An on-load tap changer is provided having a plurality of modules, each of which is operable to change taps in a transformer winding. The tap changer includes a motor connected to rotate at least one shaft. The at least one shaft is connected to the tap change modules and is operable upon rotation to cause the tap change modules to each perform a sequence of operations that effectuate a tap change. A multi-turn absolute encoder is connected to the at least one shaft. A monitoring system is connected to the encoder and is operable to determine from the position of the at least one shaft where the tap change modules are in the sequence of operations.

An on-load tap changer is provided having a plurality of modules, each of which is operable to change taps in a transformer winding. The tap changer includes a motor connected to rotate at least one shaft. The at least one shaft is connected to the tap change modules and is operable upon rotation to cause the tap change modules to each perform a sequence of operations that effectuate a tap change. A multi-turn absolute encoder is connected to the at least one shaft. A monitoring system is connected to the encoder and is operable to determine from the position of the at least one shaft where the tap change modules are in the sequence of operations.

The following steps are performed in order to test a tap changer (20) of a transformer (5; 6) which tap changer is designed to change a transmission ratio of the transformer (5; 6): generating a test signal which is supplied to a winding (1-3; 10) of the transformer (5; 6) and to the tap changer (20).

Repeatedly actuating the tap changer (20) in order to change the transmission ratio with each actuation.

Determining a curve of an electrical measurement variable (I; I.sub.1; I.sub.2) of the transformer (5; 6) over time (t) for each actuation of the tap changer (20) depending on the test signal.

Filtering the curves (41, 42) in order to prevent at least one of the curves (41, 42) from being output.

Outputting the filtered curves (41; 42).

An on-load tap changer has a switching tube, an oil suction pipe arranged centrally and coaxially along an axis inside the switching tube, and a kerosene drain screw so mounted in a base of the on-load tap changer that it is coaxial with an axis of the oil suction pipe, with the axis of the switching tube, and with an axis of the on-load tap changer. A bearing ring is so acted on by a resilient element at one side and radially with respect to the axis of the on-load tap changer that the switching tube and the oil suction pipe both mechanically positively cooperate with the bearing ring and are centered about the axis of the on-load tap changer.

The invention relates to an on-load tap changer (1) for controlling voltage, comprising semiconductor switching elements (61, 62, 71, 72), and to a method for controlling voltage for a variable transformer (2). The on-load tap changer (1) has a first load branch (6) and a second load branch (7) arranged parallel thereto. A partial winding (8) is arranged between the first and second load branches (6, 7). In the first load branch (6), a first semiconductor switching element (61) is provided upstream of the partial winding (8) and a second semiconductor switching element (62) is provided downstream of the partial winding (8). In the second load branch (7), a first semiconductor switching element (71) is provided upstream of the partial winding (8) and a second semiconductor switching element (72) is provided downstream of the partial winding (8). The on-load tap changer (1) consists of at least one switching module (5), which comprises the first load branch (6) and the second load branch (7) of the on-load tap changer.

There is provided a tap changer in which movable contacts rotate to be selectively connected to a plurality of taps. The tap changer includes a rotatable upper movable contact; a rotatable lower movable contact electrically connected to the upper movable contact; a driving shaft rotating the upper movable contact and the lower movable contact integrally; a single-type fixed contact including a single terminal connected to any one of a plurality of taps; and a dual-type fixed contact including a first terminal and a second terminal connected together to another of the plurality of taps. Since the upper movable contact and the lower movable contact are integrally rotated through the single driving shaft, the number of components and volume of the device may be reduced and an operation of the device may be facilitated.

The invention relates to a linear selector (1) for power-free preselection of tap contacts for a tapped transformer (100). The linear selector (1) according to the invention is cost-effective, simple and compactly constructed. The functions of a selector and a reverser are thus better connected. The linear selector (1) is constructed from a fine selector (2) and a reversing switch (3). The fine selector (2) and the reversing switch (3) are directly driven via a common gear unit (6).

A system for operating an on-load tap changer (OLTC) includes a plurality of legs that include mechanical switches. At least one leg switches from a first to a second tap of the OLTC on receipt of a tap change signal. At least one mechanical switch is activated to establish an electrical connection between one of the first and the second tap and a power terminal of the OLTC. Further, the system includes semiconductor switches that are parallel to the mechanical switches and when activated electrically couple one of the first and the second tap and the power terminal. The system includes a processing unit that selectively activates and deactivates the mechanical and semiconductor switches in such a way that electrical contact is maintained between at least one of the taps and the power terminal during the transition of at least one leg from the first tap to the second tap.

A method of switching taps of an on-load tap changer includes providing a main finger, a first side finger including a first solid state switch and a second side finger including a second solid state switch. The main finger, the first side finger and the second side finger are utilized to provide a connection between the taps and a power terminal of the on-load tap changer. The method also includes triggering the on-load tap changer to shift the fingers from a first tap to a second tap of the on-load tap changer when a tap change signal is received and utilizing the first solid state switch and the second solid state switch to commutate a current during the tap change operation.

A switching module is for an on-load tap-changer. The switching module has: a plate having a first side and a second side that is opposite the first side; a vacuum interrupter; and a bridge switch. The vacuum interrupter is on the first side, and the bridge switch, which is directly behind the vacuum interrupter, is on the second side.