Elevator Music (not really)

[David Farber <farber () central cis upenn edu>]

From: D.K.Kahaner, ATIP-Tokyo [kahaner () cs titech ac jp]
Re: Elevator technology
Date: 02/23/95 [MM/DD/YY]


Dr. David K. Kahaner
Asian Technology Information Program (ATIP)
Harks Roppongi Building 1F
6-15-21 Roppongi
Minato-ku, Tokyo 106
 Tel: +81 3 5411-6670; Fax: +81 3 5412-7111


ATIP: A collaboration between
   US National Institute of Standards and Technology (NIST)
   University of New Mexico (UNM)
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ABSTRACT. The Yokohama Landmark Tower, opened in 1993, has the worlds
fastest elevators. The basic technologies required are described, as well
as a comment about the marketing strategy the project illustrates.




The following report is based on material in the Japanese publication
JETRO, Jan 1995 pp2-5, describing the basic technology characteristics of
the Landmark Tower elevator system (Yokohama), currently the world's
fastest, built by Mitsubishi Electric Corporation. Following that, are some
summary comments based on discussions with Western experts.


The world's fastest passenger elevators in the Yokohama Landmark Tower
building -- opened to the public on July 17, 1993 -- travel at speeds up
to 750m/min providing a comfortable ride to the observation deck at the
69th floor in the 296 meter high-rise building from the 2nd floor in 40
seconds. Highly advanced new technologies were developed for the
manufacture of these super-high speed elevators by the Inazawa Works of
Mitsubishi Electric Corp. (MELCO), a world's leading manufacturer of
elevators.  The elevators in the Sunshine 60 Building in Tokyo,
traveling at speeds up to 600m/min -- also delivered by Mitsubishi
Electric in 1978 -- had to cede the world's high-speed record to the
Landmark Tower elevators.


The production of elevators is closely linked to the construction of
high-rise buildings. As elevators are indispensable setups to high-rise
buildings as means of vertical transportation, the demand for elevators
has been expanding steadily, and is expected to grow further worldwide,
although the building construction in Japan seems to have been
progressing at a slower pace since the end of the bubble economy period.
Construction of higher buildings and subterranean development in the
urban areas are inevitable internationally. With the increase of
gigantic buildings such as skyscrapers and subterranean constructions,
high speed and super-high speed elevators will become more and more
important in the future. In addition, there is a potentially big market
due to the increasing need for installation of elevators in lower
buildings and public facilities in view of the expanding ratio of aged
people in the society.


Elevator is a setup in which a steel cage is hoisted with ropes and
moved vertically by the drive of the ropes with a traction machine. To
keep up with the need for higher speed in concert with the construction
of higher buildings, a series of diverse innovative technological
developments have been achieved. Specifically, higher power motors for
traction machines, electronic drive control equipment, energy saving
mechanism in the overall system, higher performance safety devices, and
the progress in the machining technologies of helical reduction gears
for middle and low speed elevators. The most remarkable above all is the
recent development of power electronics which has brought up the
innovation in the drive control system for AC motors. The super-high
speed elevators of Landmark Tower employ high-output AC traction motors
with variable-voltage, variable-frequency (VVVF) drive control units
which accurately control the running of elevator cars to achieve the
world's fastest speed with good riding comforts, as well as energy
saving.


This report describes the outline of basic technologies, and the highly
advanced technologies developed for the world's fastest elevators by the
Inazawa Works of Mitsubishi Electric Corp.


 MECHANISM OF ELEVATOR
The most commonly used rope-hoisted elevator consists of a cabin car
cage, a traction machine with a drive control unit, and the hoistway in
which the car travels up and down. The cage is connected to counter
weights with ropes, and the ropes are driven by the traction machine via
the rope sheave, in which ropes role in and out. The car moves upward
and downward along the guide rails installed in the hoistway shaft.
Guide rollers absorb the vibration generated by the friction between the
cage and the rails. The counterweights are stacks of 30 to 50kg weight
units made of cast iron or concrete in steel frames.  Rails are with a
T-shape cross section similar to rollingstock rails. Up to ten wire
ropes possessing adequate strength are used to withstand the load of a
cage.


