Advanced Electronics Engineering (Industrial) Flashcards
It is a four layer pnpn or npnp device with a control mechanism. It is a solid-state semiconductor device similar to diode with an extra control terminal gate
Thyristor
The main terminals of a thyristor
Anode and cathode
control terminal of a thyristor
gate
What is the control signal for SCR?
current pulse
For GTO, what is the control signal?
voltage pulse
for LASCR, what is the control signal?
light (both light and a gate current can work to control the LASCR simultaneously)
In what type of applications are thyristors usually used?
High voltage and High current
The process where the change of polarity of the currents cause the device to automatically switch off
Zero Cross operation
Is the voltage that must be overcome which SCR enters the conduction region(Vak required to turn ON the thyristor)
Forward breakover voltage
The minimum value of Anode - Cathode current which the SCR switches from the conduction state to the forward blocking region, (required anode current for SCR to remain turned ON)
Holding Current
These are the regions corresponding to the open-circuit condition for the controlled rectifier which block the flow of charge (current) from anode to cathode
Forward and reverse blocking region
Maximum Reverse Voltage of Vak before SCR Breaks down into the Zener or avalanche region of the device
Reverse breakdown voltage
Power output of Thyristors
up to 4kA
It is a gas-filled triode vaccum tube, served as the basis for the transistor
Thyratron
Turn off time for SCR
5-30 μs
Turn off time for SCS
1-10 μs
Maximum anode current and Power dissipation of SCS
100-300 mA
100-500 mW
(SCS have much lower max. power dissipation than SCR)
It is a type of Silicon controlled Rectifier that can be turned on or off by applying a pulse of gate current and turned off by applying a pulsed negative bias
Gate Turn-Off Switch
Highly advantageous since it can be turned on or off by applying the proper pulse polarity to gate cathode
Gate triggering current for GTO
20mA
Gate Triggering current for SCR
30μA
Turn off and turn on time of GTO
1μs
How do you turn of an LASCS
remove or reverse the positive bias
This transistor has a stable negative resistance, also known as double-based diode
UJT
It is a four layer pnpn diode with only two external terminals. It is considered a unilateral or unidirectional break over device.
Shockley diode
It is a silicon diode exhibiting very high resistance up to a certain level, beyond which the device switches to low resistance conducting state
Thyrector
A DIAC is comparable to two ______ Conencted in reverse parallel
Shockley Diodes
A TRIAC is comparable to two ______ Conencted in reverse parallel
SCRs
It is used to assist in the turn off of Triac
snubber circuit
It is a unilateral or unidirectional break-over device, Similar to a Shockley Diode with a gate terminal
Silicon Unilateral Switch (SUS)
It is SUS connected back-to-back in parallel. It is a low-voltage and low-current device
Silicon bilateral switch (SBS)
Any point on the principal voltage-current characteristic for which the differential resistance is zero and where the principal voltage reaches maximum value
Breakover Point
A generic term for the current through the collector junction. Note: it is the current through main terminal 1 and main terminal 2 of a triac or anode and cathode of SCR
Principal Current
5 basic welding intervals
Squeeze Weld Hold Release Standby
It is defined as the difference in the measured value and the set or desired value.
Error/difference signal//deviation and system deviation
The condition wherein the error signal is zero
Null
Small error signal or system deviation where the system cannot correct anymore
Offset
Characteristics of a good closed-loop control system
Very small offset signal
Quick Response
High Stability
Modes of Control Systems
On-Off Proportional Proportional plus Integral Proportional plus Derivative Proportional plus Integral plus Derivative
It is a mode of control wherein the controller has only two operating states, on and off.
