Otis OVF10

The OVF10 is Otis’s entry-level variable frequency lift drive, designed for low-speed, low-rise installations and used both in new lifts and in modernisation, where it could take over most of the one-speed and two-speed AC machine motors already in the field. On a two-speed motor it drives the high-speed winding, to a maximum of 1.2 metres per second.

It runs entirely open loop, with no encoder and no tachometer. Position and levelling come from a pair of hoistway sensors, and the point at which deceleration begins is calculated from the time elapsed since the last door zone. That buys a cheaper installation at looser stopping accuracy, typically 5 mm and at worst 8 mm. The drive is built around a DCB_I control board feeding a six-transistor inverter bridge, with braking energy burned in a resistor rather than returned to the mains, in 400 volt and 220 volt three-phase versions.