Laboratory works in POWER ELECTRONICS

Department of Electrical Drives and Power Electronics

Laboratory works in POWER ELECTRONICS

Valery Vodovozov, Zoja Raud and Tanel Jalakas http://learnelectronics.narod.ru/

Tallinn 2010

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Contents Introduction ................................................................................................................. 4

Safety warnings and experimentation rules ............................................................ 4 Laboratory works guidance ......................................................................................... 6

Part I. Diode rectifiers .............................................................................................. 6 Laboratory targets ............................................................................................... 6 Preparing to the lesson ....................................................................................... 6 Experimentation .................................................................................................. 7 Report contents ................................................................................................... 7 Following discussion ........................................................................................... 8

Part II. Thyristor rectifiers ........................................................................................ 9 Laboratory targets ............................................................................................... 9 Preparing to the lesson ....................................................................................... 9 Experimentation ................................................................................................ 10 Report contents ................................................................................................. 11 Following discussion ......................................................................................... 11

Part III. Transistor dc/dc converters ...................................................................... 13 Laboratory targets ............................................................................................. 13 Preparing to the lesson ..................................................................................... 13 Experimentation ................................................................................................ 13 Report contents ................................................................................................. 15 Following discussion ......................................................................................... 15

Bibliography .............................................................................................................. 17 Annexes .................................................................................................................... 18

1. Stand “Diode rectifiers” ..................................................................................... 18 2. Stand “Line-commutated converters” ................................................................ 23 3. Stand “Self-commutated converters” ................................................................ 25

Introduction

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Introduction This is a tutorial aid to implement laboratory works in power electronics. The students are expected to have acquired knowledge of electronic components, standard electrical wiring, and electrical schematic symbols. The manual complies with the curriculum and the syllabus of the course AAV0020 Power Electronics.

Safety warnings and experimentation rules 1. Remember always that the stand is dangerous equipment. Never apply

the mains power if it may cause a danger or an injury. In the case of an accident, the sufferer must be released from the voltage, using the nearest safety switch. Thereafter the rescue service must be called (numbers 112 and 0112) and the first aid provided.

2. The stands are realized as the switchboards with the power sources and measuring devices. The power sources are supplied with 400 V voltages from the three-phase network. Their switching makes live circuits composed for the laboratory work.

3. Never switch on the mains without the instructor’s permission. In the case of overheating, smelling, the sparkles or electric arc between contacts, switch off the power source immediately. Additionally, the red safety push-button is located on the front panel of the main laboratory switchboard. In the case of an emergency, press this button to switch off all stands. After avoiding an emergency, pull out the emergency push-button to restore the supply.

4. To assemble the circuits, devices and boards are equipped with sockets and wires. The cord set of special safety wires of different length and colour belongs to the outfit of the stands.

5. When assembling the circuits, enable free access to the feeder board, stand, emergency switches, and test devices, which are adjusted during the experimentation. All equipment and appliances should be well visible and their displacement or pulling down from the table should be avoided. Connect no more than two conductors to one terminal or socket.

6. To avoid electric shock, never open the covers and do not touch with cables and wires while the mains power is applied. To change the circuit, switch off the mains power. Do not control the circuits by the device disconnecting; instead, use the panel keys and feeder board buttons.

7. Before energizing the stand, make sure that all devices and measuring instruments are suitable for operation throughout the voltage and current ranges provided by this manual. Do not run the circuits over the rated voltages and currents and do not allow their long-term overloading.

8. It is prohibited to lean and sit, to hang clothes, to place bags, cases etc. on the stands, to leave and to enter the laboratory without the instructor’s permission, to eat, drink and smoke in the laboratory, to touch the devices not needed for the given work, and to implement the experiments alone.

Introduction

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9. Submit the protocols and other results to the instructor at the end of the laboratory work. After instructor’s permission, take off the circuits, switch off and return the measuring devices and equipment onto their places, and leave the workplace in order.

10. Every student should implement the mandatory part of the works and may implement the optional part given in small print. He/she must prepare and defend the personal report having the title sheet and required contents. Compliance of the results with the theoretical aspects and standards is examined and expediency of the used methods and devices are to be evaluated in the conclusions. Special attention should be paid to the differences of the experimental and theoretical results, experiment errors, mistaken measurement readings, and their reasons.

