The present disclosure relates to a power system. In particular, the present disclosure relates to a power system for a locomotive.
A typical locomotive includes a complex electromechanical system comprising a plurality of complex systems and subsystems. Some of these systems and subsystems such as traction motors require high voltage power while auxiliary loads (such as cooling unit, air compressor, etc.) require low voltage power.
Generally the locomotive engine powers a traction alternator (also known as main alternator) and a companion alternator (also known as a secondary alternator). The traction alternator produces high power (2800V max) and transmits this high power to the traction motors. The companion alternator produces power (700V max) and transmits this low power to the auxiliary loads of the locomotive.
Chinese publication No. 202,856,629 discloses a first rectifier unit and a second rectifier unit. The first rectifier unit powers an inverter module and the second rectifier unit powers the auxiliary inverter module. The inverter module powers the main traction motors and the second rectifier unit powers the auxiliary units.
In an aspect of the present disclosure, a power system for a locomotive is disclosed. The power system includes an alternator, a first inverter system, a traction motor, a second inverter system and an auxiliary power unit. The first inverter system is coupled to the alternator and receives high voltage power from the alternator. The traction motor is coupled to the first inverter system receives high voltage power from the first inverter system. The second inverter system is also coupled to the alternator. The second inverter system steps down the high voltage power from the alternator. The auxiliary power unit is coupled to the second inverter system and receives the stepped down voltage power from the second inverter system.
In another aspect of the present disclosure, a locomotive is disclosed. The locomotive includes an engine, an alternator driven by the engine, a first inverter system coupled to the alternator and configured to receive high voltage power from the alternator, a traction motor coupled to the first inverter system and configured to receive high voltage power from the first inverter system, a second inverter system coupled to the alternator, the second inverter system configured to step down the high voltage power from the alternator and an auxiliary power unit coupled to the second inverter system, the auxiliary power unit configured to receive the stepped down voltage power from the second inverter system.
In yet another aspect of the present disclosure, a method of powering a locomotive is disclosed. The method includes driving an alternator by an engine, transmitting high voltage power generated by the alternator to a first inverter system, transmitting the high voltage power received by the first inverter system to a traction motor, transmitting high voltage power generated by the alternator to a second inverter system, stepping down the high voltage power received by the second inverter system and transmitting the stepped down power by the second inverter system to an auxiliary power unit.
Reference will now be made in detail to embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
The alternator 112 is coupled to the engine 106. The engine 106 produces mechanical energy in the form of a mechanical output and transmits it to the alternator 112. The alternator 112 receives this mechanical energy and converts the mechanical energy to electrical energy in the form of alternating current (AC). The alternator 112 may be any device configured to receive mechanical output as input and producing electrical energy as its output. In an embodiment, the alternator 112 may incorporate integral silicon diode rectifiers to provide DC traction, which is used directly. The alternator 112 also has a traction alternator field 174 coupled to it.
In the embodiment illustrated in
The first inverter system 114 and the second inverter system 116 receive the high voltage power from the DC link 140 and are configured to transform the DC (direct current) from the DC link 140 to AC (alternating current). The first inverter system 114 and the second inverter system 116 supply the transformed AC power to the traction motor 118 and the auxiliary power unit 120 respectively. In the embodiment illustrated, the first inverter system 114 and the second inverter system 116 system may be electronic devices or a series of circuits that transform direct current (DC) to alternating current (AC) and provide the transformed AC to the at least one traction motor 118 and the auxiliary power unit 120.
The at least one traction motor 118 is coupled to the first inverter system 114 using a third supply line 144. In the embodiment illustrated, the power system 110 may have at least one first inverter system 114 for converting the DC power to 3-phase AC power and supplying it to the traction motor 118, as shown in
As shown in
As shown in
In the embodiment illustrated in
The high voltage power is firstly received by the inverter module 115. The inverter module 115 is configured to transform the high voltage DC power received from the DC link to high voltage AC power. This transformed high voltage AC power is then passed to a filter module 142 coupled to the inverter module 115. The filter module 142 receives the AC from the second inverter system 116 and is configured to perform signal processing functions, specifically to remove unwanted frequency components from the AC signals received from the inverter module 115 and enhances the essential frequency components. In the embodiment illustrated, the filter module 142 is configured to remove unwanted harmonics from the AC supplied by the inverter module 115. The filter module 142 may be any of a passive filter, an active filter, an analog filter, a digital filter, a high-pass filter, a low-pass filter, a band-pass filter, a band-stop filter (band-rejection; notch), a discrete-time (sampled) filter, a continuous-time filter, a linear filter, a non-linear filter, an infinite impulse response filter (IIR type), a finite impulse response filter (FIR type) or any other filter known in the art.
