38
CHAPTER 3
INFLUENCE OF STATOR SLOT-SHAPE ON THE ENERGY
CONSERVATION ASSOCIATED WITH THE
SUBMERSIBLE INDUCTION MOTORS
3.1
INTRODUCTION
The electric submersible-pump unit consists of a pump, powered by
a medium-voltage three-phase induction motor. The power transmission
system is integrated with riser-pipes. Pipe stacks are flanged together, and
consist of riser-pipe with the power transmission system, concentrically
mounted inside of each section. The power transmission system comprises a
protective pipe with the copper conductors mounted inside. The motor is
filled with water, and is being continuously circulated inside. The motor unit
has forced-water lubrication. The water is fed down to thrust bearings and the
mechanical seal through slots in the stator and returns to the surface through
the rotor-gap/stator-gap and transmission system.
3.2
ANALYSIS APPROACH
This
chapter
presents
the
performance
improvement
of
submersible-pump sets ranging from 3-HP to 7-HP, by increasing the
efficiency of squirrel-cage induction motor. For a three-phase induction
motor, the stator winding consists of p poles and are distributed in space. The
stator winding is usually connected to a three-phase balanced voltage source.
The resulting currents in the stator produce a rotating magnetic field. The
39
rotor winding is often of squirrel-cage type with the number of poles equal to
the number of poles in the stator. The currents are induced in the rotor
conductive-bars. The interaction of the resultant magnetic field in the air-gap
with the currents in the rotor conductive-bars produces an electromagnetic
torque, which acts on the rotor in the direction of the rotation of the magnetic
field in the air-gap. The performance of a three-phase induction motor is
analyzed based on the equivalent circuit. Because of symmetry of the three
phases, a single-phase equivalent circuit is shown in Figure 3.1, it can be used
to analyze the characteristics of a three-phase induction motor.
Figure 3.1 Equivalent Circuit of a 3–phase Induction Motor
R1 is the stator resistance, X1 is the stator leakage-reactance,
comprising of stator slot leakage-reactance, end-winding leakage-reactance,
and differential leakage-reactance. X2 and R2 are the rotor leakage-reactance
and the rotor resistance, respectively. X2 includes rotor slot leakage-reactance,
end-ring leakage-reactance, differential leakage-reactance, and skew-slot
leakage-reactance. Due to the saturation phenomena in the magnetic leakage
field, both X1 and X2 are non-linear parameters. All the parameters in the
equivalent circuit are dependent on the stator and the rotor currents. In the
exciting branch, Xm denotes the magnetizing-reactance, and R c denotes the
resistance corresponding to the iron-core losses. X m is a linearized non-linear
parameter, whose value varies with the saturation degree in the main magnetic
field. Given that V1 is the external phase voltage applied to the phase
terminals, the stator phase current I1 and the rotor current I2, which have been
40
referred to the stator, can be easily computed by analysing the equivalent
circuit.
The equivalent circuit parameters can be derived from the
following geometrical and electrical parameters:
1)
Geometrical Parameters:
2)
a)
Stator and Rotor diameters (inner and outer)
b)
Axial core-length
c)
Number of slots in the Stator and the Rotor
d)
Geometrical shapes of the Stator and the Rotor slots
Electrical Parameters:
a)
Number of Poles
b)
Number of conductors in series per phase
c)
Winding pitch
d)
Cross-section of the conductor
e)
Short-circuited Cage ring section
f)
Skewing pitch of the Rotor slots
These data are derived from the electromagnetic design of the
machine. As shown in Figure 3.1, the actual rotor resistance R2 and the rotor
leakage-reactance X2 have to be referred to the stator using Equation (3.1) and
Equation (3.2), respectively.
=
(3.1)
=
(3.2)
41
The coefficient K
for referring the rotor parameters to the stator
side is shown in Equation (3.3). Nph is the number of stator conductors in
series per phase, kw1 is the stator-winding coefficient (for the air-gap
fundamental spatial harmonic), and Nbars is the number of the squirrel-cage
rotor bars.
(3.3)
It is important to note that any stator-phase-winding structure can
always be described by Nph conductors in series per phase with an equivalent
wire section (Awire) suitable to carry the phase current. This means that only
Nph and Awire are required for the equivalent circuit parameter computation,
even if some parallel paths are used for the phase-winding realization (i.e.,
single-wire-parallel or bobbin-parallel).
3.2.1
Stator and Rotor Resistances
The stator winding resistance can be evaluated using Figure 3.2 and
Equation (3.4).
Figure 3.2 Length of the Average-turn of a Winding
42
.
=
where
(3.4)
is the resistivity of conductor material, Lavg.turn is the length of the
average-turn, and Awire is the cross-sectional area of the wire. Equation (3.4) is
quite simple in itself, but some care has to be taken to define the averageturn length. As shown in Figure 3.2, this length is the addition of two
components, namely, the part of turn embedded in the slot (L core) and the
end-winding length (Lew). Equation (3.5) to Equation (3.7) gives the length of
the average- turn of the conductor in the stator winding.
= 2(
.
)
+
(3.5)
=
= 1
where
(3.6)
(
+
)
(3.7)
Dis is the inner diameter of the stator core, hs is the height of the
stator slot, and kew is the end-winding shape coefficient. The value of kew is
usually close to /2 for wire-windings, assuming a semi-circumference endwinding shape with a diameter equal to
w.
