Fundamentals of AC machines - Festo Didactic

Fundamentals of AC machines

Workbook

With CD-ROM

L1 N PE

CB

CA

U1 U2 Z1

n = f [M]

n

I

1500

P2

M 1

n Z2

1/min 1300 1200

220

2.2

1100

W

A

1000

180

1.8

900

160

1.6

800

140

1.4

700

120

1.2

600

100

1.0

500

80

0.8

400

60

0.6

300

40

0.4

200

20

0.2

100

P2 = f [M] I = f [M]

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Nm 1.2 M

Festo Didactic 571791 en

Order no. Revision level: Author: Editor: Graphics: Layout:

571791 06/2011 Jürgen Stumpp Frank Ebel Jürgen Stumpp, Thomas Ocker 11/2011, Frank Ebel, Sophia Härer

© Festo Didactic GmbH & Co. KG, D-73770 Denkendorf, Germany, 2011 Internet: www.festo-didactic.com e-mail: [email protected] Reproduction, distribution and utilisation of this document, as well as the communication of its contents to others without explicit authorisation, is prohibited. Offenders shall be held liable for payment of damages. All rights reserved, in particular the right to file patent, utility model and registered design applications.

Contents Intended use ____________________________________________________________________________ V Preface ______________________________________________________________________________ VI Introduction ____________________________________________________________________________ VIII Work and safety instructions _______________________________________________________________ IX Training package, “basic principles of AC machines” ____________________________________________X Learning objectives _______________________________________________________________________ XI Allocation of learning goals to exercises______________________________________________________ XIII Components ____________________________________________________________________________ XV Notes for the teacher/trainer______________________________________________________________ XVII Structure of the exercises ________________________________________________________________ XVIII Component designations _________________________________________________________________ XVIII CD ROM contents ________________________________________________________________________ XIX

Exercises and solutions Overview of alternating current machines ______________________________________________________3 Exercise 1: Basic principles of the single-phase AC motor with squirrel-cage rotor (capacitor motor) _____5 Exercise 2: Single-phase AC motor with squirrel-cage rotor (capacitor motor) with different loads _____ 13 Exercise 3: Single-phase AC motor with squirrel-cage rotor: measurements with DriveLab software ____ 23 Overview of direct current machines, single-phase AC machines __________________________________ 37 Exercise 4: Basic principles of the universal motor ____________________________________________ 39 Exercise 5: Universal motor with different loads ______________________________________________ 45 Exercise 6: Universal motor with different loads: measurements with DriveLab software _____________ 53

© Festo Didactic GmbH & Co. KG 571791

III

Exercises and worksheets Overview of alternating current machines ______________________________________________________3 Exercise 1: Basic principles of the single-phase AC motor with squirrel-cage rotor (capacitor motor) _____5 Exercise 2: Single-phase AC motor with squirrel-cage rotor (capacitor motor) with different loads _____ 13 Exercise 3: Single-phase AC motor with squirrel-cage rotor: measurements with DriveLab software ____ 23 Overview of direct current machines, single-phase AC machines __________________________________ 37 Exercise 4: Basic principles of the universal motor ____________________________________________ 39 Exercise 5: Universal motor with different loads ______________________________________________ 45 Exercise 6: Universal motor with different loads: measurements with DriveLab software _____________ 53

IV


Use for intended purpose The training package for “basic principles of alternating current machines” may only be used: • For its intended purpose in teaching and training applications • When its safety functions are in flawless condition The components included in the training package are designed in accordance with the latest technology as well as recognised safety rules. However, life and limb of the user and third parties may be endangered, and the components may be impaired, if they are used incorrectly. The training system from Festo Didactic has been developed and produced exclusively for training and further education in the field of automation technology. The training companies and/or trainers must ensure that all trainees observe the safety instructions described in this workbook. Festo Didactic hereby excludes any and all liability for damages suffered by trainees, the training company and/or any third parties, which occur during use of the equipment sets in situations which serve any purpose other than training and/or vocational education, unless such damages have been caused by Festo Didactic due to malicious intent or gross negligence.


