25-08-2017, 09:32 PM
Electric Locomotive Traction
[attachment=39618]
Introduction
This page offers a selection of terms used in electric locomotive traction. If you can't find it here, try our Modern Railway Glossary page or use the Search facility. There are more Articles on Electric Traction on this site as follows: Electric Traction Power Supplies - DC Traction Motor Systems - Electric Traction Drives - Multiple Unit Operation - Electronic Power for Traction
Electric Locomotive Parts
Click on the part names for a description. This diagram shows an AC electric locomotive, i.e a locomotive collecting AC power from an overhead line. The red lines on the diagram indicate the single phase AC circuit, the green lines the DC circuits and the purple lines the 3-phase AC circuits. A locomotive using DC traction current is similar, except that there is no single phase AC circuit or transformer. The current passes directly from the pantograph (or shoe) to the main and auxiliary inverters.
Asynchronous Motor
Modern traction motor type using three phase AC electrical supply and now the favoured design for modern train traction systems. Can be used on DC and AC electrified railways with suitable control electronics and on diesel-electric locomotives. See the article on AC and DC Motors.
Axle Brush
The means by which the power supply circuit is completed with the substation once power has been drawn on the locomotive. Current collected from the overhead line or third rail is returned via the axle brush and one of the running rails. See also Power Supply - return.
Balancing Speed
See here for description.
Battery
All trains are provided with a battery to provide start up current and for supplying essential circuits, such as emergency lighting, when the line supply fails. The battery is usually connected across the DC control supply circuit.
Bucholz Relay
A device inserted in the oil cooling circuits of electric locomotive transformers to detect low oil pressure. In this event the relay trips out the power system. Often a source of spurious circuit breaker trips if not carefully calibrated.
Camshaft
Most DC electric traction power circuits use a camshaft to open or close the contactors controlling the resistances of the traction motor power circuit. The camshaft is driven by an electric motor or pneumatic cylinder. The cams on the shaft are arranged to ensure that the contactors open and close in the correct sequence. It is controlled by commands from the driver's cab and regulated by the fall of current in the motor circuit as each section of resistance is cut out in steps. The sound of this camshaft stepping can be heard under many older (pre electronics) trains as they accelerate. See also Notching Relay.
Cannon Box
Sleeve used to mount a traction motor on axle in electric power bogies and sometimes including an axle brush.
Chopper Control
A development in electric traction control which eliminates the need for power resistors by causing the voltage to the traction motors to be switched on and off (chopped) very rapidly during acceleration. It is accomplished by the use of thyristors and will give up to 20% improvement in efficiency over conventional resistance control.
Circuit Breaker
An electric train is almost always provided with some sort of circuit breaker to isolate the power supply when there is a fault, or for maintenance. On AC systems they are usually on the roof near the pantograph. There are two types - the air blast circuit breaker and the vacuum circuit breaker or VCB. The air or vacuum part is used to extinguish the arc which occurs as the two tips of the circuit breaker are opened. The VCB is popular in the UK and the air blast circuit breaker is more often seen on the continent of Europe.
Contactor
Similar to a relay in that it is a remotely operated switch used to control a higher power local circuit. The difference is that contactors normally latch or lock closed and have to be opened by a separate action. A lighting contactor will have two, low voltage operating coils, one to "set" the contactor closed to switch on the lights; the other to "trip" off the lights. Click here for diagrams and more detail.
Converter
Generic term for any solid state electronic system for converting alternating current to direct current or vice versa. Where an AC supply has to be converted to DC it is called a rectifier and where DC is converted to AC it is called an inverter. The word originated in the US but is now common elsewhere.
[attachment=39618]
Introduction
This page offers a selection of terms used in electric locomotive traction. If you can't find it here, try our Modern Railway Glossary page or use the Search facility. There are more Articles on Electric Traction on this site as follows: Electric Traction Power Supplies - DC Traction Motor Systems - Electric Traction Drives - Multiple Unit Operation - Electronic Power for Traction
Electric Locomotive Parts
Click on the part names for a description. This diagram shows an AC electric locomotive, i.e a locomotive collecting AC power from an overhead line. The red lines on the diagram indicate the single phase AC circuit, the green lines the DC circuits and the purple lines the 3-phase AC circuits. A locomotive using DC traction current is similar, except that there is no single phase AC circuit or transformer. The current passes directly from the pantograph (or shoe) to the main and auxiliary inverters.
Asynchronous Motor
Modern traction motor type using three phase AC electrical supply and now the favoured design for modern train traction systems. Can be used on DC and AC electrified railways with suitable control electronics and on diesel-electric locomotives. See the article on AC and DC Motors.
Axle Brush
The means by which the power supply circuit is completed with the substation once power has been drawn on the locomotive. Current collected from the overhead line or third rail is returned via the axle brush and one of the running rails. See also Power Supply - return.
Balancing Speed
See here for description.
Battery
All trains are provided with a battery to provide start up current and for supplying essential circuits, such as emergency lighting, when the line supply fails. The battery is usually connected across the DC control supply circuit.
Bucholz Relay
A device inserted in the oil cooling circuits of electric locomotive transformers to detect low oil pressure. In this event the relay trips out the power system. Often a source of spurious circuit breaker trips if not carefully calibrated.
Camshaft
Most DC electric traction power circuits use a camshaft to open or close the contactors controlling the resistances of the traction motor power circuit. The camshaft is driven by an electric motor or pneumatic cylinder. The cams on the shaft are arranged to ensure that the contactors open and close in the correct sequence. It is controlled by commands from the driver's cab and regulated by the fall of current in the motor circuit as each section of resistance is cut out in steps. The sound of this camshaft stepping can be heard under many older (pre electronics) trains as they accelerate. See also Notching Relay.
Cannon Box
Sleeve used to mount a traction motor on axle in electric power bogies and sometimes including an axle brush.
Chopper Control
A development in electric traction control which eliminates the need for power resistors by causing the voltage to the traction motors to be switched on and off (chopped) very rapidly during acceleration. It is accomplished by the use of thyristors and will give up to 20% improvement in efficiency over conventional resistance control.
Circuit Breaker
An electric train is almost always provided with some sort of circuit breaker to isolate the power supply when there is a fault, or for maintenance. On AC systems they are usually on the roof near the pantograph. There are two types - the air blast circuit breaker and the vacuum circuit breaker or VCB. The air or vacuum part is used to extinguish the arc which occurs as the two tips of the circuit breaker are opened. The VCB is popular in the UK and the air blast circuit breaker is more often seen on the continent of Europe.
Contactor
Similar to a relay in that it is a remotely operated switch used to control a higher power local circuit. The difference is that contactors normally latch or lock closed and have to be opened by a separate action. A lighting contactor will have two, low voltage operating coils, one to "set" the contactor closed to switch on the lights; the other to "trip" off the lights. Click here for diagrams and more detail.
Converter
Generic term for any solid state electronic system for converting alternating current to direct current or vice versa. Where an AC supply has to be converted to DC it is called a rectifier and where DC is converted to AC it is called an inverter. The word originated in the US but is now common elsewhere.