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Inspection Encyclopedia: Here's Everything You Need To Know As A Technician (Part 2)


Advanced Electrical Troubleshooting: Chapter 2


Content


Electrical Inspections - Transformers


In this module, we will learn about an advanced circuit component: transformers. By the end of the module, you will be able to: Understand how a transformer works, Learn transformer components, Know how to troubleshoot a transformer Skip to quiz!


Transformers


A transformer is a passive electrical device that transfers energy from one circuit to another. A passive electrical device means that it can store energy.


Transformers transfer energy between circuits through electromagnetic induction. Electromagnetic induction is the phenomenon where placing a conductor in a magnetic field produces a voltage.


Recall that current moving through a wire will create a magnetic field. Recall also that a magnetic field can create current in a wire. Creating a transformer is based upon these ideas.


The most common function of a transformer is to adjust the voltage levels between circuits. A step-up transformer increases the voltage. The secondary coil is larger than the primary to have a higher induced voltage.


A step-down transformer decreases the voltage. The secondary coil is smaller than the primary to have a smaller induced voltage.


A transformer works based on mutual induction. Mutual inductance is the interaction between two magnetic coils. One coil has a current running through it from a power source. The second coil has an induced current due to the magnetic field produced by the first.


Transformers consist of three major components:

  1. Primary winding coil,

  2. Secondary winding coil, and

  3. The magnetic core of the transformer

Various fields, such as power generation, electricity transmission, energy consumption, and more commonly use transformers.



How to Inspect Transformers


We will use a multimeter to check voltages on the primary and secondary sides of a transformer. Look for any cosmetic damage like burns, dents, bulging, or other damage.


We need to identify the transformer terminals. Some transformers will have labels on the transformer casings, but sometimes we need to refer to a data sheet. The manufacturer will provide the datasheet.


Once the terminals have been identified, we can test each side of the transformer. The designed voltage ratings will be present on the label or the datasheet. Set the multimeter to the AC voltage setting.


Connect the multimeter probes to the secondary side of the transformer. The multimeter should read the secondary voltage rating from the label or datasheet with the power supply turned on.


Connect the multimeter probes to the primary side of the transformer. The multimeter should read the primary voltage rating from the label or datasheet. If either primary or secondary readings vary significantly from the designed ratings, the transformer is faulty.


Next, we will look at the transformer winding resistance. Detach the transformer from the circuit. Set the multimeter to the highest resistance setting.


Connect the multimeter probes across the primary terminals. If the multimeter shows “OL” or “1”, the transformer’s input winding is faulty. Repeat this process for the secondary terminals.


In this module, we learned about transformers. We now know that transformers work to change voltage levels between a high-voltage side and a low-voltage side. We also understand how transformers use magnetic fields.


We also learned the process of troubleshooting circuits with these components. First, check the voltages of the primary and secondary sides and compare them to the ratings. Then, check the resistances of both coils to look for open loops.


 

Electrical Inspections - Resistors


In this module, we will learn about a common circuit component: resistors. By the end of the module, you will be able to: Understand resistance, Get familiar with Ohm’s Law- See how to measure the resistance on a resistor Skip to quiz!


Resistors


A resistor is a device or electrical component that opposes or “resists” the flow of electric current. The symbol for a resistor in a circuit diagram is shown here.


Resistance is the measure of the opposition to the flow of current through a resistor. A higher resistance value means a stronger opposition to current flow. Recall from the video that adding obstructions slowed down the flow of the marbles.


The unit of resistance is “Ohm,” denoted by Ω. Recall that Ohm’s law is a simple equation using resistance, voltage, and current: V = I ✕ R. If 1 volt is applied across a resistor with 1 amp of current, the resistance equals 1 ohm.


Different circuits require different levels of resistance. Resistors can range anywhere from 1 Ω up to a few million Ω. Large resistors are always labeled, and small ones are color-coded to compare to datasheets.



