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Level 3 Electrical, BCIT > Electronics 💀 > Flashcards

Electronics 💀 Flashcards

(78 cards)

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1
Q

What is the conventional current flow of the diode?

A

From anode to cathode

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2
Q

What direction is electron flow in a diode?

A

From cathode to anode

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3
Q

Which diodes operate at high frequencies?

A

Signal diodes

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4
Q

How much resistance does a diode in reverse bias have?

A

Infinite. Does not conduct

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5
Q

What voltage is measured on a reverse bias diode?

A

Source voltage

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6
Q

What is the resistance of a forward bias diode?

A

Zero

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7
Q

What is forward current rating?

A

Max RMS value that the diode can handle without damage

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8
Q

What is PIV?

A

Peak inverse voltage. Max peak voltage that the diode can safely handle

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9
Q

What is breakdown voltage?

A

Voltage passed the PIV rating. Diode will not block anymore, and will conduct very large current

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10
Q

What is the main purpose of a Zener diode?

A

Voltage regulator

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11
Q

What bias do zeners conduct in?

A

Forward

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12
Q

What happens to a Zener in reverse bias?

A

Blocks until breakdown voltage is reached. Zeners can maintain a constant value of voltage by changing its resistance

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13
Q

What is anode forward current of an SCR?

A

Maximum continuous current that can flow from cathode to anode

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14
Q

What are the two most common types of SCR’s?

A

Stud type and tab type

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15
Q

What is the most common way that SCRs are damaged?

A

Excessive gate power dissipation, or too much reverse gate voltage.

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16
Q

Formula for peak to RMS

A

Vp x .707

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17
Q

Formula for RMS to peak

A

Vrms/ .707

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18
Q

Single phase half wave Vrms to Vavg

A

Vrms x 0.45

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19
Q

Single phase full wave Vrms to Vavg

A

Vrms x 0.90

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20
Q

Three phase half wave Vrms to Vavg

A

Vrms x 1.17

use phase voltage

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21
Q

Three phase full wave Vrms to Vavg

A

Vrms x 1.35
use line voltage

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22
Q

Formula for Vinsta

A

Vpeak x SINtheta

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23
Q

Formula for firing angle

A

(Vinsta / Vpeak) SIN^-1

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24
Q

Formula for three phase half wave Vmin

A

Vpk x SIN30

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25
Formula for three phase full wave Vmin
Vpk x SIN60
26
Formula for ripple volts
Vmax - Vmin
27
Formula for frequency of single phase half wave
1 x Hz
28
Formula for single phase full wave frequency
2 x Hz
29
Formula for three phase half wave frequency
3 x Hz
30
Formula for three phase full wave frequency
6 x Hz
31
When is the three phase half wave rectifier used?
In a Wye with a neutral system, when DC voltage output is low and current is high
32
What is commutation in a three phase rectification?
The switching from phase to phase
33
When is a three phase full wave bridge rectifier used?
When large amounts of DC voltage output at a high efficiency is needed.
34
Which three phase system can a full wave bridge rectifier be used on?
Any three phase system
35
Which three phase system can a half wave rectifier be used on?
Wye with a neutral only
36
Which system and rectifier usually needs no additional filtering?
Three phase full wave bridge rectifier
37
What is the benefit of replacing the diodes in a three phase full wave bridge rectifier with SCRs?
SCRs provide phase control, allowing variable DC output
38
In three phase rectifiers, the diodes must be rated for _____
Peak line to line voltage
39
What minimum value of voltage does the rectified DC wave reach in a half wave rectifier?
50% of peak voltage
40
What minimum value of voltage does the rectified DC wave reach in a full wave three phase rectifier?
86.6% of peak voltage
41
What is the form factor used for three phase half wave rectification?
1.17
42
What is the form factor for three phase full wave rectification?
1.35
43
What is another name for the inverter?
Operational amplifier
44
What is the controlled rectifier?
SCR
45
What is triggering or firing of an SCR?
Turning it on
46
What is commutating of an SCR?
Turning it off.
47
If there was no load connected in series with the SCR, what would happen?
The SCR would short circuit.
48
The maximum number of degrees that a firing angle can have is ____
180
49
True or False: an SCR can replace a single phase bridge rectifier for phase control?
True
50
What is an application for phase control with an SCR?
Varying the speed of a DC motor
51
What is the primary use of the UJT?
Generate trigger pulses for SCRs and Triacs
52
Is the UJT current or voltage sensitive?
Voltage sensitive
53
What are the current and power ratings of UJTs?
Power is usually less than one third of a watt, currents are usually in the mA’s
54
What is the firing voltage of the UJT?
A percentage of voltage across B2 and B1.
55
When will the UJT switch on?
When voltage between emitter and B1 rises to two thirds of the voltage across B1 and B2
56
What is the benefit of the UJT over the Diac?
Diac needs a specific firing voltage, the UJT can be varied and are lower than the Diac.
57
What are some benefits of a full wave over half wave rectification?
Less ripple than half wave, higher average DC output
58
What is the benefit of a six phase full wave rectifier?
Even less ripple than three phase
59
How do you test an SCR and Triac with an ohmmeter?
Connect leads with the gate open, close the gate and there should be continuity, reopen the gate and there should still be continuity as the SCR is now triggered and will stay triggered. Ohmmeter should read high resistance on both an open and closed gate
60
When an SCR and Triac is turned off it will read ___ voltage and _____ current
Source voltage, 0 current.
61
Which layer is the gate connected to in an SCR?
P
62
Which layer is the gate connected to in a triac?
N
63
In a triac, when the gate is the same polarity as M2 (anode) what wave will form?
Full AC wave
64
In a triac, when voltage applied to the gate is the opposite of M2, what wave will form?
Half wave
65
What is the PIV of a diode in a filtered rectifier?
Double the peak line
66
What is the PIV of a diode in an unfiltered rectifier?
Peak of line
67
Which thyristor can handle the highest power and frequency
SCR
68
What is the variable resistor used for in a resistor capacitive triac circuit?
Used to control charge time of the capacitor
69
What is the main purpose of a diac?
Phase shift a triac
70
What is the truth table of an AND gate?
It’s 0001. Must have all inputs high to get an output (1 AND 1)
71
What is the truth table of an Or gate?
0111. Whenever there is a 1 you get a high output.
72
If a BJT has a base, what is the same component for the FET?
Gate
73
If a BJT has a collector, what is the same component in a FET?
Drain
74
If a BJT has an emitter, what is the same component of the FET
Source
75
Which thyristor is current driven? Which is voltage driven?
Current: BJT Voltage: JFET, MOSFET, IGBT
76
Why are FETs voltage driven?
They have a very high input impedance, there is negligible current flow in the control circuit
77
What are the two main characteristics of MOSFETS?
Very high input impedance, very fast switching speed.
78
What are the benefits of the IGBT?
High input impedance, high switching speed, low saturation voltage, can handle large collector emitter current

Level 3 Electrical, BCIT (7 decks)

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