HMV1 series vacuum on-load tap-changer is suitable for rated voltage 35 ~ 220kV, the maximum rated passing current is three-phase 500A, 800A, single-phase 500A, 800A, 1200A, 1500A, frequency is 50 ~ 60Hz power transformers and industrial transformers, change the tap under the load to achieve the purpose of voltage regulation. The three-phase vacuum on-load tap-changer is used for neutral voltage regulation in the Y-connection method, and the single-phase vacuum on-load tap-changer is used for any voltage regulation method.

The product of this system is a combined vacuum on-load tap-changer. It is composed of a switching switch and a tap selector (with a polarity selector). The vacuum on-load tap-changer is mounted on the transformer box cover using a head flange and is driven by an electric mechanism mounted on the wall of the transformer box via a drive shaft and a bevel gear box.