Electronics > Beginners
Will induction motors get replaced by synchronous motors?
amyk:
--- Quote from: Zero999 on November 19, 2019, 08:01:29 pm ---Modern induction motors with copper, rather than aluminium bars in the rotor are almost efficient as rare earth magnet motors and I believe there has been some investigation into using them in electric vehicles.
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Interestingly enough, early induction motors used copper too, but switched because aluminium was cheaper...
Personally, I like the sound of a repulsion-start induction motor:
Dave:
--- Quote from: bonzer on November 19, 2019, 08:57:23 pm ---But from the driving point of view like the power electronics - is there a big difference from working with an asynchronous motor? Is it more difficult to control them? If I tried to understand them by my own? (After all synchronous motor knowledge)
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In terms of field-oriented control (FOC; controlling the torque of the motor - required in electric vehicle applications, for example), yes, it is quite a bit more involved.
The motor needs to be fairly well characterized (mutual inductance, leakage inductance, stator and rotor resistance, etc.) in order to control it well. The shift of resistance with respect to temperature also needs to be taken into account (copper and aluminium conveniently have very similar temperature coefficients - 4.04e-3 vs 3.90e-3 K-1, respectively).
On the bright side, they only require incremental encoders. You need to know the exact position of a rotor for FOC of a PMSM, but you only need to know the speed of the rotor with an induction motor. Needless to say, incremental encoders are significantly cheaper than absolute ones.
Ground_Loop:
--- Quote from: bonzer on November 19, 2019, 08:57:23 pm ---I don't know exactly why they don't care about them, maybe because there's not enought time. But the professor himself said that industry now is full of asynchronous motors so if you want we can have a lecture about them but we don't include it in the program because it's a matter of time when they are gonna be replaced with what we study.
But from the driving point of view like the power electronics - is there a big difference from working with an asynchronous motor? Is it more difficult to control them? If I tried to understand them by my own? (After all synchronous motor knowledge)
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Synchronous motors are generally started in a two-step process. Initially, the rotor winding are shorted such that the rotor can behave as a standard induction motor. Once the rotor speed has reached a certain point the rotor winding short is removed and a DC field current is applied to fix the field orientation relative to the rotor. At this point the rotor can "lock in" to the armature field rotation and behave in synchronous mode. So a synchronous motor requires a control mechanism to sense rotor speed and switch the rotor field current.
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