Transformer Maintenance and Functions Quiz
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Questions and Answers

What is the primary function of an oil conservator in a transformer?

  • To maintain a constant oil level and manage oil expansion. (correct)
  • To detect gas leaks within the transformer.
  • To cool the transformer through air circulation.
  • To prevent mechanical damage during transportation.

Which device is crucial for preventing excessive internal pressure in a transformer tank?

  • Pressure relief valves. (correct)
  • Oil filler fittings.
  • Cooling tubes.
  • Gaskets and seals.

What is the initial step in calculating cooling tubes for a transformer?

  • Determine heat load. (correct)
  • Select cooling method.
  • Check for adequate cooling.
  • Calculate required cooling capacity.

Which of the following is NOT a feature typically found on a transformer tank?

<p>Calculate oil viscosity. (B)</p> Signup and view all the answers

What is the significance of painting and coating a transformer tank?

<p>To protect against corrosion and environmental exposure. (A)</p> Signup and view all the answers

What is the primary function of the primary winding in a transformer?

<p>To receive electrical power from the source (C)</p> Signup and view all the answers

What distinguishes three-phase transformer windings from single-phase transformer windings?

<p>They have three primary and three secondary windings (B)</p> Signup and view all the answers

How does the number of turns in the secondary winding affect a transformer?

<p>It influences the voltage transformation ratio (A)</p> Signup and view all the answers

What is a unique feature of an auto-transformer compared to traditional transformers?

<p>It has only one winding serving both roles (B)</p> Signup and view all the answers

Which type of winding arrangement is known for better insulation and a compact design?

<p>Concentric Winding (A)</p> Signup and view all the answers

What is the main characteristic of high-voltage (HV) windings in transformers?

<p>They usually have fewer turns than low-voltage windings (D)</p> Signup and view all the answers

Which material provides higher conductivity for transformer windings but may be more expensive?

<p>Copper (C)</p> Signup and view all the answers

What is the purpose of sandwich winding in a transformer?

<p>To reduce leakage inductance (B)</p> Signup and view all the answers

What shape do the windings take in a Delta connection?

<p>Triangular (B)</p> Signup and view all the answers

Which factor is essential for determining the turns ratio in a transformer?

<p>Desired output voltage (C)</p> Signup and view all the answers

What is the primary purpose of the no-load current in a transformer?

<p>To establish the magnetic field (C)</p> Signup and view all the answers

What is the relationship between the magnetizing reactance (Xm) and the no-load current (I no-load)?

<p>Xm equals V divided by I no-load (B)</p> Signup and view all the answers

What type of core is typically used in transformer design for better magnetic coupling?

<p>Laminated iron core (C)</p> Signup and view all the answers

Which of the following is NOT a primary consideration when designing a transformer?

<p>Color of the wires (C)</p> Signup and view all the answers

What is a key characteristic of the primary winding in a transformer?

<p>It connects directly to the power source (D)</p> Signup and view all the answers

What happens when the secondary winding of a transformer is open-circuited?

<p>Magnetizing current flows in the primary winding (C)</p> Signup and view all the answers

Which of the following factors influences the choice of core material in transformer design?

<p>Magnetic properties and losses (A)</p> Signup and view all the answers

What do core losses in a transformer primarily consist of?

<p>Hysteresis and eddy current losses (D)</p> Signup and view all the answers

What does the turns ratio in a transformer represent?

<p>The ratio of primary winding turns to secondary winding turns (A)</p> Signup and view all the answers

How are the primary and secondary winding currents related?

<p>I1 is inversely proportional to I2 (D)</p> Signup and view all the answers

What is leakage flux in transformers?

<p>Flux that completes its path through air instead of the core (B)</p> Signup and view all the answers

What is the effect of resistance and leakage reactance in a transformer?

<p>They cause voltage drop in each winding. (B)</p> Signup and view all the answers

The frequency of the AC supply affects which component of the transformer?

<p>Induced emf in the windings (C)</p> Signup and view all the answers

What occurs to the voltage transformation ratio when N2 is greater than N1?

<p>The transformer is a step-up transformer. (A)</p> Signup and view all the answers

What type of forces primarily act within a transformer?

<p>Electromagnetic forces (B)</p> Signup and view all the answers

What does the RMS value of induced emf in the primary winding depend on?

<p>Maximum flux and frequency of the AC supply (B)</p> Signup and view all the answers

In a practical transformer, what happens to the self-induced emf due to leakage flux?

<p>It reduces energy transmission. (C)</p> Signup and view all the answers

What is the average induced emf per turn in terms of frequency and flux?

<p>4.44f Fm (A)</p> Signup and view all the answers

What causes mechanical stresses within a transformer during a short circuit?

<p>High electromagnetic forces (D)</p> Signup and view all the answers

What is the primary function of transformer oil in oil-immersed cooling?

<p>To act as both an insulator and a coolant (D)</p> Signup and view all the answers

Which cooling method uses forced air to improve heat exchange in transformers?

<p>Oil Forced Air (OFA) Cooling (C)</p> Signup and view all the answers

What component is typically included within a transformer tank for safety monitoring?

<p>Buchholz Relay (C)</p> Signup and view all the answers

What design consideration helps ensure the structural integrity of a transformer tank?