Diode rectifiers

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Laboratory works guidance

Part I. Diode rectifiers Learning uncontrolled ac/dc converters using the TTÜ stand

“Diode rectifiers”

Laboratory targets 1. Acquainting with the rectified effect of the diode ac/dc converters by

implementation the following works: DM1 – Single-phase half-wave diode rectifier M1 DM2 – Single-phase midpoint diode rectifier M2 DB2 – Single-phase bridge diode rectifier B2 DM3 – Three-phase midpoint diode rectifier M3 DB6 – Three-phase bridge diode rectifier B6

2. Study the power electronic circuits that feed resistive and inductive loads using the listed above rectifiers.

3. Recognizing the smoothing effects of the inductive load and filters.

Preparing to the lesson 1. Learn about the stand “Diode rectifiers” from Annex 1 in this manual. Find

the supply input and outputs using the stand diagrams. 2. Develop the circuit diagram of the desired rectifier outlined by the dotted

lines in Fig. A1.3, a, b. The rectifier ought to feed the resistive and inductive loads (Fig. A1.3, c) without filtering and with different filters (Fig. A1.3, d). Provide the circuit link-up with:

• dc voltmeter PV1 to measure the load dc voltage Ud • ac voltmeter PV2 to measure the load ac rms voltage Ua • dc ammeter PA to measure the load dc current Id • oscilloscope to view the load voltage waveforms Ud(t)

3. Calculate expected rectified voltage Ud(0), peak-to-peak ripple voltage Ur(0), and ac rms voltage Ua in the idle mode of operation (Id = 0) and permissible load current Id max as follows:

( )U

sd k

UU =0 , rdr KUU ⋅= (0)2 (0) , 22

(0) (0) ra

UU = , I

sd k

II max max =

where Us is the rms supply voltage, Is max − permissible supply current, assuming the following voltage, ripple, and current factors:

Rectifier KU Kr KI M1 2,22 1,57 1,57 M2 1,11 0,78 0,71 B2 1,11 0,78 1,00 M3 0,85 0,25 0,58 B6 0,42 0,06 0,82

Diode rectifiers

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4. Build expected voltage Ud(t) and current Id(t) waveforms and an expected load curve Ud(Id) for resistive load within the current swing between zero and the maximum permissible value.

Experimentation 1. Select the measuring devices and set the measuring ranges 5 A, 200 V

and sockets ±5 A, ±250 V for wiring. Choose a load rheostat, an inductor, and/or a capacitor in accordance with the permissible load current. Set the maximum resistance of the rheostat.

2. Assemble the desired rectifier using the positive and negative switchboard sockets as outputs. Connect the rectifier inputs to the required transformer. Connect the rectifier outputs to the load rheostat via the ammeter. Link up the circuit with the parallel-connected voltmeters and oscilloscope.

3. Self-examine the assembled circuit and ask the instructor to check it. Power on the assembled circuit and ensure it operates properly. If the fault occurs in any instant, power off the circuit immediately, examine it and eliminate errors.

4. Along with the smooth decreasing of the rheostat resistance, measure the load current Id and voltages Ud, Ua, fill the measured values in the protocol, and build the load diagrams Ud(Id) and Ua(Id).

5. Estimate the waveform Ud(t) at the load currents Id given by instructor. Determine the peak-to-peak voltage ripple Ur by the oscilloscope and calculate the actual ripple factor at the given load current.

6. Restore the maximum resistance of the rheostat and power off the stand. 7. Repeat the above given items 3 to 6 at the inductive load.

8. Add a filter between the rectifier and the resistive load and repeat the items 3 to 6.

9. Following the instructor’s permission, take off the circuits and introduce proper order in the workplace.

Report contents 1. Circuit diagram of the studying circuits given by an instructor, with

specification of the supply and load components. 2. Calculation of the idle voltage, ripple factors, and permissible current. 3. Table of the observed data Id, Ud, Ua, and the measured values Ur and Kr. 4. Scaled diagrams of the experimental load curves Ud(Id), Ua(Id) for resistive

and inductive loads, with/without filters. 5. Scaled diagrams of the expected current waveform Id(t) and the

experimental trace Ud(t), obtained at given current Id for resistive and inductive loads, with/without filters.

