The present invention relates to improvements in railroad trains and
more in general in electric-traction railroad rolling stock. The invention also
regards a method for traction of railroad trains or rolling stock in particular
conditions of operation.
In the framework of the present description and the attached claims,
by the term "rolling stock" is meant any self-propelled railroad means, i.e., a
train made up of one or more drawn cars or coaches and/or of one or more locomotives
which move along a rail or a system of rails. Said term hence comprises, for example,
both a railroad train made up of one or more locomotives and possibly one or more
drawn cars or coaches, and a train for metropolitan use, especially on underground
lines, made up of one or more traction units. By "traction unit" is in general meant
a self-propelled railroad vehicle, made up of one or more passenger cars or coaches
and corresponding motor. Typically, said traction units are made up of two vehicles
equipped with motors, between which there are arranged one or more drawn coaches,
which form independent units that may be combined together to make up a train of
By "drawn coach" is to be understood, in the present description and
in the attached claims, both a passenger coach (either for use over long distances
or on metropolitan stretches, possibly on underground line or on overhead lines)
and a coach designed for special services, or other purposes.
State of the Art
Rail transport is currently undergoing a period of great development,
both in urban areas, with the construction of metropolitan systems, either totally
or in part underground and/or overhead, and in long-distance transport. In the latter
case, in particular, there is the tendency to develop railroad trains capable of
reaching very high speeds, namely in the region of 300 km/h on a traditional railroad,
to provide a means of transport alternative to air transport.
Notwithstanding the solutions adopted for guaranteeing the maximum
efficiency of transport, it is not possible to rule out situations of interruption
of the electric-power supply on the line. These interruptions can be the consequence
of a failure on the line, or else of a general or local interruption of the electric-power
supply, or else of a failure of the system for receiving the electrical current
with which the railroad train or the rolling stock is equipped.
Whatever the origin of the lack of electric-power supply to the motors
of the railroad train or of the rolling stock, the result is the blocking thereof
in an undetermined point of the stretch covered. In such conditions, the only energy
available is the energy that can be absorbed by the batteries, which is sufficient
only for the supply of the emergency lights for a certain amount of time, but is
not designed for guaranteeing reasonable conditions of comfort for the passengers.
When the lack of electric-power supply occurs in metropolitan-transport systems,
there derive there from a considerable inconvenience, in addition to a high risk,
for the passengers in the case where the train is blocked in a tunnel. But such
drawbacks also exist on long-distance iines, where there are present tunnels in
which trains can get blocked. Currently, the train remains blocked in a tunnel until
a diesel locomotive arrives or until the power supply is restored on the line.
Object and Summary of the Invention
An object of the present invention is to propose a system that will
be able to overcome or reduce the drawbacks deriving from the interruption of the
electric-power supply from the electric line to the motors of the train or in general
of the rolling stock, with consequent arrest of the latter. More in particular,
one object of the present invention is to identify a system that will enable prevention
of long forced stoppages in tunnels and simultaneously guarantee an acceptable minimum
comfort for the passengers, until the anomalous conditions cease.
Substantially, according to a first aspect, the invention relates
to an electrically driven railroad train or more in general rolling stock, comprising
at least one electric motor and a system for receiving electric power from a supply
line, on which there is provided at least one emergency generator and a system of
electrical connection between the emergency generator and the electric motor or
motors of the rolling stock, so that the emergency generator will be able to supply
power for advance of the rolling stock in the event of lack of supply from the line.
In this way, when the train is blocked, for example, in a tunnel along a railroad,
it is possible, via the generation of electric power by the emergency generator,
to drive one or more motors of the rolling stock to get it to advance until it comes
out of the tunnel in which it is blocked. Another possible emergency situation is
represented by the blocking of the train on an underground line between two consecutive
stations. In this case, the power supplied by the emergency generator or emergency
generators on board the train enables advance of the train itself at least as far
as the next station. In both cases, the passengers are relieved from the situation
of serious inconvenience and of potential danger represented. by the forced stay
in a tunnel.