Typically, kew is in the range of
1.5-1.6, depending on the actual end-winding length. nr is the pitch-shortening
defined in number of slots, Npole is the number of poles (defined by the air-gap
fundamental spatial harmonic), and Nss is number of the stator slots.
Assuming the number of rotor phases to be equal to the number of
bars, the phase-resistance of the cage is referred to single bar and to two
adjacent ring sectors, as shown in Figure 3.3. The resistance contribution of a
single bar can be computed by Equation (3.8), while the resistance
contribution of one End-ring can be computed by Equation (3.9).
43
where
=
(3.8)
=
(3.9)
KR is the skin-effect coefficient for the bar resistance, Abar is the
cross-sectional area of the bar, Lbar is the bar length, Aa is the cross-sectional
area of the cage-ring, and Da is average diameter of the cage-ring.
Figure 3.3 Bar and Ring Currents in Rotor Cage
By using, Equation (3.8) and Equation (3.9), it is possible to
compute the equivalent rotor-phase resistance. As is well known, the
calculation of this equivalent resistance is based on the total rotor-cage joulelosses. The phasor diagram for the current is shown in Figure 3.4, where, Ib is
the bar current and Ia as the ring current. The relationship between the ring
current and the end-bar current is given in Equation (3.10).
44
Figure 3.4 Phasor Diagram of Ring and End-bar Current
(3.10)
As a consequence, the total joule-loss dissipated in the rotor cage (P jr) is
defined by Equation (3.11).
=
+
(3.11)
Since each rotor bar can be considered as a phase of a multi-phase winding,
the equivalent rotor-phase resistance is defined by Equation (3.12).
=
3.2.2
+
(3.12)
Classification of Magnetic Flux
To calculate the inductive parameters, it is important to classify the
magnetic fluxes through the machine. Figure 3.5 is used as a reference for this
classification.
45
Figure 3.5 Flux-path in the Machine
The flux in a rotating machine can be classified into two categories:
A)
With respect to the flux-path: The total flux linked (
total)
with a
phase winding is the addition of two contributions, namely:
1)
main,
the main flux linked due to the magnetic field lines,
crossing the air-gap. This flux is produced simultaneously by
the stator and the rotor currents.
2)
local,
the local flux linked due to the following two components:
a) The field lines close to the conductors in the slot and the
two adjacent teeth ( sl).
b) The field lines around the end-windings (
B)
hl).
With reference to the energy conservation: The total flux (
total)
linked with a phase winding is the addition of the following two
components:
46
1)
useful,
the linked flux that is due to the fundamental distribution
of air-gap flux density, and is a component of the main flux.
2)
leakage,
the linked flux that does not give appreciable
contributions to energy conversion.
With those of the above two classifications, it is possible to write the
Equation (3.13) to Equation (3.15) for the total flux linked with the winding.
=
+
=
+
=
(3.13)
+
(3.14)
+
(3.15)
As a consequence, the leakage-flux in the winding is calculated using
Equation (3.16).
=
+
+
(3.16)
The actual speed is mainly governed by the first harmonic flux;
only the fundamental flux component is conventionally considered as useful
in the electromechanical energy conversion. Flux components of higher
orders are considered as leakage-components. As a consequence, with
reference to Equation (3.15), the quantity (
) is defined as the
“air-gap leakage-flux”. This air-gap leakage flux is used for the calculation of
the leakage-inductance.
47
3.2.3
Leakage-inductance
The slot leakage-inductance (both for the stator and the rotor) can
be calculated on the basis of the magnetic energy stored in the slot defined by
Equation (3.17).
E =
where
L
I
(3.17)
is the slot-leakage-coefficient, Lslot is the length of the
winding part inside the slot, and Islot is the total current in the slot. Obviously,
this current depends on the phase current (IPhase), and on the type of phasewinding.
Figure 3.6 Distribution of Magnetic-Field in the Slot
Lslot is used as general symbol: It is equal to Lcore for the stator
winding and Lbar for the rotor cage. Assuming, the permeability of iron to be
infinite and that the magnetic field lines are parallel into the slot as shown in
Figure 3.6, the magnetic energy stored in the slot is given by Equation (3.18).
=
( )
( )
(3.18)
Given the x-coordinate, the magnetic field and the slot current are calculated
by using Equation (3.19) and Equation (3.20).
48
( ) =
=
( ) ( )
(3.19)
( )
( ) ( )
(3.20)
As a consequence, the slot-leakage-coefficient is given by Equation (3.21).
=
( )
( )
(3.21)
Since the permeability of iron is considered infinite, Equation (3.21) cannot
be applied to closed rotor slots, because, the
slot,
the slot-leakage-coefficient
should be infinite too. In this case, taking into account the inevitable heavy
saturation of the slot closing magnetic wedge, an equivalent slot-opening has
to be considered. Unfortunately, the selection of the width of the slot-opening
is not a simple task and it can be done on the basis of the actual shape of the
slot-closing zone. Generally, some “trial-and-error” steps based on the
experience of the designer are required in order to obtain reasonable results.
The phase slot leakage-inductance can be obtained by Equation (3.22).
=
(3.22)
Alternatively, the leakage-inductance (L ) of a machine can be obtained as the
sum of different leakage-inductances. According to the design-tradition of
electrical motors, the leakage-inductance (L ) can be thought of as made up of
the following partial leakage-inductances:
Air-gap leakage-inductance (Lg)
Slot leakage-inductance (Lu)
Tooth-tip leakage-inductance (Ld)
49
End-winding leakage-inductance (L w)
Skew leakage-inductance (Lsq)
The leakage-inductance of the machine is the sum of these leakage
inductances as shown in Equation (3.23).
