Design and calculation of an asynchronous motor. Squirrel cage induction motor design Induction motor design

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MINISTRY OF EDUCATION AND SCIENCE

REPUBLIC OF KAZAKHSTAN

North Kazakhstan state University them. M. Kozybaeva

Faculty of Energy and Mechanical Engineering

Department of Energy and Instrumentation

COURSE WORK

On the topic: "Designing an asynchronous motor with a squirrel cage rotor"

on discipline - "Electric machines"

Completed by Kalantyrev

supervisor

doctor of Technical Sciences, prof. N.V. Shatkovskaya

Petropavlovsk 2010

Introduction

1. Choice of main dimensions

2. Determination of the number of stator slots, turns in the winding phase of the stator winding wire cross-section

3. Calculation of the dimensions of the toothed zone of the stator and the air gap

4. Calculation of the rotor

5. Calculation of the magnetic circuit

6. Operating mode parameters

7. Calculation of losses

8. Calculation of performance characteristics

9. Thermal design

10. Calculation of performance from a pie chart

Appendix A

Conclusion

Bibliography

Introduction

Asynchronous motors are the main converters of electrical energy into mechanical energy and form the basis of the electric drive of most mechanisms. The 4A series covers a rated power range from 0.06 to 400 kW and has 17 axis heights from 50 to 355 mm.

In this course project, the following engine is considered:

Execution according to the degree of protection: IP23;

Cooling method: IС0141.

Design by mounting method: IM1081 - according to the first digit - motor on feet, with end shields; on the second and third digits - with a horizontal shaft and lower legs; on the fourth digit - with one cylindrical shaft end.

Climatic working conditions: U3 - letter by letter - for a temperate climate; digitally - for placement in closed rooms with natural ventilation without artificially controlled climatic conditions, where fluctuations in temperature and humidity, exposure to sand and dust, solar radiation are significantly less than stone, concrete, wooden and other unheated rooms outdoors.

1. Choice of main dimensions

1.1 Determine the number of pole pairs:

(1.1)

Then the number of poles

1.2 Determine the height of the axis of rotation graphically: according to Figure 9.18, b

, in accordance with, according to table 9.8 we determine the outer diameter corresponding to the axis of rotation.

1.3 Stator inner diameter

, we will calculate by the formula:, (1.2) - coefficient determined according to table 9.9. lies in the interval:.

Let's choose the value

then

1.4 Determine the pole division

: (1.3)

1.5 Determine the design power

, W:, (1.4) - power on the motor shaft, W; - the ratio of the EMF of the stator winding to the rated voltage, which can be approximately determined from Figure 9.20. For and,.

Approximate values

and take it according to the curves built according to the data of the 4A series engines. Figure 9.21, c. With kW and, and

1.6 The electromagnetic loads A and B d are determined graphically from the curves in Figure 9.23, b. When

kW and,, Tl.

1.7 Winding ratio

... For two-layer windings at 2p\u003e 2, \u003d 0.91–0.92 should be taken. Let's accept.

1.8 Determine the synchronous angular speed of the motor shaft W:

, (1.5) - synchronous rotation frequency.

1.9 Calculate the length of the air gap

:
, (1.6) is the field shape coefficient. ...

1.10 The criterion for the correct choice of the main dimensions D and

serves as the ratio, which should be within the permissible limits Figure 9.25, b. ... The l value lies within the recommended limits, which means that the main dimensions are determined correctly.

2. Determination of the number of stator slots, turns in the phase of the winding and the cross-section of the stator winding wire

2.1 Determine the limit values: t 1 max and t 1 min Figure 9.26. When

and,,.

2.2 Number of stator slots:

, (2.1) (2.2)

Finally, the number of slots should be a multiple of the number of slots per pole and phase: q. Let's accept

then
, (2.3)

where m is the number of phases.

2.3 Finally, we determine the tooth division of the stator:

(2.4)

2.4 Stator winding pre-current

(2.5)

2.5 The number of effective conductors in the slot (provided

FSBEI HPE "Ugra State University"

Department of "Energy"

Karminskaya T.D., Kovalev V.Z., Bespalov A.V., Shcherbakov A.G.

ELECTRIC CARS

Tutorial

to carry out course design on

discipline "Electrical machines"

for bachelors studying in

the direction of preparation 13.03.02 "Power and Electrical Engineering"

Khanty-Mansiysk 2013

This tutorial describes a squirrel cage induction motor design technique that is required to complete a course design assignment. In the course of course design, such tasks are solved as the choice of the main dimensions of the motor, the calculation of the parameters and the magnetic system of the stator winding, the calculation of the parameters and the magnetic system of the rotor winding, the determination of the parameters of the equivalent circuit and the construction of the mechanical and operating characteristics of the induction motor.

The textbook is compiled in accordance with the work programs of the courses "Electrical machines" for students of the direction 13.03.02 "Electric power and electrical engineering". It can be useful for students of other electrical and electromechanical fields and specialties, as well as for specialists engaged in research, design and operation of asynchronous machines for various purposes.

Introduction

Initial data for design

Options for design assignments

Chapter 1. Methodology for designing an asynchronous motor with a squirrel cage rotor

1.1. Selection of the main dimensions of the engine.

1.2. Calculation of the parameters of the stator winding

1.3. Calculation of air gap parameters

1.4. Calculation of rotor winding parameters.

1.5. Calculation of the magnetizing current

1.6. Calculation of engine operating parameters

1.7. Calculation of active losses in the engine

1.8. Calculating engine performance

1.9. Calculation of starting characteristics.

Chapter 2. The use of computers for the design of an asynchronous motor with a squirrel cage rotor.

