Brush type generator
 

Hi
Nowday aircraft use brushless type generator
why is A320 apu stil using brush type generator ?

thank you

I don't know modern Airbuses, but I suspect you are thinking of the starter motor, and DC motors have to have brushes to work.
AC generators (Alternators) have been brushless for ages.

Confusingly some motors are described as "Brushless DC motors".

They are AC motors with integrated electronics to convert the DC supply to AC for the motor. The electronics are now sufficiently efficient, light, compact and reliable for the description "Brushless DC" to be not that unreasonable. The AC's frequency can also be varied to get any desired motor speed.

The brushless alternator is very clever yet simple old technology. It is two alternators on one shaft. One generates the field for the main one and is inside out so it's field can be varied without brushes. This allows control of the field of the main alternator and thereby it's output.

I am not an expert but I believe that the above is substantially correct.

I'm afraid that's not true. The Brushless DC motor is a very different thing (electrically and magnetically) to an AC motor. A brushless DC motor is exactly what it says on the tin - it is a permanent magnet DC motor in which the commutator switching of the armature coils has been replaces with electronic switching timed by a microprocessor-control circuit. This allos the magnets to be put on the rotor and the coils swapped to the stator, but that's incidental. They do not use sinusoidal voltages, they do not use phase-shifted field coils for the magnetic field. They apply switched DC to the stator coils that interacts with the field produced by rotating permanent magnets. They have much better low-speed torque than either AC motors or stepper motors.

PDR