=
+
+
+
+
(3.23)
Air-gap inductance is given by Equation (3.24).
T
m
DL ph
g
p
L
where
2
v
o
v
,V 1
k wv
v
µ0
= Permeability of vacuum
m
= Number of phases
g
= Air-gap length
L
= Effective core-length
D
= Diameter of the core
2
(3.24)
Tph = Number of turns per phase in a winding
p
=
Number of pole-pairs
= Ordinal of the harmonic
kwv = Winding factor
The term v, when equal to 1, in the Equation (3.24), represents the
fundamental component, and thus the magnetizing-inductance (Lm) of the
machine.
The slot-inductance of a phase winding is obtained as follows:
50
Figure 3.7 shows the equivalent circuit of slot-inductance, and its
value is determined by Equation (3.25).
Figure 3.7 Equivalent Circuit of Slot-Inductance
Lu =
where
4m
Q
Q =
u
=
2
o
u
(3.25)
Number of slots
Permeance factor of the slot
Figure 3.8 Slot Model
Equation (3.26) is used to determine the permeance factor of the slot ( u),
using the dimensions of the slot model as shown in Figure 3.8.
51
h4
h3 h1
h2
b4
u = 3b + b + b + b -b ln b
4
4
1
4 1
1
(3.26)
Tooth-tip leakage-inductance is determined using Equation (3.27).
=
d
(3.27)
= Permeance factor of tooth-tip
End-winding leakage-inductance (Lw) calculation is given by Equation (3.28)
=
(3.28)
lw = Average length of the end-winding
w
= Permeance factor of end-winding
q = Number of slots per pole per phase
Equation (3.29) shows the Skew leakage-inductance (Lsq)
=
(3.29)
where
=
, the Leakage factor caused by skewing
ksq = skewing factor
=
52
3.3
CALCULATION OF PERFORMANCE PARAMETERS
The magnetic energy stored in a slot can be calculated by using any
one of the Flux analysis softwares, namely, 2-D, RMxprt, and MotorPro, after
completion of the initial design using low-loss materials. The magnetic circuit
of the motor is constituted by the lamination of the stator, the rotor, and the
air-gap. The energy conversion is assisted by the flux in the air-gap, driven by
magneto-motive-force (mmf) produced in the stator winding. The mmf
required to drive the flux is influenced by the reluctance of the magnetic
circuit. The reluctance of the magnetic circuit is determined by the length and
the relative permeability of the material as given in Equation (3.30).
=
where
(3.30)
S = Reluctance
= Length of the magnetic circuit
= Permeability of free space
= Relative permeability
A = Area of the magnetic circuit
The mean length of the magnetic circuit is influenced by the shape
of the slot and the air-gap. Material composition of stamping influences the
relative permeability and the saturation factor coefficient. Reduced reluctance
circuit needs less mmf to force the flux, and hence results in less magnetizing
current. Hence, the output power, power factor, and efficiency improve
significantly. This could be understood from the equivalent circuit shown in
Figure 3.1, and Equation (3.31) to Equation (3.37).
The electromagnetic power (P m), otherwise called as the air-gap power, is
determined by Equation (3.31).
=3
(3.31)
53
The electromagnetic torque (Tm) is calculated using Equation (3.32).
=
(3.32)
where, ‘ ’ denotes the synchronous speed in rad/s.
Equation (3.33) gives the mechanical shaft output torque (Tsh).
=
(3.33)
where, Tfw denotes the frictional and windage torque.
The output power (Po) is shown in Equation (3.34).
=
where
r
(3.34)
= (1 – s) denotes the rotor speed in rad/s.
Equation (3.35) is used to calculate the input power to the motor (Pi).
=
+
+
+
+
+
(3.35)
where Pfw, Prc, Pcl, Psc, and Pl denote the frictional and windage losses, the
rotor copper loss, the iron-core loss, the stator copper loss, and the stray loss,
respectively.
The power factor is determined by Equation (3.36).
=
(3.36)
Equation (3.37) is used to determine the efficiency.
=
× 100
(3.37)
54
3.4
ANALYSIS USING ROTATIONAL MACHINE EXPERT
Rotational Machine Expert (RMxprt) is an interactive software
package from ANSOFT Corporation used for the design and analysis of
electrical machines. When a new project is started in RMxprt, the type of
motor is to be selected. The parameters associated with the selected machine
are given as input in the property window. The property windows are
accessed by clicking each of the machine elements; for example, stator, rotor,
and shaft under machine in the project tree. Solution and output options such
as the rated output, torque, and load current, etc., are set by adding a solutionsetup in analysis of the project tree. A 3-phase, 380 V, 2-pole submersible
induction motor with the power range 3-HP to 7.5-HP has been chosen, based
on the market requirement. (Source: TEXMO Industries, CRI Pumps,
DECCAN Industries, and PSG Industrial Institute). Different stator, rotor slotshapes have been considered for optimisation. The stator and rotor slotmodels used for simulation are shown in Figure 3.9 and Figure 3.10,
respectively.
Figure 3.9 Stator Slot-models used for Optimisation
55
Figure 3.10 Rotor Slot-models used for Optimisation
The various dimensions of slots pertaining to Stator and Rotor are
shown in Table 3.1 and Table 3.2, respectively.