2.1. Description of the "AD-KP" program

2.2. An example of application of the "AD - KP" program

Conclusion

ANNEXES

Bibliography

Introduction.

An asynchronous machine is a brushless AC machine in which the ratio of the rotor speed to the frequency of the current in the circuit to which the machine is connected depends on the loads. Like any electric machine, an asynchronous machine has the property of reversibility, i.e. can operate in both motor and generator modes. However, in practice, the most widespread is the motor mode of operation of the machine. Today, an asynchronous motor is the main engine of most mechanisms and machines. More than 60% of all generated electrical energy is consumed by electric machines, with induction motors accounting for a significant share (approximately 75%). Asynchronous motors are quite widespread due to their following advantages: small overall dimensions, simple design, high reliability, high efficiency, relatively low cost. The disadvantages of an induction motor include: difficulties in regulating the speed of rotation, large starting currents, low power factor when the machine is operating in a mode close to idle. The first and second of the disadvantages can be compensated for by the use of frequency converters, the use of which has expanded the field of application of asynchronous machines. Thanks to frequency converters, the asynchronous motor is widely used in the field where other types of electrical machines have traditionally been used, primarily DC machines.

Since the existing asynchronous motors are characterized by a number of disadvantages, over time, new series of asynchronous motors are constantly being developed, having higher technical and economic indicators in comparison with the previous series of asynchronous motors, better performance and mechanical characteristics in terms of quality indicators. In addition, there is often a need for the development and modernization of asynchronous motors of special design. These engines include:

submersible asynchronous motors (SEM) used to drive installations of electric centrifugal pumps (ESP). The design feature of such engines is the limited size of the outer diameter, the dimensions of which are set by the diameter of the tubing in which the engine is located. In addition, the engine is operated at sufficiently high temperatures, which leads to a decrease in its developed power. These circumstances require the development of a special design of induction motors;

motors working in conjunction with frequency converters, which perform the functions of their regulation. Since frequency converters generate a whole spectrum of harmonic components in the motor supply voltage curve, the presence of harmonic components leads to additional losses in the motor and decreases its efficiency below the nominal value. The design of an asynchronous motor operating in conjunction with frequency converters should take into account this feature and the presence of higher harmonics in the supply voltage curve should not lead to additional power losses.

The specified list of asynchronous motors of special design can be continued, and from here the following conclusions can be drawn:

there is a need to develop new series of asynchronous motors;

there is a need to master the existing design techniques for asynchronous motors to solve the above problem;

there is a need to develop new methods for the design of asynchronous motors, allowing, with less time spent on design, to develop a new series of asynchronous motors with better technical and economic indicators.

The purpose of the assignment for course design is the development of an asynchronous motor with a squirrel-cage rotor, which has the given parameters, based on the existing and widely used in practice methodology for designing asynchronous motors.

Initial data for design.

The developed asynchronous squirrel-cage motor must have the following passport data:

Rated (phase) supply voltage U 1nf, V;

Mains supply voltage frequency f 1, Hz;

Number of supply voltage phases m 1

Rated power Р 2, kW;

Synchronous rotation speed n 1, rpm;

Rated value of efficiency η (not less), rel. units;

Rated value of power factor cos (φ) (not less), rel. units;

Constructive performance;

Impact protection design environment;

In the course of the course design, it is necessary to design an asynchronous motor with a squirrel-cage rotor having the specified passport data, and compare the main indicators of the obtained asynchronous motor with those of a similar motor produced by the industry (as analogs, consider asynchronous motors of the AIR series, the passport data of which are given in APPENDIX 1)

The results of the calculation should be drawn up in the form of an explanatory note.

Make a drawing of the developed induction motor and submit it in A1 format.

Note: this tutorial on course design is made in the form of a workbook, which can serve as a model for designing calculations in the form of an explanatory note. It also provides an example of calculating an induction motor with a squirrel-cage rotor, which has the following initial data:

n 1, rpm

not less

Cos (φ), p.u.

not less

Constructive performance - IM1001;

Execution according to the method of protection against environmental influences - IP44;

Options for design assignments.

Option number	Initial data for design
Option number		n 1, rpm	not less

For all variants of the assignment, the following passport data of the designed engines have the same values:

Supply voltage (phase value) U 1fn, V - 220;

Supply voltage frequency f 1, Hz - 50;

The number of phases of the supply voltage m 1 - 3;

Design IM1001;

Execution according to the method of protection against environmental influences IP44;

MINISTRY OF EDUCATION AND SCIENCE

REPUBLIC OF KAZAKHSTAN

North Kazakhstan State University. M. Kozybaeva

Faculty of Energy and Mechanical Engineering

Department of Energy and Instrumentation

COURSE WORK

On the topic: "Designing an asynchronous motor with a squirrel cage rotor"

on discipline - "Electric machines"

Completed by Kalantyrev

supervisor

doctor of Technical Sciences, prof. N.V. Shatkovskaya

Petropavlovsk 2010

Introduction

1. Choice of main dimensions

2. Determination of the number of stator slots, turns in the winding phase of the stator winding wire cross-section

4. Calculation of the rotor

5. Calculation of the magnetic circuit

6. Operating mode parameters

7. Calculation of losses

9. Thermal design

Appendix A

Conclusion

Bibliography

Introduction

In this course project, the following engine is considered:

Execution according to the degree of protection: IP23;

Cooling method: IС0141.