On-Off (also known as bang-bang control)
The controller has a continuous range of possible position
Proportional (P)
It is a proportional mode of control where wherein the controller is not only considering the magnitude of the error signal but as well as the time that it has persisted
Proportional plus Integral (PI)
Proportional mode of control wherein the controller is not only considering the magnitude of the error signal, but as well as its rate of change
Proportional plus Derivative(PD)
It is a mode of control wherein the controller considers the error signal magnitude, error signal period of occurrence, and error signal rate of change
Proportional plus Integral plus Derivative (PID)
It is generally due to the person using the instrument, such as incorrect reading, incorrect recording or incorrect use of instrument, AKA Human error
Gross errors
Absolute Error formula
E = Y - X
Y=expected value
X=measured value
Accuracy Formula
A = 1 - E
E = %error
A - Accuracy expressed in %
It converts a non electrical signal (pressure/temperature) into and electrical signal
Transducer
It is required to process the incoming electrical signal to make it suitable for application to the indicating device
Signal device
It is generally a deflection-type meter for such general-purpose instruments as voltmeters, current meters or choppers
Indicating device
Who patented the permanent magnet-moving-coil (PMMC)
Jacques d’Arsonval, 1881
An error due to the real ammeter’s resistance adds to the branch, in a way that it reduces the current in any real circuit
Insertion/Resistance error
Meter Accuracy Formula
%A = Iwₘ / Iwₒₘ = Rₒ/(Rₒ+Rₘ)
Rₘ=meter resistance
Rₒ=resistance of the circuit
% Insertion error in ammeter formula
%Insertion error = ( 1 - %A)x100%
Ammeter shunt Resistance formula
Rₛₕ = ( Ifₛ / (Iₜ - Ifₛ) )*Rₘ
Rₛₕ=shunt resistance, Ω
Ifₛ=full scale current, A
Rₘ=meter resistance, Ω
Iₜ=New Full Scale Current/Total Current, A
Input resistance of the shunted meter, Rᵢₙ₍ₛₕ₎
Rᵢₙ₍ₛₕ₎ = Rₘ⋅Rₛₕ / (Rₘ+Rₛₕ) (parallel)
=Vᵢₙ/Iᵢₙ
=(Ifₛ/Iₜ)Rₘ
Ayrton Shunt for multiple range ammeter formula
R₍ₛₕ₎ = Rₘ / (n - 1)
n = Iₜ / Ifₛ
n - is the factor by which you increase the Full Scale Current to a new full scale current, Iₜ
How is a simple DC voltmeter constructed?
By placing a resistor in series(Rs) with a meter and marking the meter face to read the voltage across
DC Voltmeter formula for voltage
V=(Rₛ+Rₘ)*Iₘ
Meter Sensitivity formula of a DC Meter (ammeter, ohmmeter, voltmeter)
S=1/Ifₛ (expressed as Ω/V)
S is the reciprocal of the full-scale current of the ammeter used in voltmeter
Voltmeter Accuracy
%Accuracy = Vwₘ / Vwₒₘ = (Rᵢₙ / (Rᵢₙ + Rₒ))
Rin = Rvoltmeter = Rm + Rs Ro = Resistance of circuit taken across the element/s of voltage inquiry without the influence of the Voltmeter resistance(Rm + Rs)
for 99% accuracy, Rᵢₙ>100Rₒ
for 95% accuracy, Rᵢₙ>20Rₒ
Voltmeter Loading Error
%E = (1 - A) x 100%
This device can be constructed simply with battery, an ammeter and a resistor in series
Ohmmeter
Meter deflection formula for Ohmmeter
D = Iu / Ifₛ= Rin / (Rin + Rᵤ)
Iu - current at Ru
Rin = Ro(adjustable resistance) + Rm(meter resistance)
Rᵤ = Load Resistance/ Resistance in question
AC Voltmeter - Half wave Formulas
Rₛ = (Vdc / Ifₛ) - Rₘ
=( 0.45 Vᵣₘₛ / Ifₛ) - Rₘ
Sₐc = 0.45*Sdc = 0.45 / Ifₛ
Rₛ=multiplier resistor (in series with the meter)
Ifₛ=full-scale current
Vdc=dc voltage that cause full-scale deflection
Vᵣₘₛ=ac voltage intended to measure
Sₐc=ac meter sensitivity
Sdc=dc meter sensitivity
AC Voltmeter-Full wave Formulas
Rₛ = (Vdc / Ifₛ) - Rₘ
=( .9 Vᵣₘₛ / Ifₛ) - Rₘ
Sₐc = 0.9S*dc = 0.9 / Ifₛ
Rₛ=multiplier resistor (in series with the meter)
Ifₛ=full-scale current
Vdc=dc voltage that cause full-scale deflection
Vᵣₘₛ=ac voltage intended to measure
Sₐc=ac meter sensitivity
Sdc=dc meter sensitivity
It is a DC type bridge which can accurately measure resistances. It consists of two parallel branches with each branch containing two series elements, usually resistors.
