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Power Electronics

THYRISTORS AND CONTROLLED

AC/AC CONVERTERS

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CONTENTS

1. THEORETICAL SECTION

1.1 INTRODUCTION Page 1

1.2 TRIAC Page 2

1.3 SINGLE-PHASE AC CONTROLLER W1 (W1C) Page 31.3.1 Inductive load Page 6

1.3.2 Ohmic-inductive load Page 8

1.4 HALF-CONTROLLED SINGLE-PHASE CONTROLLER W1H Page 10

1.5 THREE-PHASE CONTROLLERS Page 12

1.5.1 Fully-controlled controller W3C Page 12

1.5.2 Half-controlled controller W3H Page 15

1.5.3 Controller W3C2 with two pairs of antiparallel SCRs Page 17

2. INFORMATIONS

2.1 EXPERIMENT COMPONENTS Page 21

2.2 SETTING UP AND CONDUCTING EXPERIMENTS Page 22

2.3 MEASUREMENTS WITH OSCILLOSCOPE Page 23

2.3.1 No mains isolation Page 23

2.3.2 Power supply via a transformer with isolated windings Page 24

2.3.3 Current measurement Page 25

2.3.4 Current and voltage measurement Page 252.3.5 Isolation amplifier Page 26

2.4 SAFETY INFORMATION Page 26

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EXPERIMENTS

EXPERIMENT N1

TRIAC Page 29

EXPERIMENT N2A

Single-phase ac controller W1C, ohmic load Page 35

EXPERIMENT N2B

Single-phase ac controller W1C, inductive load Page 43

EXPERIMENT N2C

Single-phase ac controller W1C, ohmic-inductive load Page 51

EXPERIMENT N3A

Single-phase ac controller W1, ohmic load Page 59

EXPERIMENT N3B

Single-phase ac controller W1, ohmic-inductive load Page 65

EXPERIMENT N4

Half-controlled single-phase controller W1H, ohmic load Page 71

EXPERIMENT N5

Fully-controlled three-phase controller W3C, star ohmic load without neutral Page 77

EXPERIMENT N6

Half-controlled three-phase controller W3H, star ohmic load without neutral Page 83

EXPERIMENT N7

Three-phase controller W3C2, star ohmic load without neutral Page 89

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1. THEORETICAL SECTION

1.1 INTRODUCTION

The continuous control of alternating electrical energy is normally performed by means of thyristorsthat are suitable for use as static switches on account of their extremely high switching capacity.

The thyristor family includes unidirectional devices as the SCRs and bidirectional devices as the

TRIACs.As switch conducts current in both direction so two SCRs must always be connected back-to-back

(pair of antiparallel arms) while the TRIAC can be used instead of the two antiparallel SCRs.

PRIOR KNOWLEDGE

1) Knowledge of diodes and uncontrolled rectifiers (DL DCA 201.1)

2) Knowledge of SCRs and controlled rectifiers (DL DCA 201.2)

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1.2 TRIAC

A TRIAC can be considered as two parallel SCRs oriented in opposite directions and integrated into

a semiconductor chip to provide symmetrical bidirectional characteristics, as shown in the

following Fig.1.

Fig.1 TRIAC symbol and volt-ampere characteristic

TRIACs have two main terminals MT1 and MT2 and one gate terminal G.

The switching behaviour is the same as that of two back-to-back SCRs and because of its complex

structure a TRIAC can be triggered by either a positive or a negative gate signal regardless of the

voltage polarity across the main terminals.

The gate trigger modes for TRIAC are depicted in the following table, where the polarities arereferenced to terminal MT1.

Quadrant Mode MT2 G

QI

QI

QIII

QIII

I+

I-

III+

III-

+

+

-

-

+

-

+

-

Because the direction of the principal current influences the trigger current, the trigger sensitivity is

higher in the I+ and III- trigger modes.

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1.3 SINGLE-PHASE AC CONTROLLER W1 (W1C)

The most simple device used to continuously adjust the ac power is shown in the following Fig.2,

where two antiparallel SCRs can be used instead of the TRIAC.

Fig.2 Ac controller with TRIAC (W1) and with two antiparallel SCRs (W1C)

The power regulation is accomplished by varying the control angle of the TRIAC (of the twoSCRs) during each half-period, as shown in the following Fig.3.

Fig.3 Phase-angle control, ohmic load

In the case of an ohmic load, the load current rises to the instantaneous value of the sinusoidal

continuous current at the moment of firing angle and then flows in phase with the sinusoidal supply

voltage until the zero transition is reached.

The load current can be continuously varied via the control angle between the maximum value (= 0) and zero ( = 180).During the conduction phase the supply voltage is connected to the load; during the off-phase it is

present at the controller as a reverse voltage.

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All the following characteristics values apply to resistive load, neglecting losses in the controller.

1) Average value of SCR current (controller W1C)

I

U

RTAVvM

1

2 1

( cos )

2) Rms value of SCR current (controller W1C)

IU

R

sinTRMS

vM 1

4

2

2

( )

3) Average value of load current

IAV = 0 (symmetrical control)

4) Average rectified value of load current

I IU

RAV TAV

vM 21

1

( cos )

5) Rms value of load current

I IU

R

sinRMS TRMS

vM 21

2

2

2

( )

Moreover the transfer characteristic reflects the relationship between the load current and the

control angle , as illustrated in Fig.4, where IRMSo = UvM/R 2 is the rms value for the gate angle = 0.

Fig.4 Transfer characteristic of the rms values of the load current

Controller W1(W1C), ohmic load

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The power transfer characteristic reflects the relationship between the load active power P and the

control angle , as illustrated in the following Fig.4a, where Po = Uv2/R is the full drive power for

the gate control angle = 0.

Fig.4a Power transfer characteristic

Controller W1 (W1C), ohmic load

In addition the power factor PF on the supply side is

PF

P

S

P

U Iv

and results inductive even in circuits with ohmic load.

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1.3.1 Inductive load

The purely inductive load represents an ideal load: the choke coil has an ohmic dissipative

resistance which cannot be disregarded.

