K.F. Chan (Mr.) A of G Page A1 of 8

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.

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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

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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)

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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)

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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

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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)

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Holeless hydraulic elevator Telescoping “holeless” hydraulic

elevator

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Chain driven hydraulic elevator

(Adopted from The Vertical Transportation Handbook, 3rd edition by George R.

Strakosch)