408:(CEMF) opposes the applied voltage and the current that flows is governed by the difference between the two. As the motor speeds up, the internally generated voltage rises, the resultant EMF falls, less current passes through the motor and the torque drops. The motor naturally stops accelerating when the drag of the train matches the torque produced by the motors. To continue accelerating the train, series resistors are switched out step by step, each step increasing the effective voltage and thus the current and torque for a little bit longer until the motor catches up. This can be heard and felt in older DC trains as a series of clunks under the floor, each accompanied by a jerk of acceleration as the torque suddenly increases in response to the new surge of current. When no resistors are left in the circuit, full line voltage is being applied directly to the motor. The train's speed remains constant at the point where the torque of the motor, governed by the effective voltage, equals the drag - sometimes referred to as balancing speed. If the train starts to climb an incline, the speed decreases because drag is greater than torque and the reduction in speed causes the CEMF to fall and thus the effective voltage to rise - until the current through the motor produces enough torque to match the new drag. The use of series resistance was wasteful because a lot of energy was lost as heat. To reduce these losses,
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139:; for slow operation or heavy loads, two motors can be run in a series of the direct-current supply. Where higher speed is desired, these motors can be operated in parallel, making a higher voltage available at each motor and so allowing higher speeds. Parts of a rail system might use different voltages, with higher voltages in long runs between stations and lower voltages near stations where only slower operation is needed.
388:. The advantage of high current is that the magnetic fields inside the motor are strong, producing high torque (turning force), so it is ideal for starting a train. The disadvantage is that the current flowing into the motor has to be limited, otherwise the supply could be overloaded or the motor and its cabling could be damaged. At best, the torque would exceed the adhesion and the driving wheels would slip. Traditionally,
384:. The commutator collects all the terminations of the armature coils and distributes them in a circular pattern to allow the correct sequence of current flow. When the armature and the field windings are connected in series, the whole motor is referred to as "series-wound". A series-wound DC motor has a low resistance field and armature circuit. For this reason, when voltage is applied to it, the current is high due to
371:, a motor mounted to the power car's frame drives each axle; a "tripod" drive allows a small amount of flexibility in the drive train allowing the trucks bogies to pivot. By mounting the relatively heavy traction motor directly to the power car's frame, rather than to the bogie, better dynamics are obtained, allowing better high-speed operation.
194:, were awkward to apply for traction motors because of their fixed speed characteristic. An AC induction motor generates useful amounts of power only over a narrow speed range determined by its construction and the frequency of the AC power supply. The advent of power semiconductors has made it possible to fit a
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The fixed field windings consist of tightly wound coils of wire fitted inside the motor case. The armature is another set of coils wound round a central shaft and is connected to the field windings through "brushes" which are spring-loaded contacts pressing against an extension of the armature called the
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As traction motors use a reduction gear setup to transfer torque from the motor armature to the driven axle, the actual load placed on the motor varies with the gear ratio. Otherwise "identical" traction motors can have significantly different load rating. A traction motor geared for freight use with
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motors. These provide a speed-torque characteristic useful for propulsion, providing high torque at lower speeds for the acceleration of the vehicle, and declining torque as speed increases. By arranging the field winding with multiple taps, the speed characteristic can be varied, allowing relatively
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If the train starts to descend a grade, the speed increases because the (reduced) drag is less than the torque. With increased speed, the internally generated back-EMF voltage rises, reducing the torque until the torque again balances the drag. Because the field current is reduced by the back-EMF in
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Typical cooling systems on U.S. diesel-electric locomotives consist of an electrically powered fan blowing air into a passage integrated into the locomotive frame. Rubber cooling ducts connect the passage to the individual traction motors and cooling air travels down and across the armatures before
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originally had to control the cutting out of resistance manually, but by 1914, automatic acceleration was being used. This was achieved by an accelerating relay (often called a "notching relay") in the motor circuit which monitored the fall of current as each step of resistance was cut out. All the
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The DC motor was the mainstay of electric traction drives on electric and diesel-electric locomotives, street-cars/trams and diesel electric drilling rigs for many years. It consists of two parts, a rotating armature and fixed field windings surrounding the rotating armature mounted around a shaft.
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Bird-nesting (the centrifugal ejection of the armature's windings) due to overspeed can occur either in operating traction motors of powered locomotives or in traction motors of dead-in-consist locomotives being transported within a train traveling too fast. Another cause is replacement of worn or
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There are, however various schemes applied to provide a retarding force using the traction motors. The energy generated may be returned to the supply (regenerative braking), or dissipated by on board resistors (dynamic braking). Such a system can bring the load to a low speed, requiring relatively
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rating. The one-hour rating is the maximum power that the motors can continuously develop over one hour without overheating. Such a test starts with the motors at +25 °C (and the outside air used for ventilation also at +25 °C). In the USSR, per GOST 2582-72 with class N insulation, the
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maximum temperatures allowed for DC motors were 160 °C for the armature, 180 °C for the stator, and 105 °C for the collector. The one-hour rating is typically about 10% higher than the continuous rating and is limited by the temperature rise in the motor.
