The invention relates to a method for controlling a wind turbine which comprises a transformer has a variable turns ratio such as an on load tap changer transformer. The adjustment of the turns ratio is possible when a primary side current or a secondary side current of the transformer is less than a switching current threshold. The method comprises operating the wind turbine so that the primary or secondary side current is above the switching current threshold. In response to obtaining a condition for changing the turns ratio of the transformer, the wind turbine is operated so that the primary or secondary side current is reduced below the switching current threshold so that the turns ratio can be changed during the temporary current reduction.

The invention relates to a method for controlling a wind turbine which comprises a transformer has a variable turns ratio such as an on load tap changer transformer. The adjustment of the turns ratio is possible when a primary side current or a secondary side current of the transformer is less than a switching current threshold. The method comprises operating the wind turbine so that the primary or secondary side current is above the switching current threshold. In response to obtaining a condition for changing the turns ratio of the transformer, the wind turbine is operated so that the primary or secondary side current is reduced below the switching current threshold so that the turns ratio can be changed during the temporary current reduction.

A system detects physical variables of at least one component of a tapped transformer and monitors the at least one component of the tapped transformer. The system includes a computer in communicating with a measuring instrument, which is in communicating connection with a sensor for reception of the physical variables. The computer receives the physical variables, which are collected in the measuring instrument, as a function of time of the at least one sensor; filters the physical variables as a function of time to generate filtered signals, and creates from the filtered signals a highly resolved envelope representing a signal level of the physical variables; and determines a first limit value curve and a second limit value curve, the position of which is variable in a direction of an ordinate, and the first limit value curve represents the limit value.

An on-load tap changer that includes an actuator configured to adjust a turn ratio of the transformer, and a processing unit configured to control the actuator and to communicate with a control device via a digital signal connection. The processing unit is further configured to receive a status detected by a sensor. A method of manufacturing the on-load tap changer is also disclosed. Embodiments according to the present disclosure provide a digitalized on-load tap changer that allows various statuses to be monitored or controlled, by which various advantages can be achieved. For example, the life of a contact of the transformer can be predicted. Other data can be used to determine whether it is safe to adjust the contact of the transformer. Moreover, the optical fibers between the on-load tap changer and an external device enable an isolated transmission of control and data signals that almost eliminates interferences.

An on-load tap changer that includes an actuator configured to adjust a turn ratio of the transformer, and a processing unit configured to control the actuator and to communicate with a control device via a digital signal connection. The processing unit is further configured to receive a status detected by a sensor. A method of manufacturing the on-load tap changer is also disclosed. Embodiments according to the present disclosure provide a digitalized on-load tap changer that allows various statuses to be monitored or controlled, by which various advantages can be achieved. For example, the life of a contact of the transformer can be predicted. Other data can be used to determine whether it is safe to adjust the contact of the transformer. Moreover, the optical fibers between the on-load tap changer and an external device enable an isolated transmission of control and data signals that almost eliminates interferences.

In various embodiments, a control circuit for a radio frequency drive of an electrosurgical device is disclosed comprising a voltage data input configured to receive voltage data, a current data input configured to receive current data, and a switching signal output configured to source a switching signal. The control circuit is configured to adjust a frequency of the switching signal based on the voltage data and the current data. The radio frequency drive comprising a transformer comprising a first tap, a second tap, a third tap, a first portion of a primary coil, a second portion of the primary coil, and a secondary coil. Two of the first, second, and third taps are selected to drive the primary coil between the two selected taps.

A phase shifting transformer for poly-phase alternating current includes source side terminals, load side terminals, an exciting unit, and a series unit. The exciting unit includes further coils that are magnetically coupled to primary coils and to the secondary coils of the exciting unit to provide further voltages. The further coils are connected in series between the source side terminals and the series unit, so that the voltages at the load terminals are combinations of the quadrature voltages and the further voltages with the source voltages, thus modifying the voltage phase displacement between the source side terminals and the load side terminals.

The present disclosure relates to a voltage regulation circuit (100). The voltage regulation circuit (100) comprises a transformer (130) having a primary winding (132) having a first end (132A) and a second end (132B), and a first secondary winding (134) having a first end (134A) and a second end (134B), wherein the first end (132A) of the primary winding (132) is configured to receive an input voltage and the second end (132B) of the primary winding (132) is configured to produce an output voltage, wherein the first end (134A) of the first secondary winding (134) is connected to a neutral node (180), wherein the primary winding (132) produces a primary voltage based on the input voltage, and wherein a secondary voltage of the first secondary winding (134) is out-of-phase to the primary voltage of the primary winding (132); and a first switch (160) configured to connect the second end (134B) of the first secondary winding (134) with the second end (132B) of the primary winding (132), wherein, when the first switch (160) is connected, the output voltage is the secondary voltage.

A multi-level high-speed adjustable speed drive has a plurality of modular multilevel, 3-phase inverter bridges, wherein the multilevel, 3-phase inverter bridges operate with fundamental frequency, f, wherein the multilevel, 3-phase inverter bridges include at least three levels, wherein the multilevel, 3-phase inverter bridges operate in Pulse-Width Modulation (PWM) mode with 9 to 21 or operating in Fundamental Frequency Mode (FFM), wherein inverter commutation frequency equals the fundamental frequency, wherein the multilevel, 3-phase inverters operate with split phase such that one group is displaced from the other by an angle, =60/q, wherein the phase displacement of a harmonic component of order n between groups, .sub.n is n/q; a high-speed polyphase motor with phases arranged in q 3-phase groups; and electromagnetic means for blocking selected groups of harmonics while passing components at fundamental frequency, f, wherein the electromagnetic means includes coils carrying motor current linked by a magnetic core, wherein the electromagnetic means is interposed between the plurality of modular multilevel, 3-phase inverter bridges and the high-speed polyphase motor.

This consists of a system capable of integrating all the control, supervision and monitoring functions of power transformers (2) equipped with on-load tap changers bringing benefits such as design simplifications, manufacturing simplifications, reductions in manufacturing costs, optimization and reduction of maintenance costs, and increased reliability of the transformer, which is promoted to the category of intelligent transformer, ready for the Industrial Internet of Things (IIoT) and Smart Grids.