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UNIVERSITY OF HONG KONG Department of Electrical & Electronic Engineering MEBS 6000 2010 Utilities Services REFERENCES 1) CIBSE Guide D Transportation systems in buildings. CIBSE, London (1993) 2) BARNEY, Gina. Elevator Traffic Handbook – Theory and Practice. Spon Press, London (2003) 3) JANOVSKY, Lubomir. Elevator mechanical design, 3rd edition. Elevator World, Mobile, AL (1999) 4) STRAKOSCH, George R. The Vertical Transportation Handbook, 3rd edition. Wiley, New York (1998) 5) Building (Planning) Regulations, Chapter 123 6) Lifts and Escalators (Safety) Ordinance, Chapter 327 7) Factories and Industrial Undertakings (Goods Lifts) Regulations Chapter 59 Introduction There are over 60,000 lifts in Hong Kong and the number is increasing at the rate of about 1,000 a year. Some old buildings were designed on the basis of 20m2 net rentable area per person. This figure has come down to 5 to 9m2 per person. Some designs for industrial buildings and crowded commercial premises go down to as low as 3m2 per person. K.F. Chan (Mr.) A of G Page A1 of 8 Types of lifts There are in general 3 categories of lifts, viz passenger lifts, designed primarily for passenger use, the following types are also passenger lifts: → Observation lift, → Handicap lift; goods lifts, mainly for cargo but can on occasion carry passengers; and service lifts for goods only and are of such a size that passengers cannot get into the car, the following is a typical example of service lift: → Dumb waiter K.F. Chan (Mr.) A of G Page A2 of 8 Besides lifts, escalators and paternosters are also means of vertical transportation, while travellator is more horizontal than vertical people mover although escalators and travellators are very similar. There can also be other classification of lifts, such as → hydraulic drive vs → electric traction drive and → motor-room-less lift Handicap lift (Adopted from The Vertical Transportation Handbook, 3rd edition by George R. Strakosch) K.F. Chan (Mr.) A of G Page A3 of 8 Popular types of lift drives 1) Hydraulic drive (a) Hydraulic lift (contract speed of around 0.63m/s or less); leveling problem with fluctuation in oil temperature; more flexible in locating lift machine room; very slow speed; limited height traveling; not recommended for more than 3 landings and/or travel exceeding 20m (due to strength and length of the hydraulic jacks) 2) Electric traction drive (a) DC drives (contract speed of 2m/s or above); reliable and good control, good comfort, but DC generator needed, typically motor generator is used; very popular in the past. Ward Leonard drive (Adopted from BARNES, M. Variable speed drives and power electronics) Some DC driven lifts do not use motor generator but static converter to produce the DC power source. These are called Thyristor Leonard drives. (b) AC motor 2-speed (contract speed of around 1m/s or less); economical, poor comfort, difficult to control; popular in the past. Variable voltage with single speed motor, less common option. Variable voltage with 2-speed motor, less common option. (c) VVVF – variable voltage variable frequency with induction motor (contract speed of 1.5m/s or above); lower energy cost than DC, faster floor-to-floor jump time, reasonably good comfort; used to be very expensive but with the advent of power electronics VVVF has become the prime workhorse nowadays. (d) VVVF with permanent magnet synchronous motor (PSTM), compact but small rating only. (e) Linear induction motor drives (LIM) K.F. Chan (Mr.) A of G Page A4 of 8 Hydraulic drives (a) Low-traffic passenger, goods, vehicle and bullion lifts are all suitable applications for hydraulic lifts. For applications which involve very large loads, hydraulic drive often provides the best solution because the floor of the well K.F. Chan (Mr.) A of G Page A5 of 8 carries the load of the lift. In many older buildings, not originally designed to include a lift, hydraulic lifts are often the only type suitable due to restricted building height and building structural strength. For these applications hydraulic driven lifts have many advantages over electric traction lifts. However, misapplied, hydraulic lifts can cause major problems for building owners and users. (b) Mechanical anti-creep mechanisms may be used where very heavy loads (greater than 3.2 tons) are carried or forklift trucks are moving in and out of the lift. Active re-levelling systems may cause problems in these circumstances where small-wheeled trolleys are used. (c) Caution must be applied in considering hydraulic lifts for commercial buildings where continuous heavy traffic is expected since this may require lift speeds of 1m/s or above. Cooling is essential under these cases since 0.63m/s is generally accepted as the maximum for hydraulic lifts without cooling. (d) Hydraulic drives are not suitable for intensive use or for groups of lifts. Even duplex lift groups (i.e. 2 lifts) may exceed the recommended maximum number of motor starts per hour (i.e. 45) without additional cooling. When hydraulic lift is the only solution, extra cooling requirement must be considered in the design of the building itself. (Adopted from BARNEY, G..C., Elevator & Escalator Micropedia) K.F. Chan (Mr.) A of G Page A6 of 8 Holeless hydraulic elevator K.F. Chan (Mr.) Telescoping “holeless” hydraulic elevator A of G Page A7 of 8 Chain driven hydraulic elevator (Adopted from The Vertical Transportation Handbook, 3rd edition by George R. Strakosch) K.F. Chan (Mr.) A of G Page A8 of 8