Table 3.1 Dimensions of Stator Slots
Slot Type
A
B
C
D
BS0
3.90
3.90
3.90
BS1
6.03
6.90
6.90
3.90
3.90
3.90
6.03
6.17
6.25
E
F
Dimension (mm)
BS2
HS0 HS1
9.50 1.00 0.80
9.88 0.80 10.63 0.70 -
HS2
RS1 RS2
13.20 11.30 1.50 14.15 1.50 1.00
10.19
9.59
10.36
15.80
13.00
15.60
1.00
1.00
0.52
0.80
-
-
Table 3.2 Dimensions of Rotor Slots
Slot Type
1
2
3
4
BS0
1.80
1.80
1.10
1.80
BS1
5.00
5.00
5.10
5.00
Dimension (mm)
BS2 HS0 HS1
3.20
0.42
3.20
0.42
3.20 0.70 0.42
3.20
-
HS2 RS
7.50 0.20
7.50 0.20
6.30
4.60
-
1.00
1.00
56
All the design values related to each section as mentioned in
Figure 3.11 have been configured in the software, namely, machine type,
main dimensions, material characteristics, BH and BP-curves for the
stamping, type of shaft material (SS-307), and body material (cast iron,
aluminium, and SS-304). The basic process in RMxprt is illustrated with the
help of the flowchart in Figure 3.11.
Start
Define Data for 3-phase Induction Motor
General Data
Stator Data
Machine type
No. of Poles
Stray loss
Friction loss
Windage loss
Reference speed
Outer diameter
Inner diameter
Length
Type of Steel
Stacking factor
No. of slots
Slot-Model
Slot dimensions
Winding details
Rotor Data
Outer diameter
Inner diameter
Length
Type of Steel
Stacking factor
No. of slots
Slot-Model
Slot dimensions
Winding details
Skew width
Rotor type
Solution Data
Duty-cycle
Type of Load
Rated output
Rated voltage
Rated speed
Operating
temperature
Winding
connection
Frequency
Analysis of Machine
Add a solution setup
Validation check
Analyse
Design Output of Machine
Design sheet
Performance table
Performance curves
Figure 3.11 Flowchart for Basic Process in RMxprt
The iterations have been performed, using the optimetrics tool
shown in Figure 3.12, by choosing different combinations of core-length,
number of turns per phase, and magnetic loading for 3-phase, 5-HP, 380 V
submersible induction motor.
57
Start
RMxprt Model (initial design)
Define design variables and its
range of values
Add parametric setting
Define performance attributes needed
for calculation
Analyse
Apply optimum result for
initial design
RMxprt Model (optimised design)
Figure 3.12 Flowchart for Optimetrics Tool in RMxprt
Table 3.3 to Table 3.8 show the results obtained from the
simulation for different slot-model combinations. The parameters that
influence
the
magnetic
circuit,
namely,
Stator
Leakage-reactance,
Magnetizing-reactance, Rotor Leakage-reactance, Resistance corresponding
to Iron-core Loss, Stator Phase Current, and Magnetizing Current have been
considered for the selection of optimum slot-model.
58
Table 3.3 Parameters for Slot-A Combination
Parameters
Slot-1
Slot-2
Slot-3
Slot-4
Stator Leakage-reactance ( )
1.42
1.29
1.38
1.36
Magnetizing-reactance ( )
Rotor Leakage-reactance ( )
Resistance Corresponding to
Iron-core Loss ( )
Stator Phase Current (A)
57.34
5.94
64.56
5.16
56.17
5.34
60.04
6.23
1879.34
1926.23
1902.74
1911.98
9.43
8.37
9.39
8.84
3.55
3.07
3.31
3.26
Magnetizing Current (A)
Table 3.4 Parameters for Slot-B Combination
Parameters
Stator Leakage-reactance ( )
Magnetizing-reactance ( )
Rotor Leakage-reactance ( )
Resistance Corresponding to Ironcore Loss ( )
Stator Phase Current (A)
Magnetizing Current (A)
Slot-1
Slot-2
Slot-3
Slot-4
1.53
58.75
6.37
1.42
61.43
6.12
1.31
57.32
5.87
1.33
59.78
6.03
1849.56
1886.43
1842.53
1891.57
9.81
3.51
9.32
3.26
9.96
3.55
9.48
3.38
Table 3.5 Parameters for Slot-C Combination
Parameters
Stator Leakage-reactance ( )
Magnetizing-reactance ( )
Rotor Leakage-reactance ( )
Resistance Corresponding to Ironcore Loss ( )
Stator Phase Current (A)
Magnetizing Current (A)
Slot-1
Slot-2
Slot-3
Slot-4
1.51
56.38
6.06
1.36
60.64
6.13
1.45
59.34
5.76
1.38
61.06
6.57
1889.26
1906.21
1898.89
1918.98
9.43
3.74
8.79
3.32
9.89
3.46
8.69
3.28
59
Table 3.6 Parameters for Slot-D Combination
Parameters
Slot-1
Slot-2
Slot-3
Slot-4
Stator Leakage-reactance ( )
1.39
1.31
1.48
1.34
Magnetizing-reactance ( )
Rotor Leakage-reactance ( )
Resistance Corresponding to
Iron-core Loss ( )
Stator Phase Current (A)
58.76
6.02
61.63
5.52
59.17
5.94
60.46
6.17
Magnetizing Current (A)
1899.76 1912.43 1906.49 1910.38
9.37
8.89
9.24
8.91
3.74
3.39
3.61
3.45
Table 3.7 Parameters for Slot-E Combination
Parameters
Stator Leakage-reactance ( )
Magnetizing-reactance ( )
Rotor Leakage-reactance ( )
Resistance Corresponding to
Iron-core Loss ( )
Stator Phase Current (A)
Magnetizing Current (A)
Slot-1
Slot-2
