Analog Versus Digital Operation Comparison - PowerTec Regenerative Brushless DC Motor Control 1000AR Installation And Operation Instruction Manual

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AN AL O G V E R S U S D I G I TAL O P E R ATI O N
The choice between ANALOG and DIGITAL operation comes down to performance.
In ANALOG mode, a voltage sets the speed of the motor. Due to analog component tolerances, the
best accuracy you can expect is on the order of +/- 1%. It is typically 0.1% or better. The biggest problem
with Brushless DC is not the following of an analog source. It is the obtaining of a clean and stable analog
ANALOG
Speed Regulation
Speed Accuracy
Speed Drift
adequate in almost all cases. Changing load does not change the speed of the motor.
Coordinating the speed of two or more motors with analog methods requires some type of trimming
device, such as a dancer or load cell. Analog tolerances and noise make exact coordination very hard.
In DIGITAL mode, the speed of the motor is proportional to the frequency of the pulse train presented
at the TB1 terminals 11 and 9. Each pulse to the drive at these terminals will require a pulse from the
DIGITAL
Speed Regulation
Speed Accuracy
Speed Drift
really want to be able to set 1749 RPM and get that speed precisely. Motor load does not change the
speed and the speed set by DIGITAL means has a drift of 1 Speed Reference pulse (less than 3° of motor
shaft rotation).
Speed coordination of two or more motors requires DIGITAL means for systems that do not have a
trimming device. Two motors connected by DIGITAL signals will track pulse for pulse.
Even though the motors may be made to operate together or in an exact ratio, there is a possibility
that the mechanical system or the speed setting devices may not be identical. If this is the case, some
type of trimming device may be necessary in a digital system. If the material does not stretch, this will
become apparent in short order.
1000AR
Model Installation and Operation Manual
Value
0% from No Load to Full Load
+/- 1% of Speed Reference
+/- 1% of Speed Reference
Value
0% from No Load to Full Load
1 Motor Feedback Pulse for each Pulse
of Speed Reference
+/- 1 Speed Reference Pulse
6/4/2001
source to follow. Electrical noise can
be a nasty problem, and you must
use good shielding methods.
In single motor operation, the
motor does not have to follow a
precise speed or a profile generated
by another motor or other source.
The ANALOG speed reference is
motor. The EEPROM multiplier used
in the Current Controller
determines the effect of the pulse
from the motor. Analog tolerances do
not disturb the system, nor will there
be any temperature drift.
For single motor operation, use
DIGITAL methods where precise
speeds are important, that is, if you
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