6. Conclusions regarding estimation, comparison and explanation of the expected and obtained results.

7. Signed protocol.

Diode rectifiers

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Following discussion Basing on the experiments, confirm and explain the following phenomena and propositions: 1. The load curves of a rectifier depend on the load type. 2. The load curves of a rectifier depend on the filter type. 3. The load voltage and current depend on the load inductance. 4. The shape of the load voltage and current depend on the filter parameters. 5. The rectified voltages on the resistive load differ from those on the

inductive load. 6. The rms voltages on the resistive load differ from those on the inductive

load. 7. Along with the load increasing, the rms voltage of the inductive load grows. 8. An engineer may find the diode, rheostat, capacitor and inductor ratings

from different sources. 9. The current consumed by a rectifier depends on the rectifier type and

diode ratings. 10. The peak inverse voltage of a diode depends on the rectifier type and

supply voltage. 11. The forward current of the diodes depends on the rectifier type and supply

voltage. 12. The actual ripple factor differs from that calculated before experimentation. 13. Application areas of a rectifier depend on the rectifier type. 14. Using the diode ratings available from its data sheet, a diode output curve

may be built. 15. An active resistance of any electric circuit may be found using the load

curves and taking into account the diode output curve. 16. An active resistance of an inductor may be found using the load curves. 17. The circuit inductance, capacitance, and total resistance define the time

constants of a circuit. 18. The load resistance and inductance define a mathematical model of a

circuit. 19. The load resistance and filter parameters define a mathematical model of

a circuit. 20. With a given load current and time constants calculated, the minimum

frequency may be found to provide the continuous current mode. 21. With a given load current, an active power, apparent power, and a power

factor of the circuit may be found.

Thyristor rectifiers

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Part II. Thyristor rectifiers Control ac/dc converters using the Lucas-Nülle stand

“Line-commutated converters”

Laboratory targets 1. Acquainting with the control principles of the thyristor converters by

implementation the following works: SM1 – Single-phase half-wave controlled rectifier M1 SB2 – Single-phase bridge controlled rectifier B2 SB6 – Three-phase bridge controlled rectifier B6

2. Study the power electronic circuits that feed resistive and inductive loads from the controlled rectifiers.

3. Recognizing the control characteristics of the converters with resistive and inductive loads.

Preparing to the lesson 1. Learn about the stand “Line-commutated converters” from Annex 2 in this

manual. On the panel of the stand (Fig. A2, a), find the supply inputs and outputs, the power converter unit, the load, and the control units.

2. Develop the circuit diagram of the desired power converter outlined by the dotted lines in Fig. A2, b, c. The converter ought to feed the resistive R and inductive RL loads (Fig. A2, d, e). Provide the circuit link-up with:

• multimeter PS to measure the supply voltage Us, current Is, and power components − active P, reactive Q, and apparent S

• dc voltmeter PV to measure the load voltage Ud • oscilloscope or computer to plot the waveforms of the load voltage

Ud(t) and current Id(t) 3. Recognise the desired supply voltage Us and calculate expected values

Ud(0), Pd(0), P(0), S(0), Is(0), and Q(0) of an uncontrolled rectifier, using the formulae:

( )U

sd k

UU =0 – rectified voltage

( ) ( )R

UP dd

002

= – power consumed by the load R

( )RK

UPs

s2

0 = – active power

( ) ( )( )0φ

00cos

PS d= – apparent power

( ) ( )s

s USI 00 = – supply current


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( ) ( ) ( )0φ sin00 ⋅= SQ – reactive power

assuming the following voltage, circuit, and power factors:

Converter KU Ks cos φ(0)M1 2,22 2 0,29 M2 1,11 1 0,64 B2 1,11 1 0,90 M3 0,85 1 0,64 B6 0,42 1 0,95

4. Build expected voltage and current waveforms Ud(t), Id(t) at the given firing angle α and an expected control curve Ud(α) for resistive load within the firing angle swing between zero and the maximum permissible value.

Experimentation 1. Select the required overlay mask and place it above the Power converter

unit. Ensure that the Universal control unit and the Differential amplifiers A and D are connected correctly.

