EET 3136

Electrical Drives

Experiment # 1

LOAD CHARACTERISTICS OF INVERTER FED

INDUCTION MOTOR

Experiment # 2

PARAMETER SETTING OF AN INDUSTRIAL VARIABLE

SPEED DRIVES

Note: On-the-spot evaluation is carried out during or at the end of the experiment. Students

are advised to read through this lab sheet before doing experiment. Your performance,

teamwork effort, and learning attitude will count towards the marks.

Caution 1. This experiment deals with voltage supply of 415V,50Hz

2. Students will be provided with a technical manual of the system.

1

Experiment # 1

LOAD CHARACTERISTICS OF INVERTER FED

INDUCTION MOTOR

Part A: (10.71.2) Setting Parameters to the Frequency Range

Part B: (10.71.4) Load Characteristic of Inverter Fed Induction Motor

Reference

ELWE – GB 51 10 062 49/99

Setting Parameters to the Frequency Range: 10.71.2

OBJECTIVE The frequency of the frequency inverter should be adjustable between 10 Hz and 80 Hz.

The acceleration and deceleration should be as immediate as possible when the rotational

frequency setting is changed. The other parameters should conform to the standard settings

of the manufacturer. The settings required for this are to be on the frequency inverter and

checked.

REQUIREMENT EQUIPMENT

Experimental panel system

Unit description 1000 W

Frequency inverter control unit 10 10 076

Frequency inverter power unit 10 10 072

Connection cable LT/ST 15 10 015

Connection cable 55 00 307

Interface operator 15 10 013

Shaft-end cover 31 00 005

Three-phase squirrel-cage induction motor 30 27 600

Connection mask 31 25 601

PROCEDURE

1. Connecting the motor

1.1 For safety reasons, cover the motor shaft by attaching the safety guard.

1.2 Connect the motor to the frequency inverter, incl. PE.

1.3 How are the coils of the motor with a rated voltage 230/400 V to be connected to

ensure that the motor can be operated at its rated values on the frequency inverter with

one phase input to 230V mains?

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2. Commissioning the frequency inverter

2.1 Make the basic settings described above. Connect the frequency inverter to the

mains and move the mains switch to "“on"”

Describe the behavior of the motor on changing the set point value.

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2.2 Describe briefly what basic settings are to be made on the frequency inverter before

commissioning.

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3. Assigning parameters to the frequency inverter

3.1 The settings which are required on the frequency inverter in order to be able

complete the parameter assignment:

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3.2 Enter the necessary steps in the table which will allow you to assign parameters to

the frequency inverter in order to complete the task.

Settings Display Function

noP

3

- Connect control inputs for controller enabling (! Enabling direction of

rotation, internal set point)

4. Check parameter assignment

4.1 Describe the results of the check.

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4.2 Disconnect the control inputs controller enabling, setting of the standard values

specified by the manufacturer.

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Part B: (10.71.4) Load Characteristic of Inverter Fed Induction Motor

OBJECTIVE The dependence of the rotational frequency of a three-phase squirrel-cage induction

monitor on the torque at various frequencies of the output voltage of the frequency inverter

is to be examined.

REQUIRED EQUIPMENT

Experimental panel

system

Unit description 1000 W

Frequency inverter control unit 10 10 076

Frequency inverter power unit 10 10 072

Connection cable LT/ST 15 10 015

Connection cable 55 00 307

Interface operator 15 10 013

Pendulum machine 30 27 000

Brake control unit 67 10 611

Three-phase squirrel-cage induction motor 30 27 600

Connection mask 31 25 601

Coupling collar 31 00 000

Coupling cover 31 00 003

Shaft-end cover 31 00 005

Arrange the instruments according to the illusion.

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PROCEDURE

1. Putting into operation

1.1 Connect the pendulum machine and the motor with help of the coupling collar.

Positioning the safety guards.

1.2 Connect the brake control unit including the temperature sensor for the motor and

make the following basic settings:

- Rotational frequency range 1500/ 3000 rpm

- Torque range

- Function off

1.3 Switch on the brake control unit using the mains switch. Press the reset button. If the

red LED is still alight now, there must be a fault in the set-up, e.g.

- the coupling safety guard is missing

- the safety guard for the shaft-end cover is missing

- the jack plug for the temperature control of the motor has not been inserted

- the motor is too hot

1.4 Connect the motor according to its rated voltage to the frequency inverter with the

frequency inverter being switched off, including PE.

