Air Conditioning for Railway Coaches
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Questions and Answers

What is the cooling capacity of the new roof-mounted AC units per coach?

  • 5.2 TR
  • 14.0 TR (correct)
  • 7.0 TR
  • 10.4 TR

How do the compressors in the new AC units operate under normal conditions?

  • All four compressors operate simultaneously.
  • One compressor operates; others are completely shut down.
  • Three compressors operate, with the fourth as a standby. (correct)
  • Compressors run at reduced capacity.

What type of compressors are used in the modular roof-mounted AC units?

  • Open compressors
  • Reciprocating compressors
  • Centrifugal compressors
  • Hermetically sealed compressors (correct)

What is the primary purpose of the new roof-mounted AC units in railway coaches?

<p>To improve energy efficiency and comfort. (C)</p> Signup and view all the answers

What is the power requirement of the roof-mounted units under normal conditions?

<p>11.5 KW (B)</p> Signup and view all the answers

What method is used to start the compressors to reduce electric peak demand?

<p>Sequence with time delay (D)</p> Signup and view all the answers

Which type of coaches on Indian Railways utilizes a brushless alternator for power supply?

<p>Self-generating coaches (D)</p> Signup and view all the answers

What was identified as a significant cause for excessive vibration in discharge pipes?

<p>Defective packless vibration eliminator (D)</p> Signup and view all the answers

Which modification was NOT implemented to address vibration issues?

<p>Introducing flexible mounting pads (A)</p> Signup and view all the answers

What was determined to be the major contributing factor to water ingress due to rain?

<p>Inadequate drainage area (D)</p> Signup and view all the answers

What change was made to address the problem of packing dislodging due to vibrations?

<p>Implementing a single gasket under point pressure (B)</p> Signup and view all the answers

What issue was directly related to condensate water entering the corridor?

<p>Evaporator section not being water tight (C)</p> Signup and view all the answers

What is the primary power source for coaches at low speeds and during halts?

<p>110 V lead acid battery (A)</p> Signup and view all the answers

What voltage and phase is supplied by the diesel-generating sets in End-On-Generation coaches?

<p>415/750 V, three phase (C)</p> Signup and view all the answers

Which component of the air conditioning system is NOT mounted on the underframe of the coach?

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

What is a major drawback of the conventional AC system mentioned?

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

How much weight reduction does the roof-mounted AC package unit contribute compared to the conventional unit?

<p>900 Kg (B)</p> Signup and view all the answers

What advantage does the roof-mounted AC unit provide in terms of fuel consumption?

<p>Saves fuel for hauling (D)</p> Signup and view all the answers

How is the roof-mounted AC unit installed in the coach?

<p>Lowered into the false ceiling and connected (B)</p> Signup and view all the answers

What benefit does the roof-mounted AC unit provide in terms of operational costs?

<p>It pays for itself within a year (C)</p> Signup and view all the answers

What is NOT a feature of the air conditioning system in Indian Railways coaches?

<p>External cooling units (B)</p> Signup and view all the answers

What is the maximum refrigerant charge for the roof-mounted A.C. unit?

<p>3 Kg (B)</p> Signup and view all the answers

What advantage does the hermetically sealed system have over a conventional A.C. system?

<p>Lower potential for gas leakages. (D)</p> Signup and view all the answers

How long does it take to replace a defective roof-mounted A.C. unit?

<p>Two hours (D)</p> Signup and view all the answers

Which refrigerant is used in the roof-mounted A.C. unit?

<p>R-22 (A)</p> Signup and view all the answers

What is a benefit of the roof-mounted A.C. unit being installed on the roof?

<p>Negligible dirt or dust collection. (B)</p> Signup and view all the answers

What is the weight difference between the roof-mounted A.C. unit and the conventional A.C. unit?

<p>Roof-mounted is lighter by 1800 Kg (B)</p> Signup and view all the answers

How does the roof-mounted A.C. unit control humidity during monsoons?

<p>By a microprocessor-based control system. (C)</p> Signup and view all the answers

What disadvantage does the conventional A.C. system have in comparison to the roof-mounted unit?

<p>More maintenance required. (B)</p> Signup and view all the answers

What is a key feature of the roof-mounted A.C. unit that enhances its reliability?

<p>Use of 3ph AC motors. (C)</p> Signup and view all the answers

What performance metric is described as 'Nil' for roof-mounted A.C. units?

