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| Driving 3-phase motor from 2 amplifier phases |
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| Benta:
--- Quote from: Dave on December 28, 2018, 01:46:20 pm --- --- Quote from: Kalin on December 28, 2018, 01:51:43 am ---Are BLDC motors typically permanent magnet motors or squirrel cage? --- End quote --- BLDC motors always have permanent magnets inside. --- End quote --- Not necessarily. Larger types may have field windings. Those are rare, though. |
| Dave:
--- Quote from: Benta on December 28, 2018, 03:39:37 pm ---Not necessarily. Larger types may have field windings. Those are rare, though. --- End quote --- Could you please provide an example of such motor? To my understanding, you can't have a field winding on the rotor without having some sort of brushes in place to transfer the current onto the spinning rotor, therefore it would not be a brushless motor anymore (BLDC). |
| Benta:
The "brushless" part relates to commutation. Slip rings is another story. It's a question of the classification of the motor. Some automotive drives used this experimentally to cut cost, neodymium or cobalt-samarium magnets aren't cheap in the needed size. |
| Zero999:
Slip rings require brushes, so are not brushless. There is really no such thing as brushless DC motor. |
| jbb:
I’m not sure if you’re using amplifiers to drive the motor for testing or for some kind of low noise operation, but I have an efficiency concern; I expect that the power factor on your two amplifiers could be quite bad under some conditions. This could lead to unexpectedly high dissipation in a Class B amp. |
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