Fig.5 Controller W1 (W1C) with ohmic load

In the case of an inductive load the current generally lags of the angle = 90 behind the voltageand for this reason the control range of the controller is limited between ==90 and 180.The load current cannot change abruptly as in the case of ohmic load and so it is necessary to fire

the thyristors by means of a pulse train in order to ensure the on-state when the line current has

reached the latching current value.

Fig.6 Phase-angle control, inductive load

When the control angle > 90 the load current is made up of sinusoidal peaks.During the conduction phase the supply voltage is connected to the load; during the off-phase it is


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All the following characteristics values apply to inductive load, neglecting losses in the controller.


IU

TAV

vM L

( - ) cos + sin


IU

LTRMS

vM

1 1

2

3

2( ) )(cos sin cos

2




IAV = 2 ITAV =2 U vM

L( - ) cos + sin


IRMS = 2 ITRMS =U

L

vM

2 1

2

3

2( ) )

(cos sin cos

2


control angle , as illustrated in Fig.7, where IRMS90 = UvM/ 2 L is the rms value for the gateangle = 90.


Controller W1(W1C), inductive load

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1.3.2 Ohmic-inductive load

Circuits containing resistance and inductance in series are a load type frequently found in practice.

Fig.8 Controller W1 (W1C), ohmic-inductive load

The ohmic-inductive load represents a load case between ohmic and purely inductive load.

Full drive is obtained when ==arc tan L/R and so the control range of the controller is limitedbetween = and 180.

Fig.9 Phase-angle control, ohmic-inductive load

The load current is no longer sinusoidal but is made up of sinusoidal continuous current and

superimposed equalizing current decreasing with the time constant = L/R.During the conduction phase the supply voltage is connected to the load; during the off-phase it is


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All the following characteristics values apply to ohmic-inductive load, neglecting losses in the

controller.


I UTAV vM 2 R

cos cos


I

U

R L

sin sinTRMSvM

2 2

1

2 2

1

42 2 2

cos




IAV = 2 ITAV = U vM

R cos cos


IRMS = 2 ITRMS =

U

R Lsin sinvM

2 2

1

2

1

4 2 2 2

cos


control angle , as illustrated in Fig.10, where IRMS = UvM/ 22 2

[ ( ) ]R L is the rms value for

the gate angle = .


Controller W1(W1C), ohmic-inductive load

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1.4 HALF-CONTROLLED SINGLE-PHASE CONTROLLER W1H

The half-controlled controller is often used for the temperature control and it is assembled with

antiparallel connected SCR and diode, as shown in the following Fig.11.

Fig.11 Controller W1H. ohmic load

Since the SCR can be driven in the phase angle through the positive half-cycle while the diode

conducts through the entire negative half-cycle, the load voltage is not an alternating quantity but

contains a direct component.

All the following characteristics values apply to resistive load, neglecting losses in the controller.

1) Average value of the SCR current

IU

RTAV

v 1

21

( cos )

2) Rms value of the SCR current

IU

R

sinTRMS

v 1

2

2

2

( )

3) Average value of the diode current

IU

RFAV

v2

4) Rms value of the diode current

IU

R

FRMS

v

2

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IU

RAV

v 1

21

( cos )


IAV = ITAV + IFAV


IU

R

sinRMS

v 1

22

2

2

( )

8)Transfer characteristic of the rms values of the load current.

I

I

U

R

sinRMS

RMSo

v 1

22

2

2

( )

where IRMSo =Uv/R is the rms value for the gate control angle =0.

() 0 30 60 90 120 150 180

IRMS/IRMS0 1 0.99 0.95 0.87 0.77 0.72 0.707

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1.5 THREE-PHASE CONTROLLERS

When the supply voltage is a three-phase ac system it is possible the full-wave or half-wave control,

as shown in the following Fig.12 for circuits without the neutral, as normally used in motor drive

technology and as tested in the suggested experiments.

Fig.12 Fully control (W3C) and half-wave control (W3H).

Star connected load, without neutral.

1.5.1 Fully-controlled controller W3C.

Fig.13 illustrates the basic circuitry of a three-phase fully-controlled controller with symmetrical

ohmic load, star connected and without neutral.

Fig.13 Controller W3C, ohmic load.

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To understand the action of the controller it is necessary to note what follows:

1) When the pair of antiparallel SCRs is not fired, the phase voltage at associated load is equal to

zero.

2) When all pairs of antiparallel SCRs have been fired, the phase voltage at the load is equal to thesupply phase voltage (e.g. U1 = Uv10).

3) If only two pairs of antiparallel SCRs have been fired , the phase voltage at the load is equal to

half the supply line voltage associated to the conducting pairs (e.g. U1 = Uv12).

4) The line voltage at the load is equal to the supply line voltage when the associated pairs of

antiparallel SCRs are conducting (e.g. V1 and V4 on: U12 = Uv12 ):at all other times this voltage is

equal to half the supply line voltage between the respective conducting arms (e.g. V1 and V6 on:

U12 = - Uv13).

5) When the pair of antiparallel SCRs is not fired, a voltage UV is present at the pair. The voltagephasor diagram shows that this voltage is equal to 1.5 time the associated supply phase voltage,

as illustrated in the following Fig.14 for the case (V1 - V2) off/(V3 - V4) and (V5 - V6) on:

U UU

UVa vv

v 1223

12

15.

Fig.14 Voltage phasor diagram

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Fig.16 Transfer characteristic of the rms values of the load current.

Controller W3C.

The controller W3C with ohmic load can be controlled over the range = 0 to 150 (curve at cos = 1): when > 150 no current can flow since the inverse SCRs block.

1.5.2 Half-controlled controller W3H.

Fig.17 illustrates the basic circuitry of a three-phase half-controlled controller with symmetrical

ohmic load, star connected and without neutral.

Fig.17 Controller W3H, ohmic load.

To understand the action of the controller it is necessary to note that the same considerations apply

for the time profiles of the load voltages as already discussed for the full-controlled controller W3C

(1.5.1), recalling that now the antiparallel pair consists of an SCR and of a diode so the time

profiles for the positive and negative half-cycles of the load voltages are different while the voltage

UV at the pair displays only positive values.

