Converters (DC-DC, AC-DC, DC-AC, AC-AC)

Question 1

The chopper provides _____ to _____ Conversion

Answer 1

DC to DC

Question 2

Another Name for Chopper

Answer 2

Buck(Step Down) or Boost(Step up) Converter

Question 3

What does the input waveform of a Chopper Circuit Look like?

Answer 3

DC (Straight Line, above 0V potential)

Question 4

What does the output waveform of a Chopper Circuit Look like?

Answer 4

Pulsating Square Wave DC with Duty Cycle (No waveform voltage crosses the 0V x-axis, over to the negative polarity)

Question 5

A Step Down Chopper uses a _____ introduce the chopping/Duty Cycle Effect

Answer 5

Switch (BJTs, FETs, SCRs, etc)

Question 6

Formula for Average Voltage of Step-Down Chopper Output

Answer 6

Vo(ave) = δ * (Vs - Vchop)

Vs - Supply Voltage
Vchop - Voltage drop across switch
δ - Duty Cycle (ex, for 90% duty cycle, δ = 0.9)

Question 7

Formula for RMS Voltage of Step-Down Chopper Output

Answer 7

Vo(ave) = ( √δ ) * (Vs - Vchop)

Vs - Supply Voltage
Vchop - Voltage drop across switch
δ - Duty Cycle (ex, for 90% duty cycle, δ = 0.9)

Question 8

Formula for Average Power of Step-Down Chopper Output

Answer 8

Pave = [ δ * (Vs - Vchop) ] ² / RLoad

Vs - Supply Voltage
Vchop - Voltage drop across switch
δ - Duty Cycle (ex, for 90% duty cycle, δ = 0.9)
RLoad - Load Resistance

Question 9

When A Step Down Converter is used in a DC Motor, the load is (Capacitive, Inductive, Resistive)

Answer 9

Inductive

Question 10

With a Purely resistive load on a step down converter, the output waveform of Voltage compared to current looks ___________

Answer 10

the same

Question 11

With an Inductive load on a step down converter, the output waveform of current compared to voltage looks ___________

Answer 11

Different

VLoad waveform looks the same as one that has only a resistive load

But Current Waveform is different, since an inductance resists a changing current, the current looks like a charging and discharging cycle

Question 12

Formula for RMS Current of Step-Down Chopper Output (With Inductive Load)

Answer 12

Io(rms) = √( Imax*Imin + [ (Imax - Imin) / 3 ]² )

Imax and Imin - maximum and minimum current values at load

Question 13

Formula for Average Current of Step-Down Chopper Output (With Inductive Load)

Answer 13

Io(ave) = δ(Vs / R)

Vs - Supply Voltage
δ - Duty Cycle (ex, for 90% duty cycle, δ = 0.9)
R - Load Resistance

Question 14

With a Step-down converter, the switch is in _____ to the load, whereas with a step-up converter, the switch is in ______ to the load

Answer 14

Step Down: Switch in Series with Load

Step Up: Switch in Parallel with Load

Question 15

The output of the Step Up Chopper is _________

Answer 15

Pure DC (Therefore, no RMS formula)

Question 16

Formula for Average Current of Step-Up Chopper Output

Answer 16

Vo(ave) = Vs / (1 - δ)

Vs - Supply Voltage
δ - Duty Cycle (ex, for 90% duty cycle, δ = 0.9)

Question 17

A Step Up Chopper Consists of these Components:

Answer 17

Supply, Switch, Inductor in series to Supply, Capacitor in parallel to load, and a diode before the (capacitor || load) Branch

Question 18

The Phase Controlled Rectifier provides _____ to _____ Conversion

Answer 18

AC to DC Conversion

Question 19

During a time interval of time ‘0’ to ________ , the output of a Phase Controlled Rectifier is zero

Answer 19

α (Triggering angle)

Question 20

During a time interval of time ‘α(triggering angle)’ to 2π , the output of a Phase Controlled Rectifier _________

Answer 20

Follows the shape of the input waveform

Question 21

Usually, the Voltage at time ‘α(triggering angle)’ of the voltage waveform has a value of _________

Answer 21

The Forward Breakdown Voltage of an SCR (Vbr)

Question 22

A Half Bridge Phase Controlled Rectifier consists of:

Answer 22

two SCRs and two diodes

Question 23

in a Half Bridge Phase Controlled Rectifier, ____ of the two Thyristors is/are ‘Turned on’ at any given time

Answer 23

one

Question 24

Formula for Half Bridge Phase Controlled Rectifier Average Output Voltage

Answer 24

Vo(ave) = (Vm / π) * ( 1 - cos α )

α - Firing angle
Vm - Peak Input Voltage Value

Question 25

Formula for Half Bridge Phase Controlled Rectifier RMS Output Voltage

Answer 25

Vo(rms) = √{ (Vm² / 2π) * ( π - α + 0.5*sin α ) } α - Firing angle Vm - Peak Input Voltage Value

Question 26

Alternate Formula for Half Bridge Phase Controlled Rectifier Average Output Voltage, using Mean Value Theorem

Answer 26

Vo(ave) = (Vm / π) * ∫ sin θ dθ, limits from α to π α - Firing angle Vm - Peak Input Voltage Value sin θ - Waveform function, expressed in angle θ (if waveform is different, this can be changed

Question 27

Alternate Formula for Half Bridge Phase Controlled Rectifier RMS Output Voltage, using Mean Value Theorem

Answer 27

Vo(rms) = √{ (Vm² / π) * ∫ sin² θ dθ, limits from α to π } α - Firing angle Vm - Peak Input Voltage Value sin θ - Waveform function, expressed in angle θ (if waveform is different, this can be changed

