· Low voltage control in three-phase lines without neutral.
· Control of phase shift and phase sequence.
· The voltage control is independent of the supply voltage.

· Protection of permanent surge (according to article 16 and ITC-B-23 of Regulation REBT)
· Used to protect against the effects of overvoltage or undervoltage on low voltage installations.
· The breaking of a neutral or a fault in the connection also causes overvoltages which must be protected.
· It controls overvoltages over 10% of the nominal value of the supply lasting for several net cycles or permanently.