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The voltage time profiles are illustrated in the following Fig.18, where the current through the SCRs

and the diodes is sketched as a block circuit diagram.

Fig.18 Voltage time profiles W3H.

Symmetrical ohmic load.

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With ohmic load the voltage and current time profiles are identical: a complex procedure involves

the determination of the transfer characteristic of the load current and for this reason we indicate

only a graph, as shown in the following Fig.19, where IRMS0 = Uv/R is the rms value for the gate

angle = 0.

Fig.19 Transfer characteristic of the rms values of the load current.

Controller W3H, ohmic load.

The controller W3H with ohmic load can be controlled over the range = 0 to 210.

1.5.3 Controller W3C2 with two pairs of antiparallel SCRs.

With ohmic load it is possible to use only two pairs of antiparallel SCRs, one for phase, so to

control also the third phase, as shown in the following Fig.20.

Fig.20 Controller W3C2, ohmic load.

To understand the action of the controller it is necessary to note that the same considerations apply

for the time profiles of the load voltages as already discussed for the full-controlled controller W3C

(1.5.1), recalling that now the phase L2 is permanently connected to the load.

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The voltage time profiles are illustrated in the following Fig.21, where the load currents are

sketched as a block circuit diagram.

Fig.21 Voltage time profiles W3C2.

Symmetrical ohmic load.

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With ohmic load the voltage and current time profiles are identical: a complex procedure involves

the determination of the transfer characteristic of the load currents and for this reason we indicate

only a graph, as shown in the following Fig.22, where IRMS0 = Uv/R is the rms value for the gate

angle = 0.

Fig.22 Transfer characteristic of the rms values of the load currents.

Controller W3C2, ohmic load.

On account of the pair of antiparalle SCRs missing in one line the load currents differ considerably

and this also applies for the corresponding transfer characteristics.

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2. INFORMATION

2.1 EXPERIMENT COMPONENTS

1 DL 2603 Diode stack 1 DL 2605 SCR stack 1 DL 2607 TRIAC 1 DL 2613 DC power supply 1 DL 2614 Voltage reference generator 1 DL 2616 Two pulse control unit 1 DL 2617 Six pulse control unit 1 DL 2626 Mains transformer 1 DL 2628 Super-fast fuses 1 DL 2635 Universal load

1 DL 2643 Socket with shunts 1 1 DL 2109T3PV Moving-iron voltmeter (125-250-500 V) 1 DL 2109T26 Power meter 2 DL 2109T33 True rms meter 1 Storage oscilloscope

Optional

1 DL 2642 Isolation amplifier

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2.2 SETTING UP AND CONDUCTING EXPERIMENTS

All the circuits of proposed experiments must be powered via the mains transformer.

Always use safety connecting leads.

Connect potential equalisation PE throughout.

Connect the panels which have their own mains connection lead to the power mains.

Set the measuring meters to the largest range.

For current measurements using the oscilloscope use the plug-in shunt.

Do not switch on the power mains until the circuitry has been carefully checked.

When conducting experiments choose the most suitable measuring range of the meter.

The mains voltage must be disconnected before intervening in the experiment set-up and makingany changes or additions to circuitry.

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2.3 MEASUREMENTS WITH OSCILLOSCOPE

Working with a grounded conventional oscilloscope means taking certain special features into

consideration, as illustrated in the following.

2.3.1 No mains isolation

When the circuit is operated in a directly grounded mains, conventional two-channel oscilloscope

can only be used with some difficulty and only the greatest caution.

As the measurement grounds of the two channels are identical (i.e. internally connected), there is a

danger of short-circuit via the probes, also in the case of single-channel measurements.

Example N.1 Short-circuit via probe.

If you wish to investigate the line voltages or any other voltage not measured with respect to the

neutral point, this can only be accomplished by measuring differential voltage (INVert channel 2).

Example N.2 Measuring line voltage U12 = U1N -U2N

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2.3.2 Power supply via a transformer with isolated windings

Using such a transformer greatly simplifies the measuring procedures as you can connect the

ground as is most convenient.

Example N.3 Possible measuring line voltage.

As the measuring ground of the oscilloscope

has the potential of PE line, and thus ground

potential, measuring with the oscilloscope will

ground the secondary side of the transformer.

This means that when the secondary voltages

exceed the protective extra-low voltage, there

exists a danger of contact with respect to ground.

Also using such a transformer the risk of a short-circuit via the probes still exists.

Example N.4 Short-circuit via probe ground.

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2.3.3 Current measurement

The current I flowing through a load R is measured displaying on the oscilloscope the voltage drop

across a shunt Rs.

Example N.5 Measuring current: I = URS/ RS .

2.3.4 Current and voltage measurement

Simultaneous load current and voltage across the load R can be displayed on the oscilloscope using

the circuits depicted in the Examples N.6 and N.7.

Example N.6 : Simultaneous current and voltage measurement

(Correct in terms of phase)

The U voltage measurement is distorted by the voltage

drop across the shunt RS: however, where R >> Rsthis error may be ignored.

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Example N.7 Simultaneous current and voltage measurement

(Correct in terms of amplitude)

The amplitudes of voltage U and current I are measured correctly

but the current phase is 180 inverted : by pressing the INVert

button on channel 2 of the oscilloscope you can display

the current with the correct phase.

NOTE

For measurement using two-channel oscilloscope always connect only one point of the circuit to the

frame of the oscilloscope.

2.3.5 Isolation amplifier

Where possible, connect an isolating amplifier in series to the oscilloscope in order to ensure

potential-free recording of the measured value.

2.4 SAFETY INFORMATION

Laboratory work always entails a higher risk of accidents.

The device may only be operated by persons who are in a position to recognise shock hazards and

to implement the proper safety measures.

If measurements are to be made where there is a shock hazard, IT IS NOT PERMITTED TO

WORK ALONE: a second person must be informed.

In accordance with the IEC regulations, metal parts not carrying a voltage in normal operation (e.g.

housings) are to be connected to the PE ground conductor.

