Electromagnetic actuator with under voltage release
An electromagnetic actuator has a yoke for guiding a magnetic flux, and a holding plate attached to an actuating member, the holding plate and yoke forming a first magnetic circuit. Furthermore a magnetic flux generation device is provided for generating a magnetic flux in the first magnetic circuit. The magnetic flux generation device has an under voltage release coil electrically connected to an auxiliary voltage source representing the value of a voltage to be monitored.
1. An electromagnetic actuator, comprising:
a yoke configured to guide a magnetic flux;
a holding plate attached to an actuating member, the holding plate and yoke forming a first magnetic circuit;
a pre-tensioning device which exerts a pre-tension force on the holding plate away from the yoke, the pre-tensioning device comprising a device external to the electromagnetic actuator;
a magnetic flux generation device configured to generate a magnetic flux in the first magnetic circuit, the magnetic flux generation device comprising an under voltage release coil electrically connected to an auxiliary voltage source,
the auxiliary voltage source supplying a voltage value to be monitored, and the under voltage release coil being dimensioned to generate an attraction force holding the holding plate against the yoke;
a tripping coil, the under voltage release coil being able to generate a magnetic flux in the first magnetic circuit opposing a magnetic flux generated by the tripping coil; and
a closing coil configured to generate a magnetic flux in a second magnetic circuit, the second magnetic circuit being separate from the first magnetic circuit;
wherein the attraction force exceeds the pre-tension force when the auxiliary voltage exceeds a predetermined threshold value.
2. The actuator of claim 1 , wherein the under voltage release coil has a winding orientation opposite to a winding orientation of the tripping coil.
3. The actuator of claim 1 , wherein the under voltage release coil is disposed coaxial to the tripping coil.
4. The actuator of claim 1 , wherein the pre-tensioning device comprises a mechanical device.
5. The actuator of claim 1 , wherein the auxiliary voltage source is an auxiliary voltage supply in a switch gear installation,
wherein the auxiliary voltage supply provides the voltage value, which is representative for a switch gear installation main voltage.
6. A switch gear installation, comprising:
an auxiliary voltage supply which provides a voltage representing a main voltage of the switch gear installation; and
an electromagnetic actuator including:
a yoke configured to guide a magnetic flux;
a holding plate attached to an actuating member, the holding plate and yoke forming a first magnetic circuit;
a pre-tensioning device which exerts a pre-tension force on the holding plate away from the yoke, the pre-tensioning device comprising a device external to the electromagnetic actuator;
a magnetic flux generation device configured to generate a magnetic flux in the first magnetic circuit, the magnetic flux generation device comprising an under voltage release coil electrically connected to an auxiliary voltage source,
the auxiliary voltage source supplying a voltage value to be monitored, and the under voltage release coil being dimensioned to generate an attraction force holding the holding plate against the yoke;
a tripping coil, the under voltage release coil being able to generate a magnetic flux in the first magnetic circuit opposing a magnetic flux generated by the tripping coil; and
a closing coil configured to generate a magnetic flux in a second magnetic circuit, the second magnetic circuit being separate from the first magnetic circuit;
wherein the attraction force exceeds the pre-tension force when the auxiliary voltage exceeds a predetermined threshold value.