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Electricity and New Energy

Three-Phase Induction Motor Starters

Courseware Sample88197-F 0



© Festo Didactic 88197-10 III

Safety and Common Symbols

Caution, risk of danger



Safety and Common Symbols

IV © Festo Didactic 88197-10



© Festo Didactic 88197-10 V

Table of Contents



Table of Contents

VI © Festo Didactic 88197-10



© Festo Didactic 88197-10 VII

Preface



Preface

VIII © Festo Didactic 88197-10



© Festo Didactic 88197-10 IX

About This Manual

Manual objectives

Safety considerations

Prerequisite

DC Power Circuits Single-Phase AC Power Circuits Three-Phase AC Power Circuits Three-Phase Rotating Machines

Systems of units



© Festo Didactic 88197-10 XI

To the Instructor

Accuracy of measurements

Equipment installation



Sample Exercise

Extracted from

the Student Manual

and the Instructor Guide



© Festo Didactic 88197-10 7

Overcurrent protection. Overload protection.

Start up current. Consequences of extended large currents. Voltage sag.

Start-up torque.

Voltage output of a soft starter. Effect of the soft starter on the motorcurrent. Effect of the soft starter on the motor torque. Effect of the softstarter on the motor speed. How a soft starter controls voltage. Bypasscircuit. Types of soft starters.

Introduction

Direct-on-line starters

DOL Starters and Soft Starters

Exercise 1

E XERCISE OBJECTIVE

DISCUSSION OUTLINE

DISCUSSION



Exercise 1 – DOL Starters and Soft Starters Discussion

8 © Festo Didactic 88197-10

Motor protections

Overcurrent protection





Overload protection





Motor start-up phenomena

Start up current





Consequences of extended large currents





Voltage sag

Start-up torque





Soft starters





Voltage output of a soft starter





Effect of the soft starter on the motor current





Effect of the soft starter on the motor torque

Poly. (DOL)

Poly. (SS)





Effect of the soft starter on the motor speed





How a soft starter controls voltage

Poly.

(Speed

DOL(rev/min))

Poly. (SS)





Bypass circuit

Types of soft starters



Exercise 1 – DOL Starters and Soft Starters Procedure Outline


Setup and connections

In this part of the exercise, you will connect your equipment as a DOL starter,configure parameters in LVDAC-EMS so that the Four-Quadrant

Dynamometer/Power Supply emulates a flywheel, and set the Oscilloscope toobserve the motor start-up current, torque, and speed.

Power Input

Power Input

Low Power Input PowerInput

PROCEDURE OUTLINE

PROCEDURE



Exercise 1 – DOL Starters and Soft Starters Procedure


Operating Mode Dynamometer

Computer-Based Instrumentation ThyristorControl OK

Tools Friction CompensationCalibration OK OK

O I

I1

Current input I4 of the Data Acquisition and Control Interface is used tomonitor the motor current in order to protect the motor from overheating if

excessive currents flow through the stator windings. The range of current to beused for current input I4 is 40 A.





I1

I1

Sync.





Digital Output 1 DO1 D + – Remote Control

Analog Outputs T n Analog Inputs /T /n Analog Outputs A

Function Mechanical Load

Load Type Flywheel

Inertia

Friction Torque

Pulley Ratio

Note that the pulley ratio between the Four-Quadrant PowerSupply/Dynamometer and the Four-Pole Squirrel Cage Induction Motoris 24:24.

Function Direct On-Line Starter

Motor Full Load Current [FLA]

Overload On

Overload Class





I1) Analog Input 7/T Analog Input 8/n Peak Detect

Starting an induction motor using a DOL starter

In this part of the exercise, you will start the motor using a DOL starter. You willrecord the motor current, torque, and speed at start-up and analyze the results.

Status Started Start/Stop

Single Refresh Start

The above manipulation must be performed rapidly to ensure that theOscilloscope records the entire evolution of the various parameters duringmotor start-up.

Stop

Since the Oscilloscope operates in peak detect mode and a slow time base isused, it displays the envelope of the motor current rather than its waveform.

Status Stopped Start/Stop





The maximal current obtained in step 22 is a peak value. Convert this peakvalue to an rms value before making the comparison.





Soft starter setup and settings

In this section, you will modify the equipment connections so as to replace theDOL starter with a soft starter.

I1





I1





Sync.

Digital Output 1 Remote Control

T and n Analog Outputs Analog Inputs 7/T 8/n

Digital Outputs Firing Control Inputs

Range I1

Function Soft Starter

Mode Soft Start

Motor Full Load Current [FLA]

Initial Torque

Start Time Soft Starter Initial Torque

Kick Start Time

Soft Stop

Overload On

Overload Class





Starting an induction motor using a soft starter

In this part of the exercise, you will start the motor, still coupled to the samemechanical load used earlier in the exercise, using a soft starter. You will recordthe motor current, torque, and speed at start-up and analyze the results.

Single Refresh Start

The above manipulation must be performed rapidly to ensure the Oscilloscoperecords the entire evolution of the various parameters during motor start-up.

Stop





DOL starter versus soft starter

In this part of the exercise, you will compare the results you obtained with theDOL starter and the soft starter (for the same mechanical load) and try to deducewhat the advantages and limitations of each one are.



Exercise 1 – DOL Starters and Soft Starters Conclusion


Tools Reset to Default Friction Compensation Yes

CONCLUSION

REVIEW Q UESTIONS



Exercise 1 – DOL Starters and Soft Starters Review Questions




Bibliography

Foundations of Analog and Digital ElectronicCircuits

Industrial Power Engineering and Applications Handbook

Practical Variable Speed Drives and Power Electronics

The Induction Machine Handbook

Power Electronics Handbook

Electrical Machines, Drives and Power Systems

Power Conversion and Control of Wind Energy Systems

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