Converters (DC-DC, AC-DC, DC-AC, AC-AC) Flashcards
The chopper provides _____ to _____ Conversion
DC to DC
Another Name for Chopper
Buck(Step Down) or Boost(Step up) Converter
What does the input waveform of a Chopper Circuit Look like?
DC (Straight Line, above 0V potential)
What does the output waveform of a Chopper Circuit Look like?
Pulsating Square Wave DC with Duty Cycle (No waveform voltage crosses the 0V x-axis, over to the negative polarity)
A Step Down Chopper uses a _____ introduce the chopping/Duty Cycle Effect
Switch (BJTs, FETs, SCRs, etc)
Formula for Average Voltage of Step-Down Chopper Output
Vo(ave) = δ * (Vs - Vchop)
Vs - Supply Voltage
Vchop - Voltage drop across switch
δ - Duty Cycle (ex, for 90% duty cycle, δ = 0.9)
Formula for RMS Voltage of Step-Down Chopper Output
Vo(ave) = ( √δ ) * (Vs - Vchop)
Vs - Supply Voltage
Vchop - Voltage drop across switch
δ - Duty Cycle (ex, for 90% duty cycle, δ = 0.9)
Formula for Average Power of Step-Down Chopper Output
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
When A Step Down Converter is used in a DC Motor, the load is (Capacitive, Inductive, Resistive)
Inductive
With a Purely resistive load on a step down converter, the output waveform of Voltage compared to current looks ___________
the same
With an Inductive load on a step down converter, the output waveform of current compared to voltage looks ___________
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
Formula for RMS Current of Step-Down Chopper Output (With Inductive Load)
Io(rms) = √( Imax*Imin + [ (Imax - Imin) / 3 ]² )
Imax and Imin - maximum and minimum current values at load
Formula for Average Current of Step-Down Chopper Output (With Inductive Load)
Io(ave) = δ(Vs / R)
Vs - Supply Voltage
δ - Duty Cycle (ex, for 90% duty cycle, δ = 0.9)
R - Load Resistance
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
Step Down: Switch in Series with Load
Step Up: Switch in Parallel with Load
The output of the Step Up Chopper is _________
Pure DC (Therefore, no RMS formula)
Formula for Average Current of Step-Up Chopper Output
Vo(ave) = Vs / (1 - δ)
Vs - Supply Voltage
δ - Duty Cycle (ex, for 90% duty cycle, δ = 0.9)
A Step Up Chopper Consists of these Components:
Supply, Switch, Inductor in series to Supply, Capacitor in parallel to load, and a diode before the (capacitor || load) Branch
The Phase Controlled Rectifier provides _____ to _____ Conversion
AC to DC Conversion
During a time interval of time ‘0’ to ________ , the output of a Phase Controlled Rectifier is zero
α (Triggering angle)
During a time interval of time ‘α(triggering angle)’ to 2π , the output of a Phase Controlled Rectifier _________
Follows the shape of the input waveform
Usually, the Voltage at time ‘α(triggering angle)’ of the voltage waveform has a value of _________
The Forward Breakdown Voltage of an SCR (Vbr)
A Half Bridge Phase Controlled Rectifier consists of:
two SCRs and two diodes
in a Half Bridge Phase Controlled Rectifier, ____ of the two Thyristors is/are ‘Turned on’ at any given time
one
Formula for Half Bridge Phase Controlled Rectifier Average Output Voltage
Vo(ave) = (Vm / π) * ( 1 - cos α )
α - Firing angle
Vm - Peak Input Voltage Value
Formula for Half Bridge Phase Controlled Rectifier RMS Output Voltage
Vo(rms) = √{ (Vm² / 2π) * ( π - α + 0.5*sin α ) }
α - Firing angle
Vm - Peak Input Voltage Value
Alternate Formula for Half Bridge Phase Controlled Rectifier Average Output Voltage, using Mean Value Theorem
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
Alternate Formula for Half Bridge Phase Controlled Rectifier RMS Output Voltage, using Mean Value Theorem
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
Formula for Power Factor of Half Bridge Phase Controlled Rectifier
PF = Cos θ
= Pload / Psupply
= Pload / [ VsIs ]
= Pload / [ Io(rms)Vs ]
When A Half Bridge Phase Controlled Rectifier is used in a DC Motor, the load is (Capacitive, Inductive, Resistive)
Inductive
With a Purely resistive load on a Half Bridge Phase Controlled Rectifier, the output waveform of Voltage compared to current looks ___________
the same
With an Inductive load on a Half Bridge Phase Controlled Rectifier, the output waveform of current compared to voltage looks ___________
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
Formula for RMS Current of Half Bridge Phase Controlled Rectifier Output (With Inductive Load)
Io(rms) = Io(ave)*√ [ ( π - α ) / π ]
α - Firing angle
Formula for Load Power of Half Bridge Phase Controlled Rectifier Output (With Inductive Load)
Pload = Io(rms)² * R
Note: do not use Vo(rms)² / R
A Full Bridge Phase Controlled Rectifier consists of:
Four Thyristors
in a Full Bridge Phase Controlled Rectifier, ____ of the four Thyristors is/are ‘Turned on’ at any given time
two
When a Full Bridge Phase Controlled Rectifier has a purely resistive load, What are the voltage/power equations used for this setup?
Same as Half Bridge Phase Controlled Rectifier with a Purely Resistive Load
When a Full Bridge Phase Controlled Rectifier has an inductive load, What are the voltage equations used for this setup?
Vo(ave) = (2*Vm / π) * cos α
Vo(rms) = Vm / √2
The Cycloconverter provides _____ to _____ Conversion
AC to AC
Cycloconverter construction
Source voltage in series with ( diode and/or SCR in reverse parallel ) in series with load
A Halfwave Cycloconverter is constructed with:
a Diode and a thyristor in reverse parallel
the average voltage value of a Halfwave cycloconverter is always _____ with respect to the input voltage
negative
Formula for Halfwave Cycloconverter Average Output Voltage
Vo(ave) = (Vm / 2π) * ( cos α - 1 )
α - Firing angle
Vm - Peak Input Voltage Value
Formula for Halfwave Cycloconverter RMS Output Voltage
Vo(rms) = √{ (Vm² / 4π) * ( 2π - α + 0.5*sin 2α ) }
α - Firing angle
Vm - Peak Input Voltage Value
Alternate Formula for Halfwave Cycloconverter Average Output Voltage, using Mean Value Theorem
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
Alternate Formula for Halfwave Cycloconverter RMS Output Voltage, using Mean Value Theorem
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
Formula for Power Factor of Halfwave Cycloconverter
PF = Pload / [ Io(rms)*Vs ]
A Fullwave Cycloconverter is constructed with:
two thyristors in reverse parallel
Formula for RMS Voltage of Fullwave Cycloconverter
Vo(rms) = √{ (Vm² / 2π) * ( π - α + 0.5*sin 2α ) }
α - Firing angle
Vm - Peak Input Voltage Value
The Cycle of the input waveform of a cycloconverter is ____ as the output waveform
different
The Inverter provides _____ to _____ Conversion
AC to AC
Half Bridge Inverter Constructor
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
Formula for RMS Voltage of Half Bridge Inverter
Vo(rms) = Vs / 2
Full Bridge Inverter Constructor
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
Formula for RMS Voltage of Full Bridge Inverter
Vo(rms) = Vs
An inverter(Half or Full) has an average Voltage of _____
0 Volts
The output waveform of an inverter looks like a ________
Square wave, with half cycles of inverting polarity