Railway switches and signals – Cab signal or train control – Motive-power control
Patent
1997-02-13
1998-02-03
Morano, S. Joseph
Railway switches and signals
Cab signal or train control
Motive-power control
246182R, 104300, B60L 1502
Patent
active
057135410
DESCRIPTION:
BRIEF SUMMARY
1. Field of the Invention
The present invention relates to mass transit vehicles powered from external sources of electrical power and, more particularly, to systems for detecting electromagnetic interference during the operation of mass transit vehicles.
2. Background Art
An electrically powered mass transit vehicle typically includes a propulsion system connected to a direct current (DC) motor or alternating current (AC) motor for propelling the vehicle on running rails. The propulsion system is often driven by a source of DC electrical power supplied from a remote source via a supply line, such as a power rail or an overhead power line. The DC power is often supplied at a relatively high voltage to minimize power loss associated with resistive drops along the length of the supply line. A return path for the DC electric power is provided via the running rails. It is to be appreciated that the DC electrical power, and more specifically, the DC current, provided to the vehicle via the supply line also flows in the running rails. It is common to use the running rails to also provide AC control signals to track signaling equipment, e.g., wayside aspect lights, associated with the rail or track system. These AC control signals are provided at predetermined frequencies, e.g., 60 Hz and 100 Hz. To provide for operation of the track signaling equipment during operation of the vehicle, these AC control signals are superimposed on DC current in the running rails.
The electric motor of a mass transit vehicle is typically designed for variable speed operation at voltages and currents other than provided by the supply line. To accomplish variable speed operation, it is common to switchably control the power supplied to the motor. To this end, for vehicles equipped with a DC motor, the propulsion system includes a DC-DC converter for converting supplied DC to a DC useable by the motor. Similarly, for vehicles equipped with an AC motor, the propulsion system includes a DC-AC inverter for changing the supplied DC to an AC useable by the motor. In operation, the DC-DC converter or the DC-AC inverter controllably switches power from the supply line to the motor as a function of the desired operating characteristics thereof. Specifically, less power is switched from the supply line to the motor when lower vehicle speeds or motor torque are desired and more power is switched from the supply line when higher vehicle speeds or motor torque are desired. A characteristic of the operation of the DC-DC converter or the DC-AC inverter is that AC electrical noise is often conducted onto the DC current. This conducted noise is often generally referred to as Electromagnetic Interference (EMI). Importantly, EMI may contain frequency components in the range of the AC control signals for the track signaling equipment associated with the vehicle. Accordingly, there are concerns that such EMI may cause unintended operation of or undesirable interference with the track signaling equipment.
To reduce the effect of EMI on the DC current, standard propulsion systems include line filters for absorbing significant line current frequencies produced by the DC-DC converter or the DC-AC inverter and, more specifically, for absorbing line current frequencies in the range of control signals for the track signaling equipment, i.e., 60 Hz and 100 Hz. In this manner, the effect of EMI on the DC current by the operation of the DC-DC converter or DC-AC inverter is reduced.
Line filters are typically designed to provide filtration of noise within certain established levels, e.g., without limitation, amplitude, duration and/or frequency. As a result, noise outside the established levels will not be adequately filtered and will be conducted on the supply line. Moreover, if electrical components, e.g., capacitors, associated with the line filter fail or change value with age, the effective filtration characteristics of the line filter are changed and noise normally filtered thereby appears on the DC current. As discussed above, this is a particular problem wh
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Ames Richard P.
Dimasi Fred J.
Schmitz William E.
Truman William M.
Zuber Pierre A.
ABB Daimler-Benz Transportation (North America) Inc.
Morano S. Joseph
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