When the speed of the elevator exceeds the prescribed speed by 1.2-1.4
times, the overspeed governor clamps the governor rope. As the car
continues to fall, the governor rope moves the fixed operating lever to
raise the safety brake shoes of safety gear installed under the car to
grip the guide rail.  Friction between the brake shoes and the guide
rails slows the car to a halt. At the bottom of the hoistway, damper
device is installed as a precaution against the failure of the car's
landing at the right position.


 TRACTION AND CONTROL SYSTEM
Until the first half of 1980s, most of the high speed elevators employed
the Ward Leonard System in which a set of motor and generator (MG set)
is used for converting AC current into DC current. The DC current is
supplied to the DC motors, which is the driving source of the traction
machines in this system (see Fig. 2). With this system, the DC current
generator is revolved at a fixed rate by an AC motor and the output
voltage is controlled by altering the magnetic field voltage of the
generator. The electric current with the controlled voltage is fed to
the DC motors to achieve the control of the speed of the motors. As this
mechanism allows easy control of the speed of traction machine motor,
the Ward Leonard System had been used widely for high speed elevators
for a long time. For example, the elevators in the Sunshine 60, which
had been the world's fastest until the Landmark Tower elevators broke
the record in 1993, are using this Ward Leonard System.


Elevators are used intermittently but have to be kept always ready for
use so that they can start moving promptly when passengers press the
call buttons. This means, with Ward Leonard System elevators, the MG set
has to be always kept running -- although energy has to be consumed
while waiting for the use -- to avoid the long lead time before the
elevators start moving if the MG set is started upon request.


Thyristor Leonard System employs thyristor circuit which uses power
transistors to convert the AC current into DC current for the DC
traction machine motor. The response of the thyristor circuit is so
quick that it can be started only when calls for use come. Energy
consumption can be reduced by about 30% through the application of this
system.


Further progress in the power electronics has led to the development of
VVVF inverters, which has enabled a wider use of AC motors as the
driving source of traction machines. The control of AC motors is very
difficult compared to DC motors, particularly at the higher revolution
range. This fact had been preventing the wider use of AC motors despite
their higher power and easier maintenance. The VVVF inverter system
allows AC motors to be controlled with an accuracy equivalent to that
for DC motors. Now, the AC motor based system is regarded as the one
that will become the main system in the future as a result of the
development of higher performance VVVF inverter which can be used for AC
motors even for high speed and super-high speed elevators.


 HIGH SPEED ELEVATORS AND HIGH-RISE BUILDINGS
Higher speeds of elevators have been pursued in concert with the
progress of the construction of higher buildings. With elevators, high
speed means faster than 120m/min and super-high speed faster than 360
m/min.  Low speed is the range slower than 45m/min, and middle speed is
the range from 60 to 105m/min.


Superhigh-rise buildings, called skyscrapers, were first built in New
York in the U.S.  Empire State Building, with a height of 378m, was
built in 1931 and 360m/min elevators were installed. Higher building had
not been built for a long time until the World Trade Center Building --
with a height of 480m and 480m/min elevators -- was built in 1972. In
1973, the Chicago Sears Tower Building was completed with 442m height
and 540m/min elevators.


The first high-rise building in Japan was the Mitsui Kasumigaseki
Building which was built in Tokyo in 1968. The Kasumigaseki Building has
a height of 147m and 300m/min elevators were installed.  Several tall
buildings followed, and the Sunshine Building was built in 1977 with a
height of 240m and 600m/min elevators.  Recently, the New Tokyo
Municipal Government Building was completed in 1993, to which VVVF
system 540m/min elevators were installed. The 750m/min Landmark Tower
elevators followed in July 1993.


 HELICAL GEARS
The development of helical gears is a remarkable achievement in the
field of elevator technologies. With middle and low speed elevators,
gears have to be employed to reduce the revolution of motors before
supplying to the rope sheave. Gears are very important component for
lower speed elevators, while traction machines for super-high speed
elevators are with a gearless structure. Worm gears and helical gears
are known as the reduction gears.  Although the helical gears' power
transmission efficiency is higher than that of worm gears by more than
30%, worm gears have been more widely used due to the difficulty of
machining of helical gears. Unless machining of gears is made with high
precision, noises and vibrations occur. The recent progress in gear
cutting machine and advance of machining techniques have made the use of
helical gears practical, and now the elevators using the helical gears
can be operated with 15% reduction of energy consumption compared to
elevators using worm gears.