The ground conductor is provided solely for this purpose and may not be connected with the neutral

conductor N of the circuit!

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EXPERIMENTS

Foreword

All the measurement results were obtained at a mains frequency of 50 Hz.Of course, they cannot be reproduced exactly, due to the tolerance of the components,

to the measuring devices, and, besides, to voltage fluctuations.

Oscillograms are referred to a Tektronix Digital Real-Time oscilloscope TDS.

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EXPERIMENT N1

TRIAC

Objectives: Recording the volt-ampere characteristic of the TRIAC Recording the influence of variable control angle on the conduction of the device Determining the threshold voltage. Testing the behaviour of the TRIAC with reversal of connections.

Equipments:

1 DL 2607 TRIAC 1 DL 2613 Dc power supply 1 DL 2614 Voltage reference generator

1 DL 2616 Two pulse control unit 1 DL 2626 Mains transformer 1 DL 2628 Super-fast fuses (3x6.3 A) 1 DL 2635 Universal load 1 DL 2643 Socket with shunts 1 1 DL 2109T2A5 Moving-iron ammeter (2.5 A) 1 DL 2109T3PV Moving-iron voltmeter (125-250-500 V) 1 Dual-channel oscilloscope (preferred storage type)

Circuit diagram

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EXPERIMENT N1: TRIAC

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Experiment procedure

Assemble the circuit according with the foregoing topographic diagram.

1) Connections

Connect the voltage reference generator DL 2614 and the control unit DL2616 to the powersupply +15V/0/-15V.

Connect the output Uo of voltage generator to input Uc of the control unit.

Connect the terminals L/N (USYN) of the control unit respectively to terminals 2V1/2V3 of the

mains transformer.

Connect in parallel with correct polarity the pulse transformers 2 and 4 and after connect the

gate/terminal MT1 circuit of the TRIAC: socket marked with a dot to the gate (gate trigger mode

I+/III+).

2) Basic settings

2.1) Voltage reference generator DL 2614

EXT/INT switch on INT position.

(0/+10V)/(0/10V) switch on (0/+10V) position.Setpoint potentiometer to approx. 5 V.

2.2) Control unit DL 2616.

Control angle o switch on 0 position.Pulse shape switch on single pulse position.

Inhibit voltage UINH = 15 V (open).

3) Oscilloscope setting

DC coupling; XY mode.

Channel 1 (X axis): 20 V/div; probe x10.

The TRIAC voltage is applied to the X-deflecting plates (UT = UCH1).

Channel 2 (Y axis): 500 mV/div; probe x1.

The voltage applied to the Y-deflecting plates is proportional to the TRIAC current and is tapped

at shunt Rs = 1 (IT = UCH2/Rs; 0.5 A/div).

Note

When the oscilloscope makes it possible, invert channel 2 in order to display the characteristicin the usual manner, otherwise the current axis results downward orientated.

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4) Complete characteristic

Set the spot in the centre of the oscilloscope screen.

Supply the circuit and record the complete characteristic of the TRIAC.

The oscillogram reflects the dynamic characteristic I = f(U) of the TRIAC.

In the first and third quadrants the TRIAC behaves like an SCR in the first quadrant and thus

operates in the same way as two SCRs connected in antiparallel (back-to-back).

5) Variable control angle.

The gate controlled turn-on time (control angle ) can be varied altering the control voltage Uc

on the setting point potentiometer Uo.

5.1) Control voltage Uo = Uc = 10 V ( = 0).

The TRIAC is turned on and only short sections of the blocking characteristic is recorded.

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5.2) Control voltage Uo = Uc = 0 V ( = 180)

The TRIAC cannot be fired and the oscillogram only includes the blocking characteristic.

6) Forward characteristic

In order to determine the threshold voltage set the following deflection factors

channel 1: 500 mV/div; probe x10;

channel 2: 200 mV/div; probe x1.

Considering the inclined piecewise linear approximation for the TRIAC characteristic it is

possible to determine the threshold voltage

UT(TO) 0.8 V

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7) Reversal connections (Uc = 5 V)

7.1) Reversing gate/terminal MT1 connections

There is no change in the TRIAC characteristic (gate trigger mode (I-/III-).

7.2) Reversing the polarity of synchronising voltage.There is no change in the TRIAC characteristic (gate trigger mode (I-/III-).

7.3) Reversing MT1/MT2 connections.

There is no change in the TRIAC characteristic (gate trigger mode (I+/III-).

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EXPERIMENT N2A

SINGLE-PHASE AC CONTROLLER W1C, OHMIC LOAD

Objectives: Recording voltage and current time profiles Voltage and current measurements Determination of various characteristic data

Equipments:

1 DL 2605 SCR stack 1 DL 2613 Dc power supply 1 DL 2614 Voltage reference generator 1 DL 2616 Two pulse control unit

1 DL 2626 Mains transformer 1 DL 2628 Super-fast fuses (3x6.3 A) 1 DL 2635 Universal load 1 DL 2643 Socket with shunts 1 2 DL 2109T33 True rms meter 1 Dual-channel oscilloscope (preferred storage type)

Circuit diagram

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EXPERIMENT N2A: CONTROLLER W1C, OHMIC LOAD

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Assemble the circuit according with the foregoing topographic diagram, disregarding details (a) and

(b) at first.

1) ConnectionsConnect the voltage reference generator DL 2614 and the control unit DL2616 to the power

supply +15V/0/-15V.



mains transformer.

Connect the pulse transformers 1 and 3 to gate/cathode circuit of the SCRs V 1 and V3respectively: socket marked with a dot to the gate.

2) Basic settings

2.1) Voltage reference generator DL 2614EXT/INT switch on INT position.

(0/+10V)/(0/10V) switch on (0/+10V) position.Setpoint potentiometer to 10 V.




3) Voltage and current measurements

Supply the circuit and measure:

3.1) the rms value Uv of the supply voltage by the voltmeter P1;

3.2) the average value IT3AV and the rms value IT3RMS of the SCR V3 current by the ammeter P2.

