characteristics can be set is. 1. Overcurrent release for single or multi-phase publications considered: Magnetic switches and contactors are included in the German Auslegeschriften No. 1 009 702, 1 050 439. circuits provided for monitoring are switched on. 55 1 011 059. 1 sheet of drawings © 1 009 567/254 7.60