Characteristics Of AC DC Three Phase Generators Engineering Essay Essay

Purposes and Aims

The chief aim of this study is to depict the probe into runing features of AC-DC Three-Phase generators and motors.

The undermentioned topics must be covered in this study for it to successfully document the probe, these topics will be constructed utilizing a series of lab experiments and learner remarks: –

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Operating features of DC and AC generators providing resistive, capacitive and inductive tonss.

Relationship between velocity, current, power factor, and efficiency of a coop initiation motor, capacitor start initiation motor, synchronal motor and DC motor.

Analyse the consequences from each of the experiments done and supply graphical analysis of the consequences.

Introduction/ Background

It is good known that the most regular type of power to be generated around the universe is three stage AC. The grounds being are: –

Three stage power is needed for the usage of the most efficient types of industrial motors.

It is considered to be the most efficient signifier of electrical energy to bring forth and administer.

Due to the public presentation of three stage, the size and weight of devices utilizing it such as generators and motors are lower compared to devices utilizing other power systems.

Although it should be noted that the public presentation of an AC system is dependent on the power factor, non merely the burden in footings of current.

In-order to successfully look into the topic of AC vs. DC a sum of six practical trials were completed, the practical trials will be documented in the undermentioned study and analysed.

The trials completed: –

AC initiation motor torque-speed features

AC synchronal motor torque-speed features

AC capacitance start initiation motor torque-speed features

DC motor torque-speed features

DC generator end product features

AC generator end product features

AC Induction Motor Test

An initiation motor is an asynchronous motor where through electromagnetic initiation power is supplied to the revolving device. In some contexts an initiation motor can be described as a “ rotating transformer ” because the stator can be shown to be the primary twist and the rotor as the secondary twist. Induction motors can be found on a regular basis in industrial state of affairss.

Induction motors get their popularity from being rugged in building, and from non holding coppices.

There is more than one design of initiation motor a few illustrations are: –

Squirrel Cage Rotor Motor

Wound Rotor Motor

Double Cage Rotor Motor

Each of the above motor designs has its ain virtues ; the type of motor to be used in this experiment is the coop rotor motor.

Squirrel Cage Rotor Motor: –

A coop initiation motor rotor shown in the illustration below consists of a series of carry oning bars laid into slots carved into the face of the rotor and shorted at either terminal by big shorting rings. The design is known as the coop rotor because of the conducting bars, if examined they can be seen to look like a squirrel or hamsters exercise wheel.

1Squirrel Cage Motor Construction

Trial

The intent of this trial was to happen the torque-speed features of an AC initiation motor.

The features that will be analysed against torsion are: –

Speed

Current

Output Power

Power Factor

Efficiency

The basic thought behind the trial, the motor is run at full velocity and is connected to a brake unit. The brake unit can be adjusted to do the motor produce more or less sums of torsion. Get downing at low motor torsion, readings of current electromotive force and power are taken, so readings continue to be taken all they manner to near procrastinating point.

The trial equipment is as follows: –

Circuit Diagram for Cage Rotor Induction Motor Test: –

Block Diagram

To farther explain and simplify, a block diagram of the trial is included below. This shows precisely how the system operates.

Brake

Motor

Three Phase Supply

Torque Control

Speed ( rev/min )

Ammeter, V metre, watt metre

Test Procedure

A wholly extended trial process can be found in the appendix taken from the Student Guide of TecQuipment Electrical Machines FH2 refer to appendix! ! ! .

Consequences Table T.1

Torque ( Nm )

Speed ( rev/min )

Output Power ( W )

Wattmeter Wa ( W )

Wattmeter Wb ( W )

Input Power ( W )

Line Current ( A )

Line Voltage ( V )

Volt-amperes ( VA )

Power Factor

Efficiency ( p.u. )

0.1

1500

15.708

0.35

245

148.52336

0.5386

0.1963495

0.2

1450

30.369

0.38

245

161.25393

0.5891

0.3196708

0.3

1450

45.553

115

0.4

245

169.74098

0.6775

0.3961139

0.4

1440

60.319

100

130

0.42

245

178.22803

0.7294

0.4639891

0.5

1425

74.613

110

150

0.45

245

190.9586

0.7855

0.4974188

0.6

1400

87.965

120

170

0.5

245

212.17622

0.8012

0.5174388

0.7

1390

101.89

130

190

0.55

245

233.39385

0.8141

0.5362754

0.8

1360

113.94

145

210

0.57

245

241.8809

0.8682

0.5425481

0.9

1350

127.23

160

240

0.65

245

275.82909

0.8701

0.5301438

–

1.1

–

1.2

–

1.3

–

1.4

–

The values for end product power, vars, input power, power factor and efficiency were calculated utilizing the undermentioned relationships: –

