DE2420037A1 - Electromagnet excitation circuit - holding current is reduced by phase chopping control after initial full power excitation - Google Patents

Abstract

An excitation circuit for an electromagnet, permitting change-over from an initial attractive excitation to a lower value holding excitation and eliminating loss-producing series resistances or similar devices, using an electronic switching unit (7) forming part of a phase chopping control in such a way that the full power is applied initially and a change-over is made to reduced power after a time controlled by a parameter such as time, current consumption, position of the armature, or change in field strength. The system also has the advantage that a single coil only is required, and not separate attracting and holding windings.

Description

Circuit arrangement for switching an electromagnet from its Starting current to a holding current The invention relates to a circuit arrangement for switching an electromagnet, in particular a switching magnet, from a pull-in excitation on a holding excitation, with an electronic switch in the excitation circuit is arranged, wherein the electronic switch is part of a phase control known per se and is switched on in such a way that it switches through fully at the beginning of the excitation and then switched to a fixed value depending on the time in which the arriving in one direction or in both directions Cut half waves according to patent application P 23 53 396.2, using a connected to the control path of the electronic switch, the control signals for the full-wave opening of the switch-emitting capacitor.

According to the main patent application for the phase control, according to some features, either a capacitor to the control path, or if this is permanently switched on, a series resistor is switched on or upstream of this with a switch.

It has now been found that the mechanical Switch (relay) the weakest link in the otherwise electronically constructed circuit is, and also this for space and price reasons to improvement requests Cause.

It was also found that the time-dependent switchover has advantages over the parameters also mentioned in the main application, because here the coil of the electromagnet in both cases, including when the magnet armature its end position is not reached, is switched before being overloaded becomes defective.

It is the object of the invention, which is only indicated in the main application fully electronic circuit to be clearly indicated.

The solution is to go into the tax path before leaving a series resistor is connected to the capacitor, the resistance value of which is at Normal load on the control route one to timely full wave Opening the switch of the phase angle control required charging of the capacitor allowed, and that the capacitor is initially blocked, after a predetermined time Electronic switch partially opened by an R-C timer, preferably a transistor is connected in parallel.

The circuit according to the invention will now be explained with reference to the drawing.

In the drawing is an excitation winding 1 of an electromagnet via a bridge circuit of rectifier diodes 2,3,4 and 5, once with one Mains terminal 6 and on the other side via an electronic switch 7 with a power terminal 8 connected. The electronic switch 7 is designed as a thyristor shown, the control electrode 9 with one of a resistor 10 and a Trigger diode 11 existing control path 12 is connected. The control route 12 is to obtain the correct bias voltage to one of the excitation winding 1, a current-limiting resistor 13 and two oppositely directed zener diodes 14 and 15 existing voltage divider connected.

A capacitor 16 is connected on one side to the mains terminal 8, and on the other side to the control path 12 between the resistor 10 and the trigger diode 11 connected. The capacitor 16 is connected in parallel on the AC side a bridge rectifier 17, the DC side one, one Transistor 18 owns the timing circuit, the timing circuit consists of a resistor 19 and a capacitor 20, as well as one to the base of the transistor 18 verbundeaen Zener diode 21. A reverse value diode 22 connected across the resistor 19 and a high-resistance one Resistor 23 are used to discharge the capacitor 20 after the system has been switched off.

The procedure is as follows: If a When AC voltage is applied, a current flows across the bridge circuit of the diodes 2 to 5 and thus through the excitation winding 1 to the electronic switch 7, simultaneously but also via the resistors 13 and 10 to the capacitor 16 and the trigger diode 11. The resistors 10 to 13 and the capacitor 16 are designed so that on the Trigger diode 11 there is almost no time delay of the half-wave, the electronic one Switch 7 is switched through via its control electrode 9 almost in full wave. Simultaneously the timing circuit was switched on via the bridge rectifier 17. The transistor 18 is initially blocked via its collector-emitter path. About the resistance 19 but the capacitor 20 is slowly charged (approx. 1 sec.) Until the Zener voltage the diode 21 is exceeded, whereby the transistor 18 opens partially. so part of the current flowing through the resistor 10 can be sent directly to the mains terminal 8 arrive, whereby the half-wave charge of the capacitor 16 by a certain Value is delayed and the thyristor 11 opens delayed, the applied half-wave so it is only partially let through. The excitation winding 1 is therefore with reduced power. This reduced amperage can be caused by the series resistor 10 can be set.

After the mains voltage applied to terminals 6 and 8 has been switched off the capacitor 20 of the time circuit via the reverse value diode 22 and the Completely discharge resistor 23.

Claims (1)

Claim Circuit arrangement for switching an electromagnet, in particular Switching magnet, from a pull-in excitation to a bale excitation, in the case of the in the excitation circuit an electronic switch is arranged, the electronic switch being part a phase control known per se and is switched on in such a way that that he switches through fully at the beginning of the excitement and then depending on the Time is switched to a fixed value at which the in half waves arriving in one direction or in both directions 1 according to patent application P 23 53 396.2, using a to the control path of the electronic switch connected, the control signals to the full-wave Opening of the switch emitting capacitor, d u r c h ek e n n z e i c h n e t that in the control path (12) before the outlet to the capacitor (16) a series resistor (10) is switched on, its resistance value under normal load on the control path one for timely full-wave opening of the switch (7) of the phase control required charging of the capacitor (16) allowed, and that the Eondensator (16) an initially blocked, after a specified time lapse by an R-C timer (19,20) partially open electronic switch, preferably a transistor (18) is connected in parallel.