Reasonable choice of elevator speed in high-rise buildings

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Elevators are indispensable vertical transportation equipment in high-rise buildings. They are a convenient way for people to move between high floors. Whether they can meet the requirements of the building's passenger and cargo flow determines whether the elevator selection in the building is correct. Therefore, the specifications (including speed, load, control method, etc.), number and dispatching method of elevators should be reasonably selected. This is an important issue for elevators in high-rise buildings. This article focuses on analyzing and demonstrating the correct and reasonable selection of elevator speed, so as to determine the method of reasonable elevator speed. For an elevator in a high-rise building, after the maximum stroke H (m) is determined, under the standardized conditions of the rated load of the elevator, if the rated speed VN (m/s) of the elevator is selected too low, the one-time running time T (s) will be too long and the transportation capacity will be too small. In order to meet the transportation volume requirements in the building, it is necessary to install several more elevators, thus increasing the number of elevator shafts and increasing building infrastructure costs. This is a very uneconomical solution. If the rated speed of the elevator is selected too high, the time for a long-distance main lift can be shortened, and the transportation capacity of Nanchang City will be reduced. ； However, the rated speed cannot be reached during short-distance lifting. The cost of using a higher-speed elevator is very high, so it is also an uneconomical solution. Therefore, the essence of reasonable selection of elevator speed is the result of a comprehensive technical and economic comparison. At the same time, the scale, nature, characteristics of the building and some special requirements of the builder must also be considered. 1 Reasonable selection of elevator rated speed 1.1 Principles of elevator speed selection Principles of elevator speed selection: The first is a comprehensive technical and economic comparison of multiple solutions, and the second is a technical and economic comparison of a single elevator. The first method is greatly affected by many factors, especially human factors, so it is not easy to obtain a unified and simple expression model. ； The second method involves fewer influencing factors and is easy to obtain concise expressions. Therefore, this article adopts the second method, based on the dimensionless parameter analysis and calculation of elevator motion parameters established in the article "Optimal Parameters of Elevator Movement", and averages the actual parameters such as the running distance, time, one running time, maximum running speed, motor power, electric energy consumption, and motor heat and temperature rise of each section of the elevator movement into functions of the speed coefficient α, and optimizes the speed coefficient to obtain the optimal value range of α. The rated speed of the elevator is determined based on the small power and power consumption of the elevator driving motor, which is called the economic speed. At this time, α=1.1~1.2, considering the low value, 1.05~1.25. From the perspective that the elevator motor heat is small and the running time is close to the shortest, the partial speed of the elevator's short-distance operation is determined, then α=1.5. 1.2 The calculation basis for reasonable elevator speed selection is derived from the article "Elevator Movement is the Optimal Parameter": Under the conditions of a given lifting height H (m) and a set average acceleration a (m/s 2 ), the relationship between the elevator speed VN (m/s) and one running time T (s) and the speed coefficient α is VN 2 = (a-1) · (Ha) (1) T 2 = (a 2 /a-1) · (H/a) (2) From equation (1), it can be concluded that the reasonable applicable height of the elevator standard rated speed is H = V 2 N /a·1/a-1 (3) Solve equations ⑴ and ⑵ simultaneously and eliminate H, then we get T=VN /a·a/a-1 (4) Solve equations ⑶ and ⑷ simultaneously and eliminate α, then T=VN /a·H/VN (5) From formula ⑶ we can also get: Under the conditions of selecting the rated speed VN of the elevator and setting the average acceleration a, there is a minimum limit height applicable to the elevator. For a triangular running speed curve, when α=2, so Hmin=V 2 N/a. For a reasonable running speed, when α=1.5, so Hmin=2 V 2 N/a. For reasonable selection of the minimum applicable height for rated speed, when α=1.25, then Hmin=4 V 2 N /a. It can be seen from formulas ⑴ to ⑷: The reasonable speed and the most favorable running time of the elevator are both functions of the speed coefficient α, so the selection of a reasonable speed becomes a reasonable determination of the speed coefficient. For elevators with different rated speeds, the reasonable speed coefficients are shown in Table 1. 