1.49
56.37
6.04
1.33
61.32
5.68
Slot-3
1.34
57.46
5.57
Slot-4
1.41
61.08
6.05
1886.21 1912.47 1904.67 1908.43
9.38
8.78
9.27
8.89
3.72
3.39
3.58
3.44
Table 3.8 Parameters for Slot-F Combination
Parameters
Stator Leakage-reactance ( )
Magnetizing-reactance ( )
Rotor Leakage-reactance ( )
Resistance Corresponding to
Iron-core Loss ( )
Stator Phase Current (A)
Magnetizing Current (A)
Slot-1
1.48
56.46
6.08
Slot-2
1.33
62.45
5.78
Slot-3
1.41
57.34
5.68
Slot-4
1.38
60.57
6.18
1883.16 1912.06 1903.34 1907.43
9.38
3.55
8.85
3.23
9.24
3.47
9.07
3.31
60
It could be concluded from the parameters in Table 3.3 to Table 3.8
that the combination of Slot-A type stator slot with Slot-2 type rotor slot
contribute to a good magnetic circuit. The advantages of this combination
are:
Reduced Stator and Rotor Leakage-reactances
Increased Magnetizing-reactance
Increased Resistance corresponding to Iron-Core Loss
Reduced Stator Phase Current
Reduced Magnetizing Current
The output power of the underwater motor can be increased by
reducing the magnetizing current. Reduced magnetizing current will improve
the operating power factor. A cumulative operation of more number of such
motors will lead to energy-saving and the load factor of the connected
distribution transformer will come down, resulting in good voltage regulation
and high Transformer utilization factor. Existing Slot-D type stator slot and
Slot-1 type rotor slot combination shown in Figure 3.13a are compared with
the proposed Slot-A type stator slot and Slot-2 type rotor slot shown in Figure
3.13b. Submersible motors with the ratings of 3-HP, 5-HP, 6-HP, and 7.5-HP
have been considered for optimisation.
61
(a)
(b)
Figure 3.13 Stamping Models (a) Slot-D Type Stator and Slot-1 Type
Rotor (b) Slot-A Type Stator and Slot-2 Type Rotor
For analysis in RMxprt, a 3-phase, 380 V, 2-pole, 50 Hz, and starconnected submersible induction motor type has been considered with the
specifications given in Table 3.9.
Table 3.9 Specifications of the Motors
S.
No.
1
Outer diameter of the Stator (mm)
137
137
137
137
2
3
4
5
6
7
8
9
10
11
Inner Diameter of the Stator (mm)
Length of the Stator core (mm)
Air-gap (mm)
Inner diameter of the Rotor (mm)
End-Ring Width (mm)
End-Ring Length (mm)
End-Ring Height (mm)
Number of Stator Slots
Number of Rotor Slots
Conductors per slot
73
105
0.5
42
6
1
11
24
18
52
73
180
0.5
42
6.5
1
11
24
18
31
73
205
0.5
42
7.2
1
11
24
18
27
73
225
0.5
42
9
1
11
24
18
24
Parameter
3-HP 5-HP 6-HP 7.5-HP
62
The stator and rotor stampings are common for the selected range
of motors. M43_29G-grade-stamping has been used for both the stator and the
rotor. The core-length has been varied based on the power rating of the motor,
the magnetic loading, and the electric loading values are adjusted to optimize
the core-length and other performance parameters. The electric loading value
is kept slightly higher for the submersible motor compared to the normal
industry-type motor because of the forced-water cooling. The number of
conductors per slot and End-Ring width have also been changed so as to meet
the design requirements.
3.5
SIMULATION RESULTS
With fixed operating conditions, the machines have been simulated
in RMxprt and the results are tabulated as shown in Table 3.10 and
Table 3.11. Following inferences could be made from Table 3.10 and
Table 3.11:
The leakage-reactance of stator and rotor, namely, Slot, Endwinding, Differential, and Skewing Leakage-reactance values
have got reduced.
Increased
values
of
Iron-core
Loss
Resistance
and
Magnetizing-reactance reduce the loss-component current and
the magnetizing current, resulting in improvement of the
operating power factor.
The stator phase current of the proposed slot type motor is
less, when compared to that of the existing slot type motor.
There is a significant improvement in the efficiency of the
motor with the proposed slot-shape.
63
64
65
(a)
(b)
Figure 3.14 Flux Distribution (a) Existing Slot (b) Proposed Slot
Flux distribution in the Motor is shown in Figure 3.14. The flux
density with the proposed stator slot is found to be from 1.22 Tesla to
1.55 Tesla; but in the existing stator, it is from 1.20 Tesla to 1.70 Tesla. Since
the magnetic flux density is less in the proposed slot, there is a reduction in
the required magnetizing current.
3.6
REAL-TIME IMPLEMENTATION AND RESULTS
The stampings and the test setup are shown in Figure 3.15 and
Figure 3.16, respectively.