How to Inspect Resistors


The easiest way to inspect a resistor is using a multimeter. We will set the multimeter to the Ω setting.


First, turn off the power supply and disconnect the resistor from the circuit. This will ensure our safety when handling electronic components.


Connect the multimeter probes to either side of the resistor. It does not matter which probe is on the left or right, as resistance does not have any direction.


The multimeter should show a value for resistance. To get an exact resistance value, manually adjust the Ω setting until a more precise value is reached. If there is no resistance value, the resistor is faulty.


In this module, we learned about resistors. You now know that resistance is the electrical property that measures how much resistors oppose the current flow. Resistors are designed for different loads with varying resistance.


We also learned the process of troubleshooting circuits with this component. Using a multimeter on the Ω setting, we can attach to both sides of a resistor and measure continuity and resistance value.



 

Electrical Inspections - Transistors


In this module, we will learn about an advanced circuit component: transistors. By the end of the module, you will be able to: Understand transistors, Inspect a transistor Skip to quiz!


Transistors


Conductors are materials that can carry and transfer electricity through them. Insulators are materials that stop current and do not allow electricity to move through them. Semiconductors are materials that fall between conductors and insulators.


Transistors are semiconductor devices that have the properties of a switch to allow or block electricity from flowing through them.


They usually have three terminals:

  • A collector, the circuit inlet,

  • An emitter, the circuit outlet, and

  • A base, the control/switch terminal


A transistor has two p-n diodes. A p-n diode comprises p-type and n-type semiconductors. These mean a positive-type and negative-type material.


A p-type semiconductor consists of many “holes” which are positively charged. The positive charge attracts the negative parts of n-type materials.


An n-type semiconductor is negative due to its high number of electrons, which are negatively charged. When brought with a p-type, the n-type will donate its electrons and pass electricity through the circuit.


There are two types of transistors: NPN and PNP. An NPN transistor applies a positive voltage to the collector for current flow from the collector to the emitter. A PNP transistor applies a positive voltage to the emitter to allow current flow from the emitter to the collector.



How to Inspect Transistors


To inspect a transistor, we will need to disconnect it from the circuit. Make sure to turn off all power supplies. We will use a multimeter in the transistor setting.


To thoroughly test the transistor, we will check all combinations of terminals:

  1. Emitter and base,

  2. Emitter and collector, and

  3. Collector and base

Connect the red probe to the middle or P-terminal of an NPN transistor. And the black probe to any of the other terminals. A 0.45 - 0.90 V will indicate the transistor is functional. An OL will indicate the transistor is faulty.


Connect the black probe to the middle or N-terminal of the PNP transistor. And the red probe to any of the other terminals. A 0.45 - 0.90 V will indicate the transistor is functional. An OL will indicate the transistor is faulty.


In this module, we learned about transistors. You know that transistors are semiconductor devices that have the property to allow or block electricity.


We also learned the process of troubleshooting transistors. We should always set the multimeter dial should to the transistor setting. The red and black probe must be connected to the middle terminal of the NPN and PNP transistors, respectively.



 

Electrical Inspections - Inductors and Solenoid


In this module, we will learn about two common circuit components: inductors and solenoid coils. By the end of the module, you will be able to: Inspect inductors, Inspect solenoid coils Skip to quiz!


Inductors


An inductor is an electrical component that is wound up into a coil. It is a passive device that stores energy in a magnetic field. Recall that current running through a wire will create a magnetic field.


Inductors usually are made up of an insulated wire wound into a coil around a core. The core is usually a magnetic material like iron. Inductors are also called a “coil,” “choke,” or “reactor.” Inductors are a key component in transformers, motors, choke coils, and relays.



How to Inspect Inductors


The best way to inspect an inductor is by testing its continuity using a multimeter. Multimeters cannot measure inductance, so that a continuity test will be sufficient.