1.3 Graphical method for reasonable speed selection Now we use the graphical method to determine the standardized elevator speed. When the rated speed of the elevator is a fixed value and the acceleration is also constant, formula ⑸ shows that there is a linear relationship between the running time T and the lifting height H, and a straight line is drawn when the standard elevator speed is 0.5s, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 5.0, 6.0m/s and 8, 10, 12.5, 13.5, 15m/s. In order to determine the applicable height of the standard speed and the corresponding running time, the optimal value range of the speed coefficient α can be used to determine the upper and lower limits of its application. Formula (2) is used to undertake this task, so two curves with α of 1.1 and 1.2 are drawn. ； In order to have a better application range for low-speed and medium-speed elevators, two curves of α=1.25 and 1.5 are added. When the maximum operating height of a high-rise elevator is H, the reasonable speed VN and operating time T can be found from the figure. When H=100m, VN is found to be 3.5m/s or 4.0m/s ； When H=200m, VN is found to be 5.0m/s or 6.0m/s ； When H=300m, VN is 6.0m/s; when H=400m, VN is 8.0m/s ； When H=500m, VN is 80.m/s or 10.0m/s. 2 Analysis of the rated speed of elevators in several high-rise buildings There are currently many high-rise buildings in cities and towns in my country. Due to various circumstances and special requirements of the builders, the elevator speed is usually selected on the low side. For example, the height of the Xinjiang Aquatic Products Supply and Marketing Service Center is 105m, and there are 4 elevators with a speed of 1.75m/s and a capacity of 1,000kg. The Xinjiang Haide Hotel is also more than 100 meters high, and the elevator speed is 3.5m/s. ； In the book "Principles, Design, Installation and Maintenance of AC Speed-Adjusted Elevators", the building is 99.95m high, 30 floors, and the elevator speed is selected as 5m/s. The above 3 examples illustrate: The lifting height of elevators is about 100m, but the elevator speed varies greatly. Which speed should be chosen to be reasonable and economical? Another example is the speed of Mitsubishi Elevator in Japan. The elevator speed confirmed by the Guinness Book of World Records is 12.5m/s (750m/min), the lifting height is 267m, the main engine power is 120kw, and the load capacity is 1,600kg. ； Japan's Hitachi Elevator is developing an elevator speed of 13.5m/s (810m/min), with a low limit stroke of 300m and a high limit stroke of 500m. The running times are 40s and 55s respectively, and the load capacity is 1,600~2,000kg (passengers: 24~30 people). ； It was recently reported that the highest speed of Japan's Toshiba elevator is 16.67m/s (1 000m/min) ； The highest speed of KONE Elevator in Finland is 17m/s (1 020m/min). Is this kind of ultra-high-speed elevator developed to win the world's fastest elevator speed? Or is it for practical application? Probes and comments are needed. Of course, the manufacturing difficulty technology and control technology of elevators with speeds exceeding 10m/s are already at the forefront of the world. In Chapter 1, the calculation method for reasonable selection of elevator speed is introduced, and the graphical method for reasonable selection of elevator speed is given. Therefore, there is a reliable basis for analysis and comment on the elevator speed selected for the above-mentioned high-rise buildings. The comment results are shown in Table 2. 3 Some conclusions ⑴ The reasonable choice of elevator speed can generally be calculated. For low-speed elevators, it can be reduced to 0.2H, and for high-speed and ultra-high-speed elevators, it can be increased to 0.5H. ； You can also click on the picture to find out directly. ⑵It can be obtained from formula ⑸ or by looking up the picture: When VN is constant, T and H have a linear relationship. When VN is low, dT/dH is large, and the effect of increasing operating speed and shortening operating time is significant. ； When VN is high and dT/DH is small, increasing the running speed will have little effect on shortening the running time. For example, for a 300-400m high-rise building, increasing the elevator speed from 12.5m/s to 13.5m/s shortens the running time to less than 1-2s, which is obviously unnecessary. In general, the elevator speed should be 8.0m/s. If the speed is increased to 10.m/s, the running time can be shortened by 6 to 10s, but the speed coefficient α will be greater than 1.25. If it is increased to 12.5m/s or 13.5m/s, the speed coefficient has exceeded 1.5, which is obviously uneconomical and unreasonable. ⑶See Table 3 for the reasonable applicable heights and running times of elevators at different rated speeds. Note : 1) Two speeds of 1.5~2.0m/s can be replaced by 1.75m/s. 2) a=1.0m/s 2 in the table. For example, when a≠1m/s 2 , H in the table should be Ha and T should be H/a. ⑷From the dT/dH slopes of different rated speeds in Figure 1, for elevators with speeds below 3.0m/s, if the use height is expanded, the one-time running time will increase significantly, so the operating efficiency will be reduced, which should attract sufficient attention from elevator selection designers.