 MARKET FOR ELEVATORS
Annual demands for elevators are estimated to be about 30,000 units in
Japan, 20,000 in the U.S., 50,000 in Europe, and 12,000 in Southeast
Asia, making the total worldwide market size about 140,000 units a year.
Japan's demand of 30,000 a year is very large and the total number of
currently operating elevators in Japan as of the end of March 1993 is
reported to be about 380,000 units.


 THE WORLD'S FASTEST ELEVATORS
The Yokohama Landmark Tower, with a height of 296m, is the tallest
building in Japan. The building consists of a 70-story tower building
and an adjacent 5-level shopping mall complex with a hotel banquet hall,
etc. The high-rise tower contains 42 office floors up to the 48th floor
and 18 hotel floors on the 52nd floor and above, 3-level sky restaurant,
observation deck and sky lounge/banquet hall. There are 52 elevators and
8 escalators for vertical transportation in the tower complex, 28
elevators and 56 escalators -- including 2 spiral escalators -- in the
adjacent building. The 3 units out of the 52 elevators in the tower
complex are the world's fastest passenger elevators, which travel at
750m/min. The outline of the highly advanced technologies which have
made these fastest elevators possible are described below.


 TRACTION MACHINE AND DRIVE CONTROL SYSTEM
 * Traction machine
The newly developed traction machine -- which provides the required
traction drive for the super-high speed and heavy hoisting load for the
long hoistway traveling -- employs an eight-pole AC motor with large
power capacity of 120kW, and has a gearless drive mechanism. 10
suspension ropes, each 18mm in diameter, and a large sheave, 980mm in
diameter, are used to support the large load. The rigidity of the motor
was reinforced and the optimum numbers of slots of rotor and stator were
selected to reduce the magnetic noise generated by the large AC motor.
The traction machines for the Yokohama Landmark Tower are the largest
ever used by Mitsubishi Electric in output capacity and weight-output:
120kW, weight: 12.5 ton.


 * Drive control system
To supply the large electric current with optimum voltage and frequency
to the motor, inverter/converter circuit with variable-voltage,
variable-frequency (VVVF) system is employed. Six 300A transistor
modules are connected in parallel for the converters/inverters. The
input current and output currents are controlled by pulse width
modulation (PWM). A high-performance digital signal processor is mounted
for the control of the circuit. To realize good riding comfort in the
high-speed elevator, it is important to reduce the vibrations which are
substantially increased as the speed increases. Torque ripple generated
in the motor is one of the causes of the vibrations, particularly the
vertical vibration of the elevator cars. Therefore, several advanced
circuit control mechanisms -- such as a function to compensate the
voltage disturbance caused by the inverter's dead time function, etc. --
are used to reduce the torque ripple.


 * Safety devices
   Safe gear
 The safety gear, an emergency braking system installed under the car,
is equipped with safety brake shoes which gap the guide rail when a
higher-than-rated speed is detected, to slow the car to a halt by
friction between the brake shoes and the guide rail. With the 750m/min
elevator, the brake shoes have to cope with large kinetic energy, about
twice as large as that for 600m/min elevator. Conventional shoes made of
cast iron or alloys would wear out when the shoes' operating speed
reaches 800m/min due to the temperature elevation on the shoes' rubbing
surfaces, resulting in insufficient braking performance. However, the
safety device for the 750m/min elevator is required to deal with the
maximum speed of 937m/min. Therefore, it was necessary to develop new
ceramic shoes which can withstand the high temperature to assure the
desired reliable braking performance.


   Oil buffer
  The oil buffer absorbs the shock and decelerates the speed of the
elevator car at the bottom of the elevator shaft in case the car fails
to stop at the bottom floor. The developed oil buffer, the largest ever
produced for elevators, has a stroke of 4,000mm and a spring made of
high-tensile steel is installed at the end of the stroke that receives
the plunger flange.