<p>Damage due to flash floods (D)</p> Signup and view all the answers

Which type of A.C. unit has the latest technology?

<p>Roof mounted (A)</p> Signup and view all the answers

What is the range of capacity control for roof-mounted A.C. units?

<p>25% to 100% (A)</p> Signup and view all the answers

What significant problem is associated with roof-mounted A.C. units?

<p>Failure of safety cut-outs (B)</p> Signup and view all the answers

For which factor is the downtime for repair shorter with roof-mounted A.C. units compared to conventional units?

<p>Unit replacement time (C)</p> Signup and view all the answers

What is a consequence of poor maintenance for conventional A.C. units?

<p>Deterioration due to dust collection (C)</p> Signup and view all the answers

Which A.C. unit type tends to take in toilet smells?

<p>Conventional (D)</p> Signup and view all the answers

What is one of the major problems noted for roof-mounted A.C. units?

<p>Water ingress into the corridor (A)</p> Signup and view all the answers

Which reason contributed to gas leakage in one particular make of A.C. unit?

<p>Lack of vibration testing (A)</p> Signup and view all the answers

What is the downtime for repairs of conventional A.C. units described as?

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

What modification was made to address the issue of vibrations caused by the compressor mounting?

<p>Secure the compressor at the top with solid mounting pads (D)</p> Signup and view all the answers

What was identified as a primary cause of water ingress due to rain?

<p>Ineffective drainage area (C)</p> Signup and view all the answers

How was the issue of packing dislodging due to vibrations addressed in the design modifications?

<p>Introduced a single gasket under point pressure mounting (D)</p> Signup and view all the answers

What contributes to the problem of condensate water entering the corridor?

<p>Condensate carried by the blower into the duct (B)</p> Signup and view all the answers

What factor was significantly improved to reduce the risk of water ingress through the interface between the trough and the package?

<p>Apply a single gasket design with skirting (D)</p> Signup and view all the answers

What is the main advantage of the roof-mounted AC units compared to the traditional AC systems used in railway coaches?

<p>They are more energy efficient and reliable during operation. (B)</p> Signup and view all the answers

What component of the roof-mounted AC units serves as a standby during peak days of the summer?

<p>The compressors in the unit. (D)</p> Signup and view all the answers

Which system must the roof-mounted AC unit be compatible with for operation?

<p>E.O.G. systems or S.G. systems. (D)</p> Signup and view all the answers

How are the compressors in the roof-mounted AC units started to manage electricity demand?

<p>Compressors are started in sequence with time delays. (B)</p> Signup and view all the answers

What characterizes the compressors used in the modular type roof-mounted AC units?

<p>They are specially developed for dynamic conditions. (C)</p> Signup and view all the answers

What is the approximate electrical requirement of the roof-mounted AC unit under normal conditions?

<p>11.5 KW at 20 amperes. (C)</p> Signup and view all the answers

How many compressors are used in each modular AC unit fitted in railway coaches?

<p>Two compressors. (D)</p> Signup and view all the answers

What is the primary reason for the failure of the AC control panel in roof-mounted units?

<p>Vibration tests not conducted (B)</p> Signup and view all the answers

Which maintenance issue is noted as significant for conventional AC units?

<p>Deterioration from dust collection (B)</p> Signup and view all the answers

What is identified as a shortcoming specific to roof-mounted AC package units?

<p>Water ingress into the corridor (C)</p> Signup and view all the answers

How does the capacity control range of roof-mounted AC units compare to conventional units?

<p>Higher within a smaller range (A)</p> Signup and view all the answers

What type of air intake does the roof-mounted AC unit utilize?

<p>From the roof, avoiding restroom smells (C)</p> Signup and view all the answers

What is a notable performance characteristic for roof-mounted AC units compared to conventional units?

<p>Excellent performance overall (A)</p> Signup and view all the answers

What is the average downtime required to repair a roof-mounted AC unit?

<p>4 hours for unit replacement (B)</p> Signup and view all the answers

What issue is linked to cows causing heavy damage?

<p>Physical damage to the AC structure (C)</p> Signup and view all the answers

What is the primary benefit of the roof-mounted AC package units compared to conventional units?

<p>Is lighter and saves fuel for hauling (D)</p> Signup and view all the answers

What consequence does dust collection have on the conventional AC unit's performance?

<p>Quick deterioration of performance (C)</p> Signup and view all the answers

What characteristic does the latest technology in AC units possess?