First, turn off the power supply and disconnect the inductor from the circuit. Ensure no external damages on the inductor’s casing, like dents, burns, bulging, or cracks.


Connect the multimeter probes to both ends of the inductor. It does not matter which probe is on the left or right, as we are only checking for wire continuity.


If the multimeter reads “OL” or “1,” the inductor is faulty. For our continuity test, the inductor is functional if the multimeter beeps or displays a different reading.



Solenoid Coils


Like an inductor, a solenoid coil is a long piece of wire wound into a coil. When current flows through the wire, it creates a magnetic field inside the coil that is relatively uniform.


Solenoid coils are often used as electromagnets or as inductors in electronic circuits. The flow of current produces the magnetic field.


When current flows through the coil, most of the magnetic flux exists within the core material. Magnetic flux is magnetic lines of force passing through a closed surface.



How to Inspect Solenoid Coils


To inspect a solenoid coil, we will first need to disconnect it from the circuit. Make sure the power supply is off. Examine the solenoid casing and check for any external damage, like dents, burns, bulging, or anything else that doesn’t look right.


We will use a multimeter on the resistance setting, denoted by Ω. Most solenoids will have two pins, but some will have a third ground pin. We will disregard the ground pin and only test the terminals.


Attach the multimeter probes to the terminal pins. If there is a resistance value, the solenoid is working correctly.


If the multimeter shows “OL,” the solenoid coil is open-circuited and faulty. If it reads very close to 0, the solenoid coil is likely short-circuited and faulty.


In this module, we learned about inductors and solenoid coils. You learned about inductors that stores energy in the form of magnetic fields. You also learned about solenoid coils which create magnetic fields when a current flows.


We also learned the process of troubleshooting inductors and solenoid coils. A faulty inductor would show an OL in the multimeter display. Similarly, a faulty solenoid coil would also show an OL.


 

Electrical Inspections - Power Supply


In this module, we will learn about a common circuit component: Power supplies. By the end of the module, you will be able to troubleshoot a power supply. Skip to quiz!


Power Supply


All electronic devices have one thing in common, and that’s a power source. Your TV remote takes batteries, your cell phone charges up its internal battery, and your microwave needs to be plugged in to work.


The power supply is the source of power for different components in a circuit. A power supply converts different forms of energy, such as mechanical, chemical, solar, into electrical energy.


A wind turbine turns mechanical energy in its spinning blades into electricity. Your phone battery takes advantage of chemical properties to provide power to your phone. And, solar panels take light energy from the sun and convert it to electricity through chemical means.


In your home, every outlet is a power supply. The most widely used ratings are 110-120V for the US and 220-240V in Europe.



How to Inspect Power Supplies


A power supply can be easily checked using a multimeter. Be very careful when inspecting power supplies to avoid electric shock, as the power supplies must be turned on.


Set the multimeter to the AC voltage setting. Insert the black probe into the COM port and the red into mVΩ. Now, identify the neutral terminal as the larger outlet hole, usually on the left. The hot terminal is the smaller hole on the right.


Insert the black probe into the neutral terminal and the red probe into the hot pins of the power outlet. If the multimeter shows a voltage of 110-120V (for the US), then the outlet is functional. Otherwise, the power outlet may be faulty.


We can also manually inspect the power outlet by removing it from the wall. Most outlets can be taken out by removing the wall screws and simply pulling the outlet.


Check that the wires are all connected correctly to both the outlet's neutral, hot, and ground terminals. If the wires are all connected properly, connect the black probe to the neutral terminal and the red probe to the hot terminal.


With the probes on the correct terminals, the multimeter should read 110-120V (for the US). Otherwise, the power outlet is faulty.


In this module, we learned about the power supply. Power supplies are used to power different electrical components.


We also learned the process to troubleshoot power supplies. The multimeter must be set to the AC voltage for inspecting a power supply. A voltage in the range of 110 - 120V will indicate a functional power outlet.