Climatic working conditions: U3 - letter by letter - for a temperate climate; digitally - for placement in closed rooms with natural ventilation without artificially controlled climatic conditions, where fluctuations in temperature and humidity, exposure to sand and dust, solar radiation are significantly less than in the open air stone, concrete, wood and other unheated rooms.

1. Choice of main dimensions

1.1 Determine the number of pole pairs:

Then the number of poles.

1.2 Let us determine the height of the axis of rotation graphically: according to Figure 9.18, b, in accordance with, according to Table 9.8, we determine the outer diameter corresponding to the axis of rotation.

1.3 Internal diameter of the stator, calculated by the formula:

where is the coefficient determined according to table 9.9.

When lies in the interval: .

Let's choose a value, then

1.4 Determine the pole division:

(1.3)

1.5 Determine the calculated power, W:

, (1.4)

where is the power on the motor shaft, W;

- the ratio of the EMF of the stator winding to the rated voltage, which can be approximately determined from Figure 9.20. For and,.

We will take the approximate values \u200b\u200baccording to the curves constructed according to the data of the 4A series engines. Figure 9.21, c. With kW and, and

1.6 The electromagnetic loads A and B d are determined graphically from the curves in Figure 9.23, b. With kW and, , T.

1.7 Winding ratio. For two-layer windings at 2p\u003e 2, \u003d 0.91–0.92 should be taken. Let's accept.

1.8 Determine the synchronous angular speed of the motor shaft W:

where is the synchronous rotation frequency.

1.9 Calculate the length of the air gap:

, (1.6)

where is the field shape coefficient. ...

1.10 The criterion for the correct choice of the main dimensions D is the ratio, which should be within the permissible limits of Figure 9.25, b.

... The l value lies within the recommended limits, which means that the main dimensions are determined correctly.

2. Determination of the number of stator slots, turns in the phase of the winding and the cross-section of the stator winding wire

2.1 Determine the limit values: t 1 max and t 1 min Figure 9.26. For and,,.

2.2 Number of stator slots:

, (2.1)

(2.2)

Finally, the number of slots should be a multiple of the number of slots per pole and phase: q. Let's accept, then

, (2.3)

where m is the number of phases.

2.3 Finally, we determine the tooth division of the stator:

(2.4)

2.4 Stator winding pre-current

2.5 Number of effective conductors in the slot (provided):

(2.6)

2.6 We accept the number of parallel branches, then

(2.7)

2.7 The final number of turns in the winding phase and the magnetic flux:

, (2.8)

2.8 Determine the values \u200b\u200bof electrical and magnetic loads:

(2.11)

The values \u200b\u200bof electrical and magnetic loads slightly differ from those selected graphically.

2.9 The selection of the permissible current density is made taking into account the linear load of the motor:

where is the heating of the slotted part of the stator winding, we define graphically Figure 9.27, d.

2.10 Calculate the cross-sectional area of \u200b\u200bthe effective conductors:

(2.13)

We accept, then table П-3.1,,.

2.11 Finally, we determine the current density in the stator winding:

3. Calculation of the dimensions of the toothed zone of the stator and the air gap

3.1 Preselect electromagnetic induction in the stator yoke B Z 1 and in the stator teeth B a. With table 9.12, a.

3.2 Let's select the steel grade 2013 table 9.13 and the filling factor of the stator and rotor magnetic cores with steel.

3.3 Based on the selected inductions, we determine the height of the stator yoke and the minimum width of the tooth

3.4 Let us select the slot height and slot width of the half-closed slot. For motors with axle height, mm. Select the slot width from Table 9.16. For and,.

3.5 Determine the dimensions of the groove:

groove height:

dimensions of the groove in the stamp and:

Let's choose, then

height of the wedge part of the groove:

Figure 3.1. The groove of the engineered squirrel cage motor

3.6 Determine the dimensions of the groove in the light, taking into account the allowances for the burdening and assembly of the cores: and, table 9.14:

width, and:

and height:

Let's define the area cross section housing insulation in the groove:

where is the one-sided thickness of the insulation in the groove,.

We calculate the cross-sectional area of \u200b\u200bthe gaskets to the groove:

Determine the cross-sectional area of \u200b\u200bthe groove for placing the conductors:

3.7 The criterion for the correctness of the selected dimensions is the filling factor of the groove, which is approximately equal to .

, (3.13)

thus the selected values \u200b\u200bare correct.

4. Calculation of the rotor

4.1 Select the height of the air gap d graphically according to Figure 9.31. For and,.

4.2 Squirrel cage rotor outer diameter:

4.3 The length of the rotor is equal to the length of the air gap:,.

4.4 The number of slots is selected from Table 9.18,.

4.5 Determine the value of the tooth division of the rotor:

(4.2)

4.6 The value of the coefficient k B for calculating the shaft diameter is determined from table 9.19. For and,.

The inner diameter of the rotor is:

4.7 Determine the current in the rotor bar:

where k i is a coefficient that takes into account the influence of the magnetizing current and resistance of the windings on the ratio, we define graphically at; ;

The current reduction factor is determined by the formula:

Then the required current in the rotor bar:

4.8 Determine the cross-sectional area of \u200b\u200bthe bar:

where is the permissible current density; in our case .