<p>Features multiple compressors for better capacity control (A)</p> Signup and view all the answers

Which of the following issues is highlighted as a drawback of conventional AC systems?

<p>Heavy equipment weight (D)</p> Signup and view all the answers

In terms of installation, what is a characteristic feature of the roof-mounted AC units?

<p>Can be installed without specialized tools (A)</p> Signup and view all the answers

What total weight reduction does the implementation of roof-mounted AC units provide for 20 coaches?

<p>36 MT (C)</p> Signup and view all the answers

What is a major advantage of the hermetically sealed system used in roof-mounted AC units?

<p>Minimized refrigerant leakage (D)</p> Signup and view all the answers

What requirement is met by the traditional power source for coaches at low speeds and halts?

<p>Utilization of a 110 V lead acid battery (B)</p> Signup and view all the answers

Which of the following is part of the air conditioning system found in Indian Railways coaches?

<p>Open type compressor with a blower fan (D)</p> Signup and view all the answers

What is the voltage and phase supplied by diesel-generating sets in End-On-Generation coaches?

<p>415/750 V, 3 phase (D)</p> Signup and view all the answers

Which aspect of the roof-mounted AC package units contributes to their lower operational costs?

<p>Low cost of installation and maintenance (C)</p> Signup and view all the answers

What is the refrigerant used in the roof-mounted A.C. unit?

<p>R-22 (C)</p> Signup and view all the answers

What is the maximum refrigerant charge for the conventional A.C. unit?

<p>15-20 Kg (B)</p> Signup and view all the answers

What is a primary advantage of the hermetically sealed system in roof-mounted A.C. units?

<p>Reduced potential for gas leaks and breakdowns (C)</p> Signup and view all the answers

Which statement accurately describes the installation time for roof-mounted A.C. units compared to conventional units?

<p>Roof-mounted units take 4 hours while conventional units take 4 days (A)</p> Signup and view all the answers

What is a major drawback identified for conventional A.C. units?

<p>Potential for water leakage (B)</p> Signup and view all the answers

What feature of the roof-mounted A.C. unit helps to minimize dirt and dust accumulation?

<p>Location on the roof (C)</p> Signup and view all the answers

What is the approximate weight difference between the roof-mounted A.C. unit and the conventional A.C. unit?

<p>900 Kg (C)</p> Signup and view all the answers

What component contributes to the low maintenance of the roof-mounted A.C. unit?

<p>Absence of commutators and brushes (B)</p> Signup and view all the answers

Which factor enhances the A.C. unit's reliability and reduces breakdowns?

<p>Hermetically sealed system with no openings (B)</p> Signup and view all the answers

What is the minimum cooling capacity required for each roof-mounted A/C unit per coach?

<p>20,000 K.Cal/hr (C)</p> Signup and view all the answers

Which refrigerant is specified for use in the A/C package unit?

<p>R22 (B)</p> Signup and view all the answers

What type of compressor motor is used in the A/C units?

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

What is the rated current consumption of the compressor at 415V?

<p>8.25 Amps (D)</p> Signup and view all the answers

What is the diameter of the condenser fan used in the A/C units?

<p>533.4 mm (C)</p> Signup and view all the answers

What is the face area of the condenser coil in square meters?

<p>0.67 M2 (C)</p> Signup and view all the answers

What is the specified power factor of the compressor motor?

<p>0.8 (D)</p> Signup and view all the answers

Which material is used for the tubes in the condenser coil?

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

What is the airflow rate of the condenser fan in CFM?

<p>5000 CFM (D)</p> Signup and view all the answers

What is the refrigerant charge limit for each circuit in the A/C unit?

<p>3.0 Kg (B)</p> Signup and view all the answers

What feature of the branch diffuser allows for control of cool air quantity?

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

How is the power supply for lighting and fan loads transformed in the coach?

<p>415/190V transformer (B)</p> Signup and view all the answers

Which voltage is supplied to the water raising apparatus in the coach?

<p>240V AC (D)</p> Signup and view all the answers

What type of panel is provided inside the coach for distribution of the electrical system?

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

What is the specification of the emergency lighting battery provided in the coach?

<p>24V, 90AH (D)</p> Signup and view all the answers

What type of transformer unit is used for charging the emergency lighting battery?

<p>Charging transformer rectifier (A)</p> Signup and view all the answers

What is the electrical configuration of the feeders supplying the coach?