Problems: –

Before the consequences are expressed in graphical signifier and commented on, the study discusses any jobs that occurred during the lab experiment. Merely one major issue occurred during the initiation motor trial. The mistake was due to a wiring mistake. A nexus was losing on one of the W metres which caused the motor to “ individual stage ” and non revolve. It was easy to see that it was “ individual phasing ” because the current measured for one of the stages was zero, bespeaking an unfastened circuit someplace. The nexus was rapidly replaced and the trial could get down.

Graphic Analysis: –

Now the study illustrates the consequences in the tabular array T.1 in a graphical signifier, to do comparing the consequences from the trial equipment industry have been included as a usher.

Speed vs. Torque

The above graph shows the relationship between velocity and torsion, it shows that at a low torsion the velocity is at its upper limit but as the torsion increases the inauspicious happens to the velocity. This is expected because increasing the torsion of the motor is adding more mechanical burden, therefore decelerating the motor down.

2Manufactures graph of Speed versus Torque ( Cage Induction Motor )

The graph above is a representation of the consequences that the maker of the trial machines gives as a usher. It is possible to see that from a torsion of 0.1Nm to 0.9Nm the consequences are similar to the study writer ‘s. The torsion was non taken any higher than 0.9Nm in the writers test as procrastinating the motor was non a coveted result.

Output Power vs. Torque

This graph shows the relationship of end product power versus torsion taken from the lab consequences in table T.1 ; it has an obvious additive upward tendency. It is expected that the end product power additions as more burden is put on the motor, because the motor has to work harder to keep rotary motion.

3Manufactures graph of Output Power versus Torque ( Cage Induction Motor )

The industries consequences besides portion the same upward tendency as the writers, but once more the industry has taken the consequences past 0.9Nm and taken the motor into a stalling status.

Line Current versus Torsion

The graph above shows the consequences of torsion against line current, a good upward tendency is seeable. This indicates that as the torsion additions so does the line current, this once more is due to the addition in burden on the motor.

4Manufactures graph of Line Current versus Torque ( Cage Induction Motor )

The usher consequences from the industry complement the consequences that the writer recorded. A steady rise is shown from around 0.35-0.4A to 0.6-0.7A at approximately 0.9Nm.

Power Factor versus Torque

The graph is demoing the consequences from the practical lab experiment, the deliberate power factor versus the torsion. It can be seen from the upward tendency of the graph that as the torsion of the motor additions, so does the power factor. It will be subsequently seen in the study that because the power factor additions with torsion so will the efficiency.

5Manufactures graph of Power Factor versus Torque ( Cage Induction Motor )

The usher consequences above show similarities with the consequences gained through practical lab experiments.

Torque V. Efficiency

The graph is demoing the relationship between efficiency and torsion, the efficiency increases as the torsion does, this is expected because the end product power additions with the torsion. The peak efficiency occurs at around 0.75-0.8Nm after which the efficiency starts to cut down.

6Manufactures graph of Efficiency versus Torque ( Cage Induction Motor )

The graph above shows the relationship of torsion and efficiency, the industries consequences show a similar tendency to that of the writer ‘s. The consequences from the industries show more of the downward tendency after 0.8Nm to finally procrastinating point.

Decision

Overall the consequences acquired through practical experiment show encouraging consequences, both towards theory and besides towards the industries guide consequences. Some of the graphs could hold been a more steady consequences but it is non possible to acquire perfect consequences on something like this without making the trial many more times and taking mean values. The tendencies do exemplify what is expected, so this means the equipment was set up right, and the trial was carried out uniformly to industries guidelines. The initiation motor is capable of providing torsion when needed but it will non keep a changeless velocity.