V

Preface Festo Didactic’s training system for automation and technology is geared towards various educational backgrounds and vocational requirements. The training system is therefore broken down as follows: • Technology-oriented training packages • Mechatronics and factory automation • Process automation and control technology • Mobile robotics • Hybrid learning factories The training system for automation and technology is continuously updated and expanded in accordance with developments in the field of education, as well as actual professional practice. The technology packages deal with various technologies including pneumatics, electro-pneumatics, hydraulics, electro-hydraulics, proportional hydraulics, programmable logic controllers, sensor technology, electrical engineering, electronics and electric drives.

The modular design of the training system allows for applications which go above and beyond the limitations of the individual training packages. For example, PLC actuation of pneumatic, hydraulic and electric drives is possible.

VI


All training packages feature the following elements: • Hardware • Media • Seminars Hardware The hardware in the training packages is comprised of industrial components and systems that are specially designed for training purposes. The components contained in the training packages are specifically designed and selected for the projects in the accompanying media. Media The media provided for the individual topics consist of a mixture of teachware and software. The teachware includes: • Technical literature and textbooks (standard works for teaching basic knowledge) • Workbooks (practical exercises with supplementary instructions and sample solutions) • Lexicons, manuals and technical books (which provide technical information on groups of topics for further exploration) • Transparencies and videos (for easy-to-follow, dynamic instruction) • Posters (for presenting information in a clear-cut way) Within the software, the following programmes are available: • Digital training programmes (learning content specifically designed for virtual training) • Simulation software • Visualisation software • Software for acquiring measurement data • Project engineering and design engineering software • Programming software for programmable logic controllers The teaching and learning media are available in several languages. They are intended for use in classroom instruction, but are also suitable for self-study. Seminars A wide range of seminars covering the contents of the training packages round off the system for training and vocational education.

Do you have suggestions or criticism regarding this manual? If so, send us an e-mail at [email protected]. The authors and Festo Didactic look forward to your comments.


VII

Introduction This workbook is part of the learning system for automation and technology from Festo Didactic GmbH & Co. KG. The system provides a solid basis for practice-oriented basic and further training. Training package TP 1410, “Servo brake and drive system”, deals with the following topics: • Basic principles of DC machines • Basic principles of AC machines • Basic principles of 3-phase machines The workbook entitled “Basic principles of alternating current machines” provides an introduction to the topic of electric machines with AC connection. We come into contact with AC drives every day, as these motors are commonly used in household appliances, and above all in handheld electrical tools. Knowledge regarding layout, connection and applications ranges is imparted. In doing so, the machines are exposed to a wide range of simulated load situations in order to ascertain their capabilities. Technical prerequisites for setting up the circuits include: • A laboratory workbench equipped with an A4 frame • Servo brake and drive system equipment set TP 1410 • 230 V AC mains outlet • Universal motor • Capacitor motor • Components for controlling the electric machines • Laboratory safety cables The circuits for all 6 exercises are set up using the TP 1410 equipment set and the AC drives. Data sheets for the individual components are also available (universal motor, capacitor motor etc.).

VIII


Work and safety instructions

General information • Trainees should only work with the circuits under the supervision of a trainer. • Observe specifications included in the technical data for the individual components, and in particular all safety instructions! • Malfunctions which may impair safety must not be generated in the training environment and must be eliminated immediately. Mechanical components • Attach all components intended for mounting of this sort to the A4 frame. • Adhere to the instructions regarding positioning of the components. Electrical components •

The servo brake and drive system (motor test bench) may only be placed into service with an additional protective earth conductor.

Output

L1 DC+

L2

L3/N DC-

Input

PE

PE

• • • •

Always connect the motor’s thermo-switch to the “Motor ϑ” input at the motor test bench. Establish or interrupt electrical connections only in the absence of voltage! Use only connecting cables with safety plugs for electrical connections. Always pull the safety plug when disconnecting connecting cables – never pull the cable.