1.5 Switch on the frequency inverter and make the following basic settings:

- CP. 5 Rated frequency 50 Hz

- CP. 6 Boost 0%

- CP. 7 Acceleration time 0.1 seconds

- CP. 8 Deceleration time 0.1 seconds

- CP. 9 Minimal frequency 0 Hz

- CP. 10 Maximal frequency 100 Hz

- CP. 18 Slip compensation off off

- CP. 19 Auto boost off

- CP. 1 Actual frequency display

2. Load capacity of the motor

2.1 How does the power given off to the shaft of the motor increase with the rotational

frequency whilst the load torque remains constant?

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2.2 Why may a self-ventilated motor not be loaded with its rated torque permanently at

low rotational frequency?

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3. M = f ( n ) Characteristic curves of a three-phase squirrel-cage induction motor

with two pairs of poles

3.1 Find the rotational frequency of the motor at the prescribed frequencies of the

frequency inverter (parameters) dependent on the motor’s load. Connect controller

enabling. (Release of direction of rotation F!, internal setpoint)

Set “man., nconst.” On the brake with “down” (“up”) the torque values. Enter your

findings in the table.

At the end of the test series set to “off” mode and disconnect the controller release.

Boost: 0%

M

Nm

F

Hz

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

10

20

30

40

50

60

70

80

90

100

Rotational frequency in rpm

3.2 Repeat the series of measurements outlined in 3.1.

Boost: 25%

M

Nm

F

Hz

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

10

20

30

40

50

60

70

80

90

100

Rotational frequency in rpm

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3.3 Draw the M = f ( n ) characteristic curves on the basis of your findings.

3.4 Compare the change in slip with the motor under load in the armature range and in

the field attenuation and field control range.

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3.5 Compare the change in the breakdown torque in the armature range and in the field

attenuation and field control range when the frequency is changed.

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3.6 Why does to achievable torque of the monitor below the rated frequency without

boost decrease at lower frequencies?

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3.7 Why does achievable torque of the motor remains constant up to the rated frequency

when a “boost” is set appropriately?

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3.8 What causes the reduction of the achievable torque when the frequency is increased

above the rated frequency?

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Experiment # 2

PARAMETER SETTING OF AN INDUSTRIAL VARIABLE

SPEED DRIVES

1.0 THEORY

1.1 Variable Speed Drives Variable Speed Drive (VSD), in its simplest form, is a block, which can supply varying

power at the terminals of a motor. When used with an AC induction motor, VSD operates

based on the principle that the synchronous speed on the motor is given by

p

f120NS = (1)

Where NS is the speed in revolutions per minute (rpm), f is the frequency in Hz and p the

number of electrical poles of the motor. The VSD varies the frequency in (1) to vary the

speed of the motor. A range of VSDs is available commercially for use in the industry and

listed below are some of the applications, which may seem cumbersome without the use of

VSDs.

Schneider Electric’s VSDs series, the ATV18 series, includes among other useful functions

the 4 Preset Speeds function. This function makes use of two of the logic inputs (LI) of the

ATV18 to easily select any of the four speeds combinations at which the motor may be

operated. Figure 1 illustrates one of many 4 Preset Speed configurations.

HSP

SP4

SP3

LSP

0

ACC DEC

Four Preset Speeds settings

LSP and HSP are low speed and high speed respectively, which are the two basic control

speeds of the ATV18; SP3 and SP4 are the additional 3rd

and 4th

preset speeds.

1.2 Conveyor Belt Conveyor belts are used to move a continuous mass from one place to another within a

compound. Conveyor belts are a necessity in many industries where use of human labor

would result in degraded efficiency. The movement of the conveyor belt is driven by a

motor, which in most cases allows a certain degree of control to add flexibility to the flow

of the mass being transported. In mining industry conveyor belts are used to transport

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rocks from underground, in automobile industry parts are conveyed using belts and in food

industry these belts are used to pass food through washers and driers.

1.3 Ventilation Ventilation is an air exchanging process that brings air into a building and exhausting

contaminated air. Contaminated air can be hot air, cold air or even intoxicated air

depending on the application. There are quite a few types of ventilation systems out there

and each of these systems is composed of three main components, which are inlets, fans

and controllers. The motors running as fans in these systems should, among other things,

have the capability to run at different speeds and have optimum performance when

operated at low speeds.

