Utilization of Electrical Energy MCQ Quiz - Objective Question with Answer for Utilization of Electrical Energy - Download Free PDF

Explanation:

AC/DC Drives

Definition: AC/DC drives are electronic devices used to control and regulate the speed, torque, direction, and other parameters of an electric motor. These drives are widely used in industrial, commercial, and residential applications to enhance the performance and efficiency of electric motors by providing precise control over their operation.

Working Principle: The primary function of AC/DC drives is to convert electrical energy into a form suitable for the motor and to control the motor's operating parameters. For AC drives, the process involves converting the fixed-frequency AC power supply into variable-frequency AC power to control the motor speed. For DC drives, the voltage supplied to the motor is regulated to achieve the desired speed and torque. Feedback mechanisms (e.g., sensors) are often used to monitor the motor's performance and adjust the drive's output accordingly.

Parameters Controlled by AC/DC Drives:

• Speed: AC/DC drives allow precise control of motor speed by varying the frequency (in AC motors) or voltage (in DC motors). This capability is crucial for applications requiring speed adjustments, such as conveyor belts, fans, and pumps.
• Torque: Torque control is essential in applications where the force exerted by the motor needs to be regulated. AC/DC drives enable torque adjustments to match the load requirements, ensuring efficient operation and preventing motor damage.
• Horsepower: Horsepower, a measure of the motor's power output, can also be controlled using AC/DC drives. By adjusting the speed and torque, the drive indirectly manages the motor's horsepower to meet application demands.
• Direction: AC/DC drives can reverse the direction of motor rotation by altering the phase sequence (in AC motors) or reversing the polarity of the voltage (in DC motors). This feature is particularly useful in applications like robotics and material handling systems.

Advantages of AC/DC Drives:

• Enhanced energy efficiency by optimizing motor performance based on load requirements.
• Improved process control and productivity through precise parameter adjustments.
• Reduced mechanical stress on motors and connected equipment, resulting in longer service life.
• Flexibility to adapt to various applications and operating conditions.

Applications of AC/DC Drives:

• Industrial automation systems, such as conveyors, cranes, and mixers.
• HVAC systems for controlling fans, pumps, and compressors.
• Electric vehicles for managing motor speed and torque.
• Renewable energy systems like wind turbines and solar inverters.

Correct Option Analysis:

The correct option is:

Option 4: Speed, torque, horsepower, and direction of AC motor.

This option correctly identifies the parameters that can be controlled using an AC/DC drive. As explained above, AC/DC drives offer precise control over speed, torque, horsepower, and direction, making them indispensable in various applications requiring motor control.

Additional Information

To further understand the analysis, let’s evaluate the other options:

Option 1: Speed, torque, and horsepower.

While this option lists some of the parameters controlled by AC/DC drives, it omits the ability to control the direction of the motor. AC/DC drives can reverse the motor's direction, which is a critical feature in many applications. Thus, this option is incomplete.

Option 2: Torque, direction of AC motor, and speed.

Although this option includes torque, direction, and speed, it fails to mention horsepower as a controllable parameter. Horsepower is a fundamental aspect of motor performance that can be indirectly managed using AC/DC drives by adjusting speed and torque. Hence, this option is also incomplete.

Option 3: Speed and torque.

This option provides a very limited view of the capabilities of AC/DC drives. While speed and torque are indeed controllable parameters, it does not account for horsepower or direction, both of which are integral to the functionality of AC/DC drives. This makes the option inadequate.

Option 5: (Blank/Not Applicable)

This option does not provide any meaningful information and is therefore irrelevant to the question. The correct answer must encompass all the parameters controllable by AC/DC drives, as outlined in the explanation.

Conclusion:

AC/DC drives are versatile devices that offer precise control over motor parameters, including speed, torque, horsepower, and direction. These capabilities make them essential for a wide range of applications, from industrial automation to renewable energy systems. The correct option, Option 4, comprehensively captures the parameters that can be controlled by AC/DC drives, distinguishing it from the other incomplete or incorrect options. Understanding these capabilities is crucial for selecting and utilizing AC/DC drives effectively in various engineering and operational contexts.