In general, the emergency generator may comprise an internal-combustion
engine, such as a diesel or gasoline engine. More appropriately, it will comprise
a turbine engine, which presents considerable advantages in terms of weight and
smaller overall dimensions given the same power supplied and the same promptness
of starting. The engine drives an electrical generator that supplies the electric
power to the electric motor of the train or of the rolling stock. Alternatively,
it is also possible to use fuel-cell electric-power generators, with direct conversion
of chemical energy into electrical energy. This solution is able to present the
advantage of preventing emission of harmful exhaust gases, a circumstance that may
prove useful for the prevention of input of combustion gas into the cars precisely
when the train is in a tunnel.
In general, the train or rolling stock can comprise one or more electric
motors and a variable number of cars and/or locomotives. Also the number of emergency
generators may vary from one to a plurality of generators, typically one for each
car forming the train. In general, in any case, the power supplied by the emergency
generator or emergency generators is equal only to a fraction of the overall rated
power of the motor or the motors of the rolling stock. Typically, it is possible
to envisage generation via the emergency power generators equal to a percentage
ranging from 5% to 30% of the overall rated power of the motor or motors.
The energy generated by the emergency generator or emergency generators
can also be used for supplying one or more services on board. In the case of long-distance
trains, said services may comprise the system for air-conditioning of the wagons
(heating and/or cooling), the lighting system, the system for production of hot
water, the restaurant services, and the acoustic-signaling systems, including the
loudspeakers for issuing announcements to the passengers. In the case of metropolitan
trains, the services on board that must be appropriately guaranteed by the emergency
generator or emergency generators are in general exclusively the lighting and acoustic-signaling
The percentage of the rated power of the motors that the emergency
generator or emergency generators must guarantee varies according to the type of
rolling stock. In fact, in the case of long-distance railroad trains, it is necessary
to take into account the need to provide on-board auxiliary services that may even
absorb a considerable amount of power (the air-conditioning system, in particular).
Moreover, the power available must be sufficient to overcome the starting friction
of the train and its inertia, in addition to the possibie siopes that the tine may
present. Said slopes may be steeper in the case of long-distance stretches of railroad,
whilst they are very modest (but for rare exceptions) in metropolitan stretches.
Consequently, on long-distance railroad trains and in particular on high-speed trains,
there is normally envisaged a total installed power of the emergency generators
higher than what is provided for the rolling stock in use on metropolitan lines.
It should however be understood that, since the power supplied by the emergency
generators is required for traction only over limited stretches, whenever the conditions
in which the train comes to find itself are such as to require more power than the
amount provided, for example on account of a particularly steep slope or other unfavorable
conditions, the supply to the auxiliary services may also be temporarily reduced
or interrupted, to devote the power available to the motors for propulsion of the
train. Once the train has come out of a tunnel and stops outside it, the power supplied
by the emergency generators is again sent to the auxiliary services on board.
According to a different aspect, the invention relates to a method
for the traction of electrically driven railroad rolling stock in the event of lack
of voltage on the electric-supply line, characterized by generating power via at
least one emergency generator, provided on board said rolling stock, for driving
at least one motor of the rolling stock. Advantageously, the emergency generator
or emergency generators generate a fraction of the overall rated power of the motor
or motors with which the rolling stock is equipped.
Further advantageous characteristics and embodiments of the invention
are indicated in the attached claims and will be described in greater detail in
what follows with reference to the examples of embodiment.
Brief Description of the Drawings
A better understanding of the invention will emerge from the ensuing
description and the attached drawings, in which non-limiting examples of embodiment
of the invention are illustrated schematically. More in particular:
Detailed Description of the Preferred Embodiments of the Invention
- Figure 1 is a schematic representation of a railroad train to which the invention
- Figure 2 is a schematic representation of a traction unit of a metropolitan
- Figure 3 is a partial electrical diagram of the invention in the application
to the railroad train of Figure 1, in a first configuration;
- Figure 4 is a partial electrical diagram of the invention in the application
to the railroad train of Figure 1, in a second configuration;
- Figure 5 is a partial electrical diagram of the invention in the application
to the traction unit of Figure 2.
Figure 1 is a schematic illustration of a railroad train 1, made up
of a head locomotive and a tail locomotive, both designated by 3, and by a series
of coaches, wagons, or cars 7. The locomotives 3 are equipped with pantograph trolleys
9 for taking electric power from a supply line 11. Each locomotive is provided with
four axles normally equipped with respective motors, even though this is not binding
for the present description. Some or all of the cars or coaches 7 making up the
train are equipped with an emergency generator, designated as a whole by 13. The
emergency generators 13 can be made up in various ways. For example, they may comprise
a fuel-cell battery, which, in the event of necessity, directly transforms chemical
energy, supplied by a fuel, into electrical energy. Alternatively, the emergency
generator may comprise an electrical generator, typically an alternator, driven
by an internal-combustion engine, for example an alternating engine, either a diesel
or a gasoline engine. Preferably, however, the engine consists of a gas turbine
supplied by liquid fuel.