 

Question #1: Transformers use magnetic fields to induce a voltage in the secondary side of the circuit:

  1. True

  2. False

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Answer: True

The secondary coil has an induced current and voltage due to the magnetic field produced by the primary coil.


Question #2: A step up transformer ________ voltage in the secondary side because the secondary coil is ______ than the primary.

  1. Increases, smaller

  2. Decrease, smaller

  3. Increases, larger

  4. Decreases, larger

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Answer: Increases, larger

A step-up transformer induces a high voltage in the secondary coil. The secondary coil is larger than the primary.


Question #3: A step down transformer ________ voltage in the secondary side because the secondary coil is ______ than the primary.

  1. Increases, smaller

  2. Decrease, smaller

  3. Increases, larger

  4. Decreases, larger

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Answer: Decrease, smaller

A step-down transformer induces a low voltage in the secondary coil. The secondary coil is smaller than the primary.


Question #4: Which of the following is a key component of a transformer? (select all that apply)

  1. Primary coil

  2. Secondary coil

  3. Magnetic core

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Answer: Primary coil

Secondary coil

Magnetic core

The key components to any transformer are the primary and secondary coils and a magnetic core.


Question #5: _______ is checked with the power supply on, while ______ is checked with the power supply off.

  1. Voltage, Resistance

  2. Resistance, Voltage

  3. Current, Resistance

  4. Resistance, Current

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Answer: Voltage, Resistance

The power supply stays on to check for voltage. The transformer is disconnected from the power supply when checking resistance.


Question #6: Transformers will typically have how many terminals to use when troubleshooting?

  1. 2

  2. 4

  3. 6

  4. 8

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Answer: 4

Transformers will have four terminals when troubleshooting: an inlet and outlet for primary and secondary sides.


Question #7: Resistors ________ when electricity is passed through them.

  1. Accelerate current

  2. Increase capacitance

  3. Increase voltage

  4. Restrict current

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Answer: Restrict current

Resistors are named since they resist the flow of current.


Question #8: Which of the following are correct equations for Ohm’s law? (select all that apply)

  1. V = I*R

  2. I = V*R

  3. R = I/V

  4. I = V/R

  5. R = V/I

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Answer: V = I*R

I = V/R

R = V/I

The simplest form of Ohm’s law is V = I ✕ R. This equation can be rearranged to form both I = V/R and R = V/I.


Question #9: Resistors are all designed for one load and have the same resistance rating:

  1. True

  2. False

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Answer: False

Resistors are designed for many different loads and needs. There are hundreds of resistance ratings, and they are labeled or color-coded.


Question #10: Resistance is measured in Ohms, which is which symbol on the multimeter?

  1. C

  2. A

  3. Ω

  4. O

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Answer: Ω

The symbol for Ohms is Ω (greek letter omega). Multimeters will have Ω on the dial.


Question #11: When inspecting a resistor, it is important to know which probe goes on either side of the resistor:

  1. True

  2. False

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Answer: False

Resistance does not have a direction. Therefore, it does not matter which probe is on either side of the resistor.


Question #12: A transistor is a __________.

  1. Insulator

  2. Semiconductor.

  3. Conductor.

  4. None of these.

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Answer: Semiconductor.

Transistors are made of semiconductor materials. These materials have the property of both conductors and insulators.


Question #13: A p-type semiconductor consists of ____ charged ions which, attracts ____ part of n-type materials.

  1. Negatively, positive.

  2. Negatively, negative.

  3. Positively, positive.

  4. Positively, negative.

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Answer: Positively, negative.

P-type semiconductors consist of positively charged particles. These positively charged particles attract the negatively charged particles of the N-type materials.


Question #14: For checking a PNP transistor, the black probe must be connected to the _____ terminal and the red probe to the ______terminal.

  1. Middle, Remaining

  2. Left, Middle

  3. Right, Middle

  4. Middle, Right

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Answer: Middle, Remaining

In a PNP transistor, the black probe should be connected to the N or middle terminal. The red probe must be connected to any other remaining terminals.


