Magnetic river
Encyclopedia
Magnetic river is an electrodynamic suspension
magnetic levitation
(maglev) system designed by Eastham and Eric Laithwaite
in 1974.
It consists of a thin conductive plate on an AC linear induction motor
. Due to the transverse flux and the geometry, this gives it lift, stability and propulsion as well as being relatively efficient.
The levitation is 5 axis stable, and the remaining axis is neutrally stable, or can be biased to accelerate in either direction along the motor. Notably, laterally, it exhibits a 'river bank' effect, where moving the plate either side slightly causes the plate to rise on that side, and due to this the plate tries to return to the centre line under gravity.
The row of magnets for the linear motor each have two poles, with the poles arranged transverse to the 'river' with U-shaped cores, and excited with an AC current.
When energised the magnets produce an oscillating transverse field which cuts the plate. The plate then generates two eddy currents, one above each pole.
However, the edge reduces the size of the eddy current on each side, since it interferes with the circular current. Moving the plate sideways increases the current on one side, since the edge is interfering less, and this pushes that side higher. The plate then moves laterally back towards the centre under gravity, stabilising the lateral motion.
This stabilisation only works provided that the plate is not too wide or too narrow, and is also somewhat dependent on levitation height, the plate must be wider at higher lifts.
Electrodynamic suspension
Electrodynamic suspension is a form of magnetic levitation in which there are conductors which are exposed to time-varying magnetic fields. This induces currents in the conductors that creates a repulsive magnetic field which holds the two objects apart....
magnetic levitation
Magnetic levitation
Magnetic levitation, maglev, or magnetic suspension is a method by which an object is suspended with no support other than magnetic fields...
(maglev) system designed by Eastham and Eric Laithwaite
Eric Laithwaite
Eric Roberts Laithwaite was a British electrical engineer, known as the "Father of Maglev" for his development of the linear induction motor and maglev rail system.- Biography :...
in 1974.
It consists of a thin conductive plate on an AC linear induction motor
Linear induction motor
A linear induction motor is an AC asynchronous linear motor that works by the same general principles as other induction motors but which has been designed to directly produce motion in a straight line....
. Due to the transverse flux and the geometry, this gives it lift, stability and propulsion as well as being relatively efficient.
The levitation is 5 axis stable, and the remaining axis is neutrally stable, or can be biased to accelerate in either direction along the motor. Notably, laterally, it exhibits a 'river bank' effect, where moving the plate either side slightly causes the plate to rise on that side, and due to this the plate tries to return to the centre line under gravity.
Principle
In magnetic river the conductive plate is a critical width relative to the magnets underneath it.The row of magnets for the linear motor each have two poles, with the poles arranged transverse to the 'river' with U-shaped cores, and excited with an AC current.
When energised the magnets produce an oscillating transverse field which cuts the plate. The plate then generates two eddy currents, one above each pole.
However, the edge reduces the size of the eddy current on each side, since it interferes with the circular current. Moving the plate sideways increases the current on one side, since the edge is interfering less, and this pushes that side higher. The plate then moves laterally back towards the centre under gravity, stabilising the lateral motion.
This stabilisation only works provided that the plate is not too wide or too narrow, and is also somewhat dependent on levitation height, the plate must be wider at higher lifts.