Download Design Implementation of Three-Phase Squirrel

ISSN 2319-8885
Vol.03,Issue.10
May-2014,
Pages:2211-2216
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Design Implementation of Three-Phase Squirrel-Cage Induction Motor
used in Elevator
THIDAR TUN1, THET NAUNG WIN2
1
Dept of Electrical Power Engineering, Mandalay Technological University, Mandalay, Myanmar, Email: [email protected].
2
Dept of Electrical Power Engineering, Mandalay Technological University, Mandalay, Myanmar, Email: [email protected].
Abstract: In most large cities, land is scarce and consequently it is very valuable. This has led to the construction of tall
building which occupies only a small area of land while providing a lot of floor space where people can live or work. So, in
these buildings, the elevator become useful and act in the important part to carry passengers to the required floors Every
elevator must be driven by at least one motor its own and this motor must be located at the upper escalator landing. So, the
major contribution of this paper is to describe the design calculation of AC three-phase squirrel-cage Induction motor of
continuous power rating 11kW (15hp), 1500rpm,50 Hz and 4poles, reversible type with low starting torque, high starting
current and specially designed for elevator application. In this paper, the basic designs of squirrel-cage induction motor such as
sizes of stator and slots, teeth, core, rotor diameter, rotor bar area, rotor bar current efficiency, speed, and power and so on are
described.
Keywords: Elevator, Three-Phase Squirrel-Cage Induction Motor, Motor Design, Performance Test and Results.
I. INTRODUCTION
With the rapid development of city construction, the
emergence of high-rise buildings and the expansion of
buildings’ area, the use of elevator has become more
important, and the quality of elevator’s service is required
higher and higher. Therefore, the large-scaled buildings are
provided with a plurality of elevators so as to meet the
transportation needs. Elevators are prevalent throughout
many multi-level structures. They control the flow of foot
traffic between various floors of buildings, they allow
disabled persons to access upper-level floors, and they
facilitate the movement of large items (such as furniture and
office equipment) between various levels of the building.
Several different types of motor are available for elevator,
but the particular motor is chosen depending upon the supply
characteristics and quality of service to be provided. In this
paper, three phase squirrel cage induction motor is used to
drive the escalator. Due to its simple, rugged and inexpensive
construction, reduced maintenance, and excellent operating
characteristics, these squirrel-cage induction motors are
widely used in industrial, commercial and domestic
applications. So, as a rough estimate nearly 80 % of world
industrial motors are three-phase inductions motor [3] [4].
II. OVERVIEW OF ELEVATOR
A. Types of Elevator’s Arrangements
Two main types of elevator are
 Hydraulic elevators and
 Roped elevators
Hydraulic Elevator: The system includes a piston and
cylinder arrangement connected to the hydraulic system. The
tank is filled with hydraulic fluid and connected via, the
valve to the cylinder.
Roped Elevator: Roped elevator pull the elevator car using
ropes or cables .One end of the steel ropes is attached to the
elevator car while the other end is attached to a
counterbalance .The sheave is connected to a motor that turns
the sheave both clockwise and counterclockwise. When the
sheave rotates in one direction the elevator car rises, when it
rotates in the opposite direction the elevator car lowers .The
basic components of a roped elevator are (1) control system
(2)electric motors (3)sheave (4)counterweight.
B. Elevator Safety Devices
1. Molded Circuit Breaker
Molded Circuit Breaker (MCCB) protects the elevator
control equipment from unusual voltage surges in the
building power supply.
2. Over Speed Governor
It locates in the machine room and engages the governor
rope, causing activation of the elevator safety device, should
the elevator car accelerate beyond the predetermined
maximum speed in the "down" direction. Safety gear will be
gripped on car guide rails to prevent free fall.
3. Safety Gear
It locates beneath the elevator car, brings the car to a safe
stop, should the elevator over speed in the down direction.
Copyright @ 2014 SEMAR GROUPS TECHNICAL SOCIETY. All rights reserved.
THIDAR TUN, THET NAUNG WIN
4. Safety Drive Operation
When a car stops beyond DOOR (DR) zone owing to
temporary failure, it prevents passenger locking in a car by
AUTO-operating slow to the nearest service FLOOR (FLR).
5. Miscall Cancel Function
When the going floor is much more than the passengers,
this function cancels the entire going floor registered after
performing bottom service, to avoid unnecessary operation.
6. Door Open and Close Time Auto-control
Automatically control DR open/close time according to
call kind or elevator using condition in order to optimize the
operation efficiency.
7. Overload Detection
When the rated load of car exceeds 110%, prevents
an overload operation by opening the door and ringing
buzzer. The following figure 1 shows the Electric Traction
Geared Elevator.