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Above this maximum speed centrifugal force on the armature will cause the windings to be thrown outward. In severe cases, this can lead to "birdnesting" as the windings contact the motor housing and eventually break loose from the armature entirely and uncoil.
150:. Since both the armature and field current reverse at the same time, the behavior of the motor is similar to that when energized with direct current. To achieve better operating conditions, AC railways are often supplied with current at a lower
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Traditionally road vehicles (cars, buses, and trucks) have used diesel and petrol engines with a mechanical or hydraulic transmission system. In the latter part of the 20th century, vehicles with electrical transmission systems (powered by
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driver had to do was select low, medium or full speed (called "series", "parallel" and "shunt" from the way the motors were connected in the resistance circuit) and the automatic equipment would do the rest.
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Another important factor when traction motors are designed or specified is operational speed. The motor armature has a maximum safe rotating speed at or below which the windings will stay safely in place.
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a series wound motor, there is no speed at which the back-EMF will exceed the supply voltage, and therefore a single series wound DC traction motor alone cannot provide dynamic or regenerative braking.
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Damage from overloading and overheating can also cause bird-nesting below rated speeds when the armature assembly and winding supports and retainers have been damaged by the previous abuse.
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converts 90% of the engine's output into electrical energy and the traction motors convert 90% of this electrical energy back into mechanical energy. Calculation: 0.9 × 0.9 = 0.81
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on a locomotive; this allows a wide range of speeds, AC power transmission, and the use of rugged induction motors that do not have wearing parts like brushes and commutators.
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ratio will safely produce higher torque at the wheels for a longer period at the same current level because the lower gears give the motor more mechanical advantage.
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frame and the driven axle; this is referred to as a "nose-suspended traction motor". The problem with such an arrangement is that a portion of the motor's weight is
180:, the AC system allows efficient distribution of power down the length of a rail line, and also permits speed control with switchgear on the vehicle.
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New York City Subway car. The motor can be clearly seen behind the axle with the gear box with the writing on it in the center.
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230:) began to be developed—one advantage of using electric machines is that specific types can regenerate energy (i.e. act as a
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smooth operator control of acceleration. A further measure of control is provided by using pairs of motors on a vehicle in
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Because of the high power levels involved, traction motors are almost always cooled using forced air, water or a special
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Locomotives that operated from AC power sources (using universal motors as traction motors) could also take advantage of
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on their transformers to vary the voltage applied to the traction motors without the losses inherent in resistors. The
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had direct drive motors. The rotating shaft of the motor was also the axle for the wheels. In the case of French TGV
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As the DC motor starts to turn, interaction of the magnetic fields inside causes it to generate a
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A ZQDR-410 traction motor (the large, dark component on the axle with small ventilation holes)
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locomotive, with a single large traction motor above each bogie, with drive by coupling rods.
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Electric
Traction - Motive Power and Energy Supply: Basics and Practical Experience
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Individual traction motor ratings usually range up 1,600 kW (2,100 hp).
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30:"traction drive" redirects here. For the torque transmission mechanism, see
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damaged traction motors with units incorrectly geared for the application.
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705:"Deconstructing a traction motor - Associated Rewinds (Ireland) Limited"
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than the commercial supply used for general lighting and power; special
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Coney Island Truck Repair shop; many pictures regarding traction motors
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used to convert 50 or 60 Hz commercial power to the 25 Hz or
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A variant of the DC system is the AC series motor, also known as the
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Usually, the traction motor is three-point suspended between the
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rating of the traction motors is usually around 81% that of the
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684:(1st ed.). British Transport Commission. pp. 172–189.
628: ; Chapter 6 "Induction Traction Motors and Their Control"
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are simple and low maintenance, but up until the advent of
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little friction braking to bring the load to a full stop.
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motors are used in electrically powered railway vehicles (
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British
Railways (1962). "Section 13: Traction Control".
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351:, two frame-mounted motors drove each axle through a
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Dual-rotor permanent magnet induction motor (DRPMIM)
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331:Nose-suspended DC traction motor for a Czech
280:are also occasionally used, as in the French
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693:(4th ed.). pp. 107–111, 184–190.
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53:used for propulsion of a vehicle, such as
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392:were used to limit the initial current.
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300:that were very similar to those used on
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27:An electric motor for vehicle propulsion
276:known as asynchronous traction motors.
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710:Image of a nose mounted traction motor
587:Three-phase AC railway electrification
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431:was an example of such a locomotive.
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735:Detached truck with Traction Motors.
682:Diesel Traction Manual for Enginemen
639:"TGVweb - "Under the Hood" of a TGV"
556:List of traction motor manufacturers
720:Another nose mounted traction motor
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546:being exhausted to the atmosphere.