AC Synchronous Motor Test

The major feature of a synchronal motor is that it stays at a changeless velocity regardless of no burden or full burden. Under certain conditions they can bring forth a power factor that is capable of rectifying a low power factor from an inductive burden. A common usage for a synchronal motor is to drive a DC generator. They come in all sizes from little to 1000s of HP.

The synchronal motor plants by the application of three-phase AC power to the stator which causes a rotating magnetic field. The rotor sits inside this magnetic field, and is energised with a DC electromotive force. The revolving magnetic field of the stator attracts the rotor magnetic field caused by the DC electromotive force, and a strong rotating force is so imposed on the rotor shaft.

This is one of the disadvantages of the synchronal motor, it needs a DC excitement electromotive force to get down without this the rotor will non get down turning. This characteristic causes the motor to hold hapless get downing torsion, most of its torsion is when it is running at synchronal velocity.

7Showing the parts doing up a synchronal motor

Trial

The intent of this trial was to happen the torque-speed features of an AC synchronal motor.

The features that will be analysed against torsion are: –

Current

Output Power

Power Factor

Efficiency

Speed has non been considered because of the manner the motor operates, a changeless velocity should be evident throughout the trial.

In the trial the motor is ran at full velocity, and an adjustable brake unit will command the degrees of torsion the motor produces. Measurements of current, electromotive force and power are taken at low to high torsion points to acquire the torsion features of the motor.

Test Equipment: –

Circuit Diagram for Synchronous Motor Test: –

Block Diagram

To farther explain and simplify, a block diagram of the trial is included below. This shows precisely how the system operates.

Three Phase Supply

Brake

Motor

DC Rotor Supply

Torque Control

Speed ( rev/min )

Ammeter, V metre, watt metre

Test Procedure

The trial process that was followed can be found in the appendix taken from the Student Guide of TecQuipment Electrical Machines FH2, refer to appendix! ! ! .

Consequences Table T.2

Torque ( Nm )

Speed ( rev/min )

Output Power ( W )

Wattmeter Wa ( W )

Wattmeter Wb ( W )

Input Power ( W )

Line Current ( A )

Line Voltage ( V )

Volt-amperes ( VA )

Power Factor

Effieciency ( p.u. )

1500

0.05

245

21.21762

0.1885

0.05

1500

7.854

0.05

245

21.21762

0.377

0.981748

0.1

1500

15.71

0.05

245

21.21762

0.4713

1.570796

0.2

1500

31.42

0.05

245

21.21762

1.0369

1.427997

0.3

1500

47.12

0.1

245

42.43524

0.9426

1.178097

0.4

1500

62.83

0.15

245

63.65287

0.9426

1.047198

0.5

1500

78.54

0.2

245

84.87049

0.9073

1.019998

0.6

1500

94.25

0.25

245

106.0881

0.9049

0.981748

0.7

1500

110

107

0.25

245

106.0881

1.0086

1.027624

0.8

1500

125.7

125

0.3

245

127.3057

0.9819

1.00531

0.9

1500

141.4

142

0.35

245

148.5234

0.9561

0.995575

–

1.1

–

1.2

–

1.3

–

1.4

–

The values for end product power, vars, input power, power factor and efficiency are calculated utilizing the undermentioned relationships: –

Graphic Analysis: –

The study now includes graphical representation of the consequences table T.2 ; the usher graphs from the TecQuipment the machine industry have been included to compare consequence dependability.

Output Power vs. Torque

The above shows the relationship between torsion and end product power, it can be seen that as the torsion produced additions so does the end product power. This result is expected because the motor has to turn a greater burden and remain at a changeless velocity.

8Manufactures graph of Output Power versus Torque ( Synchronous Motor )

The industries graph besides shows the end product power increasing with the torsion.

Line Current versus Torsion

The line current in this graph is taking an upwards tendency indicating as the torsion produced is increased so does the line current. The motor is working harder to bring forth more torsion and hence seting more burden on the line.

9Manufactures graph of Line current versus Torque ( Synchronous Motor )

The industries graph shows a smoothing addition in line current against torsion but does compare with the consequences gained from the trial.

Power Factor versus Torque

The power factor in this graph is shown to increase to a degree above 0.8 really rapidly and remain there till the terminal of the trial ( 0.9Nm ) . Synchronous motors usually run at a really good power factor near to integrity, and this is represented in the consequences from the trial.