3.3) the rms value URMS of the load voltage by the voltmeter P3;

3.4) the rms value IRMS of the load current by the ammeter P4.

Enter the measured value as a function of the gate angle in 30 steps between 0 and180in the following table.

HINT

In order to set the gate angle, set only a half-wave of the direct voltage with the width of 9 (or 6)

grid divisions on the oscilloscope: each division then corresponds to an angle of 20 (or 30).

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4) Recording on the oscilloscope

Note

Since the basic instrument set does not normally allow simultaneous measurements, the

measures may have to be carried out successively.

4.1) Recording the load U voltage and I current.

Oscilloscope setting

DC coupling; Yt mode. Trigger: AC Line.

Channel 1 (voltage U): 50 V/div; probe x10.

Channel 2 (current I proportional to voltage at shunt RS2 =1 ): 1 V/div; probe x1.

Oscillogram ( = 90)

The load current is alternately made up of the two SCR currents.

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4.2) Recording the SCR V3 voltage UV3 and current IT3.

Oscilloscope setting.

Assemble the measuring circuit according with detail (a).

Channel 1 (UV3 voltage): 50 V/div ; probe x10.

Channel 2 (current IT3 proportional to voltage at shunt RS3 = 1 ): 1 V/div; probe x1.

Oscillogram ( = 90)

The SCR V3 controls the positive half-wave.During the SCR blocking phase the voltage in the two antiparallel SCRs is identical to the

supply voltage.

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Assemble the measuring circuit according with detail (b).

Channel 1 (UV1 voltage): 50 V/div; probe x10.


Oscillogram ( = 90)

The SCR V1 controls the negative half-wave.During the SCR blocking phase the voltage in the two antiparallel SCRs is identical to the

supply voltage.

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EXPERIMENT N2B

SINGLE-PHASE AC CONTROLLER W1C, INDUCTIVE LOAD


Equipments:



Circuit diagram

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(b) at first.


supply +15V/0/-15V.



mains transformer.


2) Basic settings




Control angle o switch on 0 position.Pulse shape switch on train pulse position.









CONTROL RANGE

In the case of inductive load the current generally lags 90 behind the voltage and for this reason

the controller can only be controlled between 90 and 180.

Increase the control voltage Uc until the oscilloscope shows the load voltage U and current I in a

sinusoidal continuous form; at this point slowly decrease the control voltage U c until the

oscilloscope shows the full drive of both SCRs at the gate angle corresponding to the load phase

angle that, on account of the dissipative choke, results less than 90.

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Approximately the load phase angle results = 85.

HINT



Another system is the use of phase shift0 in the control unit:

1) Set0 = 0 and adjust Uc in order to obtain the firing angle = 90 pointed out on the

oscilloscope and carry out the measurements.2) Set now 0 = 30 in order to obtain the firing angle = 120 and, for example, note down the

IRMS120 value.

3) Set again 0 = 0 and adjust Uc in order to obtain IRMS120 and now set again 0 = 30 in

order to obtain the firing angle = 150 and so on..

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() 90 120 150 180Uv (V) 47 47 48 48 48

UdRMS (V) 48 47 32 14 4.3

IdRMS (A) 2.84 2.72 1.35 0.35 0

IT3AV (A) 1.25 1.18 0.53 0.15 0

IT3RMS (A) 0.89 0.6 0.34 0.096 0

Evaluate the various characteristic data of the controller and compare these with the theoretical

values (see 1.3.1,page 6).

() 90 120 150 180IRMS/IRMS0 1 0.957 0.475 0.123 0

Draw the transfer characteristic IRMS/IRMS = f().

The measured transfer characteristic coincides relatively well with the theoretical curve shown in

the Fig.7, page 7.

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Note

Since the basic instrument set does not normally allow simultaneous measurements , the






Channel 2 (current I proportional to voltage at shunt RS2 = 1 ): 2 V/div; probe x1.

Oscillogram ( = 120)

The load current is basically made up of the two SCR currents with sinusoidal peaks.

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Channel 2 (current IT3 proportional to voltage at shunt RS3 = 1 ): 2 V/div ; probe x1.


The SCR V3 controls the positive half-wave.

During the SCR blocking phase the voltage in the two antiparallel SCRs is identical to thesupply voltage.

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The SCR V1 controls the negative half-wave.During the SCR blocking phase the voltage in the two antiparallel SCRs is identical to the

supply voltage.

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EXPERIMENT N2C

SINGLE-PHASE AC CONTROLLER W1C, OHMIC-INDUCTIVE LOAD


Equipments:



Circuit diagram

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(b) at first.


supply +15V/0/-15V.



mains transformer.


2) Basic settings




Control angle o switch on 0 position.Pulse shape switch on train pulse position.









CONTROL RANGE

In the case of ohmic-inductive load the current lags behind the voltage of an angle =arctgL/Rand for this reason the controller can only be controlled between and 180.Increase the control voltage Uc until the oscilloscope shows the load voltage U and current I in a

sinusoidal continuous form; at this point slowly decrease the control voltage U c until the

oscilloscope shows the full drive of both SCRs at the gate angle corresponding to the load phase

angle .

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Approximately the load phase angle results = 25.

HINT




1) Set0 = 0 and Uc = 10 V to obtain the firing angle = 0 and carry out the measurements.2) Set now 0 = 30 to obtain the firing angle = 30 and, for example, note down the IRMS30

value.

3) Set again 0 = 0 and adjust Uc in order to obtain IRMS30 and now set again 0 = 30 in order

to obtain the firing angle = 60: note down IRMS60.

4) Set again 0 = 0and adjust Uc in order to obtain IRMS60 and now set again 0 = 30 in order

to obtain the firing angle = 90 and so on.

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() 30 60 90 120 150 180Uv (V) 47 46.5 47 48 48 48 48

UdRMS (V) 47 46.5 41 31 17.2 4.8 0

IdRMS (A) 1.15 1.12 0.95 0.67 0.31 0.05 0

IT3AV (A) 0.52 0.5 0.38 0.23 0.09 0.011 0

IT3RMS (A) 0.81 0.79 0.67 0.47 0.23 0.044 0



() 0 30 60 90 120 150 180IRMS/IRMS0 1 0.97 0.83 0.58 0.27 0.044 0

Draw the transfer characteristic IRMS/IRMS = f().

