DE919548C - Electromagnet - Google Patents

Description

Electromagnet In technology, electromagnets are often used, in which there is the possibility that these briefly very large overloads have to endure. For example, there is a magnet for overcurrent releases are determined, the risk of a thermal or electrodynamic short circuit Overuse occurs. In view of the fact that such magnets with a open iron body and a movable armature, it is proportionate difficult and associated with great effort, these magnets the required dynamic To give short-circuit strength.

According to the invention can be a protection for electromagnets in the simplest possible way against such stress can be achieved in such a way that to these a choke coil is connected in parallel. Because such a throttle is a completely closed Iron core, it is much easier to build this choke short-circuit-proof than a magnet with an open iron core and a movable armature. Through the parallel connection such a choke coil becomes an effective measure for protecting the magnet against thermal and dynamic loads, especially for overcurrent releases is valuable. It is particularly advantageous to set the saturation of the throttle in such a way that that with an open armature the maximum value of the current below the saturation kink the magnetization curve f (= combination: magnet + choke) lies. In this version However, the winding of the magnet is also briefly higher loaded, however the effective ampere-turns for the tightening of the armature will be straight with an open anchor, where this is particularly important, is not affected. If wants to accept a slight impairment of these ampere turns, the saturation kink So in comparison to the current peak lays lower, it can be achieved that too protection of the magnet is achieved at the first current surge.

To explain the process is a graphic in the drawing Representation given. Hy steresis, copper and iron losses and scatter are included here neglected. With regard to the magnet, the assumption is made that the This magnet's iron circle remains below saturation. The current is distributed on the winding of the magnet (current il) and the winding connected in parallel the inductor (current i2), such that the voltage drop is the same for both currents must be big. As a result, there are also the power flows y, in the two windings same size. The sum of the two currents gives the total current i.

Fig. I shows the course of the flow as a function of the current i, namely the line a shows the flux in the choke coil, the line b the flux in Magnets when the armature is attracted and c when the armature has fallen off. Line d is the sum of the fluxes in the reactor and the magnet when the armature is attracted, f is the Sum of the fluxes in the reactor and your magnet when the armature has fallen.

In Fig. 2, the current distribution is with the anchor dropped, in Fig.3 shown with the anchor tightened.

In Fig. Q. The line b shows the flux in the magnet over time attracted armature, d is the sum of the fluxes in the reactor and magnet when the armature is attracted Armature, f is the sum of the fluxes in the reactor and magnets when the armature has dropped.

As can be seen from Fig. 2, is practical when the anchor has fallen all the current through the solenoid (current il), while Fig. 3 shows that at With the armature attracted, the current i1 through the magnet is very small and the largest Part of the current i2 flows through the winding of the choke coil.

So it can be an effective improvement in the sense of this protection of the release against thermal and dynamic loads, in particular at high short-circuit currents. This arrangement is particularly advantageous when it comes to using an existing trigger magnet in cases in which high short-circuit currents must be expected, which the release is connected to has not grown thermally or dynamically. In this case it can pass Parallel connection of such a choke is the trigger for this purpose make usable afterwards.

Under certain circumstances it is useful to give the choke a magnetization curve to give that does not have a pronounced saturation kink, d. H. at least does not run horizontally at any point in the practically interesting area. on In this way, an improvement in the holding ratio of the magnet, this is the ratio between the current value at which the armature of the magnet is attracted and the current value at which the armature is released from the magnet again, can be achieved, since the tensile force curve does not depend on the path when closing rises steeply like a hyperbola, but runs flat. Springs with kinked Characteristics to improve the holding ratio are then superfluous.

Claims (3)

PATENT CLAIMS: i. Electromagnet for uses in which temporary overloads occur as a result, especially for overcurrent releases characterized in that a choke coil as protection against overloads in the magnet winding is connected in parallel. 2. Electromagnet according to claim i, characterized in that that the choke coil is dimensioned so that it is practical when the magnet armature is open does not consume any current, while with the armature closed it absorbs most of the Stromes takes over. 3. Electromagnet according to claim i or 2, characterized in that that, in order to improve the holding ratio of the magnet, the characteristic of the reactor is chosen so that it is still within the entire work area, albeit slightly, increases.