2. Assemble the desired power converter, link it with the Isolating transformer, the measuring devices, and the Load R = 270 Ω. Following the instructor’s directions, connect one of the registration devices to the Differential amplifiers panel:

• oscilloscope to provide manual examination, or • computer to provide computer control using PHACON software

Select the required type of control by setting the knob of the Universal control unit to one of the following modes:

• RS 232 to control the rectifier from the PHACON computer program • Mode 1 Phase control for the manual control of the single-phase

rectifier with an oscilloscope • Mode 3 Phase control for the manual control of the three-phase

rectifier with an oscilloscope 3. Following the self-examination and checking the assembled circuit by the

instructor, power on the stand. 4. Switch on the DC power supply and the Multimeter. 5. Switch on the Isolating transformer. If the fault occurs in any instant, power

off it immediately, examine the circuit and eliminate errors. 6. Run the Universal control unit and ensure the circuit operates properly

using the required type of control: • to provide computer operation, run PHACON, select the required

Mode from the Settings menu and the displaying signals and scales from the Chart menu, then click the Start button, and adjust the firing angle

• to control manually, turn the Set-point potentiometer of the Universal control unit and estimate visually the waveforms Ud(t) and Id(t) by the oscilloscope


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7. Measure the actual rms supply voltage Us. 8. Using the Multimeter, define the rms supply current Is and the power

components − active P, reactive Q, and apparent S. 9. Along with the smooth changing of the firing angle α, measure the

mentioned supply values and the rectified voltage Ud, fill them in the protocol, and build the matched control and power characteristics Ud(α), P(α), Q(α) and S(α).

10. Use the computer or an oscilloscope to estimate waveforms Ud(t) and Id(t) at the given firing angles α, count their peak-to-peak values, and plot the scaled voltage and current waveforms.

11. Stop the Universal control unit and switch off the Isolating transformer. 12. Repeat the above given items 5 to 11 for the inductive load 270 Ω + 0,3 H.

13. Switch off the DC power supply and the Multimeter. After instructor permission, power off the stand, take off the circuits, and introduce proper order in the workplace.


specification of the supply and load components. 2. Calculation of Ud(0), Pd(0), P(0), S(0), Is(0), and Q(0) values for an

uncontrolled rectifier. 3. Table of the observed data − α, Ud, Is, P, Q and S. 4. Scaled diagrams of the experimental control and power characteristics

Ud(α), P(α), Q(α), and S(α) for resistive and inductive loads. 5. Scaled diagrams of the matched voltage and current waveforms Ud(t), Id(t)

obtained at given firing angle α for resistive and inductive loads. 6. Conclusions regarding estimation, comparison and explanation of the

expected and obtained results. 7. Signed protocol.

Following discussion Basing on the experiments, confirm and explain the following phenomena and propositions: 1. Load inductance affects the current conducting interval. 2. Inductance of the load causes the negative voltage transients. 3. Multi-quadrant operation mode is processed upon the negative dc

voltages. 4. Average value of the rectified voltage depends on the circuit type and the

number of phases. 5. Load inductance and resistance define the time constants of a circuit. 6. Load resistance and inductance define the circuit transients.


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7. Rectified voltage falls non-linearly along with the firing angle growing. 8. With an inductive load, rectified voltage drops as compared to the resistive

load. 9. With an inductive load, controllability of the thyristor rectifier may be

limited. 10. With an infinitely large load inductance, voltage response and control

characteristic change significantly. 11. Active power consumption changes along with the growing of the firing

angle. 12. Reactive power depends on the firing angle. 13. Load current may be interruptible or continuous depending of the circuit

parameters. 14. With an inductive load, rectified current has no longer a sinusoidal

waveform. 15. Consumed active power of the bridge circuit is higher than that of the half-

wave rectifier. 16. Inductive load causes excessive overvoltages. 17. Some methods protect thyristors against overvoltages with an inductive

load. 18. Power vector diagrams depend on the firing angle. 19. With an inductive load, a phase shift occurs between the supply voltage

and the fundamental of the supply current. 20. For the given firing angle, expected Ud(t) and Id(t) waveforms may be

plotted without an oscilloscope. 21. At some circumstances, a rectifier may be considered as a voltage source

converter.

