... transmission and chain drive elevating, its speed changed by converter which has stable transmission and slow and stable speed change. ... current meter, voltage meter, voltage potentiometer, current potentiometer, feeding, back, button, welding start and stop.This welding ... : 7000mmBoom elevating speed: 1M/minBoom expansion speed: 0.12-1.2M/minSpeed control method: frequency conversionRotating angle: ...