<p>Three-phase, 4 wire (B)</p> Signup and view all the answers

Which arrangement is used to connect adjacent coaches for power transmission?

<p>Inter vehicular couplers (C)</p> Signup and view all the answers

What does the 415V, 3-phase supply provide for the railway coaches?

<p>Light and fan loads (A)</p> Signup and view all the answers

How many parts does the transverse berth's diffuser consist of?

<p>Two parts (D)</p> Signup and view all the answers

What is the primary purpose of providing fresh air at a rate of 0.35 m³/min per person in the A.C. compartment?

<p>To maintain air quality (B)</p> Signup and view all the answers

What is the nominal current consumption of the evaporator blower fan motor at 415V, 3ph, 50Hz, AC?

<p>2.2 Amps (D)</p> Signup and view all the answers

What type of protection does the condenser motor conform to in terms of IP rating?

<p>IP 55 (A)</p> Signup and view all the answers

What is the range of RPM for the motors mentioned in the specifications?

<p>1400 +/- 10% (D)</p> Signup and view all the answers

What material is specified for the fins of the evaporator unit?

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

What is the specified face area for the evaporator unit?

<p>0.265 m² (D)</p> Signup and view all the answers

How many fins per centimeter does the evaporator unit have, considering the allowable margin?

<p>4.3 +/- 1 (C)</p> Signup and view all the answers

What is the air flow rate in CFM for the evaporator fan?

<p>2000 CFM (A)</p> Signup and view all the answers

What is the external static pressure with which the fan operates?

<p>20 mm water gauge (A)</p> Signup and view all the answers

What is the thickness of the fins used in the evaporator unit?

<p>0.19 mm (D)</p> Signup and view all the answers

Flashcards

Roof-Mounted AC Units for Coaches

Modern air conditioning units installed on the roofs of railway coaches, replacing older underframe systems.

Increased Coach Capacity

Roof-mounted AC units allow for more coaches on superfast trains like Rajdhanis.

Higher Efficiency of Roof Mounted AC units

These units use 2 higher capacity packaged air-conditioning units (7.0 TR), replacing previous units (5.2 TR each) and more efficient.

Modular Design

Roof-mounted AC units are made in prefabricated sections for easy installation and maintenance.

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Self-Generating Coaches

Coaches that generate their own electricity for AC with axle-driven alternators.

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End-On-Generation (EOG) Coaches

Type of coaches that use external power from an external source.

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Energy Efficiency

Roof-mounted units use compressors in a sequence to lower peak electrical demand, increasing energy savings.

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Low-speed power source

At low speeds and during halts, coaches use a 110V lead-acid battery for power.

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AC coach power

AC coaches get power from diesel generators on the train at 415/750V, 3-phase, 50Hz.

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Power distribution (AC)

Power is distributed to the entire train through 3-phase 415/750V feeders.

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AC equipment voltage

AC equipment in the coach operates at 415V, 3-phase, 50Hz.

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AC air conditioning

AC coaches use open-type compressors, condensers, receivers, and evaporators for cooling.

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Conventional AC drawbacks

Conventional AC systems have problems like refrigerant leakage, heavy weight, and high maintenance due to open-type compressors.

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Roof-mounted AC benefits

Roof-mounted AC units are lighter, consume less fuel, and are easier to install.

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Weight reduction (Roof-mounted)

Roof-mounted units save significant weight compared to conventional units, allowing for a possible extra coach.

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Installation simplicity

Roof-mounted units are factory-assembled, gas-charged, and easy to install by lowering into the ceiling and connecting.

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Roof-Mounted AC Unit

An air conditioning system installed on the roof of a railway coach, offering various advantages over traditional underframe units.

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Replacement Time

Replacing a faulty roof-mounted AC unit can be done quickly, within two hours, by simply lifting out the old unit and lowering in a new one.

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Water Leakage Prevention

Roof-mounted AC units are positioned outside the passenger partition wall, eliminating any risk of water leaks inside the coach.

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Fresh Air Source

Roof-mounted AC units draw fresh air from the roof through the condenser area, providing a cleaner air supply free from toilet odors.

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Hermetically Sealed System

Roof-mounted AC units utilize a hermetically sealed system with no open fittings, reducing the potential for gas leaks and breakdowns.

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Maintenance Requirement

Roof-mounted AC units are nearly maintenance-free due to their use of durable 3-phase AC motors and minimal refrigerant.