4.9 The rotor slot is determined according to Figure 9.40, b. We accept,,.

We choose the magnetic induction in the rotor tooth from the interval table 9.12. Let's accept.

Let's define the permissible tooth width:

Let's calculate the dimensions of the groove:

width b 1 and b 2:

, (4.9)

height h 1:

Let's calculate the total height of the rotor slot h P2:

Let's clarify the cross-sectional area of \u200b\u200bthe bar:

4.10 Determine the current density in the rod J 2:

(4.13)

Figure 4.1. The groove of the engineered squirrel cage motor

4.11 Calculate the cross-sectional area of \u200b\u200bshort-circuiting rings q cl:

where is the current in the ring, determined by the formula:

4.12 Calculate the dimensions of the closing rings, and the average diameter of the ring:

(4.18)

Let's clarify the sectional area of \u200b\u200bthe ring:

5. Calculation of the magnetizing current

5.1 Value of induction in rotor and stator teeth:

, (5.1)

(5.2)

5.2 Let's calculate the induction in the stator yoke B a:

5.3 Determine the induction in the rotor yoke B j:

, (5.4)

where h "j is the design height of the rotor yoke, m.

For motors with 2p≥4 with the rotor core landing on the bushing or on the finned shaft h "j is determined by the formula:

5.4 Magnetic tension of the air gap F d:

, (5.6)

where k d is the coefficient of the air gap, determined by the formula:

, (5.7)

where

Air gap magnetic voltage:

5.5 Magnetic voltage of the stator tooth zones F z 1:

F z1 \u003d 2h z1 H z1, (5.8)

where 2h z1 is the estimated height of the stator tooth, m.

H z1 is determined according to table П-1.7. When, .

5.6 Magnetic voltage of the toothed zones of the rotor F z 2:

, (5.9)

, table П-1.7.

5.7 Calculate the saturation factor of the tooth zone k z:

(5.10)

5.8 Let us find the length of the average magnetic line of the stator yoke L a:

5.9 Determine the field strength H a at induction B a according to the magnetization curve for the yoke of the accepted steel grade 2013 table P-1.6. When,.

5.10 Let us find the magnetic voltage of the stator yoke F a:

5.11 Let us determine the length of the average magnetic flux line in the rotor yoke L j:

, (5.13)

where h j is the height of the rotor backrest, is found by the formula:

5.12 The field strength H j during induction is determined by the yoke magnetization curve for the accepted steel grade, Table P-1.6. When,.

Determine the magnetic voltage of the rotor yoke F j:

5.13 Calculate the total magnetic voltage of the magnetic circuit of the machine (for a pair of poles) F c:

5.14 Magnetic circuit saturation factor:

(5.17)

5.15 Magnetizing current:

Relative value of magnetizing current:

(5.19)

6. Operating mode parameters

The parameters of an induction machine are the active and inductive resistances of the stator windings x 1, r 1, the rotor r 2, x 2, the mutual inductance resistance x 12 (or x m), and the calculated resistance r 12 (or r m), the introduction of which takes into account the effect of losses in stator steel on motor characteristics.

Phase replacement circuits of an asynchronous machine, based on bringing processes in a rotating machine to a stationary one, are shown in Figure 6.1. The physical processes in an asynchronous machine are more clearly reflected in the diagram shown in Figure 6.1. But for the calculation it is more convenient to convert it to the circuit shown in Figure 6.2.

Figure 6.1. The equivalent circuit of the phase of the winding of the reduced asynchronous machine

Figure 6.2. Converted equivalent circuit of the phase of the winding of the reduced asynchronous machine

6.1 The active resistance of the stator winding phase is calculated by the formula:

, (6.1)

where L 1 is the total length of the effective conductors of the winding phase, m;

a - the number of parallel branches of the winding;

s 115 - specific resistance of the winding material (copper for the stator) at the design temperature. For copper ;

k r - coefficient of increase in active resistance of the winding phase from the effect of current displacement.

In the conductors of the stator winding of asynchronous machines, the effect of current displacement is manifested insignificantly due to the small dimensions of the elementary conductors. Therefore, in the calculations of normal machines, as a rule, k r \u003d 1 is taken.

6.2 The total length of the conductors of the winding phase L 1 is calculated by the formula:

where l cf is the average length of the winding turn, m.

6.3 The average length of the turn l cp is found as the sum of the straight - slotted and curved frontal parts of the coil:

, (6.3)

where l П is the length of the groove part, equal to the constructive length of the machine cores. ;

l l - the length of the frontal part.

6.4 The length of the frontal part of the coil of the random stator winding is determined by the formula:

, (6.4)

where K l is a coefficient, the value of which depends on the number of pole pairs, for table 9.23;

b КТ - the average width of the coil, m, determined along the arc of a circle passing along the midpoints of the height of the grooves:

, (6.5)

where b 1 is the relative shortening of the stator winding pitch. Usually taken.

Coefficient for a loose winding, laid in the grooves before pressing the core into the body.

Average length:

Total length of effective winding phase conductors:

Active resistance of the stator winding phase:

6.5 Determine the length of the frontal overhang:

where K vyl is the coefficient determined according to table 9.23. at.

