Method for closing a contactor, and contactor having temperature compensation

Abstract

Disclosed is a method for closing the contacts of an electrical switching device during a switch-on process, wherein for a fixed first time period, the first time period and the first voltage being selected in such a way that the armature is not set into motion during the first time period, or the first voltage is applied to the coil until a certain current value is reached, the first time period being the time period until said certain current value is reached, and the first voltage being selected in such a way that the armature is not set into motion during the first time period, wherein a suitable second voltage is defined, the second voltage being greater than the first voltage and being applied to the coil during a second time period in order to move the armature from the open position into the closed position.

Claims

1. A method for closing contacts of an electrical switching device during a switch-on process, wherein the electrical switching device comprises an electromechanical drive with a coil and an armature which can be moved between an open and a closed position, and a microcontroller electrically coupled to the electrical switching device, the method comprising: energizing the coil in order to close the contacts of the electrical switching device; applying first a first voltage U.sub.1 to the coil during a first time period T.sub.1, wherein the first voltage U.sub.1 is constant; determining a measurement value; determining, based on the measurement value, a second voltage U.sub.2 from a table stored in a memory of the microcontroller, the table defining a correlation between the measurement value and the second voltage U.sub.2, wherein the second voltage U.sub.2 is greater than the first voltage U.sub.1, the second voltage U.sub.2 being constant; and applying the second voltage U.sub.2 to the coil during a second time period T.sub.2 in order to move the armature from the open position into the closed position, wherein the second time period T.sub.2 directly follows the first time period T.sub.1, and wherein either the first time period T.sub.1 is fixed, and the measurement value is a current measurement value I.sub.Mess determined at the end of the first time period T.sub.1 by measuring the current flowing in the coil, the first time period T.sub.1 and the first voltage U.sub.1 being selected in such a way that the armature is not set into motion during the first time period T.sub.1, or the first voltage U.sub.1 is applied to the coil until a certain current value I.sub.Soll of the current flowing in the coil is reached, the first time period T.sub.1 being the time period until said certain current value I.sub.Soll is reached, the first time period T.sub.1 being the measurement value, and the first voltage U.sub.1 being selected in such a way that the armature is not set into motion during the first time period T.sub.1, wherein the first time period T.sub.1 is selected in such a way that the current increases during the total first time period T.sub.1 and no stationary final current appears in the coil during the first time period T.sub.1.

2. The method according to claim 1, wherein the first time period T.sub.1 is fixed, and the measurement value is a current measurement value I.sub.Mess determined at the end of the first time period T.sub.1 by measuring the current flowing in the coil, wherein the first time period T.sub.1 and the first voltage U.sub.1 are selected in such a way that the armature is not set into motion during the first time period T.sub.1.

3. The method according to claim 1, wherein the second voltage U.sub.2 is determined in accordance with the measurement value such that the armature always reaches the same speed during the closing of the contacts independent of a temperature of the coil.

4. The method according to claim 1, wherein the second voltage U.sub.2 is determined in accordance with the measurement value such that the armature is moved into the closed position always within the same time period during the closing of the contacts independent of a temperature of the coil.

5. The method according to claim 1, wherein a definition of the second voltage U.sub.2 by means of the measurement value is effected by reading out a default value from a table stored in a memory, or by applying a calculation specification for calculating the default value by means of a measurement value.

6. The method according to claim 1, wherein the second time period T.sub.2 is fixed.

7. The method according to claim 1, wherein the second time period T.sub.2 ends when a suited sensory mechanism or evaluation recognizes that the armature is in the closed position.

8. An electrical switching device with contacts and an electromagnetic drive for closing the contacts, wherein the electromechanical drive comprises a coil and an armature movable between an open position and a closed position, wherein the electrical switching device furthermore comprises a current measuring circuit for measuring the current flowing in the coil, and wherein the electrical switching device comprises a control unit, wherein the control unit is designed and configured to carry out the method according to claim 1.

9. An electrical switching device according to claim 8, wherein the control unit comprises the microcontroller in which a table with possible measurement values and corresponding default values, or a calculation specification for calculating the default values by means of the measurement values, is stored.