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Environment-Friendly Refrigerant

Roof-mounted AC units use a more environmentally friendly refrigerant (R-22) in smaller quantities, resulting in a reduced environmental impact.

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Rooftop Mounting Advantages

Roof-mounted AC units minimize dust and dirt accumulation in condensers, reducing maintenance needs and eliminating damage from floods or cattle.

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Humidity Control Capability

Roof-mounted AC units incorporate a microprocessor-based control system, enabling them to effectively manage humidity, especially during monsoon seasons.

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Compressor Vibration

Excessive vibrations in the discharge pipe caused by a loose compressor top or faulty vibration eliminator. Other factors include long charging lines and poor brazing.

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Roof-Mounted AC Unit Advantages

Roof-mounted AC units offer several benefits, including improved performance, reduced maintenance requirements, and enhanced passenger comfort.

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Vibration Solutions

Modifications include securing the compressor and piping, replacing faulty vibration eliminators with U loops, improving general workmanship, and conducting rigorous tests.

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Roof-Mounted AC Unit Disadvantages

While offering advantages, roof-mounted AC units also have some drawbacks, such as potential damage from floods and the need for specialized repair.

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Conventional AC Unit Advantages

Conventional AC units have advantages like lower initial cost, but they often have drawbacks such as inefficient operation and potential for odor.

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Water Ingress

Water entering the train corridor, classified into problems related to rain and condensate. Common causes include poor drainage, leaks between the package and trough, and non-standard design.

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Drainage Issue

The primary cause of water ingress from rain. Inadequate or ineffective drainage areas, particularly the trough's design, contribute to water accumulation.

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Conventional AC Unit Disadvantages

Conventional AC units, typically under the coach, face challenges like dust accumulation, inefficient operation, and potential odor.

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Damage due to Flash Floods

Roof-mounted AC units are highly susceptible to damage during flash floods, as they are directly exposed to the elements.

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Condensate Water Problems

Water from air conditioning condensation either dripping into the corridor or being blown into the duct by the blower.

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Dust Collection Impact

Conventional AC units under the coach are more prone to dust accumulation, leading to performance degradation.

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AC Technology Advancement

Roof-mounted AC units utilize the latest technology, while conventional AC units often employ older, less efficient systems.

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Capacity Control

Roof-mounted AC units offer more precise capacity control with multiple compressors, allowing for fine-tuning.

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Downtime for Repair

Roof-mounted AC units have shorter downtime for repairs compared to conventional AC units, which require more complex repairs.

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Modular Design (AC Units)

These AC units are built in prefabricated sections, making them easy to install and maintain. This means they can be assembled and replaced quickly.

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Self-Generating (S.G.) Coaches

Coaches that generate their own electricity for AC using axle-driven alternators. They are independent of external power sources.

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Energy Efficiency (Roof-mounted AC)

These units use compressors in a sequence to reduce peak electrical demand, saving energy. They are more efficient than older systems.

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Hermetically Sealed Compressors

The compressors in these AC units are sealed, reducing the risk of refrigerant leaks and breakdowns. They are designed for high reliability.

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Compressor Vibration Issues

Excessive vibrations in the discharge pipe can occur due to loose compressor parts, faulty vibration eliminators, or long, poorly fitted charging lines.

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Weight Reduction

Roof-mounted AC units save significant weight compared to conventional units, allowing for a possible extra coach.

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What does EOG stand for?

EOG stands for End-On-Generation. It refers to coaches that draw power from diesel-generating sets located at the front and rear of the train.

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What's the main power source for AC coaches at low speeds?

At low speeds, AC coaches rely on a 110V lead-acid battery for power.

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What are the drawbacks of conventional AC systems?

Conventional AC systems face issues like refrigerant leakage, heavy weight, large space requirements, and high maintenance needs.

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Weight difference between conventional and roof-mounted AC?

Roof-mounted AC units weigh significantly less (900 Kg) compared to conventional units (2700 Kg).

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What's the big installation advantage of roof-mounted AC?

Roof-mounted AC units are factory-made and pre-tested, making installation simple and quick.

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What is the impact of roof-mounted AC on fuel efficiency?

Roof-mounted AC units are lighter, reducing the weight of the train and leading to lower fuel consumption.

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How does the weight difference benefit Rajdhani Express?

Weight reduction from roof-mounted AC in 20 coaches equals the weight of one coach, allowing for one additional coach on the train.