<p>Adding reinforcements to stress areas (B)</p> Signup and view all the answers

What happens when the magnetic core of a transformer saturates?

<p>It causes nonlinear behavior and increased forces. (C)</p> Signup and view all the answers

Which of these methods involves cooling transformers using water?

<p>Oil Forced Water (OFW) Cooling (B)</p> Signup and view all the answers

What does the thermal cycling of a transformer typically result in?

<p>Mechanical stresses due to expansion and contraction (D)</p> Signup and view all the answers

In which cooling method does natural convection play a key role?

<p>Oil Natural Air Forced (ONAF) Cooling (B)</p> Signup and view all the answers

What type of construction method is commonly used for transformer tanks?

<p>Welding or riveting (A)</p> Signup and view all the answers

Flashcards

Primary Winding

The coil that receives electrical power from the source, connected to the input voltage.

Secondary Winding

The coil delivering electrical power to the load, connected to the device needing power.

Single-Phase Transformer

A transformer with one primary and one secondary winding, common in household and small businesses.

Three-Phase Transformer

A transformer with three primary and three secondary windings, used for industrial power.

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Auto-Transformer

A transformer with a single winding acting as both primary and secondary, more compact and efficient.

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Concentric Winding

Transformer windings arranged concentrically (one over another) for better insulation and compact design.

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HV Winding

The winding connected to the higher voltage side of a transformer.

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Copper Winding

Transformer winding made of copper, providing high conductivity but potentially more expensive.

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Delta Connection

A winding configuration where the ends of the transformer windings are connected in a triangle (?).

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Star (Wye) Connection

A winding configuration where the ends of transformer windings are connected in a 'Y' shape.

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Transformer Design Considerations

Factors essential for designing a transformer, including core material, winding design, insulation, cooling, and more.

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Transformer Specifications

Identifying a transformer's application, voltage, current, frequency, power rating, and any special needs (impedance, voltage regulation, efficiency).

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No-load current

Current flowing through the primary winding when the transformer is energized and the secondary is open.

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Magnetizing Reactance (Xm)

Reactance of the magnetizing current in a transformer's core.

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Primary Winding

Transformer winding connected to the input electrical power source.

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Secondary Winding

Transformer winding connected to the load.

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Turns Ratio

Ratio between the number of turns in the primary and secondary windings.

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Transformer Core

Component used to increase magnetic coupling in a transformer, typically laminated iron or other magnetic materials.

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Turns Ratio

The ratio of primary winding turns to secondary winding turns (N1/N2).

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Voltage Transformation

The change in voltage from primary to secondary side, determined by the turns ratio.

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Current Relationship

Current flowing in the primary and secondary windings are related by the inverse turns ratio (I1/I2 = N2/N1).

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Leakage Flux

Flux that doesn't link both windings, producing self-induced EMF.

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Leakage Reactance

Inductive effect of leakage flux, akin to an inductive coil in series with each winding (in transformers).

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Transformer Impedance

Combined resistance and leakage reactance in either primary or secondary winding.

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EMF Equation

Formula for induced EMF in a transformer windings (E= 4.44f N Φm).

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Voltage Transformation Ratio (K)

The ratio of induced EMFs in primary and secondary windings (E1/N1 = E2/N2 = K).

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Step-Up Transformer

Transformer with a turns ratio greater than 1, increasing voltage.

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Step-Down Transformer

Transformer with turns ratio less than 1, decreasing voltage.

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Oil Conservator Function

A compartment in a transformer tank that allows oil to expand and contract due to temperature changes, maintaining a stable oil level and minimizing oxidation.

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Pressure Relief Device Purpose

A safety valve that releases excess pressure within a transformer tank to prevent damage during faults or abnormal conditions.

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Transformer Tank Cooling Calculation

Process of determining the necessary cooling systems (like tubes) to manage the generated heat from a transformer during operation and ensure safe operation temperatures.

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Transformer Tank Testing Importance

Testing procedures (e.g., pressure, vacuum, leaks) applied to ensure the tank's structural integrity, reliability, and ability to contain oil under various operating conditions.

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Transformer Tank Protection

Measures like painting and coating, gaskets, and seals, and fitting for oil filling/draining are important for the long-term protection and functionality, preventing corrosion and leakage in the transformer tank.

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Short-Circuit Forces

High electromagnetic forces created during a short circuit in a transformer, stressing windings and structure.

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Thermal Stresses

Mechanical stresses caused by temperature changes in a transformer (heating and cooling).

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Load Currents

Electrical currents flowing through transformer windings, creating magnetic fields and forces.

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Fault Currents

Significant electrical currents during faults (like short circuits), creating large electromagnetic forces.

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Core Saturation

Transformer core's magnetic saturation, affecting behavior and increasing forces.

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Transformer Oil Cooling

Oil-immersed transformer cooling method, using oil to transfer heat.

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Oil Forced Air Cooling

Transformer cooling with fans to force air over oil, enhanced cooling.

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Transformer Tank Material

Steel is commonly used for transformer tanks due to its strength and corrosion resistance.

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Transformer Tank Shape

Transformer tank shapes can be rectangular or cylindrical, depending on size and design.

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Buchholz Relay

A device installed in a transformer tank that detects gas evolution potentially caused by internal problems.

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