| Brand | Transformer Parts |
| Model NO. | VUBB Series Tap-changers |
| Methods of regulation | Positive and negative voltage regulation |
| Series | VUBB Series |
Overview
Functional description
The on-load tap-changer is a device for changing the tapping connection of a winding while the transformer is under load. The main purpose is to keep a constant voltage out from the trans-former and to compensate for variations in the load situation. The tap-changer is connected to the transformer via the tap winding. The main function is tap selection, which is done by changing the number of turns on the regulating winding.
Although numerous di¢erent circuit solutions are available, the selected solution has been found to have the best combination of technical performance and potential for economic operation. By using auxiliary contacts in combination with vacuum interrupters, the contacts are used for carrying current and the vacuum interrupters are used for the energized switching. With this solution, only two vacuum interrupters are required per phase.
The electrical circuit principle for the VUBB is shown in Figures¤03-20. The purpose of the operation is to commute the load from one tap to the other, in order to change the voltage.
Depending on in which direction the center shaft is rotating, two di¢erent contact sequences are obtained – either the main contacts operate first, or in the other direction, the transition contacts operate first. The figures show the contact sequence together with the physical position of the interrupter.
