Three Phase Tap Changer used in Oil Transformer

Henan New Electric Power Co., Ltd deals in the R&D, manufacturing and sales of various medium, high and low voltage transformer and transformer accessories. The transformer accessories mainly include Buchholz relay, tap changer, oil level gauge, butterfly valve, moisture absorber, pressure reducing valve, cross flow cooling fan, bimetal thermometer, epoxy resin insulator, etc.

The structure of off circuit tap changer consists of drum, cage, strip, disc and wedge.

1. The drum structure off circuit tap changer is usually a single-phase structure switch. The static contact column is cylindrical, and the moving contact is circular. A disk spring is installed in the circular moving contact. When the switch is changed, the moving contact is allowed to have displacement relative to the central axis. The contact pressure is determined by the displacement of the moving contact relative to the central axis. After the exchange, the moving contact is in a stable position. Drum switch is generally used for voltage regulation in the middle of winding.
2. Wedge structure off circuit tap changer Wedge structure off circuit tap changer is named because the moving contact in its contact system is wedge-shaped. The static contact is the same as the drum switch, which is also cylindrical. The moving contact is wedge-shaped. The moving contact of the wedge switch is compressed by cylindrical spring. The contact resistance is relatively stable. The overheating of the contact is less than that of the drum switch.
3. Cage structure non excitation tap changer The cage switch usually has multiple insulation columns, and the upper end and lower end are provided with metal flanges to connect the insulation columns. A fixed contact is installed on the insulating column. The center of the flange is a rotating shaft on which a moving contact is installed. The insulating shaft of the rotary switch can drive the moving contact to rotate to adjust the tapping position. When the voltage is low, the cage switch can be made into a three-phase structure. When the current is high or the voltage is high, the fixed contact of the cage switch which is usually made into a single-phase structure is cylindrical or plate shaped, the moving contact is clip shaped, and the contact spring is cylindrical spiral spring, with stable pressure and reliable contact. Cage switch is suitable for large current and high voltage. Now domestic manufacturers can produce 330kV cage switch with rated current up to 6000A.
4. Strip structure off circuit tap changer
The fixed contact of the strip switch is installed on the long insulating column or insulating plate, and the moving contact moves in a straight line along the direction of the insulating column to change the tapping position.

5. Disc structure off circuit tap changer
The fixed contact of the disc structure non excitation switch is installed on the disc shaped insulating part, and the moving contact rotates in the center of the disc to change the tapping. Disk switch is commonly used for neutral point voltage regulation of Y connection winding, three-phase structure, and the general voltage is not higher than 35kV.