10Manufactures graph of Power Factor versus Torque ( Synchronous Motor )

The industries guide graph shows a similar tendency to that of the study writers.

Efficiency vs. Torque

The above graph demoing the relationship of torsion and efficiency shows a truly good degree of efficiency produced by the motor, but the tendency is non really dependable as it would non be expected to travel past 1. Synchronous motors do hold good efficiency higher than that of initiation motors.

11Manufactures graph of Efficiency versus Torque ( Synchronous Motor )

The industries graph shows a much more dependable tendency of efficiency of the synchronal motor, but it does still demo that the motor is really efficient.

Decision

The consequences for this trial could hold been better and if the trial was to be repeated so more attempt would be made to acquire better measurings. Although with this in head the graphs make demo what is expected from a synchronal motor in footings of torsion features.

In comparing to the initiation motor, the synchronal motor has improved features of: –

Less burden in footings of current on the line.

Better Power factor ( closer to integrity )

Better Efficiency

It would be interesting to happen out the difference in get downing torque capacity of the two motors because the initiation motor would be expected to hold a greater get downing torsion than the synchronal, based on the research into the operation of these two types of motor.

AC Capacitor Start Induction Motor Test

The most common AC initiation motor in usage today is likely the individual stage initiation motor. The grounds for this are that they require small care, and are the least expensive. In the individual stage AC initiation motor the stator magnetic field does non revolve, it merely alternates mutual opposition as a consequence of the AC electromotive force altering mutual opposition. Through magnetic initiation a electromotive force is induced in the rotor, nevertheless this entirely will non do the motor to turn. This is why get downing methods are needed for individual stage AC initiation motors.

Capacitor Start

In this type of initiation motor the stator is made up of a chief twist and a starting twist. The get downing twist is connected in series with a capacitance, which offers between the two twists a stage difference of 90 grades. The consequence when the motor is started is that between the two twists a revolving magnetic field is created and is adequate to get down the motor. Once about full velocity occurs so a velocity sensitive switch cuts out the get downing twist and the motor runs as a individual stage motor. In this manner of get downing the get downing twist is non designed to give the motor high get downing torsion and so merely little motors can utilize this system.

Trial

The intent of this trial was to happen the torque-speed features of an AC initiation motor.

The features that will be analysed against torsion are: –

Speed

Current

Output Power

Power Factor

Efficiency

Test Equipment: –

Circuit Diagram for Synchronous Motor Test: –

Block Diagram

To farther explain and simplify, a block diagram of the trial is included below. This shows precisely how the system operates.

Brake

Motor

Three Phase Supply

Torque Control

Speed ( rev/min )

Ammeter, V metre, watt metre

Test Procedure

An extended trial process can be found in the appendix taken from the Student Guide of TecQuipment Electrical Machines FH2 refer to appendix! ! ! .

Consequences Table T.3

Torque ( Nm )

Speed ( rev/min )

Output Power ( W )

Input Power ( W )

Supply Current ( A )

Line Voltage ( V )

Volt-amperes ( VA )

Power Factor

Effieciency ( p.u. )

0.1

1450

15.18

250

1.7

245

416.5

0.6

0.0607375

0.2

1450

30.37

290

1.75

245

428.75

0.676

0.1047198

0.3

1450

45.55

310

1.8

245

441

0.703

0.1469455

0.4

1448

60.65

330

1.81

245

443.45

0.744

0.183799

0.5

1425

74.61

355

1.9

245

465.5

0.763

0.210177

0.6

1400

87.96

390

1.97

245

482.65

0.808

0.2255502

0.7

1390

101.9

421

2.05

245

502.25

0.838

0.2420245

0.8

1350

113.1

470

2.2

245

539

0.872

0.2406326

0.9

–

1.1

–

1.2

–

1.3

–

1.4

–

1.5

–

The values for end product power, vars, input power, power factor and efficiency were calculated utilizing the undermentioned relationships: –

Problems: –

Graphic Analysis: –

Now the study illustrates the consequences in the tabular array T.1 in a graphical signifier, to do comparing the consequences from the trial equipment industry have been included as a usher.

Speed vs. Torque

Supply Current versus Torsion

Power Factor versus Torque

Efficiency vs. Torque

Decision

Overall the consequences acquired through practical experiment show encouraging consequences, both towards theory and besides towards the industries guide consequences. Some of the graphs could hold been a more steady consequence but it is non possible to acquire perfect consequences on something like this without making the trial many more times and taking mean values. The tendencies do exemplify what is expected, so this means the equipment was set up right, and the trial was carried out uniformly to industries guidelines.