Wheatstone Bridge
Wheatstone Bridge formula for measuring unknown resistance
FORMULA ONLY HOLDS WHEN CURRENT ACROSS THE BRIDGE LOAD IS 0 A:
Ru = R3 * (R₁/R₂)
R3 - Adjustable resistor on the same branch of Ru
R1 and R2 - resistors that constitute the other branch of the wheatstone bridge
It is a simplification of the Wheatstone Bridge/ The ratio arm (R₁/R₂) is replaced by either manganin wire or german silver wire of uniform cross section with exactly 100cm long.
Slide-Wire Bridge
Slide Wire bridge formula
Ru=R*( [100/S] - 1 )
Ru - unknown resistance
R - Resistance on the same branch as Ru
S - the resistance on the sliding wire that pairs with R (imagine a bridge, S and R are the resistances at the bottom half of the ammeter bridge)
It is a modified version of the wheatstone bridge eliminating the effects of contact and lead resistance when measuring unknown low resistance
Also, determine the range of resistances it can measure
Kelvin Bridge
1Ω to about 1μΩ)
Two applications of DC bridge for loop test
Murray loop method
Varley loop method
It is used to measure the impedance of a capacitive circuit. AKA capacitance comparison bridge/series capacitance
Similar-Angle Bridge
A photoelectric instrument the optical reflectance of a reflecting surface.
Reflectometer
In fiber optics, this instrument is used to analyze the reflected light energy and helps determine the existence and location of breaks and losses in splices and connector
Optical Time Domain Reflectometer (OTDR)
A Vacuum Tube Diode Employs the process of _______ to perform Diode Rectification
Thermionic Emission
What is Thermionic Emission
The Production of electrons through heat
The heating element used to heat the plate in a vaccuum tube diode operates at what voltage? Is it AC or DC?
6.3 Volts, AC
The Supply Voltage in a Vaccuum Tube diode is connected in what manner?
Positive at the Anode, Negative at the Cathode
A Vacuum tube diode with a grid terminal
Triode
The voltage at the grid terminal is (Positive/Negative) With respect to the cathode of the device
Negative
Therefore, VGG is a negative supply
The Voltage that controls the diode current in a vacuum tube diode
Grid Voltage (VGG, supplied by a negative voltage supply at the grid terminal)
The magnitude of the Supply Voltage (Vak) must be (>,
|Vak| > |VGG|
A Popular Circuit Breaker that uses thyristors and zener diodes
Crowbar Circuit Breaker
Silicon Controlled Rectifiers (SCRs) were invented at _______ in _________
Bell Telephone Labs, 1956
Typical Power Rating of an SCR
10 MW
Typical Voltage Rating of an SCR
1.8 KV
Typical Current Rating of an SCR
2 KA
Typical Max. Operating Freq. of an SCR
50 kHz
An SCR can be represented as a _____ and ______ Transistor in tandem
PNP, NPN
Two methods of turning off an SCR
- Anode Current Interruption
- Forced Commutation
Two Types of Anode Current Interruption
- Series Interruption (Most effective method)
- Shunt Interruption
In a Series Interruption method of turning off an SCR, a ________ Switch is placed in ________ to the ________
Normally Closed/Break switch
placed in series
to the anode
In a Shunt Interruption method of turning off an SCR, a ________ Switch is placed in ________ to the ________
Normally open/Make Switch
Placed In parallel
to the Anode-Cathode terminals of the SCR
Two Types of Forced Commutation
- Place an external Triggering Capacitor in parallel to an SCR (Must have opposing Voltage to Vak)