The measured transfer characteristic coincides relatively well with the theoretical curve shown in

the Fig.10, page 9.

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Note








Oscillogram ( = 90)

The load current is basically made up of the two SCR currents with sinusoidal peaks and

smoothing effect.

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4.2) Recording the SCR V3 voltage UV3 and current IT3 .





Oscillogram ( = 90)

The SCR V3 controls the positive half-wave.During the SCR blocking phase the voltage in the two antiparallel SCRs is identical to the

supply voltage.

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4.3) Recording the SCR V1 voltage UV1 and current IT1 .





Oscillogram ( = 90)

The SCR V1 controls the negative half-wave.

During the SCR blocking phase the voltage in the two antiparallel SCRs is identical to the

supply voltage.

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EXPERIMENT N3A

SINGLE-PHASE AC CONTROLLER W1, OHMIC LOAD


Equipments:

1 DL 2607 TRIAC 1 DL 2613 Dc power supply 1 DL 2614 Voltage reference generator 1 DL 2616 Two pulse control unit

1 DL 2626 Mains transformer 1 DL 2628 Super-fast fuses (3x6.3 A) 1 DL 2635 Universal load 1 DL 2643 Socket with shunts 1 1 DL 2109T3PV Moving iron voltmeter (125-250-500 V) 1 DL 2109T26 Power meter 1 DL 2109T33 True rms meter 1 Dual-channel oscilloscope (preferred storage type)

Circuit diagram

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Assemble the circuit according with the foregoing topographic diagram, disregarding detail (a) at

first.

1) Connections

Connect the voltage reference generator DL 2614 and the control unit DL2616 to the power

supply +15V/0/-15V.



mains transformer.

Connect in parallel with correct polarity the pulse transformers 2 and 4 and after connect the

gate/terminal MT1 circuit of the TRIAC: socket marked with a dot to the gate.

2) Basic settings










3.2) the active power P on the mains side by the wattmeter P2.


3.4) the rms value IRMS

of the load current by the ammeter P4.


HINT



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1) Set0 = 0 and Uc = 10 V to obtain the firing angle = 0 and carry out the measurements.

2) Set now 0 = 30 to obtain the firing angle = 30 and, for example, note down the IRMS30value.

3) Set again 0 = 0 and adjust Uc in order to obtain IRMS30 and now set again 0 = 30 in orderto obtain the firing angle = 60: note down IRMS60 .



Uv = 45 V

() 0 30 60 90 120 150 180UdRMS (V) 45 44.5 40 29 16.1 4.7 0

IdRMS (A) 1.28 1.25 1.1 0.86 0.5 0.15 0

P (W) 59 55 43 25 7 -- 0


values (see 1.3,page 3).

() 0 30 60 90 120 150 180IRMS/IRMS0 1 0.98 0.86 0.67 0.39 0.12 0

P/P0 1 0.93 0.73 0.42 0.12 -- 0

S (VA) 58 56.3 49.5 38.7 22.5 -- 0

PF 1 0.97 0.87 0.65 0.31 -- 0

Draw the transfer characteristics of the rms values of the load current and of the active power.

The measured transfer characteristics coincide relatively well with the theoretical curves shown

in the Fig.4(page 4) and Fig.4a (page 5).

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A comparison of the active power P and apparent power S shows that P S when the controlangle = 0 ( the current is effectively sinusoidal and in phase with the voltage) while as thecontrol angle increases the active power decreases more sharply than the apparent power.

The phase-angle control produces an inductive reactive power even in circuits with ohmic load

due to the phase shift between the fundamental component and the harmonic content of the

current.


Note

Since the basic instrument set does not normally allow simultaneous measurements , the


4.1) Recording the supply Uv and the load U voltages.



Channel 1 (voltage Uv): 50 V/div; probe x100.Channel 2 (voltage U): 50 V/div; probe x100.

Oscillogram ( = 90)

The load voltage is an alternating quantity,with positive and negative phase control.

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4.2) Recording the TRIAC V voltage UV and load current I.



Channel 1 (UV voltage): 50 V/div; probe x100.

Channel 2 (current I proportional to voltage at shunt RS = 1 ): 2 V/div; probe x1.

Oscillogram ( = 90)

During the TRIAC blocking phase the voltage in the TRIAC is identical to the supply

voltage.

The load current is an alternating quantity, with positive and negative phase control.

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EXPERIMENT N3B

SINGLE-PHASE AC CONTROLLER W1, OHMIC-INDUCTIVE LOAD


Equipments:

1 DL 2607 TRIAC 1 DL 2613 Dc power supply 1 DL 2614 Voltage reference generator 1 DL 2616 Two pulse control unit

1 DL 2626 Mains transformer 1 DL 2628 Super-fast fuses (3x6.3 A) 1 DL 2635 Universal load 1 DL 2643 Socket with shunts 1 1 DL 2109T3PV Moving iron voltmeter (125-250-500 V) 1 DL 2109T26 Power meter 1 DL 2109T33 True rms meter 1 Dual-channel oscilloscope (preferred storage type)

Circuit diagram

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1) Set0 = 30 and Uc = 10 V to obtain the firing angle = 30and, for example, note down the

IRMS30 value.

2) Set again 0 = 0 and adjust Uc in order to obtain IRMS30 and now set again 0 = 30 in order

to obtain the firing angle = 60: note down IRMS60.3) Set again 0 = 0and adjust Uc in order to obtain IRMS60 and now set again 0 = 30 in order


Uv = 45 V

() 30 60 90 120 150 180UdRMS (V) 40 34 22.3 11 1.8 0

IdRMS (A) 1.1 0.95 0.67 0.33 0.06 0

P (W) 45 31 15 3.2 -- 0

Evaluate the various characteristic data of the controller.