DC Motor Test

The working rule behind any DC motor is the attractive force and repulsive force of magnets. The simplest motors use electromagnets on a shaft, with lasting magnets in the instance of the motor that attract and drive the electromagnets. The ground for utilizing electromagnets is so that it is possible to toss their magnetic field ( their North and south poles ) .

So the electromagnet is attracted to one of the lasting magnets. Equally shortly as it reaches the lasting magnet, it ‘s north and south poles flip so that it is repelled from that magnet and attracted to the other lasting magnet. This picture shows you the parts and how they fit together:

Trial

The intent of this trial was to happen the torque-speed features of an AC initiation motor.

The features that will be analysed against torsion are: –

Speed

Current

Efficiency

Test Equipment: –

Circuit Diagram for DC Motor Test: –

Block Diagram

To farther explain and simplify, a block diagram of the trial is included below. This shows precisely how the system operates.

Brake

Motor

Three Phase Supply

Torque Control

Speed ( rev/min )

Ammeter, V metre, watt metre

Test Procedure

An extended trial process can be found in the appendix taken from the Student Guide of TecQuipment Electrical Machines FH2 refer to appendix! ! ! .

Consequences Table T.4

Torque ( Nm )

Speed ( rev/min )

Voltage ( V )

Current ( A )

Input Power ( W )

Output Power ( W )

Efficiency ( p.u. )

0.05

4600

104

0.55

57.2

24.085544

0.421075938

0.1

3900

104

0.65

67.6

40.840704

0.604152433

0.15

3200

104

0.75

50.265482

0.644429262

0.2

2800

104

0.9

93.6

58.643063

0.626528449

0.25

2600

104

68.067841

0.654498469

0.3

2300

104

1.15

119.6

72.256631

0.604152433

0.35

2100

104

1.2

124.8

76.96902

0.616738942

0.4

1900

104

1.35

140.4

79.587014

0.566859073

0.45

1800

104

1.5

156

84.823002

0.54373719

0.5

1600

104

1.6

166.4

83.775804

0.503460361

0.55

1500

104

1.7

176.8

86.393798

0.488652703

0.6

1400

104

1.85

192.4

87.964594

0.457196436

0.65

1300

104

1.9

197.6

88.488193

0.447814742

0.7

1250

104

2.1

218.4

91.629786

0.419550301

0.75

1200

104

2.15

223.6

94.24778

0.421501698

The values for end product power, vars, input power, power factor and efficiency were calculated utilizing the undermentioned relationships: –

Problems: –

Graphic Analysis: –

Now the study illustrates the consequences in the tabular array T.4 in a graphical signifier, to do comparing the consequences from the trial equipment industry have been included as a usher.

Speed vs. Torque

Supply Current versus Torsion

Efficiency versus Torque

Decision

Overall the consequences acquired through practical experiment show encouraging consequences, both towards theory and besides towards the industries guide consequences. Some of the graphs could hold been a more steady consequence but it is non possible to acquire perfect consequences on something like this without making the trial many more times and taking mean values. The tendencies do exemplify what is expected, so this means the equipment was set up right, and the trial was carried out uniformly to industries guidelines.

DC Generator Output Features

Series-Wound DC Generators When the field twist of a DC generator is connected in series with the armature, the generator is called a series-wound generator ( Figure 10 ) . The A A excitement A A current A A in A A a series-wound A generator A is A the same A A A as A A A the A A A current A A A the generator A delivers to A the burden. If the burden has a high opposition and merely draws a little sum of A A A A current, A A A A the A A A A excitement current is besides little. A Therefore, the magnetic field of the series field A weaving A is A weak, A doing the A A A generated A A A electromotive force A A A low. Conversely, if the burden draws a big current, the excitement current is besides high. A Therefore, the magnetic field of the series field weaving is really strong, and the generated electromotive force is high. As you can see in Figure 11, in a series generator, alterations in burden current A A A drastically A A A affect A A A the generator A A end product A A electromotive force. A A A A A series generator has hapless electromotive force ordinance, and, as a consequence, series generators A A A are A A A non A A A used A A A for fluctuating tonss. A As is the instance for the shunt-wound generator, a series-wound generator besides exhibits A some A losingss A due A to A the opposition A of A the A twists A and armature A reaction. A A These losingss cause A a A lower A terminal A electromotive force than that for an ideal magnetisation curve

Trial

The intent of this trial was to happen the torque-speed features of an AC initiation motor.

