FIELD OF INVENTION
The invention relates to energy conservation in testing of diesel engine. More
particularly, the invention relates to an electrical feed back system adaptable for
testing of Diesel electric locomotive.
BACKGROUND OF INVENTION
The power pack (diesel engine + alternator) of Diesel Electric Locomotives is
tested by dissipating power generated through water load box. Water load box
consists of a tank filled with water in which a plurality of metal plate are dipped,
the metal plates are connected to positive terminal and the tank body is
connected to negative terminal of a rectifier connected to the alternator.
The existing load box testing system dissipates power generated by engine in the
atmosphere which causes a total loss of energy generated by the engine, besides
consumption of a lot of water, and decay of the metal plates and the tank. Thus,
, the existing testing system leads to loss of power, and water, and damage the
environment.
OBJECTS OF INVENTION
It is therefore an object of the invention to propose an electrical feed back
system for testing of diesel electric locomotives, which eliminates the
disadvantages of the prior art.

Another object of the invention is to propose an electrical feed back system for
testing of diesel electric locomotives, which allows retrieved of washable
electrical energy for channelising to the power grid.
A still another object of the invention is to propose an electrical feed back system
for testing of diesel electric locomotives, which is economic and easy to
manufacture and maintain.
Yet another object of the invention is to propose an electrical feed back system
for testing of diesel electric locomotives, which includes a device based inverter
to provide a harmonics free current by operating in continuous current mode.
A further object of the invention is to propose an electrical feed back system for
testing of diesel electric locomotives, in which the inverter includes a digital,
controller to ensure desired switching of the power semiconductor devices in the
inverter to ensure continuous operation and simultaneously maintain other
control & protection functions.
A still further object of the invention is to propose an electrical feed back system
for testing of diesel electric locomotives, which includes atleast one transformer
and tap changer arrangement for converting of variable Dc to fixed AC.
Yet further object of the invention is propose an electrical feed back system for
testing of diesel electric locomotives which recovers energy being wasted in prior
art water load box, and capable of feeding the energy back to grid for utilization
in other loads in order to reduce the operational cost.

Another object of the invention is to propose an electrical feed back system for
testing of diesel electric locomotives, which does not cause any damage to the
environment.
SUMMARY OF INVENTION
Accordingly, the present invention provides an electrical feed back system for
testing of diesel electric locomotives. Output of the alternator -
rectifier/generator mechanically coupled with the diesel engine is connected to a
3-phase inverter. Thus DC power of above power pack is converter to three
phase, 50 Hz AC supply, which is stepped up and isolated by a transformer
connected to grid feeder through a tap changer for ensuring the output voltage
to grid voltage level. Harmonics input to the grid is minimize by ensuring •
continuous current operation of the inverter.
According to the invention, the power generated by a diesel locomotive during
testing is variable DC supply starting with low voltage high current to high
voltage low current of order of 2 MW. This variable DC power is converter to 3
Phase, 50HZ, 11 KV or 33KV level with power conditioning, fed to the system for
consuming in other loads connected with grids. Thus, power is recovered and
utilized. In contrast, in the prior art, the variable DC power produced is
dissipated in water load box ( a metal tank filled with water and having metal
'plates connected to positive and negative terminals of supply. Due to flow of
current, water in tank is heated up and energy is released to atmosphere)
resulting in wastage of energy beside damage to environment.

Thus, the present invention provides an electrical feed back system, in general
for testing of high power diesel engines and in particular to testing ofpower pack
used in diesel electric locomotives used in railways. The power pack is an
assembly of diesel engine with alternator-rectifier or DC generator. The power
generated by the diesel engine is tested in directed by applying electrical load to
the power pack. The variable DC power produced by the power pack is
converted to a three-phase 50 HZ supply with the help of a power semiconductor
device inverter. The output of the inverter is connected to a three-phase
transformer, whose primary winding is connected to receptive 11 KV/33 KV
feeders thru a tape changer. Thus, the power produced by the diesel engine is
fed to the power system for further utilization.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1 - shows an electrical system for testing of diesel electric locomotive
according to prior art.
Fig. 2 - shows an electrical feed back system for testing of diesel electric
locomotive as per present invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
According to present invention, an electrical feed back system is proposed for
testing of diesel electric locomotives used in railways. The power produced by
the diesel engine during full load testing is converted from Variable DC to a fixed

voltage and fixed frequency three phase AC supply, and fed into the available
electrical grids. The detail of electrical feed back system is described below.
Power Pack (Figs 1 & 2)
The diesel engines (1) after assembly are tested at full load to establish their
proper working (a). As direct mechanical loading is not only difficult but its fine
control is almost impractical, for loading of diesel engine generally an electrical
machine (2) is connected to convert mechanical energy produced by the engine
(1) electrical energy, and the electrical machine in turn is connected to load. In
Diesel Electric Locomotive, two types of power packs (1,2) are used; diesel
engine (1) directly coupled to DC generator (2) or to an alternator - rectifier
(2,3) the later is preferred. The power pack is tested for its capacity at full load
at various predefined speeds after assembly and again at Locomotive to
configure and fine tune the control system. In the prevailing test arrangement,
Dc variable supply produced by power pack (1,2) is directly connected to a water
load box (8), wherein the electric power is converter to heat energy, which is
released into atmosphere. Thus, engine gets indirectly loaded.
Power Inverter (4)
Figures - 2 shows a six pulse, three phase inverter (4) using high current Power
semiconductor devices (many in parallel) is connected to the variable DC power
generated by the power pack (1,2). The power device of the inverter (4) is
conjunction with a digital control system (not shown) converter variable DC
supply to three phase, 50 HZ power supply at voltage corresponding to the DC

