how to make an electromagnet (calculations required)

[Abdul Manan]

i need documentation about making a strong electromagnet with minimum possible size

 

[me_guitarist]

It depends on what iron/steel u use & current that consume.

Normally high current get high holding force.
Pls explain in details & clarify yr application.

Holding force, current consumption etc...

 

[Abdul Manan]

basically i am student of final year of electrical engineering
we are assigned to make a prorotype of magnetically levitated linear motor car
for levitation we need extreamly strong electromagnets

ideally we want to levitate an object with air gap of 5mm with current consumption of 2-3amps and payload weight should be 15kg excluding the weight of electromagnets
after 2 months of struggle we can conclude that it is impossible

Added after 3 minutes:

we don't need holding force we need levitation force may be an electromagnet that has 90kg holding force can have less than 2kg lavitation force at air gap of 5mm
holding force also depends upon how goor the contact is between two objects

 

[banjo]

To levitate an object you want to use magnetic repulsion rather than magnetic attraction. For a "car", I would think that the electromagnet would be embedded in the road and the car would have a fixed magnet whose N-S polarity is such that it repels the electromagnet when energized.
Using repulsion, such a system is self regulating. If the electromagnet is too strong, then car is pushed higher to a larger air gap until the magnetic force at that distance cancels the force of gravity.
When attempting to use attraction, you need careful control of the electromagnet as the system is unstable. The attraction wants to close the air gap to zero.