Question #15: What is the correct reading range for a functional transistor.

  1. 0.45 - 0.90 V

  2. 0.50 - 0.60 V

  3. 0.00 - 0.45 V

  4. 0.45 - 1.00 V

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Answer: 0.45 - 0.90 V

A functional NPN/PNP transistor will have a 0.45 - 0.90 V across the N and P or P and N terminals.


Question #16: Inductors are related to _______ field.

  1. Electric

  2. Magnetic

  3. Gravitational

  4. Coulomb’s

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Answer: Magnetic

Inductors are passive devices that store energy in the form of magnetic fields.


Question #17: The core of inductors should be made up of _______.

  1. Iron

  2. Plastic

  3. Wood

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Answer: Iron

Inductor cores are usually made up of materials that possess magnetic properties such as iron, stainless steel, etc.


Question #18: The multimeter dial must be set to _____ setting for testing an inductor.

  1. Resistance

  2. Capacitance

  3. Continuity

  4. Voltage

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Answer: Continuity

The functionality of an inductor can be tested by a multimeter using the continuity test.


Question #19: For what value in the multimeter display would you consider an inductor faulty?

  1. A low resistance value of few Ω’s.

  2. A High resistance value of MΩ’s.

  3. An OL or 1

  4. None of the above

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Answer: An OL or 1

An inductor is considered faulty if the multimeter would display an OL (open-loop) or 1 for a continuity test. A finite resistance value followed by a beep sound indicates the inductor is functional.

Question #20: Solenoid is analogous to?

  1. Inductor

  2. Capacitor

  3. Resistor

  4. None of the above

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Answer: Inductor

The solenoid is similar to inductors. Just like inductors, solenoid stores energy in the form of a magnetic field. Solenoid coils are wound around a magnetic material in the form of coils.


Question #21: Magnetic flux is the line of forces passing through a closed surface?

  1. True

  2. False

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Answer: True

Magnetic flux is defined as magnetic lines of forces passing through a closed surface. The S.I unit of magnetic flux is Weber (Wb).


Question #22: What is the most crucial safety step while testing a solenoid coil?

  1. Connect the probes

  2. Switch OFF the power supply

  3. Discharge the solenoid

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Answer: Switch OFF the power supply

Before testing a solenoid coil, the most crucial step is switching off the power supply to the solenoid coils and disconnecting it.


Question #23: How would you know if the solenoid coil is short-circuited?

  1. The multimeter displays an OL

  2. The multimeter displays 1

  3. The multimeter displays a finite value

  4. The multimeter displays 0

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Answer: The multimeter displays 0

While testing a solenoid coil using a multimeter, if the display shows a resistance of 0 Ω or a value close to 0, it means that the solenoid coil is shorted.


Question #24: Select the correct power supply ratings used in the US from the given options.

  1. 110- 120 V

  2. 220 - 240 V

  3. 430 - 440 V

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Answer: 110- 120 V

110-120V power supply rating is used for electrical components in the US.


Question #25: Which would be the hot terminal in a power outlet?

  1. The larger rectangular hole

  2. The smaller rectangular hole

  3. The circular hole

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Answer: The smaller rectangular hole

The hot terminal is the smaller rectangular hole on the right of a power outlet.


Question #26: Which would be the neutral terminal in a power outlet?

  1. The larger rectangular hole

  2. The smaller rectangular hole

  3. The circular hole

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Answer: The larger rectangular hole

The neutral terminal is the larger rectangular hole on the left side of a power outlet.


Question #27: The multimeter must be set to ____ setting for inspecting a power outlet.

  1. DC Voltage

  2. AC voltage

  3. Resistance

  4. Continuity

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Answer: AC voltage

The multimeter must always be set to the AC voltage setting while testing the voltage across a power outlet.

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