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What is the main benefit of roof-mounted AC?

Roof-mounted AC is more efficient, lighter, and easier to install than conventional underframe units.

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Why is the roof-mounted unit considered a good investment?

Because of its lower cost and lightweight, the unit pays for itself within one year of operation.

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Condensate Water

Water from air conditioning condensation, either dripping into the corridor or being blown into the duct by the blower.

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Roof-mounted AC vs. Conventional AC

Roof-mounted AC units are newer, more efficient, and installed on the roof. Conventional AC is older, less efficient, and located under the coach.

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Advantages of Roof-mounted AC

Roof-mounted AC units offer benefits like less maintenance, better performance, and fresher air. They are also lighter and easier to install.

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Disadvantages of Roof-mounted AC

Roof-mounted AC is susceptible to damage from floods and requires specialized repair. It can be expensive to replace.

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Advantages of Conventional AC

Conventional AC units are cheaper to purchase. They may be more resistant to certain weather conditions.

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Disadvantages of Conventional AC

Conventional AC units are prone to dust, require more maintenance, and can take longer to repair. They may also smell bad.

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Why does conventional AC have more dust?

Conventional AC units are located under the coach, making them more prone to dust buildup, which affects their performance.

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What makes roof-mounted AC more efficient?

Roof-mounted AC uses the latest technology, is more energy-efficient, and has better capacity control.

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What kind of damage can roof-mounted AC face?

Roof-mounted AC units are most vulnerable to damage from floods and storms, given their exposed location on the roof.

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What is the most common problem with roof-mounted AC?

The most frequent problem with roof-mounted AC is gas leakage, caused by vibration and inadequate piping.

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Why is conventional AC prone to smell?

Conventional AC draws air from the sides, which might include odors from the toilet, leading to an unpleasant smell in the coach.

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A/C Unit Cooling Capacity

Each coach has two roof-mounted A/C units, each with a minimum cooling capacity of 20,000 K.Cal/hr (6.6TR).

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Refrigerant Compressor

The A/C unit uses hermetic or semi-hermetic refrigerant compressors working with Freon 22 (monochloro difluoro methane).

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Compressor Power Consumption

The compressor motor runs on 415V, 3Ph, 50HZ, AC power supply. It consumes 5.25KW +/-20% depending on the ambient temperature.

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Refrigerant Condenser

The condenser coil is a fin-on-tube design made of copper and aluminium. It has a large surface area for heat dissipation.

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Refrigerant Type and Amount

The A/C unit uses R22 refrigerant, with less than 3.0Kg in each circuit.

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Condenser Motor Specs

The condenser motor in the AC unit must meet specific standards for protection and performance, including IP 55 protection and adherence to IS: 325-1970, to ensure efficient and reliable operation.

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Evaporator Unit

The evaporator unit is a crucial component of the AC system responsible for cooling the air. It's designed as a fin-on-tube type with copper tubing and aluminum fins, ensuring efficient heat exchange.

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Condenser Fan

Two propeller-type condenser fans, with a diameter of 533.4 mm each, ensure sufficient airflow for heat dissipation.

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E.O.G. System

The A/C unit uses an E.O.G. (End-On-Generation) system for power supply, meaning the coaches draw power from diesel generators at the front and rear of the train.

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Fresh Air Requirement

The AC system in the coach is designed to provide at least 0.35 cubic meters of fresh air per minute for every passenger, ensuring an adequate supply of clean, conditioned air.

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Low-Speed Power

When the train is at low speeds or stopped, the coaches use a 110V lead-acid battery for power.

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Air Distribution System

The coach air distribution system is designed to efficiently distribute the cool air throughout the compartment. The system uses a combination of different types of diffusers, including Type A, Type B, Type C, and Type D, located on both main and branch ducts.

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Air Velocity

The air velocity inside the air conditioning ducts is carefully regulated to ensure optimal air distribution and passenger comfort. The system aims for a maximum air velocity of 10 meters per minutes 1.2 meters from the floor, and 15 meters per minute 150 mm below the duct or diffuser.

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Inside Temperature Control

The A/C unit can maintain inside temperatures around 24°C even when outside temperatures reach 45°C.

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Compressor

The compressor is the heart of the AC system, responsible for increasing the pressure of the refrigerant. It circulates the refrigerant and transfers heat from the inside of the coach to the outside.

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Refrigerant

Refrigerant is a special fluid used in AC systems to transfer heat. It undergoes changes in state and temperature, absorbing heat from the inside of the coach and releasing it outside.