Transistor dc/dc converters

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Part III. Transistor dc/dc converters Learning IGBT converters using the Lucas-Nülle stand

“Self-commutated converters”

Laboratory targets 1. Acquainting with control principles of the IGBT converters by

implementation the following works: TM1 – Single-quadrant dc/dc converter M1 TB2 – Multi-quadrant dc/dc converter B2

2. Study power electronic circuits feeding resistive and inductive loads from the IGBT converters.

3. Recognizing the control characteristics of the IGBT converters.

Preparing to the lesson 1. Learn about the stand “Self-commutated converters” from Annex 3 in this

manual. Using the panel diagram of the stand (Fig. A3, a), find the supply inputs and outputs of the studying system.

2. Develop the circuit diagram of the desired power converter given in Fig. A3, b, by the dotted lines and supplied from the isolating transformer (Fig. A3, c) to feed the resistive and inductive loads (Fig. A3, d, e). Provide the devices link-up with:

• Multimeter PS to measure the actual load voltage Ud, current Id and power Pd

• dc voltmeter PV to measure the actual supply voltage Us • oscilloscope or computer to plot the waveforms of the load voltage

Ud(t) and current Id(t) 3. Recognize the expected supply voltage Us accessible from the B6 rectifier

of the Isolating transformer panel. For the duty cycles q given by an instructor, calculate expected average values:

• load voltage Ud = qUs for the single-quadrant operation, or Ud = Us(2q − 1) for the multi-quadrant operation

• load current RUI d

d =

• dc power Pd = UdId

• ac power ( )qqR

UP ss −= 1

2

• active power P = Pd + Ps

• peak-to-peak current ripple ( )qtL

UkI ons

r −= 1 at the switching

frequencies 112 and 1800 Hz and load inductances 0,3 and 1,2 H (k = 0,5 for the single- and 1 for the multi-quadrant operation)

4. Build an expected control characteristic Ud(q) within the duty cycle swing 0…1 and voltage and current waveforms Ud(t), Id(t) at the given duty cycle for resistive load, low and high frequencies 112 and 1800 Hz.


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Experimentation 1. Select the required overlay mask, place it above the Power converter unit,

and assemble the desired power converter. 2. Ensure that the Universal control unit and the Differential amplifiers A and

D are connected correctly. 3. Assemble the isolating transformer, connect the power converter to the

rectifier of the Isolating transformer panel, and link it to the Load RΣ = 810 Ω. Connect the required measuring devices. Set the jumper R3 = 8,0 Ω of the Power converter unit and, in the case of B2 converter, set also the jumper Release V1…V4.

4. Following the instructor’s directions, connect one of the registration devices to Differential amplifiers:

• oscilloscope to provide manual examination, or • computer to provide computer control using the PWM software

Select the required type of control by setting the knob of the Universal control unit to one of the following modes:

• RS 232 to provide the control from the PWM computer program • PWM control LF for the manual control at low frequency of 112 Hz

with an oscilloscope • PWM control HF for the manual control at high frequency of 1800 Hz

with an oscilloscope 5. Following the self-examination and checking the assembled circuit by the

instructor, power on the stand. 6. Switch on the DC power supply and the Multimeter. 7. Switch on the Isolating transformer. If the fault occurs in any instant, power

off it immediately, examine the circuit and eliminate errors. 8. Run the Universal control unit and ensure the circuit operates properly

using the required type of control: • to control by computer, run PWM program, select the required

frequency from the Settings/Settings menu, then click the Start/Stop button, set the scales from the Chart/Properties menu, and adjust the duty cycle

• to control manually, turn the set-point potentiometer of the Universal control unit and estimate visually the waveforms Ud(t) and Id(t) by the oscilloscope

9. Measure the actual supply dc voltage Us 10. Use the computer or an oscilloscope to estimate waveforms Ud(t) and Id(t)

at the given duty cycles and count their peak-to-peak values. Then, plot the scaled on-screen voltage and current waveforms.


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11. Smoothly changing duty cycles, measure the load voltage Ud, current Id and power Pd, fill them in the protocol, and build the control and power characteristics Ud(q), Id(q) and Pd(q).