Figure 3 illustrates an electrical diagram of one of the locomotives
3 and of two of the cars 7 that make up the train. The electric power taken from
the line 11, via the trolley 9, supplies the motors M of the locomotive. Illustrated
in the diagram of Figure 3 is a single block representing one or more motors, it
being understood that the number of the motors may vary from type to type of locomotive.
As previously mentioned, some locomotives can be equipped with one motor for each
truck axle. This occurs, for example, in high-speed railroad trains of the series
ETR500, which are in service on Italian Railways. The motors M are supplied according
to this diagram through a two-stage converter made up of a DC/DC stage, designated
as a whole by 21, which converts the voltage of the contact line 11 (having a rated
value of 3000 V) into a d.c. voltage stabilized at 2400 V, and a supply inverter
23, which converts the d.c. voltage into a.c. voltage at a variable frequency for
supplying the motors M.
The train is moreover equipped with a "train line" of supply, which
traverses all the cars and is designated by 25. This is supplied through one or
more DC/DC converters 27, installed on both of the locomotives 3. The train line
25 supplies all the auxiliary services on board the various cars or coaches 7, both
when the train is traveling and during stoppages thereof, provided that the trolley
9 is in connection with the supply line 11. Represented schematically in Figure
3 for each car 7 are two generic on-board auxiliary services 31, 33 supplied by
respective DC/AC and DC/DC converters, designated by 35 and 37. These services may
be of various types and require different types of supply, as schematically represented
by the indication of two different types of converters (respectively, DC/DC and
DC/AC). For example, the services may comprise the air-conditioning system, the
lighting system, the acoustic system for announcements to the passengers, the current
outlets available to the passengers, the restaurant-car services, etc.
The emergency generator 13 of each car (or more in general of those
cars that are equipped therewith) is connected on the electrical backbone 25. In
the diagram of Figure 3, each emergency generator 13 comprises: an alternator 41,
driven in rotation by a gas-turbine engine, comprising a turbine 43; a compressor
45; and a combustion chamber 47. The alternator is connected to the train line 25
through an AC/DC converter 49, which converts the a.c. voltage produced by the generator
41 into a 600-V d.c. voltage (in the example). An emergency circuit breaker 51,
which is normally open, maintains the respective emergency generator 13 insulated
from the train line 25 when the required electric power is supplied by the external
supply line 11. The train line 25 can be connected, via a changeover switch 53,
to an "intermediate stage" 55 of the inverter 23, through which supply of the motors
M is - obtained, for operation of the train under traction in emergency conditions.
When, owing to a failure on the line 11, a generalized black-out,
failures of the trolleys 9, or any other reason, the locomotives 3 no longer receive
voltage from the line 11, the train 1 stops, and the auxiliary systems 31, 33 are
normally supplied (for very short periods of time) by emergency batteries. When
the train is equipped with one or more emergency generators 13 according to the
invention, instead, these can duly be set at once in operation and, being set in
parallel to one another, are connected to the train line 25 via closing of the circuit
breakers 51, for supplying the auxiliary services on board the train.
Furthermore, by closing the circuit via the changeover switch 53,
the power generated by the generators 13 can be exploited for supplying the motors
M of one or both of the locomotives 3. In this way, when the train stops in a point
that may entail problems or risks (for example in a tunnel), or else when it stops
in the proximity of a station instead of in a station, where the passengers could
find greater comfort than in a train that is standing still, by using the power
generated by the emergency generators 13 it is possible to move the train on, even
at low speed, until it comes out of the tunnel or else reaches the station, or in
general reaches a position that may be deemed more convenient.
