| A number of components of the power train of modern electric stock are
regulated and operated by an on-board computer. The corresponding software is
fixed by the manufacturer and usually not modified by the railway operator. In
many cases this software offers considerable potential for optimisation from an
energetic point of view. In this case a modification of existing stock in
co-operation with manufacturers is an interesting option.
The principle consists in changing the setpoints of inverter control
according to the value of other parameters such as catenary voltage, wheel-track
conditions or speed.
This includes optimising the setpoints of the following quantities:
• Voltage in DC link
• Magnetic flux in motor
• Pulse frequency of rectifier and traction inverter
• Pulse pattern in traction inverter
All the target values of these quantities have to be optimised at the same
time. The effect of such a measure on energy consumption may be illustrated for
the case of DC link voltage. Virtually all constant (as opposed to power
dependent) losses in the inverters depend quadratically on DC link voltage. The
reduction of this voltage during low load periods therefore cuts energy
consumption to a considerable extent. |
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date created: 2002-10-04
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