Description

(1) The invention will be illustrated more in detail below with reference to drawings.

(2) In the drawing:

(3) FIG. 1 shows a schematic representation of a contactor according to the invention according to one embodiment,

(4) FIG. 2 shows a wiring diagram of the contactor according to the invention of FIG. 1, and

(5) FIG. 3 shows the current characteristic in the coil of the contactor according to the invention.

(6) In the following illustrations, equal parts are designated by equal reference numerals. If a drawing contains reference numerals which are not explicitly discussed in the pertaining description of the figures, reference is made to previous or following descriptions of the figures.

(7) FIG. 1 shows a schematic representation of a contactor 1 according to the invention according to one embodiment of the present invention. The contactor 1 comprises a housing 10 only represented in sections, and a double-gap contact point. The contact point consists of the two fixed contacts 5 and the movable contact bridge 6. The contact bridge 6 is mounted on a contact support 9 via contact pressure springs 7, the contact support 9 being connected to the movable armature 3 of the electromagnetic drive of the contactor 1 via the switch rod 4. The armature 3 and the yoke 8 of the electromagnetic drive are at least partially enclosed by the coil 2 of the electromagnetic drive. During the current feed of the coil 2 by applying sufficient voltage, the armature 3 is attracted against the force of the readjusting spring 13 acting between the yoke 8 and the armature 3, so that the contacts are closed.

(8) FIG. 2 shows the wiring diagram of the contactor according to the invention of FIG. 1. A current measuring means 12 serves to measure the current flowing in the coil 2 during operation. Component 15 is a voltage measuring device for measuring the supply voltage U.sub.Vers which can be subject to certain fluctuations. The measured quantities of the current measuring means 12 and the voltage measuring means 15 are supplied to a microcontroller 11 which processes the two measured quantities and generates therefrom a control signal for the circuit breaker 17 via which the coil 2 is activated. A voltage supply 16 for the microcontroller 11, the two measuring means 12 and 15, and optionally for a driver for activating the circuit breaker 17 is connected to the supply voltage U.sub.Vers. A freewheeling diode 18 is furthermore located at the coil 2.

(9) The switching-on of the supply voltage is effected via the supply voltage switch 14.

(10) FIG. 3 shows the characteristic of the current I flowing in the coil 2 over time t. The switch-on process is divided into two phases. In the first phase during the first time period T.sub.1, a constant first voltage U.sub.1 is applied to the coil 2. In the exemplified embodiment presented here, the first time period T.sub.1 is fixed, wherein at the end of the first time period T.sub.1, the resulting current value I.sub.Mess in the coil 2 is measured. The first voltage U.sub.1 and the first time period T.sub.1 are here selected such that the armature is not set into motion during the first time period T.sub.1.

(11) In accordance with the measured current value I.sub.Mess depending on the temperature of the coil, a suited second voltage U.sub.2 is defined thereupon which is larger than the first voltage U.sub.1 and which is applied to the coil 2 during a second time period T.sub.2 directly following the first time period T.sub.1 to move the armature 3 from the open position into the closed position and thereby close the contacts. The second time period T.sub.2 thus represents the second phase of the switch-on process. The second voltage U.sub.2 corresponding to a certain current measurement value I.sub.Mess is read out, for example, from a table stored in the microcontroller.

(12) Upon completion of the switch-on process, the control unit of the contactor passes over into a holding mode. The holding mode is maintained during the third time period T.sub.3.

LIST OF REFERENCE NUMERALS

(13) 1 electrical switching device 2 coil 3 armature 4 switch rod 5 fixed contact 6 contact bridge 7 contact pressure spring 8 yoke 9 contact support 10 housing 11 microcontroller 12 current measuring means 13 readjusting spring 14 supply voltage switch 15 voltage measuring means 16 power supply 17 circuit breaker 18 freewheeling diode t time T.sub.1 first time period T.sub.2 second time period T.sub.3 third time period U.sub.Vers supply voltage U.sub.1 first voltage U.sub.2 second voltage I current I.sub.Mess current measurement value I.sub.Soll predetermined current value R coil resistance