IX

Training package, “basic principles of AC machines” The subject matter of this section of the TP 1410 training package is basic principles of AC machines. Individual components from training package TP 1410 may also be included in other packages. Important TP 1410 components • Permanently installed workstation with A4 frame • Equipment set or individual components (universal motor, capacitor motor) • Laboratory safety cables • Set of laboratory equipment Media The teachware for training package TP 1410 consists of three workbooks. The workbooks contain worksheets for each exercise, the solutions for each individual worksheet and a CD-ROM. A set of ready-touse exercises and worksheets is included for each exercise. Data sheets for the hardware components are made available along with the training package. Media Workbook

Basic principles of DC machines Basic principles of AC machines Basic principles of 3-phase machines

Digital training programmes WBT, “Electric drives 1” WBT, “Electric drives 2”

Overview of media for training package TP 1410

Software available for training package TP 1410 includes digital learning programmes entitled “Electric drives 1” and “Electric drives 2”. These programmes explore the basic principles of electric drive technology in detail. Training content is elucidated on the basis of practical case studies in a systematic, applicationsoriented fashion. Further training materials can be found in our catalogue and on the Internet. The learning system for automation and technology is continuously updated and expanded. Transparency sets, videos, CD-ROMs, DVDs and training programmes as well as additional teachware are offered in several languages.

X


Learning objectives

• • • • • • • • • • • • • • •

• • • • • • • • • • • • • • •

Basic principles of AC machines – single-phase AC motor with squirrel-cage rotor (capacitor motor) with different loads You become familiar with the basic function of the capacitor motor. You become familiar with the connection plate on the motor with all of its designations You become familiar with the motor’s circuitry including main and auxiliary windings, as well as the starter and operating capacitors. You become familiar with terminal board wiring for clockwise and anti-clockwise motor operation. You become familiar with the measuring circuit for checking the specifications in the rating plate. You become familiar with checking the specifications in the rating plate by performing measurements while the motor is idling, and while running at nominal load. You learn how to work with the motor test bench and DriveLab software. You become familiar with the measuring circuit for recording the individual points in the characteristic load curves. You become familiar with starting the motor up with various loads. You learn to calculate the missing values in the table. You learn how to create a chart with the motor’s characteristic load curves. You learn how to evaluate characteristic load curves. You learn how to calculate reactive power, efficiency and power factor. You learn how to create a graph with the calculated values. You learn how to evaluate the graph.

Basic principles of AC machines – universal motor You become familiar with the term “universal motor”. You become familiar with the ohmic resistances of the armature winding and the excitation winding in the universal motor. You learn to evaluate the resistance values of armature and excitation windings. You become familiar with the problem associated with the universal motor when idling. You become familiar with the layout of the rotor of the universal motor. You learn how to reverse the direction of rotation of the universal motor. You learn how to change the speed of the universal motor. You become familiar with possible applications for universal motors. You learn how to work with the motor test bench and DriveLab software. You will be aware of the significance of the data included on the motor’s rating plate. You become familiar with the measuring circuit for recording the individual points in the characteristic load curves. You become familiar with starting the motor up with various loads. You learn to calculate the missing values in the load table. You learn how to create a chart with the motor’s characteristic load curves. You learn how to evaluate characteristic load curves.


XI

• • • • • • • •

XII

Use of the servo brake and drive system and DriveLab software You learn how to work with the servo brake and drive system, and DriveLab software. You learn how to connect and commission the motors with the servo brake and drive system and DriveLab software. You become familiar with the programming interface for DriveLab software. You learn how to select and change measured variables at the X-axis and the Y-axis. You learn how to customise the colour and style of measured curves. You learn to adjust speed and torque from the computer. You learn to prepare and start a measurement from the computer. You learn to record and document characteristic load curves at the computer.


Allocation of learning objectives to exercises Exercise

1

2

3

4

5

6

Learning objective You become familiar with the basic function of the capacitor motor.

•

You become familiar with the connection plate on the motor with all of its designations

•

You become familiar with the motor’s circuitry including main and auxiliary windings, as well as the starter and operating capacitors.

