H u d s o n M a n u a l / R e v . 1 . 2 1
1 2
T
EKNIC
,
I
NC
.
P H O N E ( 5 8 5 ) 7 8 4 - 7 4 5 4
Servo Drive Selection
Drive Compatibility
Servo drives intended for use with a Hudson motor must have the capabilities
listed below.
Supported Methods of Commutation (see section below for details)
•
Six-Step
(trapezoidal)
•
Sine
Wave
•
Sine Wave with Vector Torque Control
Hudson motors have
•
5VDC differential encoder signals
•
5VDC,
120
°
optical commutation sensors (analogous to Hall effect
sensors)
•
8
poles
•
4 electrical cycles per revolution
Supported Commutation Methods
Each Hudson motor has a precision optical encoder disk with 120º optical
commutation sensors (analogous to Hall effect sensors). During assembly the
disk is precisely locked into position such that the commutation tracks line up
with the rotor in a known orientation.
Six-Step (Trapezoidal) Commutation
Note
: Six-step commutation (aka "trapezoidal commutation") can be used
with Hudson motors though it is generally not preferred for high precision, low
speed applications due to higher torque ripple and lower operating efficiency.
Six-step is often used in cost-sensitive, lower precision applications, and for
high speed applications where the mechanical system and motor combine to
have sufficient inertia to minimize the effect of torque ripple.
During six-step commutation, the servo drive interprets the rotating
commutation sensor codes from the motor to determine relative rotor to stator
position and uses this information to sequence and time the switching of
current into the motor phases.
Step#
Commutation Sensor State
3 channels, 120º separation
Current Flow
1
1
0
1
From phase R to phase S
2
1
0
0
From phase R to phase T
3
1
1
0
From phase S to phase T
4
0
1
0
From phase S to phase R
5
0
1
1
From phase T to phase R
6
0
0
1
From phase T to phase S
