User Manual

Trapezoidal Switching
Advanced Digital Motor Controller User Manual 101
Important Notice
It is not possible to change the motor direction by changing the Hall/Phase order. If
the motor is not turning in the desired direction, chose “Inverted” in the “Motor Di-
rection” configuration menu in the PC Utility.
Hall Sensor Alignment
It is very important that the hall sensors be precisely aligned vs the electromagnets in-
side the motor so that commutation be done exactly at the right time. Bad alignment will
cause the motor to run inefficiently.
A first, and generally reliable clue that Hall Sensors are not properly aligned is to run the
motor in the forward and then reverse direction while in Open Loop. Verify that for a given
command level in open loop, the motor reaches the identical speed and consumes the
same amount of current.
Another simple verification method is to use an oscilloscope to view the shape of the
phase voltage. While the motor is running, place a probe between ground and any of the
motor phases. Verify that the voltage looks like the shape on the figure 8-5. Look for sym-
metrical ramps on the left and right. An imbalance in the ramps indicates that the commu-
tation happens at the wrong time because of bad Hall Sensor position.
TTT/2 T/2T/2 T/2T
Correctly Timed Commutation
Wrong Timing Commutation
FIGURE 8-5. Ground to Phase voltage waveform on motor with correct and wrong commutations
The most precise evaluation of the Hall Sensors alignment is done using an oscilloscope
and the circuit described in figure 8.6. Compare the shape of the Hall Sensor signal to this
of the voltage that is generated on the motor phases as the shaft is rotated by an external
force. Verify that the zero-crossing of the phase voltages is occurring at exactly the same
time as the Hall Sensor transitions, as shown in figure 8-4.