Explanation:

Critical Consideration in Street Lighting Design and Estimation

Definition: Designing and estimating the cost of street lighting systems involves various technical, economic, and environmental considerations. One of the most critical aspects is calculating the number of light fixtures, cable requirements, and energy consumption to determine overall costs. This ensures that the lighting system meets performance standards while remaining cost-effective and sustainable.

Working Principle:

The process of designing a street lighting system begins with assessing the area to be illuminated. This involves determining the spacing and placement of light fixtures to ensure uniform light distribution. Engineers calculate the required lumen output, taking into account factors such as road width, pedestrian pathways, and traffic density. Once the layout is finalized, cable requirements are estimated based on the power supply network and the distance between fixtures. Energy consumption is then calculated to estimate operational costs and explore energy-efficient solutions.

Advantages of Proper Cost Estimation:

• Ensures adequate illumination levels to improve safety for pedestrians and drivers.
• Optimizes the use of resources, reducing waste and unnecessary expenses.
• Supports the integration of energy-efficient technologies, lowering long-term operational costs.
• Facilitates compliance with regulatory standards and environmental guidelines.

Steps Involved:

1. Determine the area to be illuminated, including roadways, sidewalks, intersections, and public spaces.
2. Calculate the number of light fixtures required based on illumination standards and area dimensions.
3. Estimate cable requirements by analyzing the power distribution network and fixture placement.
4. Evaluate energy consumption using the wattage of light fixtures and operational hours.
5. Incorporate energy-efficient lighting solutions, such as LED technology, to reduce electricity usage.
6. Factor in installation, maintenance, and operational costs to determine the total budget.

Applications:

This methodology is applied in designing street lighting systems for urban areas, highways, parking lots, and public parks. Proper estimation and design enhance public safety, reduce energy consumption, and contribute to sustainable urban development.

Correct Option Analysis:

The correct option is:

Option 1: Calculating the number of light fixtures, cable requirements, and energy consumption to determine overall costs.

This option emphasizes the importance of a comprehensive approach to street lighting design and cost estimation. By considering the number of fixtures, cable requirements, and energy consumption, engineers can create an efficient and cost-effective lighting system that meets performance standards and sustainability goals.

Important Information

To further understand the analysis, let’s evaluate the other options:

Option 2: Focusing only on the aesthetic design of the streetlights.

This option is incorrect as aesthetics alone cannot ensure the functionality, safety, and cost-effectiveness of a street lighting system. While aesthetic design is important for urban appeal, it must be balanced with technical and economic considerations to create an efficient lighting system.

Option 3: Ignoring energy efficiency to reduce initial costs.

This approach is counterproductive in the long run. Ignoring energy efficiency might lower initial installation costs but leads to higher operational expenses due to increased energy consumption. Energy-efficient solutions, such as LED lighting, provide significant savings over time and contribute to environmental sustainability.

Option 4: Eliminating the use of protective devices in the system.

Protective devices, such as circuit breakers and surge protectors, are essential for ensuring the safety and reliability of the street lighting system. Eliminating them compromises the system’s durability and increases the risk of damage due to electrical faults or power surges.

Conclusion:

Effective street lighting design and estimation require a comprehensive approach that balances technical, economic, and environmental considerations. Calculating the number of light fixtures, cable requirements, and energy consumption is fundamental to achieving a functional and cost-effective lighting system. Ignoring aspects like energy efficiency, protective devices, or focusing solely on aesthetics leads to suboptimal solutions that fail to meet the demands of modern urban infrastructure.

Explanation:

Critical Factor in Cable Selection for Outdoor Public Lighting Installations

Definition: When designing and installing outdoor public lighting systems, the selection of cables is a crucial aspect that ensures the system operates efficiently, safely, and reliably under various environmental conditions. Cables act as the medium for transmitting electrical power to the lighting fixtures, and their selection must align with the requirements of the installation environment and the electrical load.

Correct Option Analysis:

The correct option is:

Option 2: The cable's ability to withstand environmental conditions and carry the required current safely.

This option emphasizes the importance of selecting cables that can endure the specific environmental conditions of outdoor public lighting installations while also meeting the electrical load requirements. This involves considering several critical factors:

• Environmental Conditions: Outdoor cables are exposed to varying weather conditions, such as rain, extreme heat, cold, UV radiation, and potential mechanical stresses. Hence, the cables must have adequate insulation and outer sheathing to resist these factors effectively.
• Current Carrying Capacity: The cable must be capable of safely carrying the required current without overheating. This involves choosing the appropriate conductor size and material to prevent excessive voltage drops and energy losses.
• Durability and Longevity: The selected cable should be robust and designed to last for the expected lifespan of the lighting installation. This minimizes maintenance and replacement costs over time.
• Compliance with Standards: The cable must adhere to relevant national and international standards, ensuring safety and reliability in operation.