12. Stop the Universal control unit and switch off the Isolating transformer of the stand.

13. Repeat the above given items 5 to 12 at high modulation frequency of 1800 Hz.

14. Repeat the above given items 7 to 13 for the inductive load 810 Ω + 0,3 H.

15. Repeat the above given items 7 to 13 for the inductive load 810 Ω + 1,2 H.

16. Switch off the DC power supply and the Multimeter. After instructor’s permission, power off the stand, take off the circuits, and introduce proper order in the workplace.


specification of the supply and load components. 2. Calculation of Ud, Id, Pd, Ps and P values for the given duty cycle. 3. Tables of observed data q, Ud, Id, and Pd. 4. Scaled diagrams of experimental control and power characteristics Ud(q),

Id(q), and Pd(q) at low and high frequencies for resistive and inductive loads.

5. Scaled diagrams of experimental voltage and current waveforms Ud(t), Id(t) obtained at the given duty cycle at low and high frequencies for resistive and inductive loads.

6. Conclusions regarding the estimation, comparison and explanation of the expected and obtained results.

7. Signed protocol.

Following discussion Basing on the experiments, confirm and explain the following phenomena and propositions: 1. Control and power characteristics depend on the duty cycle. 2. Control and power characteristics depend on the load. 3. Control and power characteristics depend on the pulse frequency. 4. A specialist can distinguish audibly between the low and high switching

frequency of an IGBT converter. 5. Current builds up while an IGBT is switched on and decays when it is

switched off. 6. Load inductance and resistance define the time constants of a circuit. 7. Load resistance and inductance define the circuit transients.


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8. With an inductive load, the current reaches its stationary maximum state in time that depends on the given switching frequency and duty factor.

9. At the given switching frequency and duty factor, the current reaches its stationary maximum state in time that depends on the load inductance.

10. Current responses differ between the circuits with high inductance and with low one.

11. Current responses may be the same for both the high frequency supply and the low one.

12. Current responses may be different for the high frequency supply and the low one.

13. Switching frequency affects the peak-to-peak current ripple for the given duty cycle and load inductance.

14. Duty cycle affects the peak-to-peak current ripple at the given switching frequency and load inductance.

15. It is possible to change the peak-to-peak current ripple upon the different values of duty cycle.

16. Load inductance affects the dc power, ac power, and active power consumed by the circuit.

17. Duty cycle affects the dc power, ac power, and active power consumed by the circuit.

18. Switching frequency affects the dc power, ac power, and active power consumed by the circuit.

19. Freewheeling diodes are the required components of dc/dc converters. 20. Role of the freewheeling diode differs dependently of the load parameters. 21. Role of the freewheeling diode differs dependently of the frequency and

duty cycle.

Bibliography

Bibliography 1. Vodovozov, V. and Jansikene, R., Power Electronic Converters, Tallinn:

TUT, 2006, 120 p. 2. Vodovozov, V. ja Jansikene, R., Jõuelektroonika (Tõlge inglise keelde),

Tallinn: TTÜ, 2008, 120 lk. 3. Joller, J., Jõuelektroonika, Tallinn, TTÜ elektriajamite ja jõuelektroonika

instituut, 1996, 216 lk. 4. Vodovozov, V. and Jansikene, R., Electronic Engineering, Tallinn: TUT,

2006, 148 p. 5. Vodovozov, V. ja Jansikene, R., Elektroonika ja Jõupooljuhttehnika (Tõlge

inglise keelde), Tallinn: TTÜ, 2008, 140 lk. 6. Vodovozov, V. and Vinnikov, D., Electronic Systems of Motor Drive,

Tallinn: TUT, 2008, 248 p. 7. Vodovozov, V., Vinnikov, D. ja Jansikene, R., Elektriajamite elektroonsed

susteemid (Tõlge inglise keelde), Tallinn: TTÜ, 2008, 240 lk.