1.4 Textile Machine A textile machine transforms many single threads into a cloth. The threads, which may be

of different colors and textures, are held on rods called spindles. The spinning motion of

the spindles is driven by a motor, which can run at high speeds in both directions. The

spindle would rotate at low speed with high load torque when it is full; and high speed with

low load torque when it is almost empty. Synchronization of speed and tension between

spindles is critical. Thread breakage may happen as a result of poor synchronization.

2.0 APPARATUS - ATV18-MMU

- 1.5kW Squirrel Cage Induction Motor

- Stroboscope

- Connecting Cables

2.1 General Procedure To carry out this experiment, a connection of ATV18-MMU to Power Supply and motor

must be made. Please refer to the manual provided to make these connections.

1) Put all the logic input switches (SLIs) at OFF (0) position. This is necessary to

prevent the motor from running unexpectedly.

2) Depress the start button(SW1) and hold for 3 seconds until the red light vanishes. If

there is fault the red light will continue to glow and a fault message will be shown

on the Display on the ATV18, please refer on the ATV18-MMU [page 15-16] on

how to remedy the fault.

3) To RETURN all parameters to their Factory Preset Value. Go to FCS (second level

parameter) and set to YES and follow by ENT. This will initialize all parameters as

given in ALTIVAR 18 manual [Page 57-62]. Repeat Step 2.

4) Proceed with the experiment (Lab A-D)

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2.4.1 Lab A: 4 PRESET SPEEDS

Note: To set the parameters, use down and up arrow, and press data button at

respective parameters, use the down, and up arrow again to change the values/setting.

Save the changes by pressing ENT.

1. Using the Keypad and Display terminal, go to LI3 and set it to PS2. Note: Since LI3 is

a second level parameter, it may not appear in the menu; please refer to ATV18-MMU

manual to see how to enable level 2 parameters.

2. Go to LI4 and set it to PS4

3. Go to the following parameters and set the values as stated:

ACC = 5

DEC = 13

LSP = 6

HSP = 60 SP3 = 15

SP4 = 30

4. Close SLI1, the logic input 1. (The motor will rotate at the set frequency in the forward

direction). To monitor the frequency of rotation of the motor on the Display, go to rFr

using the Keypad and press DATA.

5. Use logic input switches SLI3 and SLI4 to select different motor speeds and record

their logic combinations in the table A1.

Table A1

SLI3

(1/0) SLI4 (1/0)

Assignment

on motor

Speed (Hz) Measured Speed*

(RPM)

• Set the analog setpoint to 0 (the ref. potentiometer)

• Using Stroboscope (Only for speed more than 10Hz)

2.4.2 LAB B: APPLICATION 1- CONVEYOR BELT

During this lab you will be introduced to most commonly used function parameters in

conveyor belt system such as those that convey bottles in a factory.

In this experiment we shall look at

1) Application functions

Acceleration and decelerations ramp

Preset Speeds

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2) Common problems

Resonant frequency

Fault Clearance by logic input

Procedures 1. Reset the VSD setting to factory presets by ENTering YES to FCS.

You will have to power up the VSD using the Start button after resetting the system to

factory presets

2. Switch ON SLI1 and observe the rotation of the motor. You need to increase the ref

(potentiometer if necessary)

3. Observe the acceleration (ACC) of the motor. It should accelerate in 3s since it’s a

factory preset.

4. Start the motor again by setting SLI1 to 1 (ON), then observe the acceleration, after

a while, set the L1 to 0 (OFF) then observe the deceleration. Your instructor will probably

show you a simulation of what is happening.

In the bottling industry, bottles on the conveyor belt often have to temporarily stop to be

filled up and then take off again. The acceleration and deceleration of the motor will

determine how steady will be the bottles on the belt during those starts and stops. The

factory presets are definitely not suitable for bottling application.

5. Increase both ACC and DEC to 6s and observe the difference from factory preset

settings

Extremely high values of ACC and DEC lengthen the bottling cycle time

Bottles may have to run at different speeds in between the stops in order to optimize the

bottling process. For ATV18, values set for ACC and DEC determine how well the four

preset speeds are coordinated to smoothly run the process.

6. Factory preset setting assigns logic input LI3 and LI4 to control of preset speed.

The value of these speeds of factory setting can be changed using parameters SP3 and SP4.

In this case, set SP3 to 10Hz and SP4 to 35Hz.

7. With ACC and DEC still set at 6s, use logic switches SLI3 and SLI4 to select

among the LSP, HSP, SP3 and SP4.