The filtered AC from the filter module 142 is transmitted to the step-down transformer 126 present in the second inverter system 116. The step-down transformer 126 is configured to transfer electrical energy through electromagnetic induction and decrease/step down the voltage of alternating current (2800V max to 700V max) to be passed on to the auxiliary power unit 120. In an embodiment illustrated, the step-down transformer 126 is a delta-wye transformer that employs delta-connected windings on its primary and wye/star connected windings on its secondary. A neutral wire may be provided on wye output side. In an embodiment, the delta wye transformer 126 may be a single three-phase transformer, or built from three independent single-phase units. The delta-connected windings on the primary side are configured to eliminate the circulating currents and the imbalances present in the AC received from the filter module 142. The wye-side windings of the step-down transformer 126 are configured to supply a constant output to a variable input from the inverter module 115.
The constant output from the second inverter system 116 is fed to the auxiliary power unit 120. In the embodiment illustrated in
The auxiliary rectifier 150 is configured to transform the stepped down AC power (low voltage) to stepped down DC power. The low voltage DC power is then fed to the plurality of three phase auxiliary inverters 1681 to 168n. The three phase auxiliary inverters 1681 to 168n are configured to transform the low voltage DC power into AC power. This transformed low voltage AC power is then fed to the plurality of subsystems of the auxiliary power unit 120 during operation.
The constant output from the second inverter system 116 is also fed to the auxiliary power converter 160 via the sixth supply line 176 and the contactor driven auxiliary loads 170 via the contactors 172. The contactor driven auxiliary loads 170 include auxiliary loads on the locomotive 100 (shown in
In the embodiment illustrated, the output of the second inverter system 116 is stepped further down through the first transformer 152 to further step down the low voltage AC power received from the second inverter system 116. The output from the first transformer 152 is fed to the auxiliary power converter 160. The auxiliary power converter 160 is configured to transform the low voltage AC power into constant DC power to supply low voltage control system 158 and locomotive lightings.
The constant output from the second inverter system 116 is fed to a battery charging apparatus 154 through a second transformer 156. The second transformer 156 is configured to step down the low voltage power received from the second inverter system 116. The battery charging apparatus 154 is configured to provide power to charge a battery 166. In the embodiment illustrated, the battery charging apparatus 154 is a device used to put energy into a secondary cell or rechargeable battery by forcing an electric current through it. Further in the embodiment illustrated, the battery charging apparatus 154 works by supplying a constant DC or pulsed DC power source to the battery 166 being charged. The battery 166 is configured to crank the engine 106 using the traction alternator field 174 attached to the alternator 112. The battery supplies power to the traction alternator field 174 which in turn power the alternator 112. The alternator 112 then cranks the engine 106. It may be contemplated that the battery 166 may be a device consisting of two or more electrochemical cells that convert stored chemical energy into electrical energy. In various other embodiments, the battery 166 may be any other type of battery known in the art.
In an embodiment, the power system 110 further comprises a dynamic braking (DB) grid 162. The DB grid 162 is coupled to the DC link 140, first inverter system 114 and the second inverter system 116 via a fifth supply line 164. The DB grid 162 is configured to receive power from the traction motor 118 during dynamic braking mode of operation, of the locomotive 100.
In the embodiment illustrated in
Further, the alternator 122 has an alternator engine cranking mode of operation (AEC mode of operation), as shown in
In typical locomotives, a locomotive engine powers a traction alternator (also known as main alternator) and a companion alternator (also known as a secondary alternator). The traction alternator produces high voltage power (2800V max) and transmits this high power to the traction motors. The companion alternator produces low voltage power and transmits this low power (700V max) to the auxiliary loads of the locomotive.
