There is a big ruckus now about the shortage of rare earth elements for the permanent magnet fields in motors and generators. At least in the case of large ones, why does the industry reject wound-field designs? They are a mature and proven technology. While the field windings do use a small amount of power, they allow for additional control by adjusting the field current.
thats a good idea.
but if the conductor is woud against a magnet in a motor..the rotating armature would rip the windings away.
so an improved design is required where in a metal case must be provided for the conductor of the electro magnet.
and lots of current is needed to create an elecrto magenet.
NI=B(L/u)...N=turns,i=currrent,L=length of core,u=4*3.14*10^ -7.
hence b is a small value(because of N cannot be too l;arge in a motor,cant have large i(burns the conductor),L is small ,u is very small).
Wound-rotor synchronous generators or doubly fed induction machines have a big market share in the wind power market. In traction wound-rotor motors are not as popular because at the low power ratings the field supply assembly (brushes and slip-rings or excitation machine and rectifier on the rotor) becomes relatively large and expensive. The dominant motor type in traction (tracked, OHV and road) are squirrel cage induction motors, while permanent-magnet synchronous motors, synchronous reluctance motors and hybrid designs of the latter two raising in popularity because of the higher efficiency and smaller size. Synchronous reluctance motors are the more direct contendor to PMSMs role than wound-field motors.
Mr. Shankar, The problems you describe might have occurred when such machines were first made over 100 years ago. Good engineering has long ago overcome them. When was the last time you saw a motor or generator whose windings got tangled in the rotating parts? I am well aware of the theory of electromagnets, and most engineering books indicate that the power used for field excitation is typically
Allen i think a lot of research is going into rare earth magnet alternatives,its a problem that was foreseen and now machine designers are tending towards reluctance machines and machines using other magnets like Alnico.So if the same enthusiasm is maintained then the industry wouldn't be greatly affected.
The Tesla Roadster uses a 3-phase, 4-pole electric induction motor. The seem to be ahead of the REE problem.
Mr. Brookshear, the 3-phase induction motor has been around for a century but until recently it has been single speed (determined by AC frequency). Induction motors have never used permanent magnets. Does the one in the Tesla use variable frequency to vary the speed? Even so, I am not sure it would match the dynamic speed range of the DC motor, so does the Tesla also use a multi-gear transmission to make up for limited speed range of its motor?
The Tesla Electric motor apparently is a high tech version of an Industrial motor. Most Industrial motors have a specific range of rpms they run at. The Tesla motor can run up to 14,000 rpm. The Tesla rotor conductors are made of copper instead of aluminum. It has a single speed gear box.
The problem with Tesla motors is constant burn-out due to the poor management of complex harmonics from the combination of VFDs and electronic accelerator control. We are currently working on a solution we use in industry to fix electric drive vehicles
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