# Efficiency of mag lev

Dissident Dan
This is a thread to discuss the efficiency of magnetic levetation a la monorails. I really don't know how it would compare to the traditional surface contact-based transportation. If you have some knowledge on this or know where to find it, please speak up.

The lack of friction would definitely be a plus. However, you have to provide the energy to lift the object(s) off the ground.

Greetings !

I don't really know about the energy comparison,
I'm pretty sure the efficiency is higher because
you don't use motors but the energy is abviously
probably greater. The primary problem with such
trains is not the energy but rather the costs of
the monorail which is extremely high (several million
dollars per mile for the train in Japan, for example).

Live long and prosper.

Originally posted by Dissident Dan
This is a thread to discuss the efficiency of magnetic levetation a la monorails. I really don't know how it would compare to the traditional surface contact-based transportation. If you have some knowledge on this or know where to find it, please speak up.

The lack of friction would definitely be a plus. However, you have to provide the energy to lift the object(s) off the ground.

We must distinguish between the different types of maglev. There is the http://www.skytran.net/press/sciam01.htm, which uses the motion of the train along the track to induce magnetic current in the track, using a Halbach array. This tech is cheaper to build, because generators are not needed to power the track. But it offers less savings, because the magnets cannot be used for propulsion. The main savings here is just lower friction.

Then, there are the more traditional

electromagnet maglevs,which are much more expensive and complicated to build, but offer additional benefits. In this scheme, the propulsion of the train is powered by a stationary source external to the train. This means that the power source is not part of the weight that needs to be transported.

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tot
doesn't a lot of power have to be used to run the electromagnets that lift the entire weight of the train?
It seems that a maglev train would be highly inefficient, but very quiet, fast and smooth.
Can somebody verify this?

because in a train with wheels, the lift is provided by the contact of the train with the ground. so let's say the train weights 7x10^6kilograms.
you have to power enough electromagnets on the train, and on the ground to lift 7x10^6kg, as well as enough forward force to accelerate the train as well as fight off the forces of wind drag... unless I'm missing something.. it sounds very inefficient

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Staff Emeritus
doesn't a lot of power have to be used to run the electromagnets that lift the entire weight of the train?
Hence the quest for suitable superconductors goes on ...

johnbbahm
Not my area, but from what I have read an object lifted by a virtual magnet superconductor, does not use "any" energy for the lift. The only energy is to keep the superconductor COLD! http://en.wikipedia.org/wiki/Magnetic_levitation
So when the force of gravity and the magnet/virtual magnet repulsion equal, the object floats.

qumf
I saw the wire on the rail for high speed train.(300km/h) i ever saw the cable with very big diameter for mag-left train in shanghai(about 400-450km/h). so i think the mag lev need much more electricity.