6.6 Determine the relative value of the phase resistance of the stator winding:

(6.7)

6.7 Determine the active resistance of the phase of the rotor winding r 2:

where r c is the resistance of the rod;

r cl is the resistance of the ring.

6.8 The resistance of the bar is calculated by the formula:

6.9 Calculate the resistance of the ring:

Then the active resistance of the rotor:

6.10 Let us reduce r 2 to the number of turns of the stator winding, define:

6.11 Relative value of the phase resistance of the rotor winding.

(6.12)

6.12 Inductive resistance of the phases of the rotor winding:

, (6.13)

where l p is the coefficient of magnetic conductivity of the slotted rotor.

Based on Figure 9.50, e l p is determined by the formula from Table 9.26:

, (6.14)

(the conductors are secured with a slotted cover).

, (6.15)

Frontal scattering conductivity coefficient:

The coefficient of magnetic conductivity of differential scattering is determined by the formula:

, (6.17)

where is determined graphically, at, Figure 9.51, d,.

Using the formula (6.13), we calculate the inductive resistance of the stator winding:

6.13 Determine the relative value of the inductive resistance of the stator winding:

(6.18)

6.14 Let's calculate the inductive resistance of the rotor winding phase using the formula:

where l p2 is the coefficient of magnetic conductivity of the rotor slot;

l L2 - coefficient of magnetic conductivity of the frontal part of the rotor;

l d2 - coefficient of magnetic conductivity of the differential scattering of the rotor.

The coefficient of magnetic conductivity of the rotor slot is calculated by the formula, based on table 9.27:

6.15 The coefficient of magnetic conductivity of the frontal part of the rotor is determined by the formula:

6.16 The coefficient of magnetic conductivity of the differential scattering of the rotor is determined by the formula:

, (6.23)

where .

6.17 Find the value of the inductive reactance by the formula (6.19):

Let us bring x 2 to the number of stator turns:

Relative value,:

(6.25)

7. Calculation of losses

7.1 Let's calculate the basic losses in the stator steel of an induction machine according to the formula:

, (7.1)

where is the specific loss, table 9.28;

b - exponent, for steel grade 2013;

k yes and k d z are coefficients taking into account the effect on losses in steel for steel grade 2013;

m a is the mass of the yoke, calculated by the formula:

where - specific gravity of steel.

Stator teeth mass:

7.2 Let's calculate the total surface losses in the rotor:

where p pv2 - specific surface losses, determined by the formula:

, (7.5)

where is the coefficient taking into account the effect of surface treatment of the rotor teeth heads on specific losses;

В 02 - the amplitude of the induction pulsation in the air gap, determined by the formula:

where is determined graphically with Figure 9.53, b.

7.3 Let's calculate the specific surface losses according to the formula (7.5):

7.4 Let's calculate the pulsation losses in the rotor teeth:

, (7.7)

where m z 2 is the mass of the steel of the rotor teeth;

In pool2 - the amplitude of the magnetic pulsation in the rotor.

, (7.9)

7.5 Determine the amount of additional losses in steel:

7.6 Total losses in steel:

7.7 Determine the mechanical losses:

where, with according to table 9.29.

7.8 Let's calculate the additional losses at the nominal mode:

7.9 Motor no-load current:

, (7.14)

where I х.х.а. Is the active component of the no-load current, it is determined by the formula:

where Р e.1 х.х. - electrical losses in the stator at no load:

7.10 Determine the power factor at idle:

(7.17)

8. Calculation of performance characteristics

8.1 Determine the real part of the resistance:

(8.1)

(8.2)

8.3 Motor constant:

, (8.3)

(8.4)

8.4 Determine the active component of the current:

8.5 Determine the values:

8.6 Losses that do not vary with slip change:

We accept and calculate the performance, with a slip equal to: 0.005; 0.01; 0.015; 0.02; 0.0201. The calculation results are written in Table 8.1.

P 2n \u003d 110kW; U 1n \u003d 220/380 V; 2p \u003d 10 I 0 a \u003d 2.74 A; I 0 p \u003d I m \u003d 61.99 A;

P c t + P fur \u003d 1985.25 W; r 1 \u003d 0.0256 Ohm; r ¢ 2 \u003d 0.0205 Ohm; c 1 \u003d 1.039;

a ¢ \u003d 1.0795; a \u003d 0.0266 Ohm; b ¢ \u003d 0; b \u003d 0.26 ohm

Table 8.1

Asynchronous motor performance

Calculation formula		Slide s
Calculation formula

Figure 8.1. The graph of the dependence of the engine on the power P 2

Figure 8.2. The graph of the dependence of the efficiency of the engine on the power P 2

Figure 8.3. The graph of the dependence of slip s of the engine on the power P 2

Figure 8.4. The graph of the dependence of the stator current I 1 of the motor on the power P 2

9. Thermal design

9.1 Determine the temperature rise of the inner surface of the stator core over the temperature of the air inside the motor:

, (9.1)

where at and the degree of protection is IP23, table.9.35;

a 1 - the coefficient of heat transfer from the surface, we define graphically Figure 9.68, b, .

, (9.2)

where is the coefficient of increase in losses, for the heat resistance class F.