- Use an NPN Turn off circuit (Consists of [BJT switch connected to a supply voltage] in parallel to the SCR, that when turned on, opposes Vak, turning off the device)
Formula for the Breakback Voltage (Vbb)
Vbb = Vbrf - Vhc
Vbrf - Forward Breakover voltage
Vhc - Voltage @ Holding Current
Increasing the Gate Current of an SCR (increases/decreases) the required Forward Breakover Voltage for conduction
Decreases
The current required at the gate to sustain Anode-Cathode Conduction in an SCR
Gate Trigger Current
The Maximum Anode-Cathode DC Current that an SCR can withstand
Average Forward Current
A Silicon Controlled Switch (SCS) is a __ Terminal Device
4 (Tetrode, the only tetrode in the Thyristor Family)
A Silicon Controlled Switch(SCS) has ___ gate terminals
two (Anode gate and Cathode gate)
The advantage of an SCS compared to an SCR
Increased Control and Triggering Sensitivity
An SCR has a special property, where we can easily predict its __________
Firing Situation
Describe the Firing Situation
- There is a certain firing angle α, where during this period, the device does not conduct. Only after the Firing angle does the output waveform appear. this non-conduction portion repeats every cycle of the waveform
- Looks like a “Vertical Clipping” of the waveform
Describe the Firing angle(α)
α is a period of time in a waveform, expressed as an angle (Radians), where 2π represents the angle for the whole period, and π represents the halfwave period
During the Firing angle α, the output of the device is non-conductive (No waveform appears)
A GTO (Gate Turn Off Switch) is usually doped (heavier/lighter) than a normal thyristor
Lighter
Lighter Doping in the GTO will result into a (lower/higher) AK Resistance
Higher
The required current for Turn-on/Turn-off at the gate of a GTO must be (______) * (Anode-Cathode Current)
1/5 * Anode-Cathode Current
Anoter name for the shockley diode
4 layer diode
A Shockely Diode has __ Gate terminals
0 (No gate teminal)
A Shockley Diode is similar to an SCR, only that a Shockley Diode has a ________
Fixed Forward Breakover Voltage (since there is no control gate terminal)
Typical Forward Breakover Voltage of a Shockley Diode
60 Volts
DIACs have ___ Gate Terminals
0 (No Gate terminals)
DIACs have ___ Forward Breakover Voltages
two fixed Vbrf (one Vbrf in the positive half cycle, another Vbrf in the negative half cycle)
Typical Forward Breakover Voltage of a DIAC
20-40V
A TRIAC has ____ Forward Breakover Voltages
Two Variable Vbrf (one Vbrf in the positive half cycle, another Vbrf in the negative half cycle)
Vbrf controlled by gate current)
A TRIAC has ______ Gate terminals
One (simultaneously and equally controls Vbrf’s in both current directions)
A Silicon Bilateral Switch (SBS) can operate Alternating Current.
True or False?
True
Both SUS and SBS have __ Gate terminals
one
SBSs are normally used to trigger ________
TRIACS and Control Systems
SBSs have a more pronounced _________
Negative Resistance Region
The ‘AC’ in TRIAC and DIAC stands for _______
Alternating Current
A Unijunction Transistor has ____ Terminals
3 (Emitter, Base 1, Base 2)
Hence its other name, Double Based Diode
A Unijunction Transistor has ____ Layers of semiconductors
2 layers (one P-type, one N-type)
A Programmable UJT (PUT) have _____ Layers of Semiconductors
4 layers (Similar to SCR)
The Gate Terminal of a PUT is located at the (anode/cathode) gate
Anode Gate
For an SCR, the gate terminal is located at the Cathode gate. That is the only physical difference of an SCR and a PUT
What is the required condition for PUT Conduction?
