An inductive power device with variable active winding size, comprises first circuitry, multiple winding segments and switching circuitry operable to connect selectable combinations of the winding segments serially to the first circuitry via taps. At least two of the winding segments are of unequal size, wherein said at least two winding segments are provided as sequential portions of a total winding magnetically coupled to an opposite winding, wherein the winding segments have uniform polarity with respect to said magnetic coupling. The switching circuitry comprises an arrangement of semiconductor switches which are operable to include or exclude each winding segment independently. In an embodiment, the arrangement of switches comprises at least one half-bridge structure.

A device for connecting to a high-voltage grid carrying an AC voltage and having a plurality of phases, includes an active part having at least one phase connection for connecting to a phase of the high-voltage grid, at least one step winding connected downstream of one of the phase connections and having a plurality of taps, a tap changer having, for each step winding, a selector for currentlessly switching over from a current to a desired tap of the step winding, and a load changeover switch connected downstream of the selector in series for commutating the current from the current to the desired tap, for avoiding a high short-circuit current in the step winding or in the tap changer. An impedance unit, having an impedance to be switched between a low impedance and a high impedance, is disposed between each selector and each load changeover switch.

A system includes conductive windings extending around a magnetic core and impedance-varying windings extending around the magnetic core. The impedance-varying windings include positive windings and negative windings. The conductive windings and the impedance-varying windings conduct electric current around the magnetic core. The system includes a first impedance tap changer that is electrically coupled with the positive windings of the impedance-varying windings and a second impedance tap changer electrically coupled with the negative windings of the impedance-varying windings. A controller controls the first impedance tap changer and the second impedance tap changer to change an impedance of the system by changing which portion of the positive windings and which portion of the negative windings are conductively coupled with the conductive windings, and which portion of the positive windings and which portion of the negative windings are disconnected from the conductive windings.

A magnetic tether switch for equipment or vehicles is described. The magnetic tether switch may include a base having a first magnetic assembly. The first magnetic assembly may include a magnet and a first magnetic flux return component, or multiple magnets with reversed polarization directions. The magnetic tether switch may include a cap including a second magnetic assembly. The second magnetic assembly may include a magnet and a magnetic flux return component, or multiple magnets with reversed polarization directions. Alternatively, the second magnetic assembly may be composed of a ferrous material. The base may include a circuit with multiple contacts, where attaching the cap to the base may connect or disconnect the contacts to each other by moving the magnet within the base by magnetic attraction from the cap.

The present invention relates to a method and a monitoring system, for monitoring a vacuum on-load tap changer. The tap changer includes a housing with insulating fluid, a diverter switch inside of the housing and including at least one movable contact and at least two vacuum interrupters, and at least one pressure sensor which measures the pressure in the housing. The method, which is performed by a processing circuitry in the system, includes determining a pressure signature, including two succeeding peaks within a time interval, continuously measuring the pressure, detecting when the measured pressure shows the pressure signature, determining, based on the measured pressure within the pressure signature, the time between the first rise in pressure and the second drop, and setting the determined time to represent the switch time of the diverter switch.

A resistor assembly can be used in a tap changer. The resistor assembly may include: a resistor element, which is held by at least two resistor holders; a base plate with at least one opening and on which the at least two resistor holders holding the resistor element are arranged; a plurality of guides, respectively formed in each of the resistor holders and being configured to position a first end and a second end of the resistor element with respect to a longitudinal direction between the two resistor holders; and contact points of the resistor element, the contact points being electrically contacted by contacts of the tap changer in a condition where the resistor element is inserted into the resistor holder.

The invention relates to a method for monitoring an on-load tap changer that is used to switch between winding taps of a tapped transformer without interrupting the load current and is actuated using a motor drive. According to the invention, prior to the actual load switching process, the on-load tap changer is initially moved a short distance, preferably against the direction in which the load is subsequently switched. In said initial process, it is verified whether the on-load tap changer has moved, i.e. has left its previous stationary position, and/or whether the torque on the motor drive has exceeded a predefined threshold value. The actual load switching process takes place only once the test has yielded a positive result.

An on-load tap-changer has a transmission, a motor with an output shaft, and a diverter switch with a drive shaft. The transmission has a cam disk; a drive gear wheel; and a roller coupled to the drive gear wheel. The cam disk is connected the output shaft, which lies on a rotation axis of the cam disk. The drive gear wheel is connected to the drive shaft. The cam disk has an inner and outer contour, which are followed by the roller, and which each have a first region with a constant radius of curvature and a second region in which a distance of a respective contour from the rotation axis of the cam disk changes. During a rotational movement of the cam disk, the roller follows the first region of the outer contour, the second region of the outer contour, and then the first region of the inner contour.

The present invention relates to a method and a monitoring system, for monitoring a vacuum on-load tap changer. The tap changer includes a housing with insulating fluid, a diverter switch inside of the housing and including at least one movable contact and at least two vacuum interrupters, and at least one pressure sensor which measures the pressure in the housing. The method, which is performed by a processing circuitry in the system, includes determining a pressure signature, including two succeeding peaks within a time interval, continuously measuring the pressure, detecting when the measured pressure shows the pressure signature, determining, based on the measured pressure within the pressure signature, the time between the first rise in pressure and the second drop, and setting the determined time to represent the switch time of the diverter switch.

The disclosure relates to a tap changer arranged to be connected to a regulating winding of a rated regulation voltage. The tap changer comprises a diverter switch, a tap selector and a set of tap changer contacts. The tap selector and the diverter switch are encapsulated in a shielding structure arranged to shield the tap selector and the diverter switch from an external electrical field, the shielding structure being arranged to be electrically connected to a connected tap of the regulating winding.

The disclosure further relates to transformer arrangement comprising at least one such tap changer.