RDSO/PE/SPEC/D/AC/0048-2OO3(REV. O ) SPECIFICATION FOR FIRING CIRCUIT UNIT FOR MERCURY IN GLASS THERMOSTAT. Revision

Transcription

1 Page 1 of 15 RESEARCH DESIGN & STANDARDS ORGANIZATION MINISTRY OF RAILWAY POWER SUPPLY & EMU DIRECTORATE TITLE SPECIFICATION FOR FIRING CIRCUIT UNIT FOR MERCURY IN GLASS THERMOSTAT S.No. Date of amendment Revision APPROVED EDPS

2 Page 2 of 15 SPECIFICATION FOR FIRING CIRCUIT UNIT TO BE USED FOR MERCURY IN GLASS THERMOSTATS 0. PREFACE The present design of mercury in glass thermostat can provide a temperature differential of deg. C only which causes frequent switching on & off of compressor thus affecting their reliability. Moreover as there was no specification for existing mercury in glass thermostats the reliability of thermostats is also getting affected adversely due to inadequate design of firing circuits. To overcome the above this specification has prepared by incorporating additional features of defect indication, higher temperature differential, provision for locking the settings etc. 1. SCOPE The specification covers the general guidelines for design and manufacture of firing circuit unit for Mercury in glass thermostat to be used in control panel for air-conditioned coaches to provide control signals for compressors. The specification covers the working conditions, environment, overall size and general properties of various components to be used for design ands manufacture of firing circuit. The firing circuit is used to switch ON & OFF the control supply for contactors of compressors to be able to maintain the inside coach temperature within desirable limits. The firing circuit should have necessary provisions to restrict the current flow through the mercury in glass thermostats within desirable limits to prevent any damage to them. The firing circuit should be able perform satisfactorily in the extreme service conditions normally encountered in application in railway coaches.

3 Page 3 of 15 2.BASIC GENERAL REQUIREMENT AND SERVICE CONDITIONS 2.1 Environmental conditions: Maximum ambient air temp: 57 deg.c. Average ambient air temp. : 35 Deg. C. Maximum relative humidity: 100% Atmosphere: Coastal area : Extremely dusty and desert weather and desert terrain in certain areas. The dust content in air may reach as high values as 1.6 mg/m cub. The equipment shall be designed to work in coastal area in humidity salt laden and corrosive atmosphere. The maximum value of the condition will be as under ; Annual rainfall : Max. PH Value 8.5 Sulphate 7 mg/litre Max Concentration 6 mg/litre of chlorine Max. conductivity 130 micro- Semen/CM Ranging Between 1750 to 6250 mm

4 Page 4 of 15 Altitudes : Not exceeding 1200 m 2.2 The Unit shall be suitable for rugged service normally to be met within Railway Rolling Stock, where coaches are expected to run upto a maximum speed of 160 kmph in varying climatic conditions existing throughout India. 2.3 Vibration and shocks The emergency lighting system shall withstand satisfactory vibrations and shock normally encountered in normal service as indicated blow:- (a) Maximum vertical acceleration g (b) Maximum lateral acceleration g. (c ) Maximum longitudinal acceleration g. ( g being the value of acceleration due to gravity) The vibrations are of sine wave from and frequency of vibrations is between 1 Hz and 50 Hz. The amplitude a expressed in mm is given as a function of f by a=25/f for value of f from 1 to 10 Hz. And a=250/f²for the value of F exceeding 10 Hz. and upto 50 Hz. 3. SYSTEM OF POWER SUPPLY 3.1 End on generation: The firing circuit will be fed from V AC, 50 Hz power supply on coaches working on End on generation system of power supply.

5 Page 5 of Self generating system of power supply: The air-conditioned coaches fitted with inverters will be supplied from 110 +/- 5% V AC, 50 Hz power supply obtained in the coach inverter. For the under slung type AC coaches supply will be V DC. 4.0 DESIGN OF FIRING CIRCUIT UNIT The firing circuit design should meet the following functional, performance and dimensional requirements. 4.1 Normal Operating Mode : The unit will operate in two settings of high and low for heating and cooling modes For each mode two thermostats will be used to define the lower and upper limit of temperature range for that setting as given below. Compressor/Heater ON 24 deg.c thermostat connects. (Ti>=24 deg.c) 26 deg.c thermostat connects. (Ti>=26 deg.c) 19 deg.c thermostat disconnects. (Ti<19deg.C) 17 deg.c thermostat disconnects. (Ti<17deg.C) Compressor/Heater OFF 22 deg.c thermostat disconnects (Ti<22 deg.c) 24 deg.c thermostat disconnects (Ti<24 deg.c) 21 deg.c thermostat connects (Ti>=21 deg.c) 19 deg.c thermostat connects (Ti>=19 deg.c)