Annexes

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Annexes

1. Stand “Diode rectifiers”

The stand is realized as a feeder switchboard (Fig. A1.1) with the front panel which represents the circuit composition field (Fig. A1.2). It is supplied with 400 V from the three-phase network by the feeder cable via the plug X1. To decrease the voltage, the three-phase star-connected transformer T1 and the single-phase central tapping transformer T2 are used. The main technical data of T1 are as follows:

• apparent power 250 VA • primary voltage 400 V • secondary phase-to-phase voltage 24 V • secondary phase-to-neutral voltage 14 V • primary current 0,6 A • secondary current 10 A • number of phases 3 • interconnection Y0/Y0

The main technical data of T2 are as follows: • apparent power 120 VA • primary voltage 230 V • secondary phase-to-phase voltage 48 V • secondary phase-to-midpoint voltage 24 V • primary current 0,5 A • secondary current 5 A • number of phases 1

The yellow light H1 illuminates since the feeder cable is powered. To make live the circuit composed for the laboratory work, the main switch S1 is intended with lighting the green signal H2. The red safety push-button S2 is located on the front panel. In the case of an emergency, press this button. This way, the magnetic switch K1 is switched off resulting in the red emergency light H3 illuminating. After avoiding an emergency, pull out the emergency push-button and restore the supply. The primary circuits of the T1 and T2 transformers are protected against short-circuit and overloading by the automatic circuit breaker F1 (4 A rating). The secondary circuit of the T1 transformer is protected by the automatic circuit breaker F2 (10 A rating) and the secondary circuit of the T2 transformer – by F3 (5 A rating). The circuit breakers are placed inside the switchboard. To protect the F1 circuit breaker from the great current pulses arising along with the switching on the transformer, the NTC thermistor (posistor) R1 is connected sequentially into the primary circuit of the T2 transformer. To assemble the required diode rectifiers, the stand includes six power diodes D1…D6 25F60 with the rated on-state current IF = 25 A and the maximal reverse voltage UR = 600 V. The diode data sheets are accessible at

Annexes

19

http://www.irf.com/product-info/datasheets/data/25f.pdf. The diodes have three connection sockets X11…X22 both on the cathode and on the anode terminals whereto the conductors of the composed circuit are connected. There are eight sockets X23, X24 to connect the conductors of the positive polarity (four sockets are connected sequentially with each other) and eight sockets X25 to connect the conductors of the negative polarity. The sockets of the negative polarity and the ac sockets are black and the sockets of the positive polarity are red. The cord set of special safety wires of different length and colour belongs to the outfit of the stand. The black wires connect the negative parts of the circuit and ac networks whereas the red ones connect the positive parts. To connect the network neutral, the blue wires are used. There are the wires of 0,5 m and 2 m length. For the parts of an experimental circuit, which are placed on the front panel, the wires of 0,5 m length are recommended to avoid the tackling. Connections between the switchboard and the devices on the table should be provided by the longer wires.

Annexes

20

Fig. A1.1. Circuit diagram of stand “Diode rectifiers”

Annexes

21

Fig. A1.2. Front panel of stand “Diode rectifiers”

Annexes

22

Fig. A1.3. Experimental circuits of stand “Diode rectifiers”

M3

B6

a. Experimental circuit to study M1, B2, M3, and B6 rectifiers

14 V

L1

L2

L3

400 V

PV2

M1 B2 Filter PV1

PA

Load

Rectifier

c. Resistive and inductive loads

d. C and LC filters

b. Experimental circuit to study M2 rectifier

L3

N

230 V Load Rectifier

M2

Filter

PA

PV2 PV1

24 V

24 V

Annexes

23

2. Stand “Line-commutated converters” The stand is educational equipment produced by Lukas Nülle Company to study controlled line-commutated converters built on thyristors and diodes. The stand includes the following panels shown in Fig. A2, a:

• Differential amplifiers to feed a computer by the feedback voltage and current signals: A − load voltage 150 V B − supply voltage 150 V, C − supply current 2,5 V, D − load current 2,5 V connected as shown in Fig. A2, b, c

• DC power supply of the Differential amplifiers and Universal control unit with a control switch

• Universal control unit to set the required mode of operation − manual or computer, to run/stop thyristor firing, and to adjust thyristors manually by the set-point potentiometer

• Power converter unit built on thyristors and diodes • Isolating transformer 3×400/3×2×47 V with a control switch • Load 3×270 Ω, 2×0,3 H equipped with safety fuses and filament

lamps (Fig. A2, d, e) • Multimeter to measure the rms values of voltages, currents, active

powers, reactive powers, apparent powers, and a power factor on the supply side or to measure the dc and ac voltage components on the load connected as shown in Fig. A2, b, c

Commonly, Differential amplifiers and Universal control unit are connected to DC power supply permanently before the laboratory work implementations whereas Multimeter and other panels are to be connected by the students. To simplify the circuits assembling, the overlay masks may be placed above Power converter unit before the work. Additional dc voltmeter PV measures the load voltage.

