Aerotech BAL LINEAR AMPLIFIER SERIES, User Manual

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BA Linear Series User’s Manual Installation and Operation
Version 1.5
Aerotech, Inc.
2-7
2.4. Three Phase Brushless Motors with Unconnected Phases
Most three phase brushless motors require only three connections between the servo
amplifier and the motor. This is due to the motor phases internally connected in a Wye or
Delta style. This form of connection simplifies wiring, ensuring that the servo amplifier
only controls and monitors two phase currents, since the third phase current is always the
sum of the first two phase currents.
However, this simplicity has one drawback. This drawback is phase winding imbalances
that can cause torque ripple and make it difficult to compensate, since the servo amplifier
only controls two of the three phase currents. The BAL Series amplifier over comes this
problem by providing the “RT” (return) connection for six wire motors, like the Aerotech
BLM Series linear motors.
Since the BAL Series amplifier independently controls current in each of its three phases,
six wire motors can be connected as shown in Figure 2-5. In this configuration, offset
and/or gain adjustments of current made in one phase do not affect those set in the other
two phases.
Figure 2-5. Connection of Six Wire Motors to BAL Series Amplifiers
J8
A
B
C
G
RT
HI
LO
G
Rotary or
Linear Motor