6 Page 6 of Using the logic table above we have four different states possible that will be used to get a temperature differential of 2+/-0.2 deg.c. The accuracy of cut-in and cut-out temperature in this manner will be derived from the accuracy offered by mercury thermostats, i.e., +/-0.2 deg. C Thermostats playing an active role during a particular temperature setting are said to be the active thermostats. For example if the setting is low, the active thermostats are 24 deg.c and 22 deg.c for cooling purposes The functional concept of firing circuit logic further explained as below: a) High mode: Cooling: compressors switch on when the thermostat of 26 deg. C setting triggers on and switch off when the thermostat corresponding to 24 deg. C setting triggers off. Heating: Heaters switch on when thermostat of 19 deg. C switches off and switch off when thermostat of 21 deg. C triggers off. b) Low Mode: Cooling: Compressors switch on when the thermostat of 24 deg. C setting triggers on and switch off when thermostat of 22 deg. C setting triggers off. Heating: Heaters switch on when the thermostat of 17 deg. C triggers off and switches off when the thermostat of 19 deg. C triggers off During failure of any of the active thermostat the system should work with healthy thermostat only In case of failure of both the active thermostat system will automatically switch over to only healthy thermostat left in the particular heating/ cooling mode.

7 Page 7 of In case of failure of all the three thermostats system will work in only manual mode The switching current flowing through the mercury in glass thermostat should not exceed 10 ma. 4.2 Error Diagnostics for thermostats: The triggering circuit shall diagnose the working of all the setting of thermostats using the following fact: A 26 deg. C thermostat shows electrical continuity at all temperatures above 26 deg. C. Similarly a 24 deg. C or a 21 deg. C thermostat shows continuity at all temperatures above their respective setting. Therefore when the 26 deg. C thermostats shows a continuity, any thermostats of a lower setting that does not show a continuity can be deduced to have developed a discontinuity and hence rendered defective Similarly any if any lower setting thermostat does not show continuity whereas the higher setting thermostat is showing continuity the lower setting thermostat should be treated as defective To avoid the malfunctioning of firing circuit, due to failure of higher setting thermostat (26 deg. C), the compressor should automatically switch on after 20 minute while working in cooling High mode and 26 deg. C thermostat wil l be treated as defective Similarly while working in Cooling Low mode if compressor does not switch on 24 deg. C thermostat will be treated as defective and compressor will switch on automatically An Array of 6 red LED s shall be sued in the front panel of the device to indicate defect in any of the six thermostats.

8 Page 8 of The status of defective thermostat should be reset on restarting the system. 4.3 Locking arrangement for temperature settings: To prevent change of setting by unauthorised person unit will have following provision. The firing circuit will also feature a lock for temperature selector toggle switch. The lock switch will operate as per the following methodology: The system by default will be in the lock mode The unlock switch is kept depressed continuously for 5 seconds the system enters an unlock state and stays in an unlock state for 15 seconds Temperature setting can be changed only during the unlock state duration. 4.4 Prevention of bypassing of thermostat The system should have provision to prevent the manual operation except during critical defects as given below. a) If any one of the active thermostats are defective. b) During a system power supplies failure of firing circuit unit of the system bypass should be automatically effected On occurrence of critical errors the system will automatically allow the activation of manual operation at the press of the manual toggle switch Otherwise when system is healthy even operation of manual switch will not effect the bypassing of thermostat.

9 Page 9 of Switches: The firing circuit unit will have following switches. 1) the lock/unlock switch: the key-board except for the manual switch will be kept under lock normally. The keyboard can be unlocked using the unlock algorithm provided above. 2) The bypass switch: for bypassing the thermostatic system in case of a critical failure as described above. 3) The temperature selection switch, for toggling between low and high settings. 4.6 LED The front plate of firing circuit unit will have following LEDs. 1) Power LED (1) to indicate whether power supply is working or not. 2) Setting LED: a bi-led to glow red when Hi setting is chosen and green when Low is chosen. 3) The relay status of each of the four relays corresponding to compressor1, compressor2, heater and bypass relay 4) Error LED: Array of 6 red LED s to indicate an error on one of the six thermostat. 5) All LEDs should be marked. 4.7 Enclosure The overall dimentions of firing circuit unit should be within 100mmx55mmx65mm with mounting holes at 65mmx65mm of 4 mm size. The name / identification plate to be provided on the firing circuit unit shall be of bright anodised aluminum with black letters embossed or etched on white background.

10 Page 10 of Properties of Components to be used. Electronic components used shall be as per following: (i) (ii) IC (Integrated circuit) shall be of industrial or mill grade. Electrolytic capacitor shall be rated for a maximum temperature of 105 deg. C. (iii) Paper/polyster capacitor shall be rated for a maximum temperature of 85 deg. C. (iv) The resistances shall be preferably made of metal film of adequate rating. (v) Switching devices such as transisters, MOSFETs and IGBTs shall have junction boxes 150 deg. C (vi) The devices shall have adequate thermal margin at the ambient of 55 deg. C. The protective-cum-adhesive coating used on PCBs should be clear and transparent and should not affect colour code of electronic component. The heavy components should be properly tide or fixed. The shoulder connection should be with good finished. The electronic circuits and components should generally meet the RDSO specification No Spec/E-16/1 Rev. A for Reliability Assurance quality of electronics to be used for Railway application. The hardware shall confirm to IS Specification for precision hexagonal head bolt, screws, nut and lock nuts. All mild steel hardware shall be cadmium plated and passivated to IS TESTS The following tests will be carried on the units.

