chapter 3 influence of stator slot-shape on...

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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

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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 Rc denotes the

resistance corresponding to the iron-core losses. Xm 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

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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:

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

2) 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)

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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

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=.

(3.4)

where 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 average-

turn length. As shown in Figure 3.2, this length is the addition of two

components, namely, the part of turn embedded in the slot (Lcore) 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)

= (3.6)

= 1 ( + ) (3.7)

where 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 end-

winding 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).

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= (3.8)

= (3.9)

where 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 joule-

losses. 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).

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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 (Pjr) 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).

= + (3.12)

3.2.2 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.

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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 ( hl).

B) With reference to the energy conservation: The total flux ( total)

linked with a phase winding is the addition of the following two

components:

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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.

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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 = L I (3.17)

where 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 phase-

winding.

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).

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( ) =( ) ( )

( ) (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)

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End-winding leakage-inductance (Lw)

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).

2 2vpho wv

v ,V 1

Tm kL DLg p v

(3.24)

where µ0 = Permeability of vacuum

m = Number of phases

g = Air-gap length

L = Effective core-length

D = Diameter of the core

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:

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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= 4mQ o

2u (3.25)

where Q = Number of slots

u = 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.

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u = h4

3b4+ h3

b4+ h1

b1+ h2

b4-b1ln b4

b1(3.26)

Tooth-tip leakage-inductance is determined using Equation (3.27).

= (3.27)

d = 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

=

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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).

= (3.30)

where 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 (Pm), otherwise called as the air-gap power, is determined by Equation (3.31).

= 3 (3.31)

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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).

= (3.34)

where r = (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)

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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 solution-setup 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 slot-shapes have been considered for optimisation. The stator and rotor slot-models used for simulation are shown in Figure 3.9 and Figure 3.10, respectively.

Figure 3.9 Stator Slot-models used for Optimisation

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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 TypeDimension (mm)

BS0 BS1 BS2 HS0 HS1 HS2 RS1 RS2

A 3.90 6.03 9.50 1.00 0.80 13.20 - -B 3.90 6.90 9.88 0.80 - 11.30 1.50 -C 3.90 6.90 10.63 0.70 - 14.15 1.50 1.00D 3.90 6.03 10.19 1.00 0.80 15.80 - 1.00E 3.90 6.17 9.59 1.00 - 13.00 - -F 3.90 6.25 10.36 0.52 - 15.60 - 1.00

Table 3.2 Dimensions of Rotor Slots

Slot TypeDimension (mm)

BS0 BS1 BS2 HS0 HS1 HS2 RS

1 1.80 5.00 3.20 - 0.42 7.50 0.202 1.80 5.00 3.20 - 0.42 7.50 0.203 1.10 5.10 3.20 0.70 0.42 6.30 -4 1.80 5.00 3.20 - - 4.60 -

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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.

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.

Analysis of Machine Add a solution setup Validation check Analyse

Design Output of MachineDesign sheet Performance table Performance curves

Start

Define Data for 3-phase Induction Motor

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

Stator Data

Outer diameter Inner diameter Length Type of Steel Stacking factor No. of slots Slot-Model Slot dimensions Winding details

General Data

Machine type No. of Poles Stray loss Friction loss Windage loss Reference speed

Solution Data

Duty-cycle Type of Load Rated output Rated voltage Rated speed Operating temperature Winding connection Frequency

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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.

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)

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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 1.36Magnetizing-reactance ( ) 57.34 64.56 56.17 60.04Rotor Leakage-reactance ( ) 5.94 5.16 5.34 6.23Resistance Corresponding to Iron-core Loss ( ) 1879.34 1926.23 1902.74 1911.98

Stator Phase Current (A) 9.43 8.37 9.39 8.84Magnetizing Current (A) 3.55 3.07 3.31 3.26

Table 3.4 Parameters for Slot-B Combination



Table 3.5 Parameters for Slot-C Combination



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Table 3.6 Parameters for Slot-D Combination



Table 3.7 Parameters for Slot-E Combination



Table 3.8 Parameters for Slot-F Combination



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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.

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(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 star-

connected submersible induction motor type has been considered with the

specifications given in Table 3.9.

Table 3.9 Specifications of the Motors

S.No. Parameter 3-HP 5-HP 6-HP 7.5-HP

1 Outer diameter of the Stator (mm) 137 137 137 1372 Inner Diameter of the Stator (mm) 73 73 73 733 Length of the Stator core (mm) 105 180 205 2254 Air-gap (mm) 0.5 0.5 0.5 0.55 Inner diameter of the Rotor (mm) 42 42 42 426 End-Ring Width (mm) 6 6.5 7.2 97 End-Ring Length (mm) 1 1 1 18 End-Ring Height (mm) 11 11 11 119 Number of Stator Slots 24 24 24 24

10 Number of Rotor Slots 18 18 18 1811 Conductors per slot 52 31 27 24

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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, End-

winding, 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.

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(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.

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(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.

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Table 3.12 Performance Test of 3-HP Submersible-pump-set with the

Existing slot-shape

S.No.Speed(rpm)

Delivery gauge reading

(Kgf/cm2)

Total head (m)

Rise in Tank (cm)

Time for rise (s)

Discharge(lpm)

Current(A)

InputPower(kW)

Pump output (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


Proposed slot-shape

S.No. Speed(rpm)

Delivery gauge reading

(Kgf/cm2)

Total head (m)

Rise in Tank (cm)

Time for rise (s)

Discharge(lpm)

Current(A)

InputPower (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

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(a)

(b)

Figure 3.17 Pump Performance Curve: 3-HP (a) Existing (b) Proposed

0

4

8

12

16

20

24

28

32

36

40

44

0

6

12

18

24

30

36

42

48

54

60

66

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0Discharge (lps)

Head (m) Overall Efficiency (%)Current (A) Motor Input (kW)

0

5

10

15

20

25

30

35

40

45

50

55

60

0

6

12

18

24

30

36

42

48

54

60

66

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)


69

(a)

(b)

Figure 3.18 Performance Comparison Curve: 3-HP (a) Discharge and

Current (b) Current & Power factor

0

50

100

150

200

250

300

350

0

1

2

3

4

5

6

7

8

9

10

0 1 2 3 4 5 6Delivery Gauge Reading (kgf/cm2)

.