Question 28

Formula for Power Factor of Half Bridge Phase Controlled Rectifier

Answer 28

PF = Cos θ = Pload / Psupply = Pload / [ Vs*Is ] = Pload / [ Io(rms)*Vs ]

Question 29

When A Half Bridge Phase Controlled Rectifier is used in a DC Motor, the load is (Capacitive, Inductive, Resistive)

Answer 29

Inductive

Question 30

With a Purely resistive load on a Half Bridge Phase Controlled Rectifier, the output waveform of Voltage compared to current looks ___________

Answer 30

the same

Question 31

With an Inductive load on a Half Bridge Phase Controlled Rectifier, the output waveform of current compared to voltage looks ___________

Answer 31

Different VLoad waveform looks the same as one that has only a resistive load But Current Waveform is different, since an inductance resists a changing current, the current looks like a charging and discharging cycle

Question 32

Formula for RMS Current of Half Bridge Phase Controlled Rectifier Output (With Inductive Load)

Answer 32

Io(rms) = Io(ave)*√ [ ( π - α ) / π ] α - Firing angle

Question 33

Formula for Load Power of Half Bridge Phase Controlled Rectifier Output (With Inductive Load)

Answer 33

Pload = Io(rms)² * R Note: do not use Vo(rms)² / R

Question 34

A Full Bridge Phase Controlled Rectifier consists of:

Answer 34

Four Thyristors

Question 35

in a Full Bridge Phase Controlled Rectifier, ____ of the four Thyristors is/are 'Turned on' at any given time

Answer 35

two

Question 36

When a Full Bridge Phase Controlled Rectifier has a purely resistive load, What are the voltage/power equations used for this setup?

Answer 36

Same as Half Bridge Phase Controlled Rectifier with a Purely Resistive Load

Question 37

When a Full Bridge Phase Controlled Rectifier has an inductive load, What are the voltage equations used for this setup?

Answer 37

Vo(ave) = (2*Vm / π) * cos α Vo(rms) = Vm / √2

Question 38

The Cycloconverter provides _____ to _____ Conversion

Answer 38

AC to AC

Question 39

Cycloconverter construction

Answer 39

Source voltage in series with ( diode and/or SCR in reverse parallel ) in series with load

Question 40

A Halfwave Cycloconverter is constructed with:

Answer 40

a Diode and a thyristor in reverse parallel

Question 41

the average voltage value of a Halfwave cycloconverter is always _____ with respect to the input voltage

Answer 41

negative

Question 42

Formula for Halfwave Cycloconverter Average Output Voltage

Answer 42

Vo(ave) = (Vm / 2π) * ( cos α - 1 ) α - Firing angle Vm - Peak Input Voltage Value

Question 43

Formula for Halfwave Cycloconverter RMS Output Voltage

Answer 43

Vo(rms) = √{ (Vm² / 4π) * ( 2π - α + 0.5*sin 2α ) } α - Firing angle Vm - Peak Input Voltage Value

Question 44

Alternate Formula for Halfwave Cycloconverter Average Output Voltage, using Mean Value Theorem

Answer 44

Vo(ave) = (Vm / 2π) * ∫ sin θ dθ, limits from α to 2π α - Firing angle Vm - Peak Input Voltage Value sin θ - Waveform function, expressed in angle θ (if waveform is different, this can be changed

Question 45

Alternate Formula for Halfwave Cycloconverter RMS Output Voltage, using Mean Value Theorem

Answer 45

Vo(rms) = √{ (Vm² / 2π) * ∫ sin² θ dθ, limits from α to 2π } α - Firing angle Vm - Peak Input Voltage Value sin θ - Waveform function, expressed in angle θ (if waveform is different, this can be changed

Question 46

Formula for Power Factor of Halfwave Cycloconverter

Answer 46

PF = Pload / [ Io(rms)*Vs ]

Question 47

A Fullwave Cycloconverter is constructed with:

Answer 47

two thyristors in reverse parallel

Question 48

Formula for RMS Voltage of Fullwave Cycloconverter

Answer 48

Vo(rms) = √{ (Vm² / 2π) * ( π - α + 0.5*sin 2α ) } α - Firing angle Vm - Peak Input Voltage Value

Question 49

The Cycle of the input waveform of a cycloconverter is ____ as the output waveform

Answer 49

different

Question 50

The Inverter provides _____ to _____ Conversion

Answer 50

AC to AC

Question 51

Half Bridge Inverter Constructor

Answer 51

Imagine Bridge Circuit: 1st Branch Upper: BJT1 1st Branch Lower: BJT2 2nd Branch Upper: Voltage supply(Vs / 2) 2nd Branch Lower: Voltage supply(Vs / 2) Bridge: Load resistance

Question 52

Formula for RMS Voltage of Half Bridge Inverter

Answer 52

Vo(rms) = Vs / 2

Question 53

Full Bridge Inverter Constructor

Answer 53

Imagine Bridge Circuit: 1st Branch Upper: BJT1 1st Branch Lower: BJT2 2nd Branch Upper: BJT3 2nd Branch Lower: BJT4 Bridge: Load resistance Voltage supply(Vs) in parallel to whole bridge circuit

Question 54

Formula for RMS Voltage of Full Bridge Inverter

Answer 54

Vo(rms) = Vs

Question 55

An inverter(Half or Full) has an average Voltage of _____

Answer 55

0 Volts

Question 56

The output waveform of an inverter looks like a ________

Answer 56

Square wave, with half cycles of inverting polarity