Power Brick Controller User Manual
Manual Motor Setup
135
Motor Phasing
When commutating a synchronous multi-phase motor such as a permanent-magnet brushless servo motor,
the commutation algorithm must know the absolute position of the rotor within a single commutation cycle
so it knows the magnetic field orientation of the rotor. The process of establishing this absolute position
sense is known as "phase referencing" or "phasing".
An unreliable phasing search method can lead to a runaway condition.
Test the phasing search method carefully to make sure it works properly
under all conceivable conditions, and various locations of the travel.
Make sure the fatal following error limit
Motor[].FatalFeLimit
is
active and as tight as possible so the motor will be killed quickly in the
event of a serious phasing search error.
Warning
The Power Brick Controller supports a variety of phase referencing techniques.
Unless the motor phase offset is known – mechanically – from the motor-encoder-halls assembly
manufacturer (uncommon and may be inconsistent), setting up a new motor will virtually always require
performing an automatic or manual phase referencing routine.
This routine may be implemented permanently – saved – into the PMAC for motors without hall sensors or
an absolute encoder. Otherwise, it is subsequently used for correcting hall sensors’ phasing error or
computing a phase offset with absolute encoders.
Note
The available torque from a motor is directly proportional to the
accuracy of the phase reference. The better the phasing is the less
torque loss, current consumption, and motor/drive thermal losses are.
Note
For best performance, the initial phasing routine (any method) should
be done on an unloaded/uncoupled motor.
Note
Vertical axes phasing may require higher output current to overcome
gravity, it is strongly advised to implement a balancing mechanism
(e.g. weight, air) for such cases.
