HSST and Transrapid

Different types of maglev systems have been developed in Japan and Germany. Whereas Japan has developed the High Speed Surface Transport (HSST) system, Germany has developed the Transrapid technology. Both systems coincide by using linear motors for propulsion and electromagnets for levitation. However, the two systems use different types of linear motor. The HSST is driven by linear induction motors with primary coils attached to the train body and the guideway consisting of steel rails and aluminium reaction plates. In contrast, the propulsion of Transrapid trains is realised by a linear synchronous motor. These differences may be explained historically: the Japanese and German systems were planned for different speeds. While the HSST was initially planned for speeds of 300 km/h and present development efforts focus on intra-urban trains running at about 100 km/h, the transrapid developers have been aiming at speeds of 450 to 500 km/h from the beginning.

This evaluation puts a clear focus on transrapid technology, but in great part applies to maglev systems in general.

Technical details of Transrapid

The Transrapid is both propelled and braked by means of a synchronous long-stator linear motor. Ferromagnetic stator packs and three phase stator windings are mounted on both sides along the underside of the guideway. The operation principle can be visualised best by a conventional (rotating) electric motor whose stator is cut open and unwound along the underside of the guideway. Its rotor (excitation) function is taken by the on-board levitation magnets. The vehicle is propelled by an electromagnetic travelling field produced by the longstator linear motor.

The thrust is controlled by means of power electronics on substations along the track. By varying the amplitude and frequency of the AC supply, the vehicle may be accelerated smoothly from standstill to full speed. During deceleration the linear motor becomes a generator (regenerative braking) just as in the case of conventional AC motors.

The vehicles

The planned Transrapid trains are composed of a minimum of two sections, each with about 90 seats. Depending on application and traffic volume, trains may comprise up to ten sections (two end and eight middle sections).

Freight operation

The Transrapid is also discussed as a means for transporting goods. For high-speed freight transport, special cargo cars could be combined with passenger cars or operated as dedicated cargo trains (payload up to 18 tons per section). The propulsion system being integrated in the guideway, the length of the vehicle and the payload do not affect the acceleration power.