HM1 series on-load tap-changer is suitable for rated voltage 35 ~ 220kV, the maximum rated passing current is three-phase 300A, 600A, single-phase 300A, 600A, 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 on-load tap-changer is used to regulate the neutral point of the Y connection, and the single-phase on-load tap-changer is used for any voltage regulation mode.

The product of this system is a combined on-load tap-changer. It is composed of a switching switch and a tap selector (with a polarity selector). The 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.