9.2 Temperature difference in the insulation of the slotted part of the stator winding:

, (9.4)

where П п1 is the perimeter of the cross-section of the stator slot, determined by the formula:

l eq. - average equivalent thermal conductivity of the groove part, for heat resistance class F , page 452;

Is the average value of the thermal conductivity coefficient of internal insulation. we define graphically at , , Figure 9.69.

9.3 Determine the temperature difference across the thickness of the insulation of the frontal parts:

, (9.6)

where, .

The frontal parts of the stator winding are not insulated, therefore.

9.4 Calculate the temperature rise of the outer surface of the frontal parts over the temperature of the air inside the machine:

9.5 Determine the average temperature rise of the stator winding over the air temperature inside the machine:

(9.8)

9.6 Calculate the average temperature rise of the air inside the machine over the ambient temperature:

where a in - we define graphically Figure 9.68, ;

- the sum of losses discharged into the air inside the engine:

where is the total losses in the engine at nominal conditions;

R e1 - electrical losses in the stator winding at rated mode;

R e2 - electrical losses in the rotor winding at nominal conditions.

, (9.12)

where S cor. Is the surface area of \u200b\u200bthe bed.

P p is defined graphically. At, figure 9.70.

9.7 Determine the average temperature rise of the stator winding over the ambient temperature:

9.8 Determine the air flow required for ventilation:

(9.14)

9.9 The air flow provided by an external fan with a design and dimensions adopted in the 4A series can be approximately determined by the formula:

, (9.15)

where and - the number and width, m, of radial ventilation ducts, page 384;

n- engine speed, rpm;

Coefficient, for engines with.

Those. the air flow provided by the outdoor fan is greater than the air flow required for ventilating the electric motor.

10. Calculation of performance from a pie chart

10.1 First, we determine the synchronous no-load current by the formula:

10.2 Let's calculate the active and inductive resistance of the short circuit:

10.3 Calculate the scale of the pie chart:

The current scale is:

where D to - the diameter of the circle of the diagram, is selected from the interval: , choose.

Power scale:

Scale of the moment:

(10.6)

The motor pie chart is shown below. A circle with a diameter D to with a center O ¢ is the locus of the ends of the stator current vector of the motor at different slip. Point A 0 defines the position of the end of the current vector I 0 at synchronous idle, and - at real idle of the engine. Line segment , equal to the coefficient power at idle. Point A 3 determines the position of the end of the stator current vector during a short circuit (s \u003d 1), the segment is the current I short circuit. and the angle is. Point A 2 defines the position of the end of the stator current vector at.

Intermediate points on the arc A 0 A 3 determine the position of the ends of the current vector I 1 at various loads in the motor mode. The abscissa axis of the OB diagram is the line of the primary power P 1. The line of electromagnetic power P em or electromagnetic moments M em is the line A 0 A 2. The line of the net shaft power (secondary power P 2) is the line A '0 A 3.

Figure 10.1. Pie chart

Conclusion

In this course project, an asynchronous electric motor with a squirrel-cage rotor was designed. As a result of the calculation, the main indicators were obtained for a motor with a given power s and cosj, which satisfy the maximum permissible value of GOST for a series of 4A motors. The calculation and construction of the operating characteristics of the designed machine was made.

Thus, according to the calculation data, this engine can be given the following symbol:

4 - serial number of the series;

A - kind of motor - asynchronous;

315 - height of the axis of rotation;

M - conventional length of the bed according to IEC;

10 - number of poles;

U - climatic version for a temperate climate;

Rated data of the designed motor:

P 2n \u003d 110 kW, U 1n \u003d 220/380 V, I 1n \u003d 216 A, cosj n \u003d 0.83, h n \u003d 0.93.

Bibliography

1. Design of electrical machines: Textbook. for universities / P79

I.P. Kopylov, B.K. Klokov, V.P. Morozkin, B.F. Tokarev; Ed. I.P. Kopylova. - 4th ed., Rev. and add. - M .: Higher. shk., 2005. - 767 p .: ill.

2. Voldek A.I., Popov V.V. Electric cars. AC machines: Textbook for universities. - SPb,: - Peter, 2007. –350 p.

3. Katsman M.M. Electric Machine Handbook: Tutorial for students to educate. institutions of environments. prof. Education / Mark Mikhailovich Katsman. - M .: Publishing Center "Academy", 2005. - 480 p.

Appendix A

(required)

Figure 1. Scheme of a two-layer winding with a shortened pitch,,,

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Introduction

A modern electric drive is a complex of devices and devices designed to control and regulate the physical and power indicators of an electric motor. The most common electric motor used in industry is the induction motor. With the development of power electronics and the development of new powerful asynchronous motor control systems, an electric drive based on an asynchronous motor and frequency converters is the best choice, to control various technological processes... An asynchronous electric drive has the best technical and economic indicators, and the development of new energy-saving motors allows creating energy-efficient electric drive systems.

Asynchronous electric motor, electric asynchronous machine for converting electrical energy into mechanical energy. The principle of operation of an induction motor is based on the interaction of a rotating magnetic field that occurs when a three-phase alternating current passes through the stator windings with a current induced by the stator field in the rotor windings. As a result, mechanical forces arise that make the rotor rotate in the direction of rotation of the magnetic field, provided that the rotor speed n is less than the field rotation frequency n1. Thus, the rotor rotates asynchronously with respect to the field.