•

You become familiar with terminal board wiring for clockwise and anti-clockwise motor operation.

•

You become familiar with the measuring circuit for checking the specifications in the rating plate.

•

You become familiar with checking the specifications in the rating plate by performing measurements while the motor is idling, and while running at nominal load.

•

You learn how to work with the motor test bench and DriveLab software.

•

You become familiar with the measuring circuit for recording the individual points in the characteristic load curves.

•

You become familiar with starting the motor up with various loads.

•

You learn to calculate the missing values in the table.

•

You learn how to create a chart with the motor’s characteristic load curves.

•

You learn how to evaluate characteristic load curves.

•

You learn how to calculate reactive power, efficiency and power factor.

•

You learn how to create a graph with the calculated values.

•

You learn how to evaluate the graph.

•


•

You learn how to connect and commission the capacitor motor with the motor test bench and DriveLab software.

•

You learn to connect and commission the universal motor with the motor test bench and DriveLab software.

•

•

You become familiar with the programming interface for DriveLab software.

•

•

You learn how to select and change measured variables at the X-axis and the Y-axis.

•

•

You learn how to customise the colour and style of measured curves.

•

•

You learn to adjust speed and torque from the computer.

•

•

You learn to prepare and start a measurement from the computer.

•

•

You learn to enter a new motor to the motor library.

•

•

You learn to record and document characteristic load curves at the computer.

•

•


XIII

Exercise

1

2

3

4

5

6

Learning objective

XIV

You become familiar with the term “universal motor”.

•

You become familiar with the ohmic resistances of the armature winding and the excitation winding in the universal motor.

•

You learn to evaluate the resistance values of armature and excitation windings.

•

You become familiar with the problem associated with the universal motor when idling.

•

You become familiar with the layout of the rotor of the universal motor.

•

You learn how to reverse the direction of rotation of the universal motor.

•

You learn how to change the speed of the universal motor.

•

You become familiar with possible applications for universal motors.

•


•

You will be aware of the significance of the data included on the motor’s rating plate.

•

You become familiar with the measuring circuit for recording the individual points in the characteristic load curves.

•

You become familiar with starting the motor up with various loads.

•

You learn to calculate the missing values in the load table.

•

You learn how to create a chart with the motor’s characteristic load curves.

•

You learn how to evaluate characteristic load curves.

•


Components The components included in the training package for “basic principles of AC machines” impart knowledge regarding setup, connection and the range of applications of AC machines. In order to set up functional circuits, you will also need a laboratory workstation (optionally equipped with an A4 frame), “servo brake and drive system” equipment set TP 1410, a 230 V AC power supply and controllers for the electric machines.

“Servo brake and drive system” equipment set TP 1410 Component

Order no.

Quantity

Servo brake and drive system

571870

1

Component

Order no.

Quantity

Single-phase AC motor with squirrel-cage rotor (capacitor motor)

571871

1

Universal motor

571872

1

Component

Order no.

Quantity

EduTrainer 3-phase power supply

571812

1

EduTrainer 24 V power supply

571813

1

EduTrainer contactor board

571814

1

Motor technology contactor set

571816

1

EduTrainer operator and signaling unit

571815

1

Electric machines, “basic principles of AC machines”

Controllers for the electric machines


XV

Graphic symbols, equipment set Component

Graphic symbol

Single-phase AC motor with squirrel-cage rotor (capacitor motor)

