line diagram of air conditioning and layout of ac circuit in lhb coaches.

1. MADAN MOHAN MALAVIYA UNIVERSITY
OF TECHNOLOGY
GORAKHPUR , UTTAR PRADESH 273010
INTERNSHIP REPORT ON - Line Diagram of Air Conditioning and layout of AC
circuit in LHB AC coaches .
NAME – ANKIT KUMAR YADAV
ROLL NO. – 2019031031
SECTION – A
DEPARTMENT – ELECTRICAL ENGINEERING
SUBJECT – INDUSTRIAL TRAINING
SUBJECT CODE – BEE - 45

2. WHY AIR CONDITIONING IN RAILWAY COACHES
IS REQUIRED ?
• Passengers during railway travel are adversely affected by infiltration of air unpleasantly laden
with dust due to open windows. This is more in case of high speed passenger carrying trains.
• Secondly for a tropical country like India, the temperature varies from 48-degree C during summer
to 2-degree C during winter.
• Air-conditioning of railway coaches is, therefore, necessary for the maximum comfort and well-
being of passengers in a railway travel.
• In keeping passenger comfort on priority, air conditioning of coaches for passengers is being done
by the Indian Railways.

3. BASIC REQUIREMENTS FOR COACH AIRCONDITIONING
SYSTEM
• Supply of clean fresh air at a controlled uniform temperature in the coach.
• Providing, within the confines of the Railway carriages to the continuously changing number of
on-board passengers.
• Provision for heating as well as cooling on a train that travels through areas of widely differing climate
during its journey round the year.
• Operation of the air conditioning equipment from self-generated power (Self generating coaches), power
from power cars (EOG coaches), power from locomotives (HOG coaches) and controlled on the train.
• Securing sufficient air movement throughout the various section of the railway coaches.

4. SALIENT FEATURES OF RMPU FITTED ON LHB AC COACHES
• Micro-Controller based AC Package unit. Control and regulation function of air conditioning system
(two nos. RMPU) are performed by single Microprocessor controller unit with software installed in it.
• The refrigeration system comprises two distinct refrigeration circuits i.e. two compressors, two
condensers, two cooling coils, one heater etc.
• Servo-Motor Controlled Fresh Air Damper for automatic Pre-cooling / Pre-heating.
• Micro-Processor Control (with RS 232 Port) with fault Diagnostics and Data acquisition system.
• Motors protected with Thermal switches.

5. RMPU ON LHB COACHES.

6. DETAILS OF AIR CONDITIONING SYSTEM IN LHB AC
COACH
The AC system for the LHB coaches consists of the following assemblies:
• Compact air conditioning unit .
• Duct system .
• Exhaust air system (Exhaust air unit, WC/WC exhaust fan, WC/ Switch cabinet exhaust fan) .
• Circulating air duct system .
• Fresh air screen .
• Open/closed-loop control devices .
• Sensors .

7. Microprocessor Based Controller for RMPU
The salient features of microprocessor-based controller are given below:
• It is a fully automated control and monitoring system for all capacity RMPU units
• The controller has fault diagnostic facility for continuous storage of various electrical faults in the
system, in time sequence manner.
• The fault data can be downloaded from the controller for analysis purpose.
• This unit works on 110 ± 30% V DC/AC.
• A Real Time Clock (RTC) is provided to determine the date and time at which the fault has occurred.
• Controller read the position of the Set Point Generator (7 positions) installed inside.

9. FUNCTIONS OF OPERATION OF RMPU
• The outside air (fresh air) is sucked in via the two fresh air screens and their air filters on the carriage side wall.
• The temperature inside the coach is maintained as per the temperature setting selected by the operator.
• The difference between cut in and cut out temperature shall be 2°C. The difference of 2°C reduces the duty cycle
of compressor & eventually the failures of compressors.
• Fault storage/diagnostics system: Faults are recorded automatically. Faults can be downloaded by Laptop.
Display Unit is available. Trouble shooting instructions are displayed on the screen.
• The heater is cycled with a period of 60 seconds The ON period of the heater is controlled by a control signal of
the computer.