In an aspect of the present disclosure, a power system 110 for a locomotive 100 is provided. The power system 110 includes an alternator 112, a first inverter system 114, a second inverter system 116, at least one traction motor 118 and an auxiliary power unit 120. The alternator 112 provides high voltage power to the first inverter system 114 and the second inverter system 116. The first inverter system 114 transmits the high power voltage to the traction motor 118 during operation.
The second inverter system 116 includes an inverter module 115, a filter module 142 and a step-down transformer 126. The alternator 112 provides high voltage power to the inverter module 115. For example, the alternator may transmit high power (max 2800V). This high voltage power received by the inverter module 115 is passed through the filter module 142. The filter module 142 removes the harmonics present in the high voltage power from the alternator 112. Further, it removes unwanted frequency components. The filtered high voltage power is then passed on to the step-down transformer 126. The step-down transformer 126 steps down the high voltage power (2800V max) to a low voltage power (700V max). The stepped down power (low voltage power) is fed to the auxiliary power unit 120. Thus, single alternator 112 provides high power to the traction motors 118. Further, the same alternator 112 provides low power to the auxiliary power unit 120. Thus, in the present disclosure a single alternator 112 powers the high voltage loads as well as the low voltage loads. This results to overall locomotive cost reduction. Further, using a single alternator 112 helps in reducing the hardware required by the locomotive and helps in saving locomotive mechanical rooms space.
In another aspect of the present disclosure, a method 700 for operating a locomotive 100 is disclosed. The method 700 will be explained with reference to
In an aspect of the present disclosure, the power system 110 may be in a regenerative braking mode of operation. In the regenerative braking mode of operation, the traction motor 118 acts as generator and generates 3-phase AC power, as shown in
In yet another aspect of the present disclosure, the DC link 140 may be coupled to a storage apparatus 132 via a bi-directional DC converter 134. The storage apparatus 132 is configured to store DC power. The storage apparatus 132 has first mode of operation and second mode of operation. In the first mode of operation the bi-directional DC converter 134 allows supply of DC power from the DC link 140 to the storage apparatus 132 to capture the energy generated during dynamic braking. Thus, in dynamic braking mode of operation at least a portion of the regenerated power flows into the storage apparatus 132 via the bi-directional DC converter 134. In the second mode of operation the storage apparatus 132 supplies DC power from the DC link 140 to the traction motor 118 and the auxiliary power unit 120, as shown in
In yet another aspect of the present disclosure, a dynamic braking (DB) chopper 180 is provided in the DB grids 162. The dynamic braking chopper 180 may be configured to extend the locomotive speed range via regenerative energy captured by the storage apparatus 132. Typically the DB grids 162 have contactors that close in dynamic brake mode, so all the regenerated energy from the traction motor 118 get dumped in to the DB grids 162. So when any other loads like auxiliary loads of the auxiliary power units 120 or energy storage (storage apparatus 132 and the bidirectional DC converter 134) run in parallel with the DB grids 162, the voltage on the DC link 140 goes down drastically below certain locomotive speed (for example below 30 MPH) and therefore the regenerated energy from the traction motors 118 can be used only above 30 MPH to power auxiliary loads and charging the storage device in dynamic braking mode. Adding the DB grid chopper 180 to the DB grids 162 extends the locomotive 100 speed range (for example 3 MPH) to capture regenerated energy in dynamic braking mode. That means the auxiliary loads of the auxiliary power units 120 or energy storage (storage apparatus 132 and the bidirectional DC converter 134) can be powered by regenerated energy regenerated energy from traction motors 118 when the locomotive 100 speed is higher than 3 MPH in dynamic braking mode. This results in additional locomotive fuel saving.
While aspects of the present disclosure have seen particularly shown and described with reference to the embodiments above, it will be understood by those skilled in the art that various additional embodiments may be contemplated by the modification of the disclosed machines, systems and methods without departing from the spirit and scope of what is disclosed. Such embodiments should be understood to fall within the scope of the present disclosure as determined based upon the claims and any equivalents thereof.