The purpose term paper is the design of an induction motor. By means of this design, we study the properties and characteristics of this engine, and also study the features of these engines. this work is an integral part the course of studying electrical machines.

1. Motor magnetic circuit. Dimensions, configuration, material

1.1 Main dimensions

1. Height of the axis of rotation of the induction motor:

For Рн \u003d 75 kW, n1 \u003d 750 rpm

h \u003d 280 mm, 2p \u003d 8.

2. The outer diameter of the core DН1 at the standard height of the axis of rotation h \u003d 280 mm. Under these conditions, DH1 \u003d 520 mm.

3. To determine the inner diameter of the stator core D1, we use the relationship D1 \u003d f (DН1) given in table 9-3. For DH1 \u003d 520 mm;

D1 \u003d 0.72 DH1 - 3;

D1 \u003d 0.72 520-3 \u003d 371.4 mm.

4. Let's find the average value kН \u003d f (P2) induction motors

For PH \u003d 75 kW; 2p \u003d 8;

5. For motors with squirrel-cage rotor, IP44 protection rating, preliminary values.

For PH \u003d 75 kW

6. For motors with a squirrel-cage rotor of IP44 protection, we take the cos value according to Figure 9-3, and at 2p \u003d 8

7. Design power P? for AC motors:

where is the efficiency; cos is the power factor at rated load;

8. Finding the linear load of the stator winding A1

A1 \u003d 420 0.915 0.86 \u003d 330.4 A / cm.

9. Finding the maximum value of the magnetic induction in the air gap B

B \u003d 0.77 1.04 0.86 \u003d 0.69 T.

10. To determine the length of the stator core, let us set the preliminary value of the winding coefficient kоb1, at 2р \u003d 8

11. Find the calculated length of the core l1

l1 \u003d 366.7 + 125 \u003d 426.7

12. Structural length of the stator core l1 is rounded to the nearest multiple of 5:

13. Ratio

425 / 371,4 = 1,149

14. Find max R4 \u003d 1.1

max \u003d 1.46-0.00071 DH1;

max \u003d 1.46 - 0.00071 520 \u003d 1.091

max \u003d 1.091 1.1 \u003d 1.2

1.2 Stator core

The core is assembled from separate stamped sheets of electrical steel with a thickness of 0.5 mm, with insulating coatings to reduce losses in steel from eddy currents.

For steel 2312 we use varnishing of sheets.

Number of slots per pole and phase:

According to the selected value q1, the number of slots in the stator core z1 is determined:

where m1 is the number of phases;

z1 \u003d 8 3 3 \u003d 72.

1.3 Rotor core

For a given height of the axis of rotation, select steel grade 2312.

The core is assembled from separate stamped electrical steel sheets with a thickness of 0.5 mm.

For the core, we take the same sheet insulation as for the stator - varnishing.

The filling factor of the steel is taken equal to

The size of the air gap between the stator and the rotor is taken.

With h \u003d 280 mm and 2p \u003d 8;

Bevel of grooves ck (without bevel of grooves)

Outside diameter of the rotor core DH2:

DH2 \u003d 371.4 - 2 0.8 \u003d 369.8 mm.

For a height of rotation h 71 mm, the inner diameter of the rotor sheets D2:

D2 0.23 520 \u003d 119.6 mm.

To improve cooling, reduce mass and dynamic moment of inertia of the rotor in the rotor cores with h250, circular axial ventilation ducts are provided:

The length of the rotor core l2 at h\u003e 250 mm.

l2 \u003d l1 + 5 \u003d 425 + 5 \u003d 430 mm.

The number of slots in the core for a motor with a squirrel-cage rotor at z1 \u003d 72 and 2p \u003d 8

2. Stator winding

2.1 Parameters common to any winding

For our engine, we accept a separate two-layer concentric winding made of PETV wire (heat resistance class B), which is laid in rectangular half-open grooves.

Typically, the stator winding is six-zone; each zone is equal to 60 electrical degrees. With a six-zone winding, the distribution coefficient kP1

kР1 \u003d 0.5 / (q1sin (b / 20));

kР1 \u003d 0.5 / (3 sin (10)) \u003d 0.95.

The shortening of step 1 is taken equal to

1 \u003d 0.8, with 2p \u003d 8.

We perform a two-layer winding with a shortened step yP1

yП1 \u003d 1 z1 / 2p;

yP1 \u003d 0.8 72/8 \u003d 7.2.

Shortening factor ky1

ky1 \u003d sin (1 90) \u003d sin (0.8 90) \u003d 0.95.

Winding coefficient kОБ1

kOB1 \u003d kР1 · ky1;

kOB1 \u003d 0.95 0.95 \u003d 0.9.

The preliminary value of the magnetic flux Ф

Ф \u003d B D1l1 10-6 / p;

Ф \u003d 0.689 371.4 42510-6 / 4 \u003d 0.027 Wb.

The preliminary number of turns in the phase winding? 1

1 \u003d kнU1 / (222 kОБ1 (f1 / 50) Ф);

1 = 0,96 380/(222 0,908 0.027) ?66.9.

The number of parallel branches of the stator winding a1 is selected as one of the divisors of the number of poles a1 \u003d 1.