() 30 60 90 120 150 180IRMS/IRMS0 1 0.86 0.6 0.3 0.05 0

P/P0 1 0.69 0.33 0.07 -- 0

S (VA) 49.5 42.8 30.1 14.9 2.7 0

PF 0.9 0.73 0.5 0.2 -- 0

Draw the transfer characteristics of the rms values of the load current and of the active power.

The transfer characteristics have the same profile as determined in Experiment N.3A.

The power factor is lower than in the case of ohmic load on account of the inductive load

component.

The controller can be controlled only in the range between ==arctg R/L 30 and 180.

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Note



4.1) Recording the supply Uv and the load U voltages.



Channel 1 (voltage Uv): 50 V/div; probe x100.


Oscillogram ( = 90)

The feed voltage drops at the load impedance when the TRIAC is switched on.

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4.2) Recording the TRIAC V voltage UV and load current I.



Channel 1 (UV voltage): 50 V/div; probe x100.

Channel 2 (current I proportional to voltage at shunt RS = 1 ): 2 V/div; probe x1.

Oscillogram ( = 90)

During the TRIAC blocking phase the voltage in the TRIAC is identical to the supplyvoltage.

The load current is basically made up of smoothed sinusoidal peaks.

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EXPERIMENT N4

HALF-CONTROLLED SINGLE-PHASE CONTROLLER W1H, OHMIC LOAD


Equipments:

1 DL 2603 Diode stack 1 DL 2605 SCR stack 1 DL 2613 Dc power supply 1 DL 2614 Voltage reference generator

1 DL 2616 Two pulse control unit 1 DL 2626 Mains transformer 1 DL 2628 Super-fast fuses (3x6.3 A) 1 DL 2635 Universal load 1 DL 2643 Socket with shunts 1 2 DL 2109T33 True rms meter 1 Dual-channel oscilloscope (preferred storage type)

Circuit diagram

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(b) at first.


supply +15V/0/-15V.



mains transformer.

Connect the pulse transformer 3 to gate/cathode circuit of the SCR V3: socket marked with a dot

to the gate.

2) Basic settings










3.3) the average value UAV and the rms value URMS of the load voltage by the voltmeter P3;

3.4) the average value IAV and the rms value IRMS of the load current by the ammeter P4.


HINT



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2) Set now 0 = 30 to obtain the firing angle = 30 and, for example, note down the IRMS30value.

3) Set again 0 = 0 and adjust Uc in order to obtain IRMS30 and now set again 0 = 30 in orderto obtain the firing angle = 60: note down IRMS60.



() 0 30 60 90 120 150 180Uv (V) 45 46 46 46 46 47 47

UAV (V) 0 1.9 7.7 11.8 17 20 20.5

URMS (V) 45 45 41 38 34 33 32

IAV (A) 0 0.052 0.23 0.35 0.48 0.58 0.6

IRMS (A) 1.3 1.28 1.12 0.85 0.49 0.13 0.04

IT3AV (A) 0.57 0.52 0.35 0.24 0.11 0.02 0

IT3RMS (A) 0.88 0.86 0.72 0.58 0.33 0.1 0


values (see 1.4,page 10).

() 0 30 60 90 120 150 180IRMS/IRMS0 1 0.99 0.94 0.86 0.76 0.74 0.73

Draw the transfer characteristic IRMS/IRMS0 = f().

The measured transfer characteristic coincides relatively well with the theoretical values.

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Note






Channel 1 (voltage U ): 50 V/div; probe x10.


Oscillogram ( = 60)

The load voltage and current are not alternating quantities but each contains a direct

component.

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Oscillogram ( = 60)

The SCR V3 controls the positive half-wave.

4.3) Recording the diode V1 voltage UV1 and current IF1.

Oscilloscope setting.Assemble the measuring circuit according with detail (b).



Oscillogram ( = 60)

The diode conducts throughout the entire negative half-cycle.

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EXPERIMENT N5

FULLY-CONTROLLED THREE-PHASE CONTROLLER W3C, STAR OHMIC LOAD

WITHOUT NEUTRAL


Equipments:

1 DL 2605 SCR stack 1 DL 2613 Dc power supply 1 DL 2614 Voltage reference generator 1 DL 2617 Six pulse control unit

1 DL 2626 Mains transformer 1 DL 2628 Super-fast fuses (3x6.3 A) 1 DL 2635 Universal load 1 DL 2109T3PV Moving-iron voltmeter (125-250-500 V) 2 DL 2109T33 True rms meter 1 Dual-channel oscilloscope (preferred storage type)

Circuit diagram

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first.

1) Connections

Connect the voltage reference generator DL 2614 and the control unit DL 2617 to the power

supply +15V/0/-15V.


Connect the terminals L1/L2/L3/N (USYN) of the control unit respectively to terminals

2U1/2V1/2W1/2U3 of the mains transformer.

Connect the pulse transformers 1,2,3,4,5 and 6 to gate/cathode circuit of the SCRs V1, V2 V3, V4,V5 and V6: socket marked with a dot to the gate.

2) Basic settings





Analog control switch on position.Control angle o switch on 0 position.Pulse shape switch on single pulse position.

Select MAIN+SEC PULSE.




3.1) the rms value Uv10 of the supply voltage by the voltmeter P1;

3.2) the rms value I1RMS of the line current by the ammeter P2;

3.3) the rms value U12RMS of the load line voltage by the voltmeter P3;

3.4) the rms value U3RMS of the load phase voltage by the voltmeter P4.


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HINT

In order to set the gate angle it is possible the use of phase shift0 in the control unit:


2) Set0 = 30 to obtain the firing angle = 30.

3) Set now 0 = 60 to obtain the firing angle = 60 and, for example, note down the I1RMS60

value.4) Set again 0 =0 and adjust Uc in order to obtain I1RMS60 and now set again 0 =30 in order

to obtain the firing angle = 90.

5) Set now 0 =60 to obtain the firing angle = 120 and, for example, note down the I1RMS120value.

6) Set again 0 = 0and adjust Uc in order to obtain I1RMS120 and now set again 0 = 30 in

order to obtain the firing angle = 150 and so on.