For this purpose, the total power of the emergency generators 13 does
not need to be equal to the overall rated power of the motor or motors installed
on the train. For example, if the train is an ETR500, normally in service on Italian
Railways, the locomotives of which are each equipped with four 1100-kW motors, for
a total installed power of 8800 kW per train, it is found that the use of ten gas
turbines having a power of 134 kW each is sufficient to displace the train. The
total power supplied by the emergency generators 13 is, in this case, 1340 kW, which
is equal to 16.75% approximately of the rated power of the electric motors of the
locomotives. Said reduced power is in any case sufficient to overcome the starting
friction, to accelerate the train and keep it in motion at a speed of 10 km/h approximately
even on slopes of 25‰, which represents a considerable value-for a railroad
line, notwithstanding the low value of efficiency of motors operating in the condition
of maximum torque, maximum current, and reduced voltage.
Figure 4 illustrates an electrical diagram of a train of a traditional
type operating in a d.c. electrified system. Reference numbers that are the same
designate parts that are the same or equivalent to those of the diagram of Figure
3. The locomotive 3 comprises, in this case, one or more motors M supplied by a
DC/AC converter stage, designated as a whole by 22. The cars 7 of the train are
electrically connected by a "REC" line 25, which receives the supply directly from
the trolley 9 of the locomotive. On this line, therefore, there is a voltage equal
to the line voltage, typically for example 3000 Vdc. Said characteristics
of the line voltage can obviously change from country to country.
Each car is equipped with generic auxiliary systems designated by
31 and 33, which - in this schematic example - are supplied by the line 25 via a
single DC/AC converter. On the cars 7 (on all or some of them) there are provided
generator units 13 composed as described with reference to the diagram of Figure
3 and connected to the line 25 via an AC/DC converter again designated by 49, which
transforms the voltage produced by the respective generator 41 to a voltage compatible
with the supply of the auxiliary services 31, 33 and with the input to the conversion
stage 22, which supplies the motor or the motors M. In the example illustrated,
where the rated voltage is 3000 Vdc, the converters 49 can be designed
for supplying at output a voltage of 2000 Vdc, which is sufficient to
run the auxiliary services and the motor or motors.
Also in this case, in the absence of voltage through the trolley 9,
the auxiliary services of the train and the motor or the motors M are supplied by
bringing into operation the emergency generator units 13, the power of which, albeit
lower than the rated power of the motors of the train, is still sufficient to move
the train on for the desired stretch and to run the on-board auxiliary services.
The inventive idea illustrated in the preceding description with reference
to a long-distance railroad train, or in any case for extra-urban services, typically
a high-speed train, can be used also for rolling stock designed for use on metropolitan
lines, whether underground or surface lines. Normally, metropolitan trains are made
up of one or more traction units of the type indicated as a whole in Figure 2. Each
traction unit, designated by 61, is made up of two power cars 63 and an intermediate
drawn car or coach, designated by 65. The supply line is again designated by 11,
and the trolleys, via which the power cars 63 take power for supplying the electric
motors and the on-board auxiliary services, are designated by 9. The electric line
11 is typically a 750-Vdc or 1500-Vdc line.
Also in this case, each power car 63 may present one or more motors,
typically an motor for each truck axle and thus, in the example illustrated, four
motors for each power car 63. Set on board the drawn car or coach 65 is an emergency
generator, once again designated by 13. It may be electrically connected to one
or the other or to both of the power cars 63 so as to supply a sufficient number
of motors of the traction unit in the event of failure on the line or interruption
of the voltage to the network, i.e., in the event of failures of the trolleys 9.
The emergency generator 13 will moreover supply the current for powering the essential
auxiliary services, such as typically the lighting and the audio system to enable
provision of the necessary information to the passengers.
The diagram of Figure 5 shows the electrical connection of the motor
or motors M, via a DC/AC converter stage 24, to the trolley 9. The reference number
25 designates the electrical backbone, which connects together the coaches and to
which there is connected the DC/AC converter 35 that supplies the auxiliary services
31 and 33. The emergency generator 13, which is represented in an idealized way
and is made up of the components 41, 43, 45, and 47 already described previously,
can be connected to the line 25 via an AC/DC converter 49 and a changeover switch
Also in the case of the traction unit 61, the power supplied by the
generator may be a fraction of the overall rated power of the motors of the unit
itself. A power of the order of 10% of the rated power may normally be sufficient,
considering also the gentler slopes that normally characterize metropolitan lines.
It is understood that the drawings only show a possible embodiment
of the invention, which may vary in its forms and arrangements, without thereby,
however, departing from the scope of the underlying idea, as this is defined in
the ensuing claims.