are elevators which are powered by a piston that travels inside a cylinder. An electric motor pumps hydraulic oil into the cylinder to move the piston. The piston smoothly lifts the elevator cab. Electrical valves control the release of the oil for a gentle descent.
Hydraulic elevators are used extensively in buildings up to five or six stories high. Sometimes, but rarely, up to 8 stories high. These elevators, which can operate at speeds up to 61 meters (200 ft) per minute, do not use the large overhead hoisting machinery the way geared and gearless traction systems do.
All modern hydraulic pumps are either equipped with a Solid-State Contactor or a mechanical Y-Delta starter. Solid-State Contactor starters are better for the motor and the building’s power supply, as the windings last longer and there are no voltage drops across the line of the building’s power supply. Y-Delta starters use two contactors to start the motor on a reduced speed, then kick on full speed. Old hydraulic elevators just started up abruptly, sending mains power at full blast right into the motor. This puts a lot of strain on the motor which, in turn, makes it burn out faster than motors on Y-Delta or Solid-State Contactor starters.