Current in the Proposed Design (A) Current in the Existing Design (A)Discharge in the Existing Design (lpm) Discharge in the Proposed Design (lpm)

0

0.2

0.4

0.6

0.8

1

0

1

2

3

4

5

6

78

9

10

0 1 2 3 4 5 6Delivery Gauge Reading (kgf/cm2)

.

Current in the Existing Design (A) Current in the Proposed Design (A)pf in the Existing Design pf in the Proposed Design

70


Existing slot-shape

S.No.Speed(rpm)

Delivery gauge

reading (Kgf/cm2)

Total head (m)

Rise in

Tank (cm)

Time for rise (s)

Discharge(lpm)

Current(A)

InputPower(kW)

Pump output(kW)

Overall efficiency

(%)

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


Proposed slot-shape

S.No.Speed(rpm)

Delivery gauge

reading (Kgf/cm2)

Total head(m)

Rise in

Tank (cm)

Time for

rise (s)

Discharge(lpm)

Current(A)

InputPower(kW)

Pump output(kW)

Overall efficiency

(%)

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 0.00 0.00 0 5.17 1.96 0.00 0.00

71

(a)

(b)


0

5

10

15

20

25

30

35

40

45

0

10

20

30

40

50

60

70

80

90

0 1 2 3 4 5 6 7Discharge (lps)


0

10

20

30

40

50

60

0

10

20

30

40

50

60

70

80

90

0 1 2 3 4 5 6 7 8 9Discharge (lps)


72

(a)

(b)


Current (b) Current and Power factor

0

100

200

300

400

500

0

2

4

6

8

10

12

0 1 2 3 4 5 6 7 8Delivery Gauge Reading (kgf/cm2 )

.


0

0.2

0.4

0.6

0.8

1

0

5

10

15

0 2 4 6 8 10

Delivery Gauge Reading (kgf/cm2 )

.


73


Existing slot-shape

S.No.Speed(rpm)

Delivery gauge

reading (Kgf/cm2)

Total head (m)

Rise in

Tank (cm)

Time for rise (s)

Discharge(lpm)

Current(A)

InputPower(kW)

Pump output(kW)

Overall efficiency

(%)

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


Proposed slot-shape

S.No.Speed(rpm)

Delivery gauge

reading (Kgf/cm2)

Total head (m)

Rise in

Tank (cm)

Time for rise (s)

Discharge(lpm)

Current(A)

InputPower(kW)

Pump output(kW)

Overall efficiency

(%)

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

(a)

(b)


0

10

20

30

40

50

60

0

20

40

60

80

100

120

140

0.0 1.0 2.0 3.0 4.0 5.0Discharge (lps)

Head (m) Oveall Efficiency (%) Current (A) Motor Input (kW)

0

5

10

15

20

25

30

35

40

45

0

10

20

30

40

50

60

70

80

90

100

110

120

130

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0Discharge (lps)

Head (m) Oveall Efficiency (%) Current (A) Motor Input (kW)

75

(a)

(b)



0

50

100

150

200

250

300

350

0

2

4

6

8

10

0 2 4 6 8 10 12 14Delivery Gauge Reading (kgf/cm2)

.

Current in the Existing Design (A) Current in the Proposed Design (A)

Discharge in the Existing Design (lpm) Discharge in the Proposed Design (lpm)

0.0

0.2

0.4

0.6

0.8

1.0

0

2

4

6

8

10



76

Table 3.18 Performance Test of 7.5-HP Submersible-pump-set with the

Existing slot-shape

S.No.Speed(rpm)

Delivery gauge

reading (Kgf/cm2)

Total head (m)

Rise in

Tank (cm)

Time for rise (s)

Discharge(lpm)

Current(A)

InputPower(kW)

Pump output(kW)

Overall efficiency

(%)

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 0.00 0 10.96 3.65 0.00 0.00

Table 3.19 Performance Test of 7.5-HP Submersible-pump-set with the

Proposed slot-shape

S.No.Speed(rpm)

Delivery gauge

reading (Kgf/cm2)

Total head (m)

Rise in

Tank (cm)

Time for rise (s)

Discharge(lpm)

Current(A)

InputPower(kW)

Pump output(kW)

Overall efficiency

(%)

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 0.00 0 9.13 3.48 0.00 0.00

77

(a)

(b)

Figure 3.23 Pump Performance Curve: 7.5-HP (a) Existing (b) Proposed

0

5

10

15

20

25

30

35

40

45

50

0

20

40

60

80

100

120

140

160

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)

Head (m) Overall Efficiency (%) Current (A) Motor Input (kW)

0

10

20

30

40

50

60

70

0

20

40

60

80

100

120

140

160

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0

Discharge (lps)

Head (m) Overall Efficiency (%) Current (A) Motor Input (kW)

78

(a)

(b)

Figure 3.24 Performance Comparison Curve: 7.5-HP (a) Discharge and


0

50

100

150

200

250

300

350

400

450

0

5

10

15

20

0 2 4 6 8 10 12 14 16Delivery Gauge Reading (kgf/cm2)

.


0

0.2

0.4

0.6

0.8

1

0

2

4

6

8

10

12

14

16


.


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.

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