I've been trying to understand why induction motors can't hold a permanent magnetic field. I know they operate on AC power, but I'm curious about the specific reasons behind it. Can someone break it down for me?
2 Answers
It's important to remember that induction motors basically act like a transformer. But instead of a secondary winding being connected to a load, the rotor is shorted and spins. The induced current creates the rotor's magnetic field—hence, it's asynchronous. If the rotor and the magnetic field matched speed, there wouldn't be any induction happening.
Energy loss is a reality in these motors, mainly due to heat and friction as well as the slip.
Induction motors produce their magnetic field using electromagnetic induction instead of permanent magnets. When you apply AC power, the stator windings create a rotating magnetic field. This field induces currents in the rotor, which then generates its magnetic field, but only while the motor is powered. Once you cut the power, that rotor magnetic field disappears. Plus, since the rotor speed never exactly matches the rotating field, it relies on what's called slip to keep the induction going—this adds to the reason why a constant, permanent magnetic field isn't possible.
That makes sense! So it’s all about how induction motors work differently compared to other motor types.
Right, and don’t forget that because they work with AC, the direction of the magnetic field keeps changing, which also makes it hard to maintain a fixed field.
Good point! But what about the energy loss during that induction?