C. Classifications of Elevator’s Sizes, Capacity
TABLE I: ELECTRICAL DESIGN GUIDE FOR SPEED 200
FT/MIN
Figure1. Electric Traction Geared Elevator.
D. Model Elevator
Figure 2 shows model elevator. It is constructed with four
floors. The car, cable, elevator motor (stepper motor), control
equipment, counterweight, hoist way, rails, limit switch
(phototransistor) and seven-segment display unit make up the
principle parts of this elevator project installation. The car
and the car load are suspended on a roped connected to the
Figure2. Elevator’s Arrangements.
International Journal of Scientific Engineering and Technology Research
Volume.03, IssueNo.10, May-2014, Pages: 2211-2216
Design Implementation of Three-Phase Squirrel-Cage Induction Motor Used in Elevator
counterweight by means of a friction sheave which the motor
A. Stator
drives. The size of the counterweight is equal to the total
This is the fixed part of the motor. A cast iron or light
weight of the car and half of the car load. Thus the smallest
alloy frame surrounds a ring of thin laminations (around0.5
possible load differences are achieved. The motor load is at a
mm thick) made of silicon steel. The laminations are
maximum with a fully loaded up traveling car or empty down
insulated from one another by oxidation or an insulating
traveling car. Due to the friction present, no load running
varnish. The "lamination" of the magnetic circuit reduces
occurs with approximately a ¼ loaded car traveling up or a ¾
losses via hysteresis and eddy currents. The laminations have
loaded car traveling down. In this paper, the elevator design
slots in them for holding the stator windings that produce the
is (carrying load of 1500lb and car speed of 200 ft/min
rotating field (three windings for a 3-phase motor).
(1m/s)) used in 150ft high building (9 stories).
B. Rotor
This is the moving part of the motor. Like the magnetic
Over head (OH)
= 132 in (11ft)
circuit of the stator, it is made up of a stack of thin
Pit depth (P)
= 48 in (4ft)
laminations insulated from one another, forming a keyed
Machine room high (MH) = 87 in(7.25ft)
cylinder on the motor shaft. Two different technologies can
Therefore, the total travel for elevator is
be used for this part, which separate asynchronous motors
TL = 150-OH-P
into two distinct families: those with a “squirrel-cage” rotor
= 150-11-4
and those with a wound rotor which are referred to as “slip= 135 ft
ring”. But in my thesis, a squirrel-cage rotor is used (see fig
For 10 passenger (1500lb), car speed of 200ft/ min and
4). [4]
400V of main lines
Motor capacity
=15hp (11kW)
Power supply capacity
= 9kVA (12hp)
Lead- in wire size
= 0.304 in2
Earth wire size
= 2.238 in2
In order to drive this elevator, rating 11kW (15hp),
1500rpm,50 Hz and 4 poles, reversible type AC three-phase
squirrel-cage induction motor is chosen according from table
1.Therefore, the details design calculation for this squirrelcage induction motor is described with the next sections.
III. CONSTRUCTION OF THREE-PHASE SQUIRREL
CAGE INDUCTION MOTOR
A three-phase squirrel cage induction motor consists of
two main parts: stator and rotor (see fig 3).
Figure4. Typical squirrel-cage rotor.
C. Advantages of Squirrel-Cage Rotor over Wound Rotor
There are several advantages of squirrel-cage over wound
rotor induction motor. They are rugged in construction ,no
slip rings, brush gears, etc , minimum maintenance, trouble
free performance, cheaper, better cooling conditions, better
pullout torque and overload capacity.
D. Four Types of Squirrel-Cage Rotor
There are several types of squirrel-cage rotor. They are
 Resistive squirrel-cage rotor
 Single squirrel-cage rotor
 Double squirrel-cage rotor
 Rotor with deep slots
Figure3. Detail construction of three-phase squirrel-cage
induction motor [4].