When Vak > Vgate
Vgate controlls the turn on voltage
A DIAC and a TRIAC have ____ anodes
two anodes (A1 and A2)
Three functions of Instruments
- Indicating
- Controlling
- Recording
The Comparison of a quantity to an accepted standard quantity
Measurement
Governing Body that Facilitates International Standards
International Bureau of Weights and Measures (Located in Paris)
Pertains to standards at a National Level
Primary Standards
Standards in Industrial Labs, in which measuring tools are calibrated based on Primary Standards
Secondary standards
Standards in General Laboratory Instrument Calibrations
Working Standards
Three Categories of Error
- Gross Error
- Systematic Error
- Random Error
Errors that persist due to the instruments and/or the environment
Systematic Error
The accumulation of small, unavoidable errors
Random Error
Formula for % Error
%E = (Absolute error / Expected Value) x100%
Formula for Presicion
Note: Requires a sample space/set of data
P = 1 - abs| (Xn - Xn(bar)) / Xn(bar) |
Xn - Datapoint in inquiry
Xn(bar) - Mean Value of data points
Three types of DC meters
- Permanent Magnet Moving Coil (PMMC, D’Arsonval)
- Iron Vane
- Electrodynamometer
Two types of moving coils in a DC meter
- Jewel and Pivot
- Taut Band Suspension
Maximum Full Scale Current of a Jewel and Pivot moving coil
Ifs = 50μA
Maximum Full Scale Current of a Taut Band Suspension moving coil
Ifs = 2μA
The Advantages/Disadvantages of a Taut Band Suspension VS Jewel and Pivot
ADV: More sensitive
DISADV: More Expensive
Part of a PMMC that is attached to the needle tail, and eliminates the gravitational influence on the needle
counterweight
Part of a PMMC that counters the deflecting force of the electromagnetic force
Spring
Part of a PMMC that contains a pivot, which will allow movement proportional to the current passing through it
moving coil
Part of a PMMC that provides the visual indicator of measurement
Pointer
Part of a PMMC meter that provides the magnetic field for the moving coil
magnet
Part of the PMMC that allows pointer calibration for re-positioning to initial position when Current through the moving coil is zero
Zero Adjustable Control
The 3 Forces involved in a PMMC
- Deflecting Force
- Damping Force
- Controlling Force
The force in a PMMC that prevents pointer oscillation
Damping Force
The force that returns the pointer to initial position @ I = 0A
Controlling Force
Force exerted by the moving coil in the presence of a current through it
Deflecting Force
The most Basic DC Metter
Ammeter
The current through the moving coil that causes Full Scale Deflection of the pointer
Full scale current (Ifs)
An Ideal ammeter have the following properties:
- Meter resistance (Rm) is equal to zero
- deflection is linearly proportional to current through the moving coil
Error in measurement attributed to inaccurate meter face, not properly marked
Calibration Error
Formula for Calibration Error
CE = +- 3% of Ifs
Insertion Error is usually expressed in _______
% Accuracy
For a DC Meter, the Ideal Accuracy/ Ideal Error is:
100% Accuracy, 0% Error
In order to obtain ‘n’% Accuracy, Rwom must be ___ times greater than the Meter Resistance (Rm)
For ‘n’% Accuracy:
Rwom = n*Rm
Rwom - Resistance without the meter
Rm - Meter Resistance
n - desired percentage of accuracy(do not include %; ex. for 99% accuracy, Rwom = 99*Rm)
An Ammeter Configuration that allows a greater current measurement
Ammeter Shunt (Shunting an Rsh to the ammeter)
When the load changes, the Full scale current of a DC meter __________
DOES NOT CHANGE
Ifs is an unchanging inherent property of the meter alone
With an ammeter, The higher the resistance of the circuit to be measured (Rwom) is compared to the Meter Resistance (Rm), the higher the __________ will become
Accuracy
When we are to design an ammeter that can detect a new Full Scale Current (Iₜ2) that is ‘n’ times greater than the current full scale current (Iₜ1) of a specific ammeter(that has an existing shunt resistor (Rsh1) designed for Ifs1), what is the value of the new shunt resistor to adjust for the new Iₜ2 current?
If Iₜ1 is to become Iₜ2 = n*Iₜ1, then the new resistor shunt is to be changed from Rsh1 to:
Rsh2 = Rsh1 / n
The Shunt resistance must be _______ than Meter Resistance
Much much lesser
Two Types of Multirange Ammeters
- Switched Shunt
- Ayrton Shunt
Disadvantage of a Switched Shunt
There are moments when a shunt resistor will not stay shunted to the meter when transitioning from one shunt resistor to another, allowing all the current to pass through the meter, damaging it
Advantage of an Ayrton Shunt
while switching, there is no instance that there is no shunted resistance to the ammeter, preventing damage
The Shunt Resistances in the Ayrton Shunt are connected in ________
Series
The Voltmeter Resistance (Rin = Rm +Rs) is ideally
∞ Ohms
Formula for Series Resistance of Voltmeter
Derived from Voltmeter Voltage Formula:
Rs = (Vt / Ifs) - Rm
The Ohmmeter resistance (Ro) is adjustable because it is used to:
Correct for battery aging
How is the Adjustable Ohmmeter resistance (Ro) adjusted?