66
(a)
(b)
Figure 3.15 Stampings (a) Existing (b) Proposed
(a)
(b)
Figure 3.16 Test Set-up (a) Testing Panel (b) Pump Loading
The performance test reports for 3-HP, 5-HP, 6-HP, and 7.5-HP
pump-sets, with the existing and the proposed motor slot-shape are shown in
Table 3.12 to Table 3.19.
67
Table 3.12
Performance Test of 3-HP Submersible-pump-set with the
Existing slot-shape
Delivery
Total
Speed gauge reading
head
S.No.
(rpm)
2
(Kgf/cm )
(m)
Rise in
Tank
(cm)
Input Pump
Time for Discharge Current
Power output
rise (s)
(lpm)
(A)
(kW) (kW)
Overall
efficiency
(%)
1
2851
0.00
1.90
30.00
54.69
331
5.35
2.49
0.10
4.11
2
2840
1.00
11.82
20.00
40.40
298
5.63
2.66
0.58
21.55
3
2828
2.00
21.76
20.00
45.16
267
5.92
2.83
0.96
33.40
4
2817
3.00
31.68
10.00
26.91
224
6.05
2.90
1.17
39.76
5
2836
4.50
46.58
9.80
40.81
145
5.66
2.68
1.11
40.96
6
2858
5.00
51.54
10.00
56.78
106
5.24
2.42
0.90
36.80
7
2899
5.50
56.51
5.00
78.03
39
4.32
1.79
0.36
19.79
8
2911
5.70
58.50
0.00
0.00
0
3.83
1.42
0.00
0.00
Table 3.13
Performance Test of 3-HP Submersible-pump-set with the
Proposed slot-shape
S.No.
Delivery
Total
Speed gauge reading
head
(rpm)
(m)
(Kgf/cm2)
Input
Rise in
Time for Discharge Current Power
Tank
rise (s)
(lpm)
(A)
(cm)
(kW)
Pump
output
(kW)
Overall
efficiency
(%)
1
2873
0.00
1.94
30.00
51.84
349
4.53
2.19
0.11
5.10
2
2865
1.00
11.88
20.00
37.15
324
4.90
2.37
0.63
26.75
3
2854
2.00
21.80
20.00
41.71
289
5.00
2.54
1.04
40.87
4
2844
3.00
31.72
10.00
24.71
244
5.10
2.63
1.27
48.51
5
2862
4.50
46.59
9.80
37.21
159
4.90
2.38
1.22
51.28
6
2883
5.00
51.55
10.00
51.98
116
4.44
2.13
0.98
46.17
7
2927
5.50
56.51
5.00
72.41
42
3.38
1.50
0.39
25.71
8
2939
5.70
58.50
0.00
0.00
0
3.00
1.12
0.00
0.00
68
Head (m)
Overall Efficiency (%)
Current (A)
Motor Input (kW)
66
44
60
40
54
36
48
32
42
28
36
24
30
20
24
16
18
12
12
8
6
4
0
0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
Discharge (lps)
(a)
Head (m)
Current (A)
66
Overall Efficiency (%)
Motor Input (kW)
60
60
55
54
50
45
48
40
42
35
36
30
30
25
24
20
18
15
12
10
6
5
0
0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
Discharge (lps)
(b)
Figure 3.17 Pump Performance Curve: 3-HP (a) Existing (b) Proposed
69
Current in the Proposed Design (A)
Current in the Existing Design (A)
Discharge in the Existing Design (lpm)
Discharge in the Proposed Design (lpm)
10
350
.
9
300
8
250
7
6
200
5
150
4
3
100
2
50
1
0
0
0
1
2
3
4
5
6
Delivery Gauge Reading (kgf/cm2)
(a)
Current in the Existing Design (A)
Current in the Proposed Design (A)
pf in the Existing Design
pf in the Proposed Design
.
10
1
9
0.8
8
7
6
0.6
5
4
0.4
3
2
0.2
1
0
0
0
1
2
3
4
Delivery Gauge Reading (kgf/cm2)
5
6
(b)
Figure 3.18 Performance Comparison Curve: 3-HP (a) Discharge and
Current (b) Current & Power factor
70
Table 3.14
Performance Test of 5-HP Submersible-pump-set with the
Existing slot-shape
Delivery
Input Pump Overall
Total Rise Time
Speed gauge
Discharge Current
in
for
head
S.No.
Power output efficiency
Tank rise
(rpm) reading
(lpm)
(A)
(m)
(%)
(kW) (kW)
(cm)
(s)
(Kgf/cm2)
1
2848
0.00
1.53 30.00
47.46
383
9.37
4.63
0.10
2.1
2
2843
2.00
21.41 30.00
53.81
338
9.63
4.84
1.21
25.01
3
2844
4.00
41.27 30.00
66.06
275
9.63
4.87
1.90
38.93
4
2851
5.00
51.22 30.00
74.34
244
9.47
4.73
2.08
44.05
5
2864
6.00
61.15 30.00
90.15
201
9.20
4.59
2.05
44.53
6
2875
7.00
71.07 20.00
85.38
142
8.47
4.01
1.67
41.64
7
2896
7.50
76.02 10.00
76.41
79
7.53
3.21
1.00
31.26
8
2929
7.90
80.00 0.00
0.00
0
6.37
2.23
0.00
0.00
Table 3.15
Performance Test of 5-HP Submersible-pump-set with the
Proposed slot-shape
Delivery
Input Pump Overall
Total Rise Time
Speed gauge
Discharge Current
in
head
output efficiency
for
S.No.