Among them by using the double squirrel-cage rotor and
deep bars rotor, the low starting torque of a squirrel- cage
induction motor can be changed to get the high starting
torque condition. [5]
International Journal of Scientific Engineering and Technology Research
Volume.03, IssueNo.10, May-2014, Pages: 2211-2216
THIDAR TUN, THET NAUNG WIN
IV. DESIGN PROCEDURE OF THREE-PHASE
Sectional area of rotor bar, A  I b
INDUCTION MOTOR
b
b
The specifications of three- phase induction motor are:
Rated output power
: 11 kW
Equivalent rotor resistance, r '  Rotor copper losses
r
Rated voltage
: 400 V
3  I 'r2
Speed
: 1500 rpm
D. Calculation of Performance
Numbers of pole
: 4 poles
2
No load current per phase, I0  I2
Numbers of phase
: 3 phase
m  I mμ
Frequency
: 50 Hz
I
No load power factor, cosφ  μ
Connection of stator winding
: Star
0
I0
Types of rotor
: Squirrel-cage rotor
V
Magnetizing reactance, X  ph
A. Motor Output
m
Im
The output equation relates the output of the induction
Total
reactance,
X
=
Xs+
Xh+
Xo+ Xz
motor with the main dimensions of the stator and is the basic
tool to initiate the design. Output of three-phase induction
Total equivalent impedance, Z  R 2 + X 2
motor is given by,
Output in kW, Q = Co D2Lns
Input to three-phase
Induction motor = 3V phIphcosφ×10-3kW
Output coefficient, Co = 11Bav q cosφηkw10-3
(1)
(2)
(3)
B. Detail Design of Stator
In this paper, to obtain the best power factor in an
induction motor, the following equation is used.
Number of turns per phase,
Hence, internal diameter of stator, D = 0.135P L
(4)
Induced e.m.f per phase, Eph= 4.44 fϕTphkw
(5)
E ph
Thus, turns per phase, T 
(6)
ph
4.44fφk w
Sectional area of the stator conductor, a s  I s
(7)
Stator current per phase, I 
s
Q/
3  Vph  cos 
Size of the stator slot = b s × h s
Stator winding resistance per phase,
0.021 L mts  Tph
rs 
as
K wr  S r  Z
s
'
r
 Z'
r
(23)
(24)
Z
R
Z
Total losses at full load=stator losses + no load losses
Output
Efficiency at full load,  
%
Output  total losses
(25)
(26)
(27)
Full load efficiency for small size motor should be
between0.82 to 0.85, for medium size between 0.85 to 0.88
and for large machine between 0.88 to 0.92.
(9)
Maximum output =
(13)
C. Detail Design of Rotor
Number of rotor slot is selected based on the following
equation.
Length of air-gap, L g = 0.2 + DL mm
(14)
K ws  Ss  Z
(22)
(29)
(12)
Ib 
(21)
Percentage slips at full load, S  rotor copper losses
rotor input
Total stator copper losses = 3I2s× r s
Depth of stator core, d  A cs
s
Li
Bar current,
(20)
(8)
s
(11)
'
cossc 
(19)
(28)
Mean flux density in stator teeth, B '  I s
t
Outer diameter of rotor, Dr= D – 2 L g
Short circuit power factor,
E ph
(18)
Starting torque = [I sc⁄ I ′r]2× slip × full load torque
(10)
s
Short circuit current per phase, I sc 
(17)
(15)
(16)
I -I


3
sc
0
3V ph 
  10 KW
2(1

Cos

)


sc 
(30)
The maximum output developed by three-phase induction
motor normally lies between 2 to 2.5 times its full load
ratings.
E. Result Design Data Sheet
According to the design procedure, firstly the design
specifications of three phase induction motor are mentioned
with the following Table II.
TABLEII: Specifications of Three-Phase Induction Motor
Specification
Symbol
Unit
Design Value
Full Load output
kW
11
Line voltage
V
Volts
400
Frequency
F
Hz
50
Number of pole
P
4
Number of phase
3
Squirrel-cage
Rotor types
rotor
International Journal of Scientific Engineering and Technology Research
Volume.03, IssueNo.10, May-2014, Pages: 2211-2216
Design Implementation of Three-Phase Squirrel-Cage Induction Motor Used in Elevator
By using the above equations 1 to 13 the following details
The parameters of performance tests are showed as the
design data for stator shows in Table III.
following Table V by using the above equations 18 to 30.