The features that will be analysed against torsion are: –

Speed

Current

Efficiency

Test Equipment: –

Circuit Diagram for DC Motor Test: –

Block Diagram

To farther explain and simplify, a block diagram of the trial is included below. This shows precisely how the system operates.

Brake

Motor

Three Phase Supply

Torque Control

Speed ( rev/min )

Ammeter, V metre, watt metre

Test Procedure

An extended trial process can be found in the appendix taken from the Student Guide of TecQuipment Electrical Machines FH2 refer to appendix! ! ! .

Consequences Table T.5

Consequences Output Current ( ma )

Output Voltage ( V )

1.5

100

2.4

150

3.2

200

3.8

250

4.6

300

5.4

350

6.2

400

6.8

450

7.5

500

8.6

550

9.8

600

10.4

650

700

11.6

750

800

12.7

850

12.8

900

13.2

950

13.2

1000

1100

12.6

1200

Graphic Analysis: –

Now the study illustrates the consequences in the tabular array T.4 in a graphical signifier, to do comparing the consequences from the trial equipment industry have been included as a usher.

Output Voltage vs. Output Current

Decision

Overall the consequences acquired through practical experiment show encouraging consequences, both towards theory and besides towards the industries guide consequences. Some of the graphs could hold been a more steady consequence but it is non possible to acquire perfect consequences on something like this without making the trial many more times and taking mean values. The tendencies do exemplify what is expected, so this means the equipment was set up right, and the trial was carried out uniformly to industries guidelines.

Synchronous Motor “ V ” Curves

Synchronous motors are used in applications such as fabric Millss where changeless velocity operation is critical. Most little synchronal motors contain squirrel coop bars for get downing. In this experiment, synchronal motor starting is demonstrated. After get downing, the motor is locked into synchrony by using a rotor field current. The field current is so varied to exemplify control of the reactive power from positive to negative. When the reactive power is zero, the machine is runing with unity power factor and the armature current drawn from the beginning is a lower limit. The armature current is aforethought versus field current to obtain the classical “ V-curves ” .

Trial

The intent of this trial was to happen the torque-speed features of an AC initiation motor.

The features that will be analysed against torsion are: –

Test Equipment: –

Circuit Diagram for DC Motor Test: –

Block Diagram

To farther explain and simplify, a block diagram of the trial is included below. This shows precisely how the system operates.

Brake

Motor

Three Phase Supply

Torque Control

Speed ( rev/min )

Ammeter, V metre, watt metre

Test Procedure

An extended trial process can be found in the appendix taken from the Student Guide of TecQuipment Electrical Machines FH2 refer to appendix! ! ! .

Consequences Table T.6

A

Line Current

Excitement Voltage

Torque = 0.1 Nm

Torque = 0.15 Nm

Torque = 0.2 Nm

Torque = 0.25 Nm

Torque = 0.3 Nm

Torque = 0.35 Nm

Torque = 0.4 Nm

120

0.23

0.24

0.25

0.26

0.28

0.29

0.32

110

0.2

0.21

0.23

0.24

0.26

0.28

–

100

0.18

0.2

0.21

0.23

0.24

0.27

–

0.16

0.18

0.19

0.22

0.24

–

0.15

0.16

0.18

0.21

–

0.13

0.15

0.18

–

0.13

0.15

–

0.13

–

Graphic Analysis: –

Now the study illustrates the consequences in the tabular array T.4 in a graphical signifier, to do comparing the consequences from the trial equipment industry have been included as a usher.

Line Current Vs Excitation Voltage

Decision

Overall the consequences acquired through practical experiment show encouraging consequences, both towards theory and besides towards the industries guide consequences. Some of the graphs could hold been a more steady consequence but it is non possible to acquire perfect consequences on something like this without making the trial many more times and taking mean values. The tendencies do exemplify what is expected, so this means the equipment was set up right, and the trial was carried out uniformly to industries guidelines.