11 Page 11 of 15 a) Prototype Tests The following tests shall be conducted during prototype test. i) Visual Test ii) Performance test iii) Dielectric Test iv) Insulation Test v) Temperature rise test (Dry heat run test) vi) Temperature rise test ( Damp heat test ) vii) Vibration and Shunting Shock test viii) Burn in test ix) Surge and Transient Test x) Combined Dust heat and Humidity Test xi) Reverse polarity Test xii) Electrical Endurance Test b) Acceptance Test The following tests shall be conducted during acceptance test. i) Visual Test ii) Insulation Test iii) Performance test iv) Reverse polarity Test c) Routine Test The following tests shall be conducted during routine test. i) Visual Test ii) Dielectric Test iii) Insulation Test iv) Performance test v) Reverse polarity Test

12 Page 12 of 15 i) Visual test : The unit should be checked visually for dimensions. The general workmanship should be good with all the component properly secured and sharp edges rounded off. The overall dimensions with mounting arrangement will be as per specification. ii) Performance test: The unit shall be tested for its functioning at upper voltage limit, lower voltage limit and rated voltages of supply system. The unit should work satisfactorily, giving switching on and off control signal. The unit should also be tested for meeting the performance requirements mentioned in para 4 of the specification. During acceptance test performance test will be carried out on 10% of offered quantity with minimum on 2 pieces. iii) Dielectric test: The dielectric test shall be conducted as per IEC for supply voltage range between 72 V and 125 V with rms value of test voltage as 1000 V. iv) Insulation test: The insulation resistance of the unit between earth and current carrying parts shorted together shall be more than 10 mega ohm at a ambient temperature of 55 degree C measured with 500 V megger. v) Temperature rise tests: (Dry heat run test) The tests shall be carried out as per clause 5.6 of IEC on the complete electronic assembly in closed condition as during normal operation, on full load, placed in test chamber where temperature is

13 Page 13 of 15 progressively raised from ambient from 70 degree C as per IEC 571. At the end of this test the performance test is repeated. vi) Temperature rise test (Damp heat test) The temperature rise test (Damp heat test) to be conducted as per clause 5.7 of IEC At the end of this test the performance test is repeated. vii) Vibration and shock te sts: Vibration and shock test to be conducted as per clause and 5.10 of IEC at 3g in each of three directions. viii) Burn in test: The unit will be kept in energised and switched on condition by using external supply placed in a chamber for 48 hours. During the test the temperature in the test chamber shall be maintained at 55 degree C. On completion of the test the unit should not show any signs of deterioration in the performance or any other failure. ix) Surge and Transient Tests: The test shall be conducted as per clause 22 of IEC 571 and performance to be checked after the test. x) Combined Dust, humidity and heat tests: Dust, humidity and heat tests to be conducted as clause 5.9 of IEC 571. The performance test should be repeated after the test.

14 Page 14 of 15 xi) Reverse polarity test: The unit shall remain functional after applying 200V for one minute in correct polarity as well as in reverse polarity. xii) Electrical endurance test: The unit will be subjected to switching operations with maximum 15 seconds on period and 15 seconds off period. None of the unit s component should show signs of damage. 7.0 DEVIATIONS The tenderer shall furnish clause by clause comments on this specification while making the offer clearly bringing out the deviations, if any.

15 Page 15 of 15 DISTRIBUTION: 1 CEE / Eastern Railway, Fairlie Place, Kolkata 2 CEE / Northern Railway, Baroda House, New Delhi 3 CEE / Central Railway, Mumbai CST 4 CEE / Northeast Frontier Railway, Maligaon, Guwahati 5 CEE / North Eastern Railway, Gorakhpur 6 CEE / South Central Railway, Secunderabad 7 CEE / Southern Railway, Park Town, Chennai 8 CEE / South Eastern Railway, Kolkata 9 CEE / Western Railway, Churchgate, Mumabi 10 CEE / North Central Railway, Hasting Road, Allahabad 11 CEE / Western Central Railway, Jabalpur 12 CEE / Integral Coach Factory, Chennai. 13 CEE / East Coast Railway, Bhuvneshwar 14 CEE / East Central Railway, Hajipur 15 CEE/ Rail Coach Factory, Kapurthala 16 CEE./ North Western Railway, Jaipur 17 Director / IRIEEN, Nasik Road 18 Director / CAMTECH, Gwalior 19 Secy.(Elec.) Railway Board, New Delhi 20 DDSE/DOC. 21 ADE-9 22 Unit Supervisor