Power
Tank
(rpm) reading
(lpm)
(A)
(m) (cm) rise (s)
(kW)
(%)
(kW)
2
(Kgf/cm )
1
2872
0.00
1.76
30.00 39.53
460
8.40
4.38
0.13
2.99
2
2867
2.00
21.57 30.00 45.64
399
8.87
4.52
1.44
30.75
3
2869
4.00
41.36 30.00 57.83
315
8.83
4.56
2.17
46.13
4
2876
5.00
51.28 30.00 65.56
277
8.90
4.44
2.36
51.81
5
2885
6.00
61.19 30.00 80.15
226
8.57
4.32
2.30
51.97
6
2913
7.00
71.09 20.00 76.48
158
7.30
3.68
1.86
49.53
7
2930
7.50
76.03 10.00 69.51
87
6.63
2.84
1.10
37.76
8
2959
7.90
80.00
0
5.17
1.96
0.00
0.00
0.00
0.00
71
Head (m)
Current (A)
90
Overall Efficiency (%)
Motor Input (kW)
45
80
40
70
35
60
30
50
25
40
20
30
15
20
10
10
5
0
0
0
1
2
3
4
Discharge (lps)
5
6
7
(a)
Head (m)
Current (A)
Overall Efficiency (%)
Motor Input (kW)
90
60
80
50
70
60
40
50
30
40
30
20
20
10
10
0
0
0
1
2
3
4
5
Discharge (lps)
6
7
8
9
(b)
Figure 3.19 Pump Performance Curve: 5-HP (a) Existing (b) Proposed
72
Current in the Proposed Design (A)
Discharge in the Existing Design (lpm)
12
Current in the Existing Design (A)
Discharge in the Proposed Design (lpm)
500
.
10
400
8
300
6
200
4
100
2
0
0
0
1
2
3
4
5
6
Delivery Gauge Reading (kgf/cm2 )
7
8
(a)
Current in the Existing Design (A)
pf in the Existing Design
Current in the Proposed Design (A)
pf in the Proposed Design
1
15
.
0.8
10
0.6
0.4
5
0.2
0
0
0
2
4
6
8
10
Delivery Gauge Reading (kgf/cm2 )
(b)
Figure 3.20 Performance Comparison Curve: 5-HP (a) Discharge and
Current (b) Current and Power factor
73
Table 3.16
Performance Test of 6-HP Submersible-pump-set with the
Existing slot-shape
Delivery
Input Pump Overall
Total Rise Time
Speed gauge
Discharge Current
in
for
head
S.No.
Power output efficiency
Tank rise
(rpm) reading
(lpm)
(A)
(m)
(%)
(kW) (kW)
(cm) (s)
(Kgf/cm2)
1
2898
0.00
2.06
20.00 45.37
266.03
8.06
3.380
0.091
2.68
2
2883
2.00
22.01 20.00 50.25
240.54
8.58
3.780
0.878
23.22
3
2874
4.00
41.96 20.30 58.50
209.84
9.05
4.135
1.461
35.34
4
2867
6.00
61.92 10.00 33.29
181.65
9.41
4.389
1.867
42.54
5
2866
8.00
81.87 10.00 42.94
140.77
9.40
4.424
1.911
43.20
6
2873
9.00
91.85 10.00 53.12
113.77
9.24
4.270
1.732
40.57
7
2889
10.00
101.82 5.00 38.90
77.62
8.64
3.830
1.308
34.15
8
2913
11.00
111.80 2.00 38.09
31.68
7.65
3.033
0.585
19.29
Table 3.17
Performance Test of 6-HP Submersible-pump-set with the
Proposed slot-shape
Delivery
Input Pump Overall
Total Rise Time
Speed gauge
in
for Discharge Current
head
output efficiency
S.No.
Power
Tank rise
(rpm) reading
(lpm)
(A)
(m)
(%)
(kW) (kW)
(cm) (s)
(Kgf/cm2)
1
2908
0.00
2.15
20.00 39.25
308.99
7.12
3.171
0.110
3.46
2
2898
2.00
22.12 20.00 46.34
297.34
7.67
3.570
1.091
30.55
3
2889
4.00
42.06 20.30 53.65
266.68
8.09
3.918
1.862
47.52
4
2887
6.00
62.01 10.00 28.43
215.88
8.52
4.168
2.221
53.28
5
2896
8.00
81.94 10.00 38.32
174.69
8.44
4.211
2.373
56.36
6
2906
9.00
91.89 10.00 47.17
148.67
8.29
4.052
2.265
55.89
7
2912
10.00
101.84 5.00 33.16
94.81
7.75
3.620
1.598
44.14
8
2921
11.00
111.80 2.00 34.22
34.39
6.71
2.812
0.635
22.58
74
Head (m)
Oveall Efficiency (%)
Current (A)
Motor Input (kW)
45
130
120
40
110
35
100
90
30
80
70
25
60
20
50
40
15
30
10
20
5
10
0
0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Discharge (lps)
(a)
Head (m)
Oveall Efficiency (%)
Current (A)
Motor Input (kW)
60
140
120
50
100
40
80
30
60
20
40
10
20
0
0
0.0
1.0
2.0
3.0
4.0
5.0
Discharge (lps)
(b)
Figure 3.21 Pump Performance Curve: 6-HP (a) Existing (b) Proposed
75
Current in the Existing Design (A)
Current in the Proposed Design (A)
Discharge in the Existing Design (lpm)
Discharge in the Proposed Design (lpm)
.
