Key Concepts in Electrical Maintenance and Safety

Damaged or insufficient filter capacitor

Cause of voltage ripples

Wear an antistatic wristwrap while handling components and use a temperature controlled soldering iron

Safety precaution when soldering

If the resistance being measured by a digital multimeter is too high, the meter will display a specific reading indicating this condition.

Display of digital multimeter for high resistance

What type of equipment recommended for electronic installations in hazardous locations.

OL (over limit or open loop)

Which search protection device is recommended for use in telecommunications, power systems and industrial control circuits.

Intrinsically safe equipment or explosion-proof

Which type of grounding is essential for telecommunication systems to minimize potential differences and interference.

Hybrid protection system

What is the recommended method for cleaning a contactor to ensure proper operation.

Bonded grounding

What is the recommended frequency for inspecting equipment grounding connections.

Wipe off dust with a dry lint-free cloth

When should transformer oil be replaced or purified.

At least annually or after electrical modifications

Which of the following instruments is used to detect discontinuities or breaks in electrical conductors.

When there is high moisture content in the oil

What is the main purpose of applying lubrication to make an electric component in electrical equipment.

Cable tester

What is the main objective of preventative maintenance for electrical equipment.

To reduce friction and wear

How does the frequency of an LC circuit change when the capacitance is reduced to half of its original value.

To prevent an unexpected failure before it occurs and extend equipment's lifespan

What is the primary function of the base terminal in BJT.

The frequency increases by a factor of square root of 2

How does an inductor with a ferromagnetic core differ from an air core inductor.

To control the current flow between the emitter and collector

How is a varistor typically connected in a circuit.

Ferromagnetic core inductors have higher inductance

Which of the following factors can lead to inaccurate current readings in an ammeter connected in series with a highly inductive circuit.

In parallel with the load to protect against voltage spikes

Which of the following is a disadvantage of power transmission.

Sudden additional phase shift in the current

In an ideal transformer, if the secondary voltage is increased by a factor of 4 how will the secondary current change.

It allows limited electrical isolation between circuits

What type of waveform is produced by the output of a DC generator before rectification by the commutator.

Decrease by a factor of 4

Why should a clamp meter be clamped around only one conductor when measuring current.

Pulsating DC

What is the advantage of the time domain reflectometer over an oscilloscope.

To ensure accurate measurement of current

Why might a capacitance meter give an inaccurate reading when measuring the capacitance of a capacitor with significant resistance.

TDR can analyze impedance mismatches

How does using a high impedance voltmeter affect voltage measurement across a resistive load with significant current draw.

The leakage current will reduce the capacitance value

What error may occur when measuring the inductance of an inductor with an LC ammeter if the measurement frequency is considerably different from the inductor's resonant frequency.

Load voltage reading will be affected by the voltage drop

What is the primary benefit of using a closed loop control system in a DC motor.

Lower measured inductance than actual value

Which factor should be expected after replacing brushes in a DC motor.

It keeps motor's speed constant

What key aspect should be checked during routine maintenance to circuit breaker.

Brush contact angle pressure seating and alignment

What type of motor rotates due to interaction of magnetic fields generated by the stator windings.

Arc chute wear and alignment, insulation condition and mechanical operation

Which is an important safety precaution when soldering to avoid damaging electronic components.

Induction motor

wear an antistatic wristwrap while handling components and use a temperature controlled soldering iron

antistatic wristwrap

to prevent unauthorized or accidental reenergization of equipment

procedure blackout or logout

capable of detecting loose connections, predetecting abnormal heat patterns

IR thermal scanner

deenergize the equipment and ensure proper grounding

high voltage equipment handling

most commonly used in power plants to generate the ac power

synchronous generator

achieves its highest efficiency at full load with power factor of 1

transformer efficiency

widely used in electric vehicles, including tesla due to its high efficiency, high power density and efficient power conversion

