Commutation Modes; Feedback - Copley Controls Accelnet Plus BEL Series User Manual

Accelnet & Stepnet Plus Panels User Guide
Using EtherCAT, the distributed clock feature can be used to establish PWM switching frequency synchronization
among the network connected drives. Typically one drive acts as the Sync 0 message producer. The master then
adjusts the Sync 0 frequency and phase in the slaves to so that they are all in-sync.
Over CANopen, one drive produces a Sync message that carries a high-resolution time-stamp. The other
drives on the network receive the Sync message and adjust their internal clocks so that all of the drives on the
network have their PWM frequencies synchronized.
In a MACRO ring, the master frequency must be a multiple of the drive's current loop frequency.
When this is done the PWM frequencies of all the drives will be synchronized.
3.2 C
OMMUTATION
The servo drive models (Bxx) support three commutation modes to drive brush and brushless motors:
AC brushless sinusoidal, DC brushless trapezoidal, and DC brush.
In most applications, sinusoidal commutation is preferred over trapezoidal, because it reduces torque ripple
and offers the smoothest motion at any velocity or torque. In the sinusoidal commutation mode, an encoder or
resolver is required for brushless sinusoidal commutation. Halls are sufficient for trapezoidal commutation.
When driving a DC brush motor, the drive operates as a traditional H-Bridge drive. No feedback is required for
torque (current) control but is needed for velocity or position control.
Stepper drives in microstepping mode have no need for commutation because the motor rotor is always
following the current vector created by the master. If operating in servo-mode, Stepnet drives use the encoder
feedback to auto-phase when the drive is enabled (wake-and-shake, or wake-and-wiggle).
3.3 F
EEDBACK
E R
NCODER AND
The standard versions of the Accelnet & Stepnet Plus Panel drives support digital quadrature encoders, analog
sin/cos encoders, and a variety of absolute encoder formats. These versions normally require the use of Hall
switches for the commutation of brushless motors when incremental encoders are used. Absolute encoders
provide position and commutation feedback thus Halls are not required.
The resolver versions, designated by "–R" in the model number, support standard, single speed, resolvers.
Resolvers provide absolute position feedback of the motor rotor and are sufficient for commutation as well as
high-resolution motor rotor position reporting.
DC brush motors are self-commutating and only require feedback that reports the rotor position in either
absolute or incremental format.
M -M P
ULTI ODE ORT
The multi-mode port on the control connector can be configured for various functions, depending on type of
drive.
• Output buffered digital encoder A/B/X signals from a digital incremental motor encoder.
• Output emulated digital A/B encoder signals derived from analog sin/cos encoder or resolver.
• Output emulated digital A/B encoder signals from an absolute encoder
• Input a secondary digital encoder to be used in the dual encoder position mode. In this mode, an encoder
attached to the load provides position loop feedback, and the motor encoder or resolver provides velocity
loop feedback.
M
ODES
S
ESOLVER UPPORT
16-01339 Rev 07