To control the stand, computer with installed software PHACON may be used or it may be performed manually with the set-point potentiometer of Universal control unit. The required mode of operation is selected by the knob on Universal control unit. Similarly, to examine the signal waveforms, PHACON may be applied or an oscilloscope connected to the Differential amplifiers panel. Before the computer measurements, the process should be calibrated and tuned from menus Calibrate, Settings, and Chart. To plot the waveforms on an oscilloscope, use the auto-tuning button or tune it manually.

Annexes

24

Fig. A2. Diagrams of stand “Line-commutated converters”

0,3 H 270 Ω 270 Ω

d. Resistive load e. Inductive load

a. Panels of the stand

Diff. amps

DC power supply

Universal control

unit

Power converter

unit

Isolating transformer Load

Multimeter

Switch Switch Switch Mode Set-pointRun

R2

R1 L1

N

400 V

47 V

47 V

2L1

Power converter Load

b. Single-phase experimental circuit

PV

PS I I U

Ud

A 2 1

Id

D2 1

47 V 2L1

2L3

L1

L2

L3

400 V R1

Power converter Load

R2

c. Three-phase experimental circuit

PV

PSU I I

2L2

Id

D2 1

Ud

A 2 1

Annexes

25

3. Stand “Self-commutated converters” The stand acts as an educational equipment produced by Lukas Nülle Company to study self-controlled converters built on IGBTs. The stand includes the following panels shown in Fig. A3, a:

• Differential amplifiers panel to feed the control equipment by the feedback voltage and current signals: A − load voltage 400:2,5 and D − load current 2,5:2,5 connected as shown in Fig. A3, b

• DC power supply panel with a control Switch • Universal control unit panel to set the manual or computer operation

by the Mode knob, to permit IGBTs gating by the Run/Stop switch, and to adjust IGBTs manually by the Set-point potentiometer

• Power converter unit panel built on IGBTs and diodes • Isolating transformer panel 3×400/3×2×47 V with the control Switch

and the rectifier connected to the isolating transformer as shown in Fig. A3, b, c

• Load panel 3×270 Ω, 2×0,3 H equipped with safety fuses and filament lamps connected as shown in Fig. A3, d, e

• Multimeter PS to measure the average voltage, current and power of the load connected as shown in Fig. A3, b

Commonly, the Differential amplifiers and the Universal control unit are connected to the DC power supply permanently before the laboratory work whereas the Multimeter and other panels are to be connected by the students. To simplify the circuits building, the overlay masks may be placed above the Power converter unit before the assembling. Additional dc voltmeter PV measures the supply voltage.

To control the dc/dc converter, computer with installed software package PWM may be used. Contrariwise, any dc/dc converter may be operated manually with the Set-point potentiometer of the Universal control unit. The required mode of operation is selected by the knob Mode. To examine the signal waveforms, the PWM software package may be applied or an oscilloscope may be connected to the Differential amplifiers panel. To commencing the measurements on the computer, the process should be calibrated and tuned using menus Calibrate, Settings, and Chart. To plot the waveforms on an oscilloscope, use the auto-tuning button or tune it manually.

Annexes

26

Fig. A3. Diagrams of stand “Self-commutated converters”

d. Resistive load

270 Ω 270 Ω 270 Ω

47 V 2L1

2L3

L1

L2

L3

400 V

c. Isolating transformer

2L2

47 V

e. Inductive load

270 Ω 270 Ω 270 Ω

a. Panels of the stand

Diff. amps

DC power supply

Universal control

unit

Power converter

unit Isolating

transformer Load

Multimeter

Switch

Switch

Switch Mode Set-point Run Jumpers

L+

L-

2L1

2L3

2L2 Power

converter Load

R3 8 Ω

Id

D2 1

Ud

A 1 2

b. Experimental circuit

R1 1 Ω

R2 1,8 Ω

AC

DC

+

- PV

PS I U

Documents

Laboratory works in POWER ELECTRONICS