10
350
300
8
250
6
200
4
150
100
2
50
0
0
0
2
4
6
8
10
Delivery Gauge Reading (kgf/cm2)
12
14
(a)
Current in the Existing Design (A)
pf in the Existing Design
Current in the Proposed Design (A)
pf in the Proposed Design
1.0
10
8
0.8
6
0.6
4
0.4
2
0.2
0
0.0
0
2
4
6
8
10
Delivery Gauge Reading (kgf/cm2)
12
14
(b)
Figure 3.22 Performance Comparison Curve: 6-HP (a) Discharge and
Current (b) Current and Power factor
76
Table 3.18
Performance Test of 7.5-HP Submersible-pump-set with the
Existing slot-shape
Delivery
Input Pump Overall
Total Rise Time
Speed gauge
Discharge Current
in
for
head
S.No.
Power output efficiency
Tank rise
(rpm) reading
(lpm)
(A)
(m)
(%)
(kW) (kW)
(cm) (s)
(Kgf/cm2)
1
2880
0.00
2.20
30.00 54.50
331
13.94
6.12
0.12
1.95
2
2873
2.00
22.15 20.00 39.09
308
14.27
6.37
1.12
17.65
3
2864
4.00
42.09 20.00 42.84
282
14.57
6.61
1.96
29.61
4
2856
6.00
62.04 10.00 23.53
257
14.79
6.78
2.64
38.85
5
2851
8.00
81.98 10.00 26.78
226
14.96
6.90
3.06
44.40
6
2849
10.00
101.93 10.00 32.00
189
14.89
6.89
3.20
46.48
7
2853
12.00
121.88 10.00 41.13
147
14.49
6.60
2.98
45.17
8
2861
13.00
131.85 5.00 25.75
118
13.86
6.16
2.58
41.94
9
2903
14.50
146.80 0.00
0
10.96
3.65
0.00
0.00
0.00
Table 3.19 Performance Test of 7.5-HP Submersible-pump-set with the
Proposed slot-shape
Delivery
Input Pump Overall
Total Rise Time
Speed gauge
in
for Discharge Current
head
S.No.
Power output efficiency
Tank rise
(rpm) reading
(lpm)
(A)
(m)
(%)
(kW) (kW)
(cm) (s)
(Kgf/cm2)
1
2898
0.00
2.48
30.00 48.43
427
12.24
5.94
0.17
2.92
2
2891
2.00
22.61 20.00 33.16
413
12.93
6.17
1.52
24.71
3
2882
4.00
42.77 20.00 36.57
379
13.28
6.46
2.65
41.04
4
2874
6.00
63.10 10.00 18.37
367
13.56
6.63
3.79
57.08
5
2870
8.00
83.24 10.00 21.45
320
13.92
6.74
4.35
64.57
6
2868
10.00
103.72 10.00 27.34
259
13.78
6.81
4.39
64.51
7
2873
12.00
124.10 10.00 36.27
204
13.23
6.54
4.14
63.29
8
2881
13.00
134.36 5.00 21.37
179
12.61
6.08
3.93
64.54
9
2924
14.50
149.30 0.00
0
9.13
3.48
0.00
0.00
0.00
77
Head (m)
Overall Efficiency (%)
Current (A)
Motor Input (kW)
50
160
45
140
40
120
35
100
30
80
25
60
20
15
40
10
20
5
0
0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
Discharge (lps)
(a)
Head (m)
Overall Efficiency (%)
Current (A)
160
Motor Input (kW)
70
140
60
120
50
100
40
80
30
60
20
40
10
20
0
0
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
Discharge (lps)
(b)
Figure 3.23 Pump Performance Curve: 7.5-HP (a) Existing (b) Proposed
78
Current in the Proposed Design (A)
Discharge in the Existing Design (lpm)
20
Current in the Existing Design (A)
Discharge in the Proposed Design (lpm)
450
.
400
350
15
300
250
10
200
150
5
100
50
0
0
0
2
4
6
8
10
12
Delivery Gauge Reading (kgf/cm2)
14
16
(a)
Current in the Existing Design (A)
pf in the Existing Design
Current in the Proposed Design (A)
pf in the Proposed Design
1
16
.
14
0.8
12
10
0.6
8
0.4
6
4
0.2
2
0
0
0
2
4
6
8
10
Delivery Gauge Reading (kgf/cm2)
12
14
(b)
Figure 3.24 Performance Comparison Curve: 7.5-HP (a) Discharge and
Current (b) Current and Power factor
79
Performance Comparison Curves for 3-HP, 5-HP, 6-HP, and
7.5-HP, Pump-sets have been depicted in Figure 3.17 to Figure 3.24. From the
performance curves, the following inferences have been made:
The current drawn from the supply gets reduced by 1 to 1.7 A,
and the power factor has also got significantly improved.
Input power consumed by the pump-set gets significantly
reduced by 130 to 300 W.
There is an increase in speed of the pump-set by 15 to 30 rpm,
and this results in increase in the discharge of water by 30 to
70 lpm.
The overall efficiency of the pump-set has gone up by 3 to 7 %.
Therefore, the adoption of these motors in the agriculture field can
give immense benefits to the user, as well as to the country and the global
environment at large.