winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
Something to consider: the wasting of energy in the magnetic field does not depend upon braking or regeneration.
You could have a motor with no load at all, and if you supply excessive terminal voltage then you will get excessive magnetizing current and heating. If you connect a 240V motor to a 480V supply, then even without load it will soon overheat and fail.
Even without saturation, increasing the applied voltage means increased magnetizing current flow and thus increased heating in the wires.
Saturation adds to this issue. The rate change of magnetic flux must match the applied voltage, so a higher applied voltage means a higher rate change of magnetic flux and a higher peak flux...but once the iron saturates, it takes far more current to create this flux. So if you increase the applied voltage to the point where you saturate, you will see _much_ higher magnetizing current flow, and thus much higher heating in the stator conductors.
On top of this, the stronger magnetic field means higher losses in the iron, from eddy currents and hysteresis.
There are probably other loss terms.
Any heating in the motor must be supplied from somewhere. This heating consumes power that would otherwise go to charging the capacitors.
-Jon
You could have a motor with no load at all, and if you supply excessive terminal voltage then you will get excessive magnetizing current and heating. If you connect a 240V motor to a 480V supply, then even without load it will soon overheat and fail.
Even without saturation, increasing the applied voltage means increased magnetizing current flow and thus increased heating in the wires.
Saturation adds to this issue. The rate change of magnetic flux must match the applied voltage, so a higher applied voltage means a higher rate change of magnetic flux and a higher peak flux...but once the iron saturates, it takes far more current to create this flux. So if you increase the applied voltage to the point where you saturate, you will see _much_ higher magnetizing current flow, and thus much higher heating in the stator conductors.
On top of this, the stronger magnetic field means higher losses in the iron, from eddy currents and hysteresis.
There are probably other loss terms.
Any heating in the motor must be supplied from somewhere. This heating consumes power that would otherwise go to charging the capacitors.
-Jon