   Cabin cage
  Riding comfort of elevator is particularly affected by lateral
vibration and aerodynamic noise. Lateral vibration, mainly caused by
curvatures of the guide rails, increases in proportion to speed. The
degree of lateral vibration varies, depending upon the degree of forced
displacement, frequency of the displacement and the vibration
characteristics of the car. The reduction of car vibration is vitally
important to achieve a comfortable ride with super high-speed elevators.
It was possible to reduce the vibration by 20% through the reduction of
the curving degree of the guide rails, and through the improvement in
the vibration characteristics of the car-by using a roller-guide with
newly developed oil-filled dampers that reduce lateral movement, and
placing additional dampers between the car frame and cabin. Elevators
are also subject to aerodynamic noise which is caused by the airflow
around the traveling car. With high speed elevators, the aerodynamic
noise becomes a more serious problem than the mechanical noise caused by
the contact between an elevator and the guide rails because the
aerodynamic noise becomes larger in proportion to the wind velocity to
the (approximately) sixth power -- aerodynamic noise is usually louder
than the mechanical noise at 750m/min. Therefore, it is very important
to reduce the aerodynamic noise.  Streamlined covers, designed according
to the results from experimental analysis, were mounted at the top and
bottom faces of the car. Aerodynamic noise is likely to enter the car
through door due to the clearance between the doors and the cabin for
the door open/close structure. As a solution, sound insulation shields
were applied to seal the clearance when the doors were closed. A
double-wall structure, separating the inner walls from outer, is also
employed to reduce the noise caused by the vibration of car walls due to
air pressure fluctuation.  Also, to suppress the reverberation of the
noise which enters the car, a double-floor structure of punching metal
and an air gap underneath -- with a carpet made of sound-absorbing
porous material placed on top -- was developed.


 SIMULATION
 Integrated simulation tools of computer software, including a
finite-element method (FEM), as well as testing equipment/devices, were
indispensable for the development of the 750m/min elevators.  For
example, such a super-high speed elevator requires testing of
acceleration and deceleration in the hoistway as long as 200m or over,
far longer than the hoistway of the testing tower. Therefore,
simulations on computer were made and many tests were carried out
through the specially developed traction drive control simulators on the
ground to verify and analyze the results gained from the computer
simulations, obtaining more information on the dynamic characteristics.
A traction motor was connected to a load-supplying motor via a flywheel,
and the actual control panel was installed to supply voltages and
currents according to the designated speeds for acceleration and
deceleration, or running at fixed speeds. The load-supplying motor
supplies the equivalent torques for motoring and regenerative braking
according to the loads demanded by the car. In this way, testings were
conducted under almost the same conditions as the actual runs.


 The three-dimensional finite element method (FEM) program "ANSYS" was
used to analyze the temperature characteristics of the shoes' rubbing
surface, and the result indicated that the temperature on the rubbing
surface would be elevated to a temperature higher than 750'C at
900m/min. "Shoe material selection test" was conducted with a disk test
device, in which the shoe was activated at the predetermined speed by
the rotation of the disk. Then, a free-fall test was made using a
1/10-scale model car to confirm the accuracy and consistency of data
gained from computer simulations.  After the two tests, the braking
performance of the safety device was confirmed by a test made in the
test tower of the Inazawa Works under conditions equivalent to the
actual elevator setup.


 For the design of the oil buffer, dynamic characteristics of elevator
car were analyzed in the deceleration simulation taking the actual speed
and load into consideration in order to achieve the desired buffer
functions. Also, for researching ways to improve car vibration
characteristics, the model characteristics were simulated by a FEM
program followed by simulations using a vibration test device.


 INAZAWA WORKS AND MANUFACTURE OF ELEVATORS
 Mitsubishi Electric Corp. started the production of elevators and
escalators in 1931, and the Inazawa Works was established in 1964 as a
specialized production facility for the manufacture of
elevators/escalators. The works is the world's largest factory in this
field with a labor force of 1,470, a land area of 184,000m^2 and a floor
area of 93,400m^2.


