VVVF elevators

     In 1982,Mitsubishi Electric successfully developed a special frequency converter for elevators by using GTR module and 16-bit microprocessor,and took the lead in introducing fully computerized AC VVVF elevators in the world.Driven by AC motors and controlled through vector transformation and PWM,VVVF elevators have their operational performances reaching or surpassing those of nearly all previous elevators adopting various AC and DC drive systems,and a lot of energy is saved in addition.At the beginning of the nineties,with the appearance of more advanced IGBT and further development of computer technology and LSI,Mitsubishi Elevator has timely applied up-to-date technology and elements to VVVF elevators,thus achieving high performance and reliability in digitized and miniaturized products and keeping its VVVF elevators in the leading position in the world.At present,Mitsubishi Elevator VVVF is fully applied to elevators,hydraulic elevators,escalators and moving walks,covering elevators with a speed range of 0.45m/s 12.5m/s.

   For any elevator speed,Mitsubishi VVVF 
drive systems using PWM and vector transformation can accurately adjust the motor rpm in accordance with the optimal speed curve.The frequency conversion system designed specifically for elevator systems integrates IGBT module or IPM module,high-speed CPU and LSI.Its accurate computing capacity,quick response capability and excellent disturbance resistance make it possible for speed variations at start,travel and stop to fully adapt to the psychological feeling of the human body and for the passengers to enjoy comfortable and stable up and down travels.Furthermore,elevators adopting Mitsubishi VVVF can save nearly 50% energy,when compared with conventional AC voltage variable speed-regulated elevators,in addition to reduced capacity of power supply equipment.
 Ⅰ  Description of Mitsubishi speed curve:

A. Start:The digital linear weighing device weighs accurately the load in the car.The car isstarted after a torque is applied accurately according to the measured weight,so as to avoid start impact due to the car load.
B.  Acceleration/deceleration:The drive system conducts accurate computation,responds quickly and effectively suppresses disturbance so as to achieve a perfect actual speed curve to ensure good travel comfort.
C.  Stop:Accurate control and zero speed stop avoid braking and stopping impact.
Ⅱ   Description of ordinary elevator curve:
A.  Start:Switch-type weighing device and non-linear switching output can not accurately measure the load in the car.When released,the brake can not make effective compensation for unbalanced load,so that start impact is likely to happen.
B.  Acceleration/deceleration:relatively slow response,poor resistance to disturbance,many burrs on the actual speed curve,low travel comfort.
C.  Stop:low control accuracy,no zero-speed stop,impact with braking/stopping.
     Applying VVVF for elevator drive to the door operator system,Mitsubishi has designed a special VVVF-driven intelligent door operator system.Dual closed loop control for speed and current is applied for effective control of the speed and torque for door opening/closing.

    Door weight (heavy stainless steel door or light painted steel door,for example) on each floor is memorized in an intelligent way,and based on that,the door opening/closing torque is regulated automatically to realize quick,smooth and quiet door opening/closing.In the meanwhile,flexible current measurement and torque control enable quick inspection and reverse opening in case of door closing being blocked (by hand of the passenger for instance),thus reducing impact upon the blocking object,improving passenger safety,and avoiding possible damage of the door system by heavy blocking objects.

Development of Chinese elevator industry

An elevator is a permanent transport device that serves a number of specific floors within a building and whose cabs run on at least two columns of rigid orbital motion perpendicular to the horizontal plane or inclined at an angle of less than 15 ° with the vertical.Also stepped, stepping board mounted on the track to run continuously, commonly known as the escalator or automatic sidewalk.

After 30 years of development,China's elevator industry has become an indispensable part of the modern society. It played an irreplaceable role to improve the people's quality of life and achieve the policy "energy-saving land-saving" of China's construction industry.Cause the close relationship between elevator and safety of daily life,it has been defined as special equipment by our country for many years.And its development has always been concerned by the government and the people.

      As one of the earliest industries in China's opening up to the outside world,foreign brand monopoly market share has been more than 95% .But in recent years, a number of Chinese elevator companies began to rise, changing the pattern of the elevator market.At present, China has become the main battlefield of the global elevator giants competition.China elevator industry is facing reshuffle of the industry, the national brands should use the support of the national policy, the capital market to support or any other aspects of favorable factors  to win more market.

    At the beginning of Chinese economic reform, In view of the fact that lack of both capital and technology, the country decided to introduce foreign capital, so the elevator industry become the first foreign investment in China.From 1980,Tianjin elevator factory, Shanghai elevator factory, Shenyang elevator factory and other large domestic elevator enterprises, all joint venture with  foreign brands such as Otis,MITSUBISHI.At present, the international elevator market is mostly monopolized by Otis, KONE,Schindler,thyssenkrupp,MITSUBISHI, Toshiba, Hitachi, Fujitec.Their sales and service outlets throughout all big cities over the world, and their sales accounted for more than 90% of the global total sales.

    China has now become the world's largest elevator consumer market, the huge demand has attracted all the world famous elevator companies to invest in China.China also provide a fair competitive mechanism for those world's most competitive elevator companies.Foreign brandselevator whether

choose well-known local elevator companies as partners, or build their won world-class factories and a lot of them have transferred their own production center and R & D center to China.These famous foreign elevator enterprises have monopolized the Chinese elevator market more than 70% of the share for a long time.

    According to the report from China Elevator Association statistics,by 2010,foreign elevator enterprises sole proprietorship or joint venture have monopolized the Chinese elevator market more than 70% of the share,Imports accounted for 1% of the market share ,and local elevator elevator enterprises the rest 29%.

prises have monopolized the Chinese elevator market more than 70% of the share for a long time.

     Since last century, 90s, a large number of private enterprises began to intervene in the elevator industry.They do matching from foreign companies or joint ventures with foreign enterprises, continuous learning in the production process and digestion technology, brought from foreign enterprises in the international technical standards, installation and maintenance system and management system etc.,The Independent Chinese elevator brand improved their technology, quality, management, services, and quickly entered the ranks of internationalization.and gradually developed into occupied a certain market share, began to break the monopoly of foreign brands.

As the industrial layout ,China elevator machine and parts manufacturing is concentrated in the Yangtze River Delta, the Pearl River Delta region.Elevator production in the Yangtze River Delta region accounted for more than 60% of the country.