M 1

Universal motor

M

XVI


Notes for the teacher/trainer Learning objectives The overall learning objective of this workbook is familiarisation with the basic principles of AC machines. Direct interplay of theory and practice ensures fast progress and long-lasting learning. The more specific learning objectives are documented in the matrix. Concrete, individual learning objectives are assigned to each exercise. Required time The time required for working through the exercises depends on the learner’s previous knowledge of the subject matter. For apprentices in the field of electrical engineering: approx. 3 days With training as a skilled worker: approx. 1 day Components The workbook and the components are designed to be used together. A single-phase AC motor with squirrel-cage rotor (capacitor motor) is required for exercises 1 through 3. A universal motor is required for exercises 4 through 6. Standards The following standards apply to this workbook: EN 60617-2 through EN 60617-8: Graphic symbols for circuit diagrams EN 81346-2: Industrial systems, installations and equipment and industrial products; structuring principles and reference designations Identification of solutions Solutions and supplements in graphics or diagrams appear in red. Identification in the worksheets Texts which require completion are identified with a grid or grey table cells. Graphics and diagrams which require completion include a grid. Notes for the lesson Additional information regarding the individual components and the circuits is provided here. These notes are not included in the worksheets. Learning topics Allocation of the fields of learning offered by vocational schools to the training subject matter of “basic principles of AC machines” is provided below for selected vocations.


XVII

Vocation

Topic

Electronics engineer for automation technology

Analysing electrical systems and testing their functions Analysing and adapting control systems Analysing systems and testing their safety

Mechatronics technician

Installation of electric equipment, taking technical safety aspects into account Examination of the flow of energy and information in electrical, pneumatic and hydraulic assemblies Implementation of mechatronic subsystems Commissioning, troubleshooting and repair

Structure of the exercises All 6 exercises have the same structure and are broken down into: • Title • Learning objectives • Problem description • Positional sketch • Project assignments • Work aids • Worksheets The workbook includes the solutions for all of the worksheets.

Component designations The components in the circuit diagrams are identified in accordance with EN 81346-2. Letters are assigned as appropriate to each component. Multiple components of the same type within a single circuit are numbered. Relays: Switches/pushbuttons: Contactors: Fuses: Indicators:

XVIII

K, K1, K2, … S, S1, S2, … Q, Q1, Q2, … F, F1, F2, ... P, P1, P2, ...


Contents of the CD-ROM The workbook is included on the accompanying CD-ROM as a PDF file. The CD-ROM also provides you with additional media. The CD-ROM contains the following folders: • Operating instructions • Illustrations • Data sheets Operating instructions Operating instructions are provided for various components included in the training package. These instructions are helpful when using and commissioning the components. Illustrations Photos and graphics of components and industrial applications are made available. These can be used to illustrate individual tasks or to supplement project presentations. Data sheets The technical data for the components included in the training package are available as PDF files.


XIX

XX


Contents Exercises and solutions Overview of alternating current machines ______________________________________________________3 Exercise 1: Basic principles of the single-phase AC motor with squirrel-cage rotor (capacitor motor) _____5 Exercise 2: Single-phase AC motor with squirrel-cage rotor (capacitor motor) with different loads _____ 13 Exercise 3: Single-phase AC motor with squirrel-cage rotor: measurements with DriveLab software ____ 23 Overview of direct current machines, single-phase AC machines __________________________________ 37 Exercise 4: Basic principles of the universal motor ____________________________________________ 39 Exercise 5: Universal motor with different loads ______________________________________________ 45 Exercise 6: Universal motor with different loads: measurements with DriveLab software _____________ 53


1

2


Overview of alternating current machines

AC machines

Transformers

Single-phase transformer

Rotating machines

Three-phase transformer

Special transformers e.g. leak and auto transformers

Motors

Synchronous machines

Generators

Asynchronous machines

Single-phase machines

Three-phase machines

Motors with auxiliary winding or capacitor

Motors with squirrel-cage rotor

Special machines e.g. pole switching and repulsion motors

Motors with slip-ring rotor

Special machines e.g. linear and collector motors


3

4


Exercise 1 Basic principles of the single-phase AC motor with squirrel-cage rotor (capacitor motor) Learning objectives After completing this exercise: • You will be familiar with the basic function of the capacitor motor. • You will be familiar with the connection plate on the motor with all of its designations • You will be familiar with the motor’s circuitry including main and auxiliary windings, as well as the starter and operating capacitors. • You will be familiar with terminal board wiring for clockwise and anti-clockwise motor operation. • You will be familiar with the measuring circuit for checking the specifications in the rating plate. • You will be familiar with checking the specifications in the rating plate by performing measurements while the motor is idling, and while running at nominal load.