Why this Option is Correct: In outdoor public lighting installations, cables must perform safely and reliably in challenging environmental conditions while meeting the electrical demands of the lighting fixtures. Option 2 captures these critical requirements, making it the correct choice.

Important Information

To further understand the analysis, let’s evaluate the other options:

Option 1: Ignoring voltage drop calculations to reduce costs.

This option is incorrect because ignoring voltage drop calculations can lead to significant problems, such as insufficient power reaching the lighting fixtures, reduced efficiency, and potential damage to the equipment. Voltage drop calculations are essential to ensure the cables can deliver the required voltage to the lighting fixtures over long distances.

Option 3: Selecting the cheapest cable available.

This option is incorrect as it prioritizes cost over safety and performance. While cost considerations are important, selecting the cheapest cable without considering its suitability for the application can lead to safety hazards, reduced lifespan, and increased maintenance costs. Proper cable selection balances cost with performance, durability, and compliance with safety standards.

Option 4: The colour of the cable insulation.

This option is incorrect because the colour of the cable insulation is not a critical factor in its selection for outdoor public lighting installations. While insulation colour may have specific uses (e.g., identifying different circuits), it does not influence the cable's performance or ability to withstand environmental conditions and carry the required current.

Option 5: Not provided in the given data.

Since the data does not specify an Option 5, it is not relevant to the analysis of the correct answer.

Conclusion:

The correct answer, Option 2, highlights the critical factors in selecting cables for outdoor public lighting installations, focusing on their ability to withstand environmental conditions and carry the required current safely. This ensures the safety, reliability, and efficiency of the lighting system while adhering to necessary standards and minimizing long-term costs. Careful consideration of these factors is essential in achieving a successful and durable lighting installation.

The derived SI unit of illuminance is the lux (lx).

The correct answer is Cleaning.

Key Points

Explanation:

Electroplating: This involves the process of depositing a layer of any desired metal on another material by means of electricity. In this case, the electric current is used to reduce dissolved metal cations such that they form a thin metal coating on the electrode.

• It is the process of coating the surfaces of the components with another metallic coating to achieve decorative or protective surfaces against corrosion
• The component to be plated is dipped in the electrolyte and made as a cathode as shown in the figure
• The electrolyte supplies the metal ions of materials to be deposited from the anode to the cathode

From the diagram, it is visible that the work to be coated is on the cathode.

•  Before the electroplating process, proper cleaning is done for the purpose of reduction of Dirt, Grease, and any other surface impurities.

Additional Information

• Buffing: Buffing operation is carried out after polishing with a finer abrasive to further smoothen the surface and to provide the surface with a lustrous, grainless finish
• Soldering: Soldering is the process by which metallic materials are joined with the help of another liquified metal (solder).
• Polishing: In polishing, surface irregularities are removed from the workpiece by using abrasive particles which are glued to a flexible wheel or a belt
• Electropolishing: Electropolishing is a reverse process of electroplating.

Luminous efficiency: It is also known as radiant efficiency. It is defined as the ratio of energy radiated in the form of light, produces sensation of vision to the total energy radiated out by the luminous body.

Radiant efficiency = energy radiated in the form of light / total energy radiated by the body

Lamp efficiency is measured in lumen/watt.

Important Points:

Power dissipation in a lamp,

Since both bulbs are rated at the same voltage, we can say that resistance of each bulb is inversely proportional to its rated power. Therefore, the resistance of 60 W bulb (R60) is greater than the resistance of 100 W (R100) bulb.

Since lamps connected in parallel, the voltage across the both bulb is same.

The power dissipated across 60 W lamp, 

The power dissipated across 100 W lamp,

As R60 > R100, the power dissipated across 100 W is greater than 60 W.

Hence 100 W bulb will glow brighter in parallel connection.

Different light bulbs last for a different time period. Out of the given lamps, incandescent lamps have the shortest life span in working hours.

