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Type BWT and BWU Changeover Switches for Traction Motor Circuits The different circuit arrangements of the comm utator-type motors of electric traction vehicles are set up by change- over switches. These changeover - direction reversers, - motoring/braking changeover - converter or traction motor discon- nect switches, - series/parallel grouping switches, - power system selector switches or, - transformer tapchangers. In every case switching always takes place in the de-energized state and there are either two or three switch positions. The switches themselves are not designed as load...

Changeover Switches Two of the most common uses of the changeover devices are for selecting either the motoring or braking circuit and for reversing the direction of travel. Figure 1 shows examples of how rotat- ing selector switches, contactors, cam- switch assemblies and linear switches perform these functions. Contactors or cam-switch assemblies are used when it is anticipated that residual currents will have to be interrupted. Contactors of type BMS/BPS are recommended For the sake of simplicity, the type are of the linear type. Figure 2a shows a basic circuit diagram of the device with...

Fig. 3 - Basic circuit diagram of a linear selector with three pneumatically controlled switch positions. Fig. 4 - Basic circuit diagram of a linear selector with two switch positions. Type BWU 15.08 changeover switch with a maximum of 14 levels and 5 rows of 4 moving contacts (vertical position). Fig. 5 - Contact unit for a type BWT/BWU changeover switch.

switch with pneumatic drive, used as a direction reverser for two traction motor circuits of shuttle-service motorcoaches operating on Swiss standard gauge Max. traction motor voltage 750 V Max. traction motor current 1050 A One-hour traction motor current 600 A Technical data of type BWT/BWU changeover devices (linear selector switches) Rated voltage Rated current Dynamic limit current Ambient temperature Mechanical lifetime Changeover time Drive voltage Pneumatic drive - operating pressure range Electro-motive drive Control switch 3 million switching operations BWT: 12 auxiliary contacts;...

Fig. 7 - Assembly drawing of the type BWU 15.08 changeover switch. 1.1 = Optional compressed-air connection. 4.1 = Handle for manual operation. 5 = Contact units for main circuits, 5.1 = Fixed contacts with main power 5.2 = Contact unit in drive carriage. n = Number of contact levels. The changeover switches of each series differ in the maximum number of terminals they offer: The Table shows the technical data over switches. 3000 V) consist of the following, modu- - Contact modules comprising a linear contact unit and fixed contacts. - Drive carriages of variable length. - Control switch...

switch with electro-motive drive, used in the traction motor circuit of all-electric two-coach trainsets class Be 8/8 on the Forch line, Zurich (mounted horizontally beneath the coach floor). Rated traction motor voltage 1200 V Max. traction motor current 500 A One-hour traction motor current 350 A Fig. 9 - Main equipment unit of multi- purpose main-line locomotive Re 4/4 IV of the Swiss Federal Railways for oper- ation with single-phase a.c. at 15 kV/162/a Main equipment unit for the two dual-excited pulsating current traction motors of the driving bogie. The phase-angle controlled...

Fig. 10 - Main equipment unit of class 250 multi-purpose main-line locomotive of Espaholes (RENFE) for operation with Main equipment unit for the d.c. series- wound dual traction motor (single-motor bogies) of the contactor-controlled vehicle. The locomotive is driven by pulsating current motors with rheostatic brakes separately Bank of electro-pneumatic contactors of type BPS (with arc chutes raised). Linear changeover switches of the following actuated motoring/braking selector switch. actuated direction reverser. One type BWT 30.08 manually actuated traction motor selector (disconnect...

Fig. 11 - Main equipment unit of class EL 1 main-line locomotive of the National Railways of Zimbabwe (NRZ) for operation with single-phase a.c. at 25 kV/50 Hz. would be capable of withstanding high short-circuit currents. Springs set the contact pressure to 46 + 5 N. Exact operation with greased contacts guar- antees resistance to mechanical wear. Such contact systems, however, have no breaking capacity, i.e. the contacts are only capable of interruptions in which there is no arc. The upper current limit is 500 mA; this demonstrates the changeover devices as selector swit- The switch is...

- Heat tests - Mechanical tests involving up to three million switching operations without maintenance - Surge current tests in accordance The results of the tests came up to all expectations. Despite the lighter and more compact design of the newly developed changeover devices, it has been possible to achieve the high relia- bility for minimum wear required for traction applications, in which switch- ing is frequent. Previous experience has shown that when switches are assembled and maintained according to instructions and operating condi- tions are acceptable, there is practically The...