Problem description 230 V single-phase alternating voltage (L1 and N) is the only option available for operating an air compressor. Due to the fact that high-inertia starting conditions can be expected with the compressor, a capacitor motor with starter and operating capacitors will be used as a drive. The motor needs to be tested for suitability in the training workshop. The examination results will need to be documented in a report.

Air compressor


5

Exercise 1 – Basic principles of the single-phase AC motor with squirrel-cage rotor (capacitor motor)

1. 2. 3. 4. 5. 6.

• • • • • •

6

Project assignments Describe the basic function of a single-phase AC motor with squirrel-cage rotor (capacitor motor). Complete the specifications for the motor’s connection plate. Complete the motor circuit with main and auxiliary windings, as well as the starter and operating capacitors. Complete the specifications for clockwise and anti-clockwise motor operation. Complete the measuring circuit for checking the specifications in the rating plate. Check the specifications on the motor’s rating plate for no-load operation and operation at nominal load by means of measurement and calculation.

Work aids Textbooks, books of tables Excerpts from manufacturers’ catalogues Data sheets Servo brake and drive system manual Internet WBT, “Electric drives 1”



1. Basic function of the capacitor motor a) Describe the layout of a capacitor motor. U1

U2

M 1

Z2

Z1

Capacitor motor – basic arrangement of the two windings

Two windings are arranged at a 90° angle to each other within the stator’s laminated core. This is the main winding with the designations U1 and U2. It occupies two thirds of the stator slots. The auxiliary winding with the designations Z1 and Z2 is accommodated in the remaining slots. Depending on starting conditions, the single-phase motor is also equipped with starter and operating capacitors.

b) Describe the function of the capacitor motor. In order to achieve phase displacement between the two windings, resulting in a rotating field, a capacitor must be connected in series to the auxiliary winding. In the case of a single-phase motor with an operating capacitor, the auxiliary winding is continuously energised along with the series connected main winding. In the event of high-inertia starting conditions, a starter capacitor is connected in parallel to the operating capacitor. The starter capacitor is switched off by a centrifugal switch after the motor has been started up.

c)

Which function does the operating capacitor fulfil? Operating capacitor CB assures a smooth running motor and a better power factor. The capacitance of the operating capacitor should be dimensioned such that the auxiliary winding does not become impermissibly hot. The capacitance of the operating capacitor accommodates close to 1 kvar of reactive power per kilowatt of motor power.


7


d) Which function does the starter capacitor fulfil? In order to increase the motor’s starting torque, the capacitor’s capacitance value must also be increased. The increase in capacitance is achieved by connecting starter capacitor CA in parallel. The starter capacitor is switched off by a centrifugal switch after the motor has been started up, assuring that the auxiliary winding does not become impermissibly hot.

2. Motor connection plate –

Designate the individual terminals at the connection plate on the capacitor motor.

U1

U2

Main winding, terminals U1 and U2

Z1

Z2

Auxiliary winding, terminals Z1 and Z2

Starter capacitor, terminals CA and CA CB

CB

Operating capacitor, terminals CB and CB

Centrifugal switch, terminals 11 and 12

Motor temperature monitoring, terminals 21 and 22

8



3. Capacitor motor circuit including main and auxiliary windings, as well as starter and operating capacitors –

Complete the circuit for the motor.

L1 N PE

CA

CB U1

U2

n> Z2

M 1

Z1

4. Wiring for clockwise and anti-clockwise motor operation –

Complete the wiring diagrams for clockwise and anti-clockwise motor operation.

L1

L1

N

N

PE

PE

U1

Z1

U1

Z1

Z2

U2

Z2

U2

CA

CB U1

CA

U1

U2

M 1

CB

n Z2

Z1


U2

M 1

n> Z2

Z1

9


5. Measuring circuit for checking the specifications in the rating plate a) Complete the measuring circuit for checking the specifications in the rating plate. Set up the circuit and start up the motor.