 The flow of manufacturing process up to shipment in the factory is
controlled dividing components into the following 5 blocks taking the
convenience for the installation at customer sites into consideration,
as the production process of elevators completes when they are installed
in the buildings.


 Block(A) Cabin entrance components (destination button, entrance unit,
threshold, door, etc.)


 Block(B) Power/control components (control panel, traction machine,
frames for traction machine fitting, rope shackle beam, overspeed
governor, etc.)


 Block(C) Hoist room components (guiderail, buffer, buffer base, etc.)


 Block(D) Cabin structural components (cage frame, cage floor, safety
gear, brake shoes, suspension rope, counterweight, tension sheave, etc.)


 Block(E) Cabin components (cabin body panel, cabin door, door control
unit, etc.)


 Elevators are manufactured with diverse specifications for individual
orders with a system in which the manufacture, delivery and installation
of each block of components are made in concert with the timing required
by the progress of building construction work. Maintenance technical
service after the installation is also an integral part of the total
system, for which Mitsubishi Electric provides a network of more than
220 service centers throughout Japan.


 The topic making achievements by Mitsubishi Electric in the elevator
manufacture field are described here to illustrate the development of
elevator production technology.


 1935-First elevators and escalators delivered.


 1966-Total number of elevators and escalators manufactured passes the
10,000 mark.


 1970-Superhigh-speed elevator (300m/min) developed.


 1972-New group-control system elevator, the OS System 700, marketed.
Superhigh-speed elevator (450m/min) developed.


 1974-Total number of elevators and escalators manufactured passes the
50,000 mark.


 1978-World's fastest passenger elevators (600m/min) delivered.


 1982-inclined elevator marketed. Japan's first VVVF inverter controlled
elevator marketed.


 1983-Total number of elevators and escalators manufactured passes the
100,000 mark.


 1988-World's first zig zag elevators delivered.


 1989-Total number of elevators and escalators manufactured passes the
150,000 mark (including 30,000 units for overseas).


 1990-Delivered elevators for use in a skyscraper owned by the Bank of
China in Hong Kong (the tallest building in Asia, 368 meters).


 1993-Delivered the world's fastest passenger elevator (750m/min) Total
number of elevators and escalators manufactured passes the 200,000 mark
(including 39,000 units for overseas).


 *Inazawa Works, Mitsubishi Electric Corporation
 1, Hishimachi, Inazawa City, Aichi Pref. 492 JAPAN
 Tel:+81-587-23-1111; Fax: +81-587-24-5674


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COMMENT:
Most elevator companies are aware of the MELCO Landmark Tower elevator
and related technical developments. It illustrates several key points
about the construction industry and related building systems markets in
Japan.


1. In the construction industry in Japan, it is common that member
companies of the same keiretsu work together on large or showcase
projects. The Landmark Tower is a showcase for Mitsubishi Estate and
Mitsubishi Electric. This coupling between developers and building
systems makers of the same keiretsu is common particularly for such
large projects. For example, a close working relationship exists between
Sumitomo Realty and NEC, who are both members of the Sumitomo Group. NEC
manufactures building systems such as HVAC controllers, building
management systems, security systems, etc.


2. The high speed elevator in Yokohama also illustrates the single
attribute development strategy of elevator makers in Japan. In this
case, MELCO selected speed as the primary attribute to develop for this
project. Although many other technologies had to be improved, such as
safety devices, the thrust of the development effort was on improving
cab speed.


The Landmark Tower elevator is clearly the fastest elevator in the
world. The top speed of the elevator is not confirmed yet. Latest
figures in the technical literature indicate a top speed of 800m/min.


3. The Landmark Tower elevator was developed and installed to fulfill a
need and also as a showcase project. Customer demand for elevators that
travel at speeds of 750m/min is not large, but MELCO created a distinct
marketing advantage by developing the fastest elevators in the world.
This approach is particularly effective in the construction industry of
Japan, which is hierarchical, and where owner-vendor interactions are
limited. In addition, having a product that certifiably excels in a
noteworthy characteristic is highly desired by Japanese customers.




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