While observing the speed change, notice on the ATV18 display that the frequency

gradually changes to the selected value and it does so with increments/decrements of 0.1

Hz. The changing frequency, while trying to reach the selected value, it may interfere with

the resonant frequency of the surrounding system here degrading the conveyor’s operation.

For some conveyor belt systems, the critical frequency is 43 Hz (arbitrarily chosen).

Resonance frequency of conveyor system is usually determined by observing the conveyor

runs at various speeds. The conveyor tends to vibrates and run noisier when it resonate.

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8. Set JPF to 43Hz. Put both SLI3 and SLI4 at OFF positions while keeping SLI1 at

ON position.

9. With frequency of operation displayed on the ATV18, use the analog ref to

gradually vary the frequency from LSP to HSP.

Note: You can identify this frequency using parameter “ rFr ” during acceleration and

deceleration.

2.4.3 Lab C: APPLICATION 2- VENTILATION

During this lab you will be introduced to most commonly used function in ventilation

system

Application functions

Acceleration ramp

Low speed

Preset Speeds

Noise Reduction

Common problems

Catching a spinning load

Resonant Frequency

Procedures 1. Using the Keypad and Display terminal on the ATV18, find a second level

parameter LI3 in the parameter list and set it to PS2. Assign OFF to both LI2 and LI4

parameters.

(Note: If the logic inputs-LI2, LI3 and LI4-parameters are not available in the list you may

have to enable them, please refer to the manual provided).

2. Start the “Fan” (motor) using the logic inputs. (Recall the assignment of these logic

inputs).

Write down what happen when each of logic inputs activated (logic 1).

SLI1 (LI1)………………………………………………………………………..

SLI3 (LI3)………………………………………………………………………..

3. In order to start the fan as quickly as possible, you can reduce the acceleration

ramp. Depending to the fan inertia this may cause an erratic run up to speed. If this occurs

the acceleration ramp is not followed. You can resolve this problem by extending the ramp

time and modifying the gain FLG.

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To simulate a high inertia fan, start the motor and let it run at 50Hz. Go to ‘LCr’ and

monitor the current value while applying load to the shaft. Apply load till current value

indicated is 4A. Now Stop the motor.

Set the ACC to 1s run the motor (arbitrarily count how many second it takes to reach max

speed). Try to set ACC to 1s and set gain FLG to 20%. Observe the differences.

4. Fans are normally used for maintain good quality of the air. If the degree of

pollution is low the fan runs at low speed LSP. Low speed is always relatively high to

maintain efficiency.

Set the LSP to 25Hz and observe. Make sure the “ref” is set to 0.

5. When the degree of pollution increases (eg. Underground car park), the speed

controller automatically changes the high speed HSP to enable removal of polluted air.

This change the high speed is initiated by switching a logic input SLI3 (LI3) in this

example.

Start the fan (SLI1). Motor runs at Low speed (LSP). Activate LI3 and Observe. Normally

the LI3 will be controlled by a sensor e.g. CO2 sensor

6. Motor noise caused by switching frequency may be unacceptable particularly in

area where comfort is a priority, for example in air-conditioning system or hospital. You

have a possibility of reducing this noise level by selecting a high switching frequency

using parameter SFr.

By default the switching frequency is SFr = 4kHz. Change the switching frequency from

4kHz to 8kHz and then to 12kHz..

(Note: SFr can be configured on the fly, i.e. it can be configured while the motor is running

(SLI1 at logic 1)

7. During a short supply interruption, the fan changes the free wheel operation. When

the supply comes back ON, the speed controller stops the fan to restart. This causes jolting,

which may damage the machinery particularly when the inertia is high. To prevent this

phenomenon you can select catching spinning load. When the supply is switch back ON

the fan is restarted at the level of speed calculated by speed controller.

a. Using Keypad and Display terminal, set LSP and HSP to 0 and 50 Hz

respectively

b. Start the motor in a forward direction by activating SLI1.

c. Increase the ‘ref’ input until the speed of the motor is at set maximum

HSP.

d. While observing the rotational motion of the motor, depress STOP

button followed by START allowing 2s between the state transitions

e. Using Keypad and Display terminal, find SPr parameter and set YES to

it to activate the automatic spinning load catching function with speed

search

f. Repeat step 7(d)

2.4.4 Lab D: APPLICATION 3- TEXTILE MACHINE During this lab you will be introduced to some of the most commonly used function in

textile machines

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Application functions

2 directions of operation

JOG

Fast stop

Common problems

Stop on ramp on power failure

Catching a spinning load

Procedures Each of the functions in this section is activated or deactivated using a single Logic Input

of the ATV18. The first logic input (LI1), for instance, is assigned permanently to run the

motor in forward direction while other Logic Inputs can be assigned any of the other

functions supported by ATV18. Since some of its functions do the opposite of what other

functions do, ATV18 sets functions priority to maintain its operational integrity.