L1 N PE -P1

V -P2

A

-P3

W

CB

CA

U1

U2 -A1.1

n>

-M1

M 1

n

Z2

Z1

Quantity

Identification

Designation

1

-M1

Capacitor motor

2

-P1, -P2

Digital multimeter

1

-P3

Single-phase power meter

1

-A1.1

Motor test bench, servo brake and drive system

Equipment list

10



b) Set up the circuit. –

Use the 230 V capacitor motor (order no. 571872).

6. Checking the specifications in the rating plate by means of measurement and calculation a) The motor is connected to the motor test bench in order to perform measurement. The motor test bench is switched on but it is not connected to the PC. The motor is switched on.

b) Measurement is performed first of all during no-load operation. Enter the measured values to the “Noload” column in the table.

c)

For measurement at nominal load, the motor is loaded by the test bench up to nominal current (see rating plate), and the measurements are documented. Enter the measured values to the “Nominal load” column the table. No-load

Nominal load

V [V]

228

228

I [A]

1.2

1.86

P [W]

216

352

n [rpm]

1480

1400

d) Calculate values for apparent power, power factor and reactive power on the basis of the measured values in the table for no-load and nominal load operation. No-load Apparent power S:

S = U ⋅ I = 228 V ⋅ 1,2 A = 274 VA

Power factor cos φ:

cos ϕ =

Reactive power Q:

Q = S ⋅ sin ϕ = 274 VA ⋅ 0,63 = 173 var


P 216 W = = 0,78 S 274 VA

11


Nominal load Apparent power S:

S = U ⋅ I = 228 V ⋅ 1,86 A = 424 VA

Power factor cos φ:

cos ϕ =

Reactive power Q:

Q = S ⋅ sin ϕ = 424 VA ⋅ 0,56 = 237 var

P 352 W = 0,83 = S 424 VA

Monitoring capacitance of CA

Measured values:

U = 230 V I = 1.75 A

Reactance XC:

XC =

Capacitance C:

C=

UC 230 V = = 131,42 Ω IC 1,75 A

1 1 = = 24,2 μF 2 ⋅ π ⋅ f ⋅ X C 2 ⋅ π ⋅ 50 s-1 ⋅ 131,42 Ω

Monitoring capacitance of CB

12

Measured values:

U = 220 V I = 0.7 A

Reactance XC:

XC =

Capacitance C:

C=

U C 220 V = 314,28 Ω = 0,7 A IC

1 1 = = 10,13 μF -1 2 ⋅ π ⋅ f ⋅ X C 2 ⋅ π ⋅ 50 s ⋅ 314,28 Ω


Contents Exercises and worksheets Overview of alternating current machines ______________________________________________________3 Exercise 1: Basic principles of the single-phase AC motor with squirrel-cage rotor (capacitor motor) _____5 Exercise 2: Single-phase AC motor with squirrel-cage rotor (capacitor motor) with different loads _____ 13 Exercise 3: Single-phase AC motor with squirrel-cage rotor: measurements with DriveLab software ____ 23 Overview of direct current machines, single-phase AC machines __________________________________ 37 Exercise 4: Basic principles of the universal motor ____________________________________________ 39 Exercise 5: Universal motor with different loads ______________________________________________ 45 Exercise 6: Universal motor with different loads: measurements with DriveLab software _____________ 53


1

2


Overview of alternating current machines

AC machines

Transformers

Single-phase transformer

Rotating machines

Three-phase transformer

Special transformers e.g. leak and auto transformers

Motors

Synchronous machines

Generators

Asynchronous machines

Single-phase machines

Three-phase machines

Motors with auxiliary winding or capacitor

Motors with squirrel-cage rotor

Special machines e.g. pole switching and repulsion motors

Motors with slip-ring rotor

Special machines e.g. linear and collector motors


3

4


Exercise 1 Basic principles of the single-phase AC motor with squirrel-cage rotor (capacitor motor) Learning objectives After completing this exercise: • You will be familiar with the basic function of the capacitor motor. • You will be familiar with the connection plate on the motor with all of its designations • You will be familiar with the motor’s circuitry including main and auxiliary windings, as well as the starter and operating capacitors. • You will be familiar with terminal board wiring for clockwise and anti-clockwise motor operation. • You will be familiar with the measuring circuit for checking the specifications in the rating plate. • You will be familiar with checking the specifications in the rating plate by performing measurements while the motor is idling, and while running at nominal load.