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Roof-Mounted AC Advantage

Roof-mounted AC units offer several advantages over conventional underframe units, including lighter weight, reduced fuel consumption, easier installation, and minimal maintenance.

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Diffuser on Branch Ducts

Diffusers on branch ducts of railway coach air conditioning systems are angled to direct cool air towards lower berths, ensuring comfortable air distribution for passengers.

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Adjustable Vanes in Diffusers

Branch diffusers on the longitudinal side of the coach are equipped with adjustable vanes for controlling the volume of cool air delivered to specific berths.

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Diffuser Design for Transverse Berths

The diffuser for transverse berths is composed of two parts, each directing cool air towards the lower berths of the bay, ensuring even cooling across the coach.

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Coach Electrical Supply

The electrical load of a railway coach is powered by two sets of 415V, 3-Phase, AC, 4-wire feeders connected through inter-vehicular couplers.

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Control Panel Function

Each coach has a 415V control panel for managing the distribution of electrical power, including switching feeders and controlling the supply to the entire coach.

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Transformer Role in AC Supply

A 415/190V transformer converts the 415V, 3-phase supply to 190V for powering lights and fans, ensuring safe and efficient operation.

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Control Panel/Junction Box for 190V System

A separate control panel inside the coach manages and distributes the 3-phase, 4-wire, 190V (110V, 1-phase) system for lights and fans.

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Interlocked Couplers for Power Transmission

Latched and electrically interlocked couplers with cable and plug sockets transmit electrical power between adjacent coaches, ensuring continuous supply throughout the train.

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Emergency Lighting Battery

A 24V, 90AH emergency lighting battery is installed on the underframe of the coach to provide power to emergency lights in case of power failure.

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Battery Charging Transformer Rectifier Unit

A dedicated battery charging transformer rectifier unit situated on the underframe is responsible for charging the emergency lighting battery continuously.

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Study Notes

Roof Mounted Air-Conditioning Package Units for Railway Coaches

  • Roof-mounted AC units for Indian Railways coaches offer more comfort and allow for more coaches on superfast trains (e.g., Rajdhani Expresses).
  • These new units are more efficient and lightweight, manufactured domestically.
  • Two high-capacity (minimum 7.0 TR cooling) packaged units replace the previous underframe units (5.2 TR each).
  • The new units are placed above the toilets on both ends of the coach, supplying conditioned air throughout.
  • Four compressors are fitted per unit, but typically three operate, with one as a backup for peak summer demand.
  • This advanced system is more energy-efficient and reliable than existing open systems.
  • The units are suitable for both electric-originated generation (EOG) and self-generating (SG) coach systems.

Existing Systems

  • Current systems use open-type compressors, creating refrigerant leakage and maintenance issues, along with higher energy consumption.
  • Self-generating (SG) coaches use axle-driven alternators, generating 110V DC power, supplementing with batteries for low speeds and halted operation.
  • End-On-Generation (EOG) coaches use diesel-generating sets for power. These sets operate at 415/750 V, 3 phase, 50 Hz AC and power the train and distributed through feeders.

Roof-Mounted AC Package Unit Features

  • Lightweight (~900 kg) compared to traditional units (~2700 kg)
  • Faster installation (4 hours) versus traditional systems
  • Environmentally friendly refrigerant (R-22 or R-134A, lower than 3kg)
  • Less dust/dirt build-up, lower maintenance due to roof-mounted position
  • Protected from flood damage
  • Less likely to be damaged from cattle moving about.

Performance Comparison

  • Roof-mounted units significantly outperform conventional units.
  • Key performance indicators for roof-mounted units highlight improved performance in comparison with conventional units

Performance Issues and Solutions

  • Gas leakage, water ingress, and tripping of packages are common issues with current systems.

  • Problems in control panel components and switchgear lead to problems.

  • Solutions include:

    • Improved design for better water drainage
    • Increased robustness for vibration control
    • Standardization of control panel designs
    • Upgrade to better quality components.

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Related Documents

Roof Mounted Air-Conditioning Package Units for Railway Coaches PDF
A/C 3Tier Sleeper Coach PDF

Description

Explore the advancements in roof-mounted air-conditioning units for Indian Railways coaches. This quiz covers the efficiency, design, and technology behind the new systems replacing older models. Dive into details about their cooling capacity and energy-saving features.

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