- ) Short the Ohmmeter
- ) Adjust the Adjustable Ohmmeter Resistance (Ro) until full scale deflection is achieved in the face of the meter
Formula for Ro when voltmeter is shorted
Ro = (Vaged / Ifs ) - Rm
Vaged - the current voltage of the aged battery
Ifs - fullscale curent (remember, this property does not change regardless of battery aging or load)
Rm - meter resistance
3.) Un-short the ohmmeter
The Value of Deflection Factor(D) when Ru(unknown resistance) is 0 ohms (short circuit)
D = 1
The Value of Deflection Factor(D) when Ru(unknown resistance) is (Rin / 3) ohms
(Rin = Ro (adjustable resistance of ohmmeter) + Rm(meter resistance)))
D = 0.75
The Value of Deflection Factor(D) when Ru(unknown resistance) is (Rin) ohms
(Rin = Ro (adjustable resistance of ohmmeter) + Rm(meter resistance)))
D = 0.5
The Value of Deflection Factor(D) when Ru(unknown resistance) is (3*Rin) ohms
(Rin = Ro (adjustable resistance of ohmmeter) + Rm(meter resistance)))
D = 0.25
The Value of Deflection Factor(D) when Ru(unknown resistance) is (∞) ohms (open circuit)
(Rin = Ro (adjustable resistance of ohmmeter) + Rm(meter resistance)))
D = 0
A Deflection Factor of 1 means that the pointer is located at the __________ of the meter face
Rightmost portion of the meter face
A Deflection Factor of 0 means that the pointer is located at the __________ of the meter face
Leftmost portion of the meter face
What Device is placed in series with a DC Voltmeter circuit to become an AC Halfwave Voltmeter
Diode
What Device is placed in series with a DC Voltmeter circuit to become an AC Fullwave Voltmeter
Transformer + Diode Bridge Curcuit
or
Center tapped transformer with two diodes
A Peak Detector consists of:
A diode-capacitor circuit (looks like a clamper)
and a Voltmeter across the capacitor
The most accurate type of DC meter
DC Bridge Meter
When a bridge is balanced in a DC Bridge meter, the load in between the two nodes will have a current of _____ amperes through it
0
Following up on the fact that the bridge is balanced, and that the current through the load is 0 A, what can you say about the voltages on either end nodes of the load resistor?
they are equal in value
in a Wheatstone Bridge, what is the element connected as the “Bridge” of the circuit?
Ammeter (Checks if current at bridge is 0A, to determine if the bridge is balanced)
A DC Bridge used to measure fault distances
Varley Loop
A DC Bridge used to measure fault distances, but it is a simplified varley loop
Murray Loop
A wheatstone bridge used to measure reactances and impedances
AC Bridges
The AC Bridge that measures an unknown Inductance given a capacitance in its branch
Maxwell Bridge
Maxwell Bridge Construction
1st branch, above: Capacitor || potentiometer
1st branch, below: potentiometer
2nd branch, above: Fixed Resistor
2nd Branch, below: unknown Inductor (including coil resistance in series)
The AC Bridge that is similar to the Maxwell Bridge, but the branch where a potentiometer and a capacitor are in parallel, is connected in series instead
Hay Bridge
Maxwell Bridge Construction
1st branch, above: Capacitor in series with potentiometer
1st branch, below: potentiometer
2nd branch, above: Fixed Resistor
2nd Branch, below: unknown Inductor (including unknown coil resistance in series)
The AC Bridge extensively used for measuring capacitances and dissipation factors
Schering Bridge
Schering Bridge Construction
1st branch, above: Variable Capacitor || fixed resistor
1st branch, below: Fixed capacitor
2nd branch, above: Fixed Resistor
2nd Branch, below: unknown Capacitor (including unknown stray resistance in series)
The AC Bridge extensively used to measure Frequency
Wein Bridge
Wein Bridge Construction
1st branch, above: Capacitor(C1A) in series with fixed potentiometer(Rpot1A)
1st branch, below: Capacitor(C1B) || with fixed potentiometer(Rpot1B)
2nd branch, above: Fixed Resistor(Rfix2A)
2nd Branch, below: Fixed Capacitor(Rfix2B)
UNKNOWN: Frequency of the AC source connected to the circuit
Formula for frequency measured by a wein bridge
1.) Adjust potentiometers so that Bridge is balanced:
Rfix2A / Rfix2B = (Rpot1A / Rpot1B) + (C1B / C1A)
2.) f = 1 / { 2π*sqrt(C1A * C1B * Rpot1A * Rpot1B) }
