Elevators & Escalators
Quality in Motion
History of the Elevator Mitsubishi Monumental Elevators Elevator Structure and Equipment Basic Operations Emergency Operations Systems Special Features Glossary
1. Driving System
(1) Traction Method
Two types of driving systems for rope-type elevators include drum method (winding-drum type elevator) and traction method (traction type elevator). The traction method comprises the following:
(a) Geared
Motor rotation (speed) is reduced by 1/10th using a speed reducer equipped with worm or helical gears, and transmitted to the traction sheave of the traction machine.
(b) Gearless
The traction sheave is connected directly to the shaft of the traction motor, and the motor rotation (speed) is transmitted directly to the traction sheave without any intermediate gearing.

Traction Method
(2) Hydraulic Type
With the hydraulic type driving system, the hydraulic power unit forces oil into the hydraulic jack (a combined plunger and cylinder) and the plunger pushes the car upwards using energy stored in the oil under pressure. The car descends automatically as the oil returns to the cylinder along the same route. Car-and-jack combinations are described in the table below.

Following the introduction of the machine-room-less traction method elevator, production figures for hydraulic-type elevators have been falling each year.
(a) Direct Acting (direct plunger driving)
Plunger pushes up car directly at a 1:1 ratio of plunger-to-car movement.
(b) Indirect Acting (suspended type or roped hydraulic drive)
Plunger is connected to car by roping using a deflector and suspension sheave, moves car up and down at a 1:2 ratio of plunger-to-car movement.

Hydraulic Type
2. Roping Systems
There are various roping systems as shown in the figures and tables below. Although they vary according to the traction speed, rated load, and other factors, roping should be kept as simple as possible. Reducing the number of deflectors and suspension sheaves improves longevity and efficiency of the ropes.

With 2:1 or 4:1 roping, car speed is reduced to 1/2 or 1/4, respectively, of the rope speed, because suspension sheaves are provided above (or below) the car and counterweight, and both ends of the rope are attached to the machine room beams. With these roping systems, loads on the rope is reduced to 1/2 or 1/4 as well, hence the diameter and number of ropes can be reduced.
Fig. Elevator Roping Systems
(a) (b) (c) (d) (e)
(f) (g) (h) (i)
Elevator Roping Systems
Fig. Roping Roping method Principal use
a 1:1 Half wrap (Single wrap) Mid-, low-speed elevators
b 1:1 Full wrap (Double wrap) High-speed elevators
c 1:1 Drum winding Home elevators
d 1:1 Drum winding Small, low-speed elevators
e 2:1 Full wrap (Double wrap) High-speed elevators
f 2:1 Half wrap (Single wrap) Freight elevators
g 2:1 Half wrap (Single wrap) Machine-room-less elevators
h 3:1 Half wrap (Single wrap) Large freight elevators
i 4:1 Half wrap (Single wrap) Large freight elevators
Control System
For current rope-type elevators, the trend is toward use of VVVF Inverter Drive control systems due to their ease of control and energy conservation qualities.
VVVF Inverter Drive
AC power is first converted into DC through a converter, then DC is converted back into three-phase AC. Voltage and frequency are varied to control rotation of the electric motor. By controlling motor rotation speed and torque, this control method delivers superb ride comfort and excellent landing accuracy at each floor.
Energy Use Comparison (with previous Mitsubishi Electric control system)
Control system Conservation
VVVF (Variable Voltage & Variable Frequency) for high-speed elevators Can conserve between 5% and 10% of energy, reduce required power supply by approx. 30% and save space compared to conventional Thyristor-Leonard control.
VVVF (Variable Voltage & Variable Frequency) for low- or middle-speed elevators Can conserve approx. 50% of energy compared to conventional feedback control.