Uv10 = 46 V

() 0 30 60 90 120 150

U3RMS (V) 46 45 37 23 7.4 0 U12RMS

(V)

81 79 64 41 12 0

I1RMS (A) 0.47 0.46 0.38 0.24 0.022 0

Evaluate the various characteristic data of the converter and compare these with the theoretical


() 0 30 60 90 120 150IRMS/IRMS0 1 0.978 0.8 0.53 0.21 0

Draw the transfer characteristic I1RMS/I1RMS0 = f().

The measured transfer characteristic coincides relatively well with the theoretical curve.

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Note



4.1) Recording the load phase voltages U1 and U2.



Channel 1(U1 voltage): 50 V/div, probe x10.


Oscillogram ( = 30)

Oscillogram ( = 60)

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4.2) Recording the load line voltage U12 and the voltage UV3 at SCR V3Oscilloscope setting.


Channel 1 (U12 voltage): 50 V/div ; probe x10.


Oscillogram ( = 30)

Oscillogram ( = 60)

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EXPERIMENT N6

HALF-CONTROLLED THREE-PHASE CONTROLLER W3H, STAR OHMIC LOAD

WITHOUT NEUTRAL

Objectives:

Recording voltage and current time profiles Voltage and current measurements Determination of various characteristic data

Equipments:

1 DL 2603 Diode stack 1 DL 2605 SCR stack 1 DL 2613 Dc power supply

1 DL 2614 Voltage reference generator 1 DL 2617 Six pulse control unit 1 DL 2626 Mains transformer 1 DL 2628 Super-fast fuses (3x6.3 A) 1 DL 2635 Universal load 1 DL 2109T2A5 Moving iron ammeter (2.5 A) 1 DL 2109T3PV Moving-iron voltmeter (125-250-500 V) 2 DL 2109T33 True rms meter 1 Dual-channel oscilloscope (preferred storage type)

Circuit diagram

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first.

1) ConnectionsConnect the voltage reference generator DL 2614 and the control unit DL 2617 to the power

supply +15V/0/-15V.




Connect the pulse transformers 1,3 and 5 to gate/cathode circuit of the SCRs V 1, V3, and V5:

socket marked with a dot to the gate.

2) Basic settings





Select MAIN PULSE.





3.2) the rms value I1RMS of the line current by the ammeter P2;

3.3) the rms value U12RMS of the load line voltage by the voltmeter P3;

3.4) the rms value U3RMS of the load phase voltage by the voltmeter P4.


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HINT





value.4) Set again 0 = 0 and adjust Uc in order to obtain I1RMS60 and now set again 0 = 30 in

order to obtain the firing angle = 90.

5) Set now 0 = 60 to obtain the firing angle = 120 and, for example, note down the I1RMS120value.



Uv10 = 47 V

() 0 30 60 90 120 150 180

U3RMS (V) 47 46 42 36 26 15.5 4 U12RMS

(V)

82 81 74 63 47 27 7.2

I1RMS (A) 0.48 0.47 0.43 0.37 0.27 0.16 0.043



() 0 30 60 90 120 150 180IRMS/IRMS0 1 0.98 0.89 0.77 0.56 0.33 0.09

Draw the transfer characteristic I1RMS/I1RMS0 = f().


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Note








Oscillogram ( = 30)

Oscillogram ( = 60)

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Channel 1 (U12 voltage): 50 V/div; probe x10.


Oscillogram ( = 30)

Oscillogram ( = 60)

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EXPERIMENT N7

THREE-PHASE CONTROLLER W3C2,STAR OHMIC LOAD WITHOUT NEUTRAL


Equipments:

1 DL 2605 SCR stack 1 DL 2613 Dc power supply 1 DL 2614 Voltage reference generator 1 DL 2617 Six pulse control unit

1 DL 2626 Mains transformer 1 DL 2628 Super-fast fuses (3x6.3 A) 1 DL 2635 Universal load 1 DL 2109T3PV Moving-iron voltmeter (125-250-500 V) 2 DL 2109T33 True rms meter 1 Dual-channel oscilloscope (preferred storage type)

Circuit diagram

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EXPERIMENT N7: CONTROLLER W3C2, OHMIC LOAD

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first.

1) ConnectionsConnect the voltage reference generator DL 2614 and the control unit DL 2617 to the power

supply +15V/0/-15V.




Connect the pulse transformers 1,2,5 and 6 to gate/cathode circuit of the SCRs V1, V2, V5 and

V6: socket marked with a dot to the gate.

2) Basic settings





Select MAIN PULSE.





3.2) the rms value I1RMS of the line 1 current by the ammeter P2;

3.3) the rms value U1RMS of the R1 load phase voltage by the voltmeter P3;

3.4) the rms value I2RMS of the line 2 current by the ammeter P4;

3.5) the rms value U2RMS of the R2 load phase voltage by the voltmeter P5.


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HINT


1) Set0 =0 and Uc = 10 V to obtain the firing angle = 0 and carry out the measurements.



value.4) Set again 0 = 0 and adjust Uc in order to obtain I1RMS60 and now set again 0 =30 in order

to obtain the firing angle = 90.

5) Set now 0 = 60 to obtain the firing angle = 120 and, for example, note down the I1RMS120value.



Uv10 = 47 V

() 0 30 60 90 120 150

U1RMS (V) 48 44.5 32 17 4.7 0.6 U2RMS (V) 48 47.5 45 40 27 16.5

I1RMS (A) 0.48 0.45 0.33 0.18 0.049 0.001

I2RMS (A) 0.48 0.47 0.44 0.4 0.275 0.17



() 0 30 60 90 120 150IRMS/IRMS0 1 0.94 0.96 0.38 0.1 0

I2RMS/I2RMS0 1 0.98 0.92 0.83 0.57 0.35

Draw the transfer characteristic IRMS/IRMS0 = f() of the line currents.


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Note








Oscillogram ( = 30)

Oscillogram ( = 60)

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Channel 1 (U23 voltage): 50 V/div; probe x10.


Oscillogram ( = 30)

Oscillogram ( = 60)

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