permanent magnet synchronous motor

high cost and thermal runaway risk

lithium ion batteries disadvantage

200V-800V

electric vehicle battery pack voltage range

prevents short circuits between windings

transformer insulation material

because power factor is not considered

transformer rating in KVA

the core will overheat due to increase flux

transformer operation at lower frequency

efficiency decreases

transformer efficiency at low load

to maintain the generator's speed under varying loads

governor in a system

determined by the no. of poles and the rotor speed

frequency of AC power output

electrical shock and arc flash

hazard of high voltage work

use a voltage detector to verify de-energization

safety measure for energized circuit

inspect if any are loose or faulty component

IR thermal hotspot inspection

to identify subnormal heat patterns caused by increase resistance

IR for loose electrical connections

SF6 ckt breaker

circuit breakers for high voltage

arc chute

arc extinguishing component in circuit breaker

by ensuring proper brush seating and alignment

minimizing excessive arcing in DC motor

poor commutator service condition

excessive brush overwear in DC motor

excessive sparking at the commutator

burnout brushes symptom in DC motor

commonly used in battery operated vehicles

series DC motor application

responsible for reducing sparking at the brushes

interpoles in DC motor

the inductor behaves like a capacitor

inductor measurement at high frequency

primarily measures inductance, capacitance and resistance

LCR meter function

it prevents excessive current thru and prevents it from intruding

high input impedance voltmeter

it does not read minimal current and does not affect the ckt

advantage of high impedance voltmeter

not a typical application is an appearing waveforms of digital signals

time domain reflectometer application

primarily measures signal reflection and cable faults

time domain reflectometer measurement

use dielectric surface ground

telecomms establishment according to PEC

ability to measure current without breaking the ckt

clamp meter advantage

measure current without breaking the ckt

primary function of clamp meter

shape of the output waveform of an AC generator

output waveform of an AC generator

A wave that describes a smooth periodic oscillation.

sinusoidal wave

In an ideal transformer, the primary and secondary voltages are 180 degrees out of phase.

phase relationship in an ideal transformer

If the number of turns in the primary windings are doubled while keeping the secondary unchanged, the primary current halves.

primary current when turns are doubled

If exposed to a voltage higher than its weighted clamping voltage, its resistance decreases allowing it to absorb excess voltage.

varistor exposure to high voltage

To protect against voltage surges like clamping excessive voltage.

primary function of a varistor

The terms 'SHOULD' or 'SHOULD NOT' are permissive rules.

permissive rules in PEC

The most common failure mode of a BJT due to overheating is that the transistor enters a permanent short circuit condition.

common failure mode of a BJT

The common recommended method for testing if a BJT is functional is using a multimeter in diode mode to check its continuity.

testing a BJT

Ensuring a certain configuration of proper heat sinking.

important consideration for BJT installation

Checking for proper heat restitution to avoid overheating.

key maintenance practice for BJT

The phase difference between voltage and current in a purely inductive LC circuit at resonance is 0 degrees.

phase difference in purely inductive LC circuit

An infrared thermographic camera is commonly used to detect overheating in electrical panels and connections.

tool for detecting overheating

A tool commonly used to detect a live wire without making direct contact.

non-contact voltage tester

Below 5 ohms.

recommended resistance for good electrical connection

A cable fault locator.

device for detecting faults in underground cables

To provide insulation and cooling.

primary function of transformers

Investigate the cause of the trip before resetting.

safest way to reset a tripped circuit breaker

An electrical system should undergo a thermal scan at least annually to detect overheating components.

thermal scan instruction frequency

Turn off power supply and verify this connection.

first step before electrical maintenance

Insulated Safety Glasses and Arc rated clothing.

PPE for Electrical Maintenance

Investigate the underlying issue causing the trip.

action if circuit breaker repeatedly trips

Use a properly rated voltage tester or multimeter.

safest way to check voltage

In PEC, the term 'shall' or 'shall not' refers to mandatory rules.

electrochemical relays in cleaning systems

To provide a safe path for current and prevent electric shocks.

primary purpose of grounding

Over Limit or Open Loop Condition.

meaning of OL in digital multimeter

To absorb voltage spikes and suppress surges.

role of a Metal Oxide Varistor

To prevent explosions from occurring in a surrounding environment.

purpose of explosion proof equipment

Tachometer.

instrument to measure speed of rotating auxiliary

To generate test signals for circuit analysis.

purpose of a signal generator

WYE-STAR or DELTA.

winding connection in 3-phase generator

Synchronous generator requires an external power source to start.

difference between synchronous and induction generator

Transformers, cables, and switch gear.

components tested with high path testing

Using capacitors to correct phase displacements.

improving power factor of a generator