10. MODES OF OPERATION OF RMPU
The following are the main modes of operation:
-- Pre-Heating Mode
-- Pre-Cooling Mode
-- Normal Operating mode
-- Cooling Mode
-- Heating Mode
-- Dehumidification mode
-- Shut down Mode
-- Manual Mode

11. Pre-Heating Mode
 If the Ambient Temperature & Room Temperature is less than 14-degree C, the controller decides to
operate in Pre- Heating mode.
 In this mode the fresh air/re-circulating air flap set to 100% re-circulation air and exhaust fans are
turned off.
 Heaters are operated at its maximum duty cycle (55 seconds ON and 5 seconds OFF)
 This cycle runs for 30 minutes, after that depending on temperature, mode changed to
Cooling/Heating.
Pre-Cooling Mode
 If the Ambient Temperature & Room Temperature is greater than 28-degree C, the controller decides to
operate in Pre-cooling mode.
 In this mode the fresh air/re-circulating air flap set to 100% re-circulation air and exhaust fans are
turned off.
 Both Compressor are turned ON for maximum Cooling.
 This cycle runs for 30 minutes, after that depending on temperature, mode changed to Cooling /
Heating.
Normal Operation Mode
 Depending on the Ambient Temperature, controller selects Heating or Cooling
mode.

12. Cooling Mode
 During Cooling mode, the controller selects depending on the difference in
temperature between SET temperature and Room Temperature.
 If the difference in temperature is less than 5-degree C and greater than 2-degree C,
Condenser & one compressor turns ON.
 If the difference in temperature is greater than 5-degree C, Condenser with both
compressors ON
Heating Mode
 During Heating mode, the controller selects depending on difference in
temperature between SET temperature and Room Temperature for one of the 3
Heating cycle duty cycles:
• Minimum duty cycle - 5 sec ON & 55 sec OFF.
• Medium duty cycle - 30 sec ON & 30 sec OFF.
• Maximum duty cycle - 55 sec ON & 5 sec OFF.
De-Humidification
 Dehumidification process starts, if the relative humidity of return air is more than
60%.
 During 5 min cycle in this process, first compressor and heater are ON, while Second
compressor remains in OFF position.
 The heater Duty Cycle is 30 sec ON and 30 sec OFF.
 After 5 minutes the Relative Humidity is again monitored, and if still it is more than
60%, the cycle repeats till the RH is reached less than 60%.

13. Shut Down Mode
 Air Conditioning system will be shut down when the Air-Con switch is turned OFF or
when there is no 400 V level supply.
 Controller selects the corresponding mode at which the operating will be shut down
sequentially i.e., if it is in Heating mode / Pre-Heating Mode, Heaters are switched
OFF and if it is in Cooling / Pre-Cooling mode, compressors and condensers are
switched OFF with the time delays assigned between them.
Manual mode
 The Manual mode can only be activated through serial interface and application
software with the help of laptop. This Mode makes testing of the individual outputs
of the system.

14. VAPOUR COMPRESSION CYCLE .
Main component of Vapour compression cycle are:
Compressor (Compression)
Refrigerant is drawn from evaporator in dry vapour & low-pressure state by suction strokes of the compressor. In
compression stroke, the refrigerant pressure being increased due to increase pressure of vapour, temperature of
vapour increases and send to the condenser unit for condensation. (Refrigerant in high pressure & in vapour form)
Condensor ( Condensation )
It is intended for cooling the hot gas & liquefying it. It may be air cooled or water cooled. High temperature
refrigerant in vapour state is received in condenser unit where the heat is rejected with the help of natural air of
condenser fan, which results refrigerant returns to liquid state. (Refrigerant in high pressure & in liquid form).

15. Expansion Valve (Expansion)
Expansion valve is provided just before evaporator unit. After condensation, the liquid refrigerant passes
through this valve and enters this evaporator unit at low pressure & low temperature. Its function is to control
& regulate the rate of flow of liquid refrigerant under high pressure and allow it into the evaporator under low
pressure or expended the refrigerant. The expansion valve admits more refrigerant when air conditioning load
is high & reduces it to minimum when load is low. (After expansion refrigerant in low pressure & in liquid
form).
Evaporator (Evaporation)
Expanded low pressure liquid refrigerant enters into the evaporator unit and converted into vapour form by
gaining latent heat through circulating air with the help of blower fan thereby cooling the space and thus
refrigeration cycle is completed.

16. VAPOUR COMPRESSION CYCLE .

17. THANK YOU …