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620:Oldenbourg Industrieverlag, 2008
412:and trains (before the advent of
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498:gas turbine-electric locomotives
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359:" electric locomotives built by
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649:from the original on 2017-06-13
429:Pennsylvania Railroad class GG1
1147:Timeline of the electric motor
691:The Railwayman's Diesel Manual
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259:series-wound brushed DC motors
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1:
932:Dahlander pole changing motor
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416:) were normally equipped for
158:power stations are used, or
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976:Brushless DC electric motor
689:Bolton, William F. (1963).
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406:counter-electromotive force
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224:internal combustion engines
202:Transportation applications
105:diesel-electric locomotives
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597:Diesel–electric powertrain
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257:Traditionally, these were
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592:Brushed DC electric motor
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306:Pennsylvania Railroad DD1
248:Rhaetian Railway Ge 6/6 I
113:battery electric vehicles
1181:Experimental, futuristic
1098:Variable-frequency drive
578:Electric vehicle battery
508:. This assumes that the
458:train driver or motorman
217:battery electric vehicle
196:variable frequency drive
1198:Superconducting machine
836:Coil winding technology
418:series-parallel control
213:Hybrid electric vehicle
137:series-parallel control
130:are the oldest type of
119:Motor types and control
77:electric multiple units
448:Automatic acceleration
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324:through a gear drive.
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67:electric multiple unit
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1239:Power-to-weight ratio
1103:Direct torque control
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278:Synchronous AC motors
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124:Direct-current motors
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1234:Open-loop controller
1127:Ward Leonard control
851:DC injection braking
510:electrical generator
470:Electric locomotives
410:electric locomotives
192:power semiconductors
1137:History, education,
783:Alternating current
304:. Examples are the
184:AC induction motors
148:alternating current
83:including electric
1300:Dolivo-Dobrovolsky
1259:Voltage controller
1214:Blocked-rotor test
1152:Ball bearing motor
1122:Motor soft starter
1076:AC-to-AC converter
937:Wound-rotor (WRIM)
899:Electric generator
666:Сидоров 1980, p.47
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288:Mounting of motors
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232:regenerative brake
188:synchronous motors
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1229:Open-circuit test
1068:Motor controllers
949:Synchronous motor
771:Electric machines
540:dielectric liquid
414:power electronics
404:internally. This
302:steam locomotives
160:rotary converters
81:electric vehicles
63:hydrogen vehicles
16:(Redirected from
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1406:Locomotive parts
1244:Two-phase system
1224:Electromagnetism
1172:Mouse mill motor
1139:recreational use
1013:Permanent magnet
942:Linear induction
795:Permanent magnet
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573:Electric vehicle
361:General Electric
318:Swiss Crocodiles
316:and the various
274:induction motors
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101:conveyor systems
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178:transformers
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126:with series
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89:trolleybuses
79:) and other
71:
46:
44:
1162:Lynch motor
927:Shaded-pole
813:accessories
726:Subway car.
506:prime mover
456:train, the
353:quill drive
107:, electric
85:milk floats
55:locomotives
1400:Categories
1058:Axial flux
1048:Ultrasonic
1023:Servomotor
1003:Doubly fed
998:Reluctance
894:Alternator
886:Generators
856:Field coil
841:Commutator
801:commutated
799:SC - Self-
653:2017-12-12
626:3835631322
604:References
502:horsepower
474:continuous
382:commutator
369:power cars
335:locomotive
263:thyristors
228:fuel cells
211:See also:
1375:Steinmetz
1290:Davenport
1088:Amplidyne
988:Universal
966:Homopolar
954:Repulsion
866:Slip ring
420:as well.
390:resistors
386:Ohm's law
152:frequency
93:elevators
1380:Sturgeon
1310:Ferraris
1295:Davidson
1117:Metadyne
1033:Traction
981:Unipolar
961:DC motor
917:AC motor
821:Armature
647:Archived
561:See also
487:low gear
478:one-hour
454:electric
375:Windings
363:for the
357:Bi-Polar
345:unsprung
296:through
265:and the
251:Krokodil
238:Railways
132:traction
73:Traction
69:trains.
59:electric
1370:Sprague
1365:Siemens
1340:Maxwell
1305:Faraday
1254:Starter
1193:Railgun
1188:Coilgun
1028:Stepper
876:Winding
534:Cooling
402:voltage
355:. The "
171:⁄
111:), and
1360:Saxton
1345:Ørsted
1330:Jedlik
1325:Jacobi
1315:Gramme
1280:Barlow
1268:People
1093:Drives
1008:Linear
909:Motors
871:Stator
712:on an
624:
585:&
500:, the
465:Rating
452:On an
246:Swiss
99:, and
49:is an
1385:Tesla
1355:Pixii
1320:Henry
1285:Botto
1275:Arago
861:Rotor
831:Brush
793:PM -
787:DC -
781:AC -
341:bogie
65:, or
1350:Park
1335:Lenz
1053:TEFC
622:ISBN
496:and
476:and
322:axle
312:and
267:IGBT
215:and
186:and
724:R38
714:R46
492:In
349:GG1
310:FF1
282:TGV
61:or
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20:)
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