Thus, amongst the given options Eureka has the lowest operating temperature.

• Space to height ratio is the ratio of space between luminaires (S) to their height above the working plane (Hm).
• Manufacturers specify the recommended space to height ratio (SHR) for each of their luminaires.
• Typically, a recommended space to height ratio (SHR) is 1 : 2.

 

Electric Traction Systems:

• Electric traction is meant locomotion in which the driving (or tractive) force is obtained from electric motors. It is used in electric trains, tramcars, trolleybuses, and diesel-electric vehicles, etc.
• They involve the use of electric energy at some stage or the other.
• Examples: battery-electric drive, diesel-electric drive, railway electric locomotive fed from overhead AC supply, tramways, and trolly buses supplied with DC supply.

Railway Track Electrification System:

Direct Current Traction System:​

• In all cases, contact systems are fed from substations which are spaced 3 to 5 km for suburban lines and 40-50 km for main lines Service.
• Substation receive power from 110/132 kV, 3-phase network (or grid). At these substations, this high-voltage 3-phase supply is converted into a low-voltage single-phase supply with the help of Scott-connected or V-connected 3-phase transformers.
• Next low AC voltage is converted to the suitable DC voltage by using suitable rectifiers or converters (like rotary converter, mercury-arc rectifier, metal or semiconductor rectifiers).
• DC motors are better suited for frequent and rapid speed control than AC motors.
• DC train equipment is lighter, less costly, and more efficient than similar AC equipment.
• When operating under the same conditions, the DC train consumes less energy than a Single-phase AC train.
• The erection cost and maintenance cost of the conductor rail is less than that of a single-phase AC system.
• No electrical interference with overhead communication lines in the DC traction system.
• The only disadvantage of the DC system is the necessity of locating AC/DC conversion sub-stations at relatively short distances apart.
   

Single-Phase Low-frequency AC Traction System:

• In this system, AC voltages from 11 to 15 kV at the frequency (50 Hz), (50/2 Hz), (50/3 Hz) Hz are used.
• Electric supply is taken from the high voltage transmission lines at 50 Hz, then in addition to a step-down transformer, the substation is provided with a frequency converter.
• supply is fed to the electric locomotor via a single over-head wire (running rail providing the return path).
• A step-down transformer carried by the locomotive reduces the 15-kV voltage to 300-400 V for feeding the AC series motors.
• To overcome the low power factor and commutation problem in the AC Series motor, a low-frequency AC supply is used.
• Another advantage of employing low frequency is that it reduces telephonic interference.
• Substations are 50 to 80 km apart.
   

Three-phase Low-frequency AC System:

• It uses 3-phase induction motors which work on a 3 kV to 3.6 kV at (50/3 Hz) supply.
• Sub-stations receive power at a very high voltage from 3-phase transmission lines at the usual industrial frequency of 50 Hz.
• This high voltage is stepped down to (3 kV to 3.6 kV) by transformers and frequency is reduced from 50 Hz to (50/3 Hz) by frequency converters.
• This system employs two overhead contact wires and the track rail forming the third phase.
• Induction motors used in the system are quite simple and robust and give trouble-free operation.
• The induction motor used in this traction system has high efficiency and the ability of automatic regenerative braking.
   

Kando System (Single-phase AC to Three-phase AC):

• In this system, the single-phase 16-kV, 50 Hz supply from the sub-station is picked up by the locomotive through the single overhead contact wire.
• It is then converted into a 3-phase AC supply at the same frequency by means of phase converter equipment carried on the locomotives.
• This 3-phase supply is then fed to the 3-phase induction motors.
• Kando system is likely to be developed further.
   

Single-phase AC to DC System:

• This system combines the advantages of high-voltage AC distribution at the industrial frequency with the DC series motors traction.
• It employs an overhead 25-kV, 50-Hz supply which is stepped down by the transformer installed in the locomotive itself.
• The low-voltage AC supply is then converted into a DC supply by the rectifier which is also carried on the locomotive.
• This DC supply is finally fed to the DC series traction motor fitted between the wheels.
• The system of traction employing 25-kV, 50-Hz, 1-phase AC supply has adopted by Indian Railway.

The classification of electrical heating is shown below.

So, eddy current heating or induction heating comes under the category of high-frequency heating.