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| D | E | M | U | Diesel-Electric Multiple Unit Car Shed |
| S | H | E | D | Northern Railway, Jalandhar City |
Last updated: May 21, 2001 01:16 PM
Frequently Asked Questions
I have tried to cover as many questions that usually cross one's mind as possibe. However, if you want any specific information, please email me.
A DEMU or a Diesel-Electric Multiple Unit is a self-powered train set which can move in either direction. It is powered by an on-board diesel engine on one of the cars and consistes of two or more cars with a provision for the driver on either end of the train set. They are usually air-braked and enjoy a fast acceleration and deceleration. The transmission of the power from the diesel engine to the wheels is done by converting the mechanical energy into electrical energy (hence the electrical in its nomenclature) and feeding the electrical energy to traction motors on the wheels. The conversion of energy may be into DC/ AC and hence the transmission may be DC-DC, AC-DC or AC-AC. DEMUs are very popular and widespread being energy-efficient on almost all Railways (or railroads as our American friends would call it) of the world.
2. What is the difference between a DMU and a DEMU?
A Diesel Multiple Unit (DMU) can be of one of the following types:
Diesel Mechanical Multiple Unit (DMMU)
Diesel Hydraulic Multiple Unit (DHMU), or
Diesel Electric Multiple Unit (DEMU)
They are basically divided into such categories on the basis of the mode of tranmission of energy from the diesel engine to the wheels. In the DMMU and DHMU, the diesel engine is normally underslung (mounted under the underframe of the car); whereas the diesel engine in a DEMU is onboard (mounted above the underframe of the car).
The DEMU is powered using a diesel engine.
4. How is the DEMU controlled?
The DEMU is controlled on either end of the train set. The four 19-pin control cables run through the length of the train and are interconnected from one car to the other using couplers. The diesel engine is governed by an electronic Load and Speed Control card supplied by Governors America Corp (GAC). This controls the fuel supply to the fuel actuator and hence controls the supply of fuel into the diesel engine by sensing the load of the train.
5. How many persons does the DEMU carry?
A three car DEMU set can carry a total of 603 passengers ( standees and sitting accomodation). The train set is vestibuled to facilitate passenger movement within the train.
6. Where does the DEMU run on Indian Railways?
The DEMUs run on the following divisions of Indian Railways:
Firozepur Division: Linking almost all major places in Punjab.
Delhi Division: Delhi-Shamli section.
Varanasi Division: Varanasi-Allahabad section.
Danapur Division: Patna-Mughalsarai section.
Rajkot Division: Ahmedabad-Abu Road section and Mehsana (MG DEMU)
Vijaywada Division: Linking almost all major non-electrified territories on the division.
Bangalore Divison: Bangalore-Mysore section.
DEMUs also run on the Chennai, Tiruchirapalli and Ernakulam divisions.
7. What are the alternatives to the DEMU?
The conventional unidirectional train - a locomotive with coaches/cars attached is the train the DEMU replaces usually. On electrified territorry, the alternative mode of (rail) transport is the Electrical Multiple Unit (EMU) which is similar in construction, except that it does not carry a diesel engine and is dependent on the electric supply for traction.
8. What is the power of the DEMU?
There are two variants of the DEMUs:
the 700hp three car set (conventional DEMU)
the 1400hp four car set (High horse power DEMU)
9. Who has manufactured the DEMU?
In India, the DEMU is manufactured by the Integral Coach Factory (ICF), Chennai.
10. On which power-pack / diesel engine does the DEMU run?
The 700 hp DEMU homed at Jalandhar runs on a Cummins diesel engine model VTA 1710 L. This engine is also used on some models of the Diesel Electric Tower Car (DETC) and the Tie-tamping machines (TTM) on the Indian Railways.
11. How are its axles powered?
The power to the axles of the DEMUs are transmitted using an AC-DC transmission i.e. the power of the diesel engine is converted into electrical (AC) energy using a Traction Alternator. This is then rectified on the underslung main rectifier set. The DC is then charged into the Traction Motors, which are mounted on all the four axles of the Driving Power Car (DPC). The four traction motors are permanantly connected in two series-parallel connection with the provision of isolating upto two traction motors in case of a fault.
12. What is the speed potential of the DEMU?
Presently, the DEMUs on Indian Railways run at a top speed of 100 kmph (about 60 mph).
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Car Shed, Northern Railway, Jalandhar 2001 - 2005. All rights
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