Electrical Machines-II
Experiment No. 5
Experiment No. 5
1.0
Title :To Design main dimensions & Conductor size of 3 Phase Induction Motor.
To prepare design sheet and drawing to the scale.
2.0
Prior Concepts:•
•
•
•
3.0
Principle of operation, construction of three phase I. M.
Types and detail specifications of I. M.
Type of connections & starter required.
Concept of design sheet.
New Concepts:Proposition 1 : Design of 3 phase Induction Motor :It includes design of stator, rotor and Conductor size. Design data sheet and drawings are essential
for manufacturing of three phase Induction Motor.
Concept Structure 1:-
Proposition 2:- Design of Main Dimensions:It includes design of stator bore (armature diameter) (D) and stator core length (L). These are
known as main dimensions of the rotating machine.
Concept Structure 2 :-
Proposition 3: Design Data sheet:It includes the given data, standard and assumed design data, and calculated design
parameters.
Concept Structure 3 :-
Proposition 4 : Total Loadings (Magnetic & Electric):•
Total Magnetic loading: It is the total flux, around the stator periphery, at the air gap. (þ.Ø)
•
Total Electric Loading: It is the total number of ampere conductors around the stator
periphery (Iz.Z).
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♦ 29
Experiment No. 5
Electrical Machines-II
Concept Structure 4 :-
4.0
Learning Objectives :4.1
4.2
5.0
Intellectual Skills:•
•
To read & interpret the standard design data tables.
To select the proper values of design data, from the standard tables.
Motor Skills:•
•
•
To determine the different design parameters as per required specifications.
To prepare a design sheet, for the specified 3 phase Induction Motor.
To draw the sheet to the scale, showing main dimension of three phase Induction
Motor.
Design Problem:
(Note :The subject teacher shall give three different design problems to different groups) Design
main dimensions, Conductor size and prepare a design sheet. Also draw the diagrams to the scale
on a drawing sheets for the three phase Induction motor having the following specifications.
Type of Motor :Rated output Capacity ____HP or _____kW ,
Stator Voltage/Motor rated Voltage ____ Volt, Frequency ___ Hz.
Synchronous Speed ______r.p.m., Type of starter used _______
Efficiency _________ , % , Power factor at full load = _______
6.0
Points to be considered:•
•
•
•
•
7.0
Design Procedure:1.
2.
3.
4.
5.
6.
7.
30 ♦
Select the appropriate values of design data from the standard tables.
While selecting the appropriate values cooling, temperature rise limit etc. shall be considered.
Select the appropriate values of Bav , ac , kW for the performance characteristics, size & cost
of the Induction Motor.
Select appropriate value of the ratio L/τ for required efficiency & power factor.
Select the specific conductor & insulation material to be used & accordingly select the value
of diameter of bare & insulated conductor.
Note down the given design data carefully.
Calculate the number of poles by using the relation P = 2f / ns
Select the proper value of Bav , ac, kw as per the manufacturing concept (Either cost /size
or performance characteristics)
Calculate Co, Q and D2L
Select the ratio L/τ w.r.t. design constraint.
Calculate the value of D, L and τ.
Calculate the area of conductor i.e. as & diameter of bare conductor i.e.d .
MAHARASHTRA STATE BOARD OF TECHNICAL EDUCATION
Electrical Machines-II
8.
9.
10.
11.
8.0
Read the table for the conductor material & select the nearest standard conductor diameter
(i.e.d1 & d1)
Calculate the area of conductor used & the current density in the conductor.
Prepare a design sheet.
Prepare a drawing sheet to the scale by using the calculated values/dimensions.
Observations:8.1
8.2
9.0
Experiment No. 5
Given Data:•
Type of Motor: ————— type Induction Motor; …….. kW /
HP ———V ——A ———rpm
•
Type of Starter required to start the motor
__________________ Starter.
•
Motor Rating :-
_________HP/______kW.
•
Motor rated voltage/Stator Line Voltage
________ Volts.
•
Frequency of the Supply
_______ Hz.
•
Rated Speed
_______ r.p.m.
•
Stator Connection
___________
•
Full Load Efficiency
_________ %
•
Full Load Power Factor
__________ (lag / Lead)
Design Data:- (Selected from standard tables /Assumed Design Constraints.)
•
Specific magnetic loading (Bav)
= ……………..Wb/m2.
•
Specific electrical loading (ac)
= ……………..A/m
•
Winding factor
= ……………..
•
The ratio Stator core length / Pole pitch = L/ t
= ……………..
•
Current Density in stator (ds)
= …………….. A/mm2
•
Diameter of bare conductor of stator (d)
= ……………..
•
Diameter of Insulated Conductor of stator (d’ )
= ……………..
•
Area of Stator Conductor used (a’s)
= ……………..
(Kw)
Calculations:•
Calculation of No. of Poles :
Given Synchronous speed is _________ r.p.m., i.e. ns
& Frequency of the supply (f)
No. of Poles (P) = 2f / ns = …………
= _________ r.p.s.
= ____ Hz
= ……….
P=
•
Selection of Bav, ac, Kw :
Assume, Induction Motor is to be designed for
……………………………………………………........................................................
…………………………………………………………………………………………......
Bav
= _________ wb/m2
ac
= _________ A/m
Kw
= ___________
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Experiment No. 5
Electrical Machines-II
Calculation of D2L :
Output Coefficient (Co) = 11 Kw Bav · ac X 10-3
= …………………………….
Co =
kVA input to Induction Motor (Q)
Rated output in kW
= —————————————η * p.f.