The preliminary number of effective conductors in the groove NP1

NP1 \u003d 1a1 (pq1);

NP1 \u003d 155.3 1 / (4 3) \u003d 5.58

The value of NP1 is taken by rounding NP1 to the nearest integer value

Choosing an integer, we specify the value 1

1 \u003d NP1pq1a1;

1 = 4 4 3/1 = 72.

Magnetic flux value Ф

Ф \u003d 0.023 66.5 / 64 \u003d 0.028 Wb.

Induction value in air gap B

B \u003d B? one/ ? one;

B \u003d 0.8 66.9 / 72 \u003d 0.689 T.

Pre-value of rated phase current I1

I1 \u003d Рн 103 / (3U1cos);

I1 \u003d 75 103 / (3 380 0.93 0.84) \u003d 84.216 A.

A1 \u003d 10Nn1z1I1 (D1a1);

A1 \u003d 6 13 72 84.216 / (3.14 371.4) \u003d 311.8 A / cm.

Average value of magnetic induction in the back of the stator ВС1

With h \u003d 280 mm, 2p \u003d 8

BC1 \u003d 1.5 T.

Toothed pitch along the inner diameter of the stator t1

t1 \u003d p 371.4 / 72 \u003d 16.1 mm.

2.2 Stator winding with rectangular semi-closed slots

We accept the preliminary value of the magnetic induction at the narrowest point of the stator tooth

31max \u003d 1.8 T.

Toothed stator pitch at the narrowest point

Preliminary tooth width at narrowest point

Preliminary width of half-open and open slot in the die

Half-open slot slot width

Permitted width of an effective conductor with coiled insulation

b? eff \u003d () / \u003d 3.665mm;

Number of effective conductors along the groove height

Stator backrest provisional height

Ф 106? (2 kc l1 Bc1);

0.027 106? (2 0.95 425 1.5) \u003d 22.3 mm.

Preliminary groove height

\u003d [(D H1 - D1) / 2] - h c1;

\u003d \u003d [(520-371.4) / 2] -22.3 \u003d 53 mm.

Permissible height of the effective conductor with coiled insulation

Effective conductor area

Preliminary number of elementary conductors

The number of elementary conductors in one effective

A preliminary number of elementary conductors in one effective

Increase to 4

The size of the elementary elementary conductor along the groove height

The final number of elementary conductors

Smaller and larger sizes of bare wire

Groove height dimension

Dimension according to the width of the groove in the stamp

Groove height

\u003d [(D H1 - D1) / 2] - h c1;

\u003d \u003d [(520-371.4) / 2] -18.3 \u003d 56 mm.

Adjusted tooth width at the narrowest part

Refined magnetic flux density at the narrowest part of the stator tooth

Current density in the stator winding J1

J1 \u003d I1 (c S a1);

J1 \u003d 84.216 / (45.465 1) \u003d 3.852 A / mm2.

A1J1 \u003d 311 3.852 \u003d 1197.9 A2 / (cm mm2).

(A1J1) add \u003d 2200 0.75 0.87 \u003d 1435.5 A2 / (cm mm2).

lv1 \u003d (0.19 + 0.1p) bcp1 + 10;

lv1 \u003d (0.19 + 0.1 3) 80.64 + 10 \u003d 79.4 mm.

Average tooth pitch of the stator tСР1

tСР1 \u003d (D1 + hП1) / z1;

tСР1 \u003d р (371.4 + 56) / 72 \u003d 18.6 mm.

Average width of the stator winding coil bСР1

bСР1 \u003d tСР1 уП1;

bCP1 \u003d 18.6 7.2 \u003d 133.6 mm.

The average length of the frontal part of the winding ll1

ll1 \u003d 1.3 \u003d 279.6 mm

Average length of a turn of a winding lcp1

lcp1 \u003d 2 (l1 + ll1) \u003d 2 (425 + 279.6) \u003d 1409.2 mm.

The length of the overhang of the winding frontal part lв1

3. Squirrel cage rotor winding

asynchronous magnetic stator phase

Let's use a rotor winding with bottle slots, because h \u003d 280 mm.

Groove height from fig. 9-12 is equal to hp2 \u003d 40 mm.

Estimated height of the rotor back hc2 at 2p \u003d 8 and h \u003d 280 mm

hc2 \u003d 0.38 Dн2 - hп2 -? dk2;

hc2 \u003d 0.38 369.8 - 40 -? 40 \u003d 73.8 mm.

Magnetic induction in the back of the rotor Vs2

Bs2 \u003d Ф 106 / (2 kc l2 hc2);

Bc2 \u003d 0.028 106 / (2 0.95 430 73.8) \u003d 0.464 T.

Toothed pitch on the outer diameter of the rotor t2

t2 \u003d pDn2 / z2 \u003d p 369.8 / 86 \u003d 13.4 mm.

Magnetic induction in the rotor teeth Vz2.

Ws2 \u003d 1.9 T.

Literature

1. Goldberg O.D., Gurin Y.S., Sviridenko I.S. Design of electrical machines. - M .: high school, 1984 .-- 431s.

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Design and calculation of an asynchronous motor. Squirrel cage induction motor design Induction motor design

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Chapter 1. Methodology for designing an asynchronous motor with a squirrel cage rotor

Chapter 2. The use of computers for the design of an asynchronous motor with a squirrel cage rotor.

5.4 Magnetic tension of the air gap F d:

6. Operating mode parameters

(the conductors are secured with a slotted cover).

7. Calculation of losses

Power scale:

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