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Main >> Applications >> Sample problems >> Electropermanent magnet relay

Electropermanent magnet relay

A relay of conventional design develops a pull-in force for any polarity current. By adding a permanent magnet to the structure, a polarized relay is obtained. It can develop both pulling and pushing forces.

Problem type:
Axisymmetric problem of Magnetostatics.


Electropermanent magnet relay model

Permanent magnet coercive force Hc = 500 kA/m;
Winding material is copper;
Winding number of turns: 600;
Nominal current I0 = 0.01 A;
Expected short-circuit current Imax = 1 A.
The core and anchor material is steel with a nonlinear dependence B(H):

Determine the force acting on the anchor of the relay, with the operating current and short circuit current, as well as in the absence of the current in the winding.

Using the integration contour, QuickField calculates the force acting on the ferromagnetic object. The calculation is carried out by integrating along the contour which surrounds the object. At the transition between ferromagnetic and air where the magnetic properties change significantly, field calculation error is relatively high. Therefore, in order to reduce the computational error, the contour should be shifted away from the ferromagnetic-air boundary and drawn through the air, around the anchor.


Winding current

Anchor force

no current

-2.3 N


-2.2 N


+0.47 N

The field picture and magnitude of the force for the short-circuit case of the electropermanent magnet relay operation:

The field picture of the electropermanent magnet relay

  • Download simulation files (files may be viewed using any QuickField Edition).

    QuickField 6.4