The UC types of on-load tap-changers come in a wide range of models with a rating suitable for every application. They are usually mounted inside of the transformer tank, suspended from the transformer cover. The UC types operate with conventional arc quenching in oil and the VUC types operate with arc quenching in vacuum interrupters.
UCL is the medium size of the UC types, covering up to 525 kV and 1000 MVA.