TABLE III: Detail Design Stator Sheet
Symb
Design
Specification
Unit
ol
Value
Specific magnetic
Bav
Tesla
0.46
loading
Specific electric
q
Ampcond/m
255000
loading
Internal diameter of
D
m
0.19
stator
Gross core length
L
m
0.13
Turns per phase
Tph
-
122
Numbers of slots
-
-
36
Conductors per slots
-
-
Full load current
Is
Cross-sectional area
of conductor
TABLE V: Parameters Of Performance Tests
Specification
Symbol Unit
Design Value
Total iron losses
Friction and windage
losses
-
W
507
-
W
110
No load current
Io
A
5.719
No load power factor
cos  o
-
0.16
Short circuit current
Isc
A
84.36
Total losses at full
load
Short circuit power
factor
-
W
1528
cosφsc
-
0.3
20
Total copper losses
-
W
911
A
21.1
Efficiency at full load
η
%
88
as
mm2
5.5162
Slip at full load
S
%
3.3
Width of slot
bs
mm
7.704
-
-
Height of slot
hs
mm
36.72
Ratio of starting
torque to full load
torque
Maximum output
-
kW
B't
Tesla
1.225
rs
Ω
0.4
-
W
534
dcs
m
0.0317
Flux density in
stator teeth
Resistance of stator
winding
Copper losses in
stator winding
Depth of stator core
1.3
21.12
V. MOTOR PERFORMANCE
In this paper, we point out that the variation of slip can
change output torque of the motor by using the following
equations from (31) to (33). The output torque reaches 161Nm which is the highest in the case of slip at 0.2 and shows in
Fig7. Further using Eq.33, total output torque developed may
TABLE IV: Detail Design Rotor Sheet
Specification
Symbol
Unit
Design Value
Length of air gap
Lg
mm
0.514
Diameter of rotor
Dr
m
0.189
Number of rotor slots
-
-
45
Bar current
Ir
A
274.1232
2
Bar area
ar
mm
46.4616
Width of slot
br
mm
4.5
Height of slot
hr
mm
12.5
Resistance of rotor
bar
rb
Ω
0.0813×10
Rotor copper losses
-
W
289
Equivalent resistance
of rotor
r'r
Ω
0.4
-3
Figure5. General torque-slip characteristics of induction
motor.
be represented as a function of operating slip by changing the
four angular frequency values such as 94.25, 125.66, 157.08,
188.50 rad/sec is shown in Fig7. However, this escalator
motor is running with the output torque at 157.08 rad/sec as
International Journal of Scientific Engineering and Technology Research
Volume.03, IssueNo.10, May-2014, Pages: 2211-2216
THIDAR TUN, THET NAUNG WIN
this machine is only needed this torque. Figure 5 shows the
general three different torque-slip curves due to different
rotor resistance at possible maximum slip. So, the rotor
resistance of motor in this paper is low as the maximum
torque which occur the value of slip at 0.2.
TABLE VI: Required Parameters for Performance
Calculation
Stator resistance (r1)
0.4Ω
Stator reactance(x1)
0.912 Ω
Rotor resistance(r2)
0.4 Ω
Rotor reactance(x2)
1.7061 Ω
Magnetizing reactance( xm)
40.88 Ω
r1
jx2
jx1
Figure8. Characteristics of Output Torque-Speed Curves.
Both the figures 6 and 8 show the Equivalent Circuit
Diagram of an Induction Motor and Characteristics of Output
Torque-Speed Curves.
+
Vth
Vph
jxm
r2/s
-
Figure6. Equivalent Circuit Diagram of an Induction
Motor.
Vth = Vth  Vph 
Zth
=
jx m
r1  jx 1  jx m
(r1  jx1 )(jx m )
r1  jx1  jx m
(31)
(32)
The output torque can be calculated with the following
equation,
VI. CONCLUSION
Elevator is a moving up and down case-a conveyor
transport device for carrying people between floors of
building. The motor used in elevator is AC three-phase
squirrel-cage induction motor of continuous power rating
11kW(15hp),1500rpm,50Hz and 4 pole, reversible type with
low starting torque, high starting current and specially
designed for elevator application. Although it’s starting
torque is 57.8% N-m and its maximum output torque is 161
N-m. Due to its simple, rugged and inexpensive construction,
reduced maintenance, and excellent operating characteristics,
these squirrel-cage induction motors are widely used in
industrial, commercial and domestic application. Although it
has low starting, the running performance is excellent. So,
squirrel-cage induction motors are very appropriate for
driving elevator.
VII. ACKNOWLEDGMENT
The author would like to express her gratitude to Dr Khin
Thu Zar Soe, Associated Professor and Head of Electrical
Power Engineering Department, Mandalay Technological
University and U Thet Naung Win, Lecturer, Department of
Electrical Power Engineering, Mandalay Technological for
her encouragement and helpful suggestion and supervision.
The author wishes to thanks all my teachers. Thanks are also
extended to her dear parents and friends for their support.
Figure7. Torque-Slip Curves of an Induction Motor.
Tout =
(33)
VIII. REFERENCES
[1] Hoboken: John Wiley & Sons, 2006, Mechanical and
Electrical Equipmentfor buildings.
[2] http://www.elevatordrives.com
[3] Annett F.A, 1935, Electric Elevators, Second Edition,
Printed by McGraw-Hill Book Company,Inc.
[4] Hubert Charles I., 1991, Electrical Machine(Theory,
Operation, Applications, Adjustment and Control).
[5] MittleDr,V.N. and MitalArvind, 1996, Design of
Electrical Machine,Fourth Edition.
International Journal of Scientific Engineering and Technology Research
Volume.03, IssueNo.10, May-2014, Pages: 2211-2216