1. With SL1 to SLI4 at position 0, use the Keypad and Display terminal to set the HSP

parameter to 25 Hz and assign rrS to LI2 while making sure that OFF is assigned to

both LI3 and LI4.

2. Increase the analog reference to 10V (Maximum).

3. Start the motor by putting SLI1 at logic 1. (Notice the direction of rotation of the

motor).

a) With the motor still running, put SLI2 at logic 1. What happens to the

direction of torque of the motor?

b) Put SLI1 back to logic 0. Is the direction of rotation still the same?

c) Put SLI2 at logic 0 to stop the motor.

d) Set SLI2 to logic 1 and notice the direction of rotation.

e) With the motor still running, switch SLI1 to logic 1. Does the direction of

rotation change?

f) Put SLI2 back to logic 0. Does the direction of rotation change?

4. Using Keypad & Display terminal, set LI3 parameter to JOG.

A low speed adjustment function is commanded by logic input LI3. Also to enable starting

inputs LI1 and LI4 must be activated. If logic input LI4 is deactivated its commands the

machine to stop. This is positive safety feature, if the supply fails the machine stops.

5. JOG. This function enables the machine to be set up at low speed. The acceleration and

deceleration ramps are set at 0.1s if logic input LI3 is activated before LI1. If LI1 is

activated before LI3 it is ramp settings that are used.

Set the JOG function to 5Hz. Start the motor by activating LI3 and then LI1. Then try

to start the motor by LI1 and after LI3. Observe the differences.

6. On the power failure, it is necessary to keep the thread tense, hence to maintain a

deceleration ramp. Validate the stop on supply failure function STP = YES (stop on

ramp). Basically the energy stored in the speed controller enables deceleration take

place following the ramp in spite of power failure.

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Set STP = YES .Start the motor LI1 once it reaches maximum speed, switch off the

power supply by depressing stop button (SW2).

7. Catching a spinning load ;this function is used during short power interruption to

calculate the speed of rotation of the motor and take this into account on restarting.

Without this function restarting begins at zero speed.

Set the SPr = YES. On the motor (LI1) and try to create power supply interruption as

created in Lab C- Step 7.

Exercises

For Lab A Calculate Slip when the motor runs at these switches’ combinations.

a) SL3=1, SL4=1

b) SL3=0, SL4=1

For Lab B What is the range of frequencies that are skipped by ATV18-MMU in step 9?

For Lab C a. In Step 6, explain the differences found as switching frequency increased.

b. In Step 7, what are differences observed by enabling SPr. Explain what would happen

to the system if the feature is not available?

Lab D a. Referring to Step 3. What can you say about the priorities of forward and reverse

function?

Write in your own words, how does a variable speed drive help to save energy in industry?

Marking Scheme for experiment 1

Lab-1

(10

marks)

Assessment

Components

Details

Hands-On & Efforts

(2.5 marks)

Lab assessments are done based on the hands-on

capability of the students and their efforts during the lab

sessions.

On the Spot

Evaluation (2.5

marks)

On the spot evaluations based on the theory concerned

with the lab experiments and the observations are done

for students.

Lab Report

(5 marks)

Student should submit a hard copy lab-report after 3

days of performing the lab experiment. The lab-report

consists of introduction, recorded experiment data,

discussion, and conclusion. The experiment may be

done by the team working of 2-3 students, but the lab-

report preparation is done individually.

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Marking Scheme for experiment 2

Lab-2

(10

marks)

Assessment

Components

Details

Hands-On & Efforts

(2.5 marks)

Lab assessments are done based on the hands-on

capability of the students and their efforts during the lab

sessions.

On the Spot

Evaluation (2.5

marks)

On the spot evaluations based on the theory concerned

with the lab experiments and the observations are done

for students.

Lab Report

(5 marks)

Student should submit a hard copy lab-report after 3

days of performing the lab experiment. The lab-report

consists of introduction, recorded experiment data,

discussion, and conclusion. The lab-report preparation is

done individually.

An average total marks of Lab-1 and Lab-2 will be considered as 10% for final marks.