= …………………. kVA
Q=
As
kVA
Q = CoD2Lns,
Q
D2L = ——— = —————
Co.ns
D2L = ________
2
DL=
•
m
3
Selection of the ratio L/ τ :
As the machine is to be designed for ………………………………..............................…….
……………………………………….............................…………........................................ ,
The value of ratio (L/ τ ) is selected as __________
•
Calculation of main dimensions (D & L) , Pole pitch :
τ = ΠD / P
Since (L/ τ ) = ……………..and
L.P / Π.D = …………. ;
L = …….. D
= ……….. D mt.
L = --------- D mt.
Put this value of L in D2L
Diameter of Stator bore
= ……………..
D = _________ mt,
But, L = __________ D = ……………. mt.
Stator core length
L=
mt.
Pole pitch (τ) = Π.D / P = ………….. mt.
τ=
•
D mt.
Calculation of stator conductor size (Ts , as, a’s, d, d’, d1) :
The machine is to be designed for ___________ Connection
Stator Voltage /Phase = Eph = Es
= ………….. volts.
Flux per pole (Φm) = Bav. τ .L = ………………wb.
32 ♦
MAHARASHTRA STATE BOARD OF TECHNICAL EDUCATION
Electrical Machines-II
Experiment No. 5
Φm =
wb
Stator Turns/Phase (Ts) = Es / 4.44 . Φ . Fm . Kw
Ts =
Stator current / phase (Iph)= Is = kVA input X 103 / (3 · Es) = ………………
IS = …………….. A
Stator Line Current (IL) = ________Amp.
Area of Stator Conductor required (as) = Is / δ= …….. =
as =
mm2
Diameter of bare Conductor of Stator (d) = ……… = ……….
d =
mm
Assume that the stator conductor is …………………………………………..,
The value of nearest standard conductor has a bare diameter
(From the table …………………….. )
d’ =
The area of stator conductor used (a’s) =(πd’ 2/4)
= ……….. =
……… mm2
a’s =_________mm2
The current density in the stator conductor (δs) = Is / a’s= ……. = …….A/mm2
δs = …….. A/mm2
The diameter of enameled conductor, using ……………………. Covering
(from table = …………….)
d1 =
mm
10.0 Result:1)
2)
3)
The stator bore (D) = ……… m; Stator length (L) = …….. m. And
conductor diameter (d) = ………… mm .
The main dimensions of the 3 phase Induction motor is as shown in the
drawing (to the scale) on the drawing sheet.
The design data sheet is as below.
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Experiment No. 5
Electrical Machines-II
DESIGN SHEET
A.
B.
Given Data (Specifications)
Sr. No.
SPECIFICATIONS
Quantity/Value
01
HP/kW Rating
HP
02
No. of phases
03
Rated Voltage/ Stator Line Voltage
04
Stator Connection
05
Supply Frequency
06
Type of Induction Motor
07
Synchronous Speed
08
Full Load Power Factor
09
Full Load Efficiency
η fl.
%
10
kVA input
Q
kVA
11
Full Load Line Current
IL
Amp.
wb/m2
Volts
f
Hz.
CosØ
Standard Design and Calculated Data :
Sr. No.
Loading
01
Specific magnetic loading
Bav
02
Specific Electric Loading
ac
03
Output Coefficient
Co
04
34 ♦
kW
2
A/m
m3
D L Product
Sr. No.
Main Dimensions
01
No. of Poles
P
02
Pole Pitch
τ
m
03
Stator Core Length
L
m
04
Diameter of Stator Bore
D
m
Sr. No.
Stator and Stator Conductor
01
Connection
02
Phase Voltage
Es
Volts
03
Flux per Pole
Øm
wb
04
Turns per phase
Ts
05
Current Density
a) Assumed
b) Actual
∆
δs
A/mm2
A/mm2
Is
Amp.
06
Current /Phase
07
Line Current
IL
Amp.
08
Stator Conductor Area
a) Calculated
b) Selected
as
a’s
mm 2
mm 2
09
Diameter of Bare Conductor
a) Calculated
b) Selected
d
d’
mm
mm
10.
Diameter of Insulated Conductor
a) Selected
b) Material of
insulation
d1
mm
MAHARASHTRA STATE BOARD OF TECHNICAL EDUCATION
Electrical Machines-II
Experiment No. 5
11.0 Questions:(Note :- Teacher shall distribute the following questions in Three different groups)
1)
State the factors affecting the size of rotating machine.
2)
State the specific magnetic loading and factors on which it depends.
3)
State the specific electric loading and factors on which it depends.
4)
State the equation for output coefficient (Co) and its importance.
5)
Differentiate specific magnetic loading and total magnetic loading.
6)
Differentiate specific electric loading and total electric loading.
7)
State the different types of stator slots; which one is normally preferred.
8)
Which point should be taken into account to select the stator conductor current density?
9)
State the significance of winding factor (Kw).
10)
State the purpose of design data sheet.
11)
If the Power Factor and efficiency of the motor is changed then which design parameters will
change.
12)
Prepare a table for selection of L/D ratio for calculation of D & L of Induction Motor.
13)
State the reason for using long core length in Design.
14)
State the factors increasing the cost & size of the Induction Motor.
15)
State the factors affecting the performance characteristics of Induction Motor.
Space for answers
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♦ 35
Experiment No. 5
Electrical Machines-II
Space for answers
36 ♦
MAHARASHTRA STATE BOARD OF TECHNICAL EDUCATION
Electrical Machines-II
Experiment No. 5
Space for answers
Remark / Grade
Date :-
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