input. Thus, output of the Inverter (4) is variable voltage, fixed frequency AC
supply. The selected topology of the inverter (4) does not require snubber circuit
across each device. The normal, over load Andover current protection has been
provided. The Inverter (4) is housed in as cubicle with its cooling arrangement,
protection, and the digital control system.
Figure - 2 further shows a step - up transformer (5) and tap changer (6)
arrangement. A three-phase transformer (5) with two secondary windings and
one primary winding having many tapings is used. A s-phase tap changer (6)
having equivalent number of contacts as the taping in the primary winding of the
transforming is connected between the transformer (5) and the main feeder (9)
of 11 KV or 33 KV. The tap changer (6) at primary side is controlled by the digital
control system in such a way that voltage at secondary winding of the
transformer (5) are always at level suitable for operation of the inverter (4). Two
secondary windings of the transformer (5) can be connected in series for high
voltage requirement and in parallel for high current requirement. The
transformer - tap changer combination (5,6) is connected to the available feeder
(9) through a switchgear and protection (not shown) system at primary side, to
the output of the inverter (4) at secondary side.
A digital control system responsible for:
Proper switching of the power devices of the inverter (4) to ensure continuous
current operation mode of the inverter (4) thereby ensure harmonics free
output; switching of the tap changer (6), to ensure availability of voltage at
appropriate level at transformer secondary winding, for proper operation of the

inverter (4) ; connecting transformer secondary winding in parallel or series
depending upon load requirement of the power pack (1,2) for high voltage or
current, regulation of load at desired level with fine adjustment for proper testing
the of power pack (1,2); data acquisition and retrieval means; report generation
thru laptop computer; normal control and protection means.
The digital control system of the inverter uses various sensors for feedback of
various parameters such as load voltages, load current, input voltages etc for
control and protection. It generates graphical display as well as printable
document for each testing. The control system is configurable and upgradable. It
is capable for connection to existing data acquisition system and remote control.
Synchronizing Arrangement
The one of the major feature of the proposed system is the synchronization
arrangement. When ever any power generation equipment is to be connected to
grid, it has to be properly synchronized for phase sequence, voltage, and
frequency. The special equipment and control system are required for this
purpose. In the proposed system, the inverter (4) is operated in line operation
mode i.e. the AC supply from secondary winding of transformer (5) is already
being made available at its output terminals and power devices are switched
accordingly. Since the AC supply at output of the inverter (4) is a grid voltage
stepped downed by the transformer-tap changer combination (5,6) hence no
separate synchronization is required.

WE CLAIM
1. An electrical feed back system for testing of the diesel electric
locomotives, comprising :
- a diesel engine (1) after assembly positioned for testing at full load;
- an electrical machine (2) operably attachable to the diesel engine
(1) for converting the mechanical energy produced by the engine
(1), the electrical machine (2) being connected to load;
characterized by comprising :
- a power inverter (4) having a plurality of semiconductor devices
including a digital control device connected to the electrical
machine (2) outputting a variable d.c. power, the inverter (4) with
the control device converting the variable d.c. supply to a three
phase. 50HZ power supply corresponding to the d.c. input;
- a step-up transformer (5) with two secondary windings and one
primary winding having a plurality of tappings connected to the
output of the power transformer (5); and

- a tap changer (6) having corresponding number of tappings
connected between the transformer (5) and the main feeder (9),
the digital control device controlling the voltage at the primary
winding of the transformer (5) such that the inverter (4)
continuously receiving desired voltage at the secondary windings.
2. The system as claimed in claim 1, wherein the transformer -tap changer
combination (5,6) is connected at one end to the main feeder- (9) via a
switchgear and protection means, and at the other end to the inverter (4)
at the secondary windings.
3. The system as claimed in claim 1, wherein the secondary windings of the
transformer (4) is connectable in series to output high voltage.
4. The system as claimed in claim 1 or 3, wherein the secondary windings of
the transformer (4) is connectable in parallel to receive high current.
5. An electrical feed back system for testing of the diesel electric
locomotives, as substantially described herein and illustrated with
reference to the accompanying drawing.

ABSTRACT

TITLE : 'AN ELECTRICAL FEED BACK SYSTEM FOR TESTING OF THE
DIESEL ELECTRIC LOCOMOTIVES'
This invention relates to an electrical feed back system for testing of the diesel
electric locomotives, comprising; a diesel engine (1) after assembly positioned
for testing at full load; an electrical machine (2) operably attachable to the diesel
engine (1) for converting the mechanical energy produced by the engine (1), the
electrical machine (2) being connected to load; a power inverter (4) having a
plurality of semiconductor devices including a digital control device connected to
the electrical machine (2) outputting a variable d.c. power, the inverter (4) with
the control device converting the variable d.c. supply to a three phase. 50HZ
power supply corresponding to the d.c. input; a step-up transformer (5) with two
secondary windings and one primary winding having a plurality of tappings
connected to the output of the power transformer (5); and a tap changer (6)
having corresponding number of tappings connected between the transformer
(5) and the main feeder (9), the digital control device controlling the voltage at
the primary winding of the transformer (5) such that the inverter (4)
continuously receiving desired voltage at the secondary windings.