Problem description 230 V single-phase alternating voltage (L1 and N) is the only option available for operating an air compressor. Due to the fact that high-inertia starting conditions can be expected with the compressor, a capacitor motor with starter and operating capacitors will be used as a drive. The motor needs to be tested for suitability in the training workshop. The examination results will need to be documented in a report.

Air compressor


5


1. 2. 3. 4. 5. 6.

• • • • • •

6

Project assignments Describe the basic function of a single-phase AC motor with squirrel-cage rotor (capacitor motor). Complete the specifications for the motor’s connection plate. Complete the motor circuit with main and auxiliary windings, as well as the starter and operating capacitors. Complete the specifications for clockwise and anti-clockwise motor operation. Complete the measuring circuit for checking the specifications in the rating plate. Check the specifications on the motor’s rating plate for no-load operation and operation at nominal load by means of measurement and calculation.

Work aids Textbooks, books of tables Excerpts from manufacturers’ catalogues Data sheets Servo brake and drive system manual Internet WBT, “Electric drives 1”

Name: __________________________________ Date: ____________



1. Basic function of the capacitor motor a) Describe the layout of a capacitor motor. U1

U2

M 1

Z2

Z1

Capacitor motor – basic arrangement of the two windings

b) Describe the function of the capacitor motor.

c)

Which function does the operating capacitor fulfil?


Name: __________________________________ Date: ____________

7


d) Which function does the starter capacitor fulfil?

2. Motor connection plate –

8

Designate the individual terminals at the connection plate on the capacitor motor.

U1

U2

Z1

Z2

CB

CB

Name: __________________________________ Date: ____________



3. Capacitor motor circuit including main and auxiliary windings, as well as starter and operating capacitors –

Complete the circuit for the motor.

L1 N PE

CA

CB U1 U2

n> Z2

M 1

Z1

4. Wiring for clockwise and anti-clockwise motor operation –

Complete the wiring diagrams for clockwise and anti-clockwise motor operation.

L1

L1

N

N

PE

PE

U1

Z1

U1

Z1

Z2

U2

Z2

U2

CA

CB U1

U1

U2

M 1

CA

CB

n Z2

Z1


U2

M 1

n Z2

Z1

Name: __________________________________ Date: ____________

9


5. Measuring circuit for checking the specifications in the rating plate a) Complete the measuring circuit for checking the specifications in the rating plate. Set up the circuit and start up the motor.

L1 N PE

V

A

W

CB

CA

U1 U2

M 1

n

Quantity

Identification

n>

Z2

Z1

Designation

1

Capacitor motor

2

Digital multimeter

1

Single-phase power meter

1

Motor test bench, servo brake and drive system

Equipment list

10

Name: __________________________________ Date: ____________



b) Set up the circuit. –

Use the 230 V capacitor motor (order no. 571872).

6. Checking the specifications in the rating plate by means of measurement and calculation a) The motor is connected to the motor test bench in order to perform measurement. The motor test bench is switched on but it is not connected to the PC. The motor is switched on.

b) Measurement is performed first of all during no-load operation. Enter the measured values to the “Noload” column in the table.

c)

For measurement at nominal load, the motor is loaded by the test bench up to nominal current (see rating plate), and the measurements are documented. Enter the measured values to the “Nominal load” column the table. No-load

Nominal load

V [V] I [A] P [W] n [rpm]

d) Calculate values for apparent power, power factor and reactive power on the basis of the measured values in the table for no-load and nominal load operation. No-load


Name: __________________________________ Date: ____________

11


Nominal load

Monitoring capacitance of CA

Monitoring capacitance of CB

12

Name: __________________________________ Date: ____________
