Rockwell Automation 1395 DC Drive, 800-1250 Hp, FRN 5.XX-9.30 - Manual (Page 37)

Chapter 3
Functional Description
3-4
Communication Control
The Communication Control block controls all of the data transfer. The
Programming Terminal communicates with the drive through an RS-422
serial communication link. Internal communication in the drive is
accomplished using a Microbus which is a specialized microprocessor bus
designed by Allen-Bradley. In addition to internal communication, transfer
of data between the drive and up to two Adapter Boards is provided
through the Microbus. The hardware used for this interface is known as a
Microbus Port. Two ports (labeled A and B) are available. Adapter
Boards provide an interface between external control hardware such as
discrete devices, PLC’s, etc.
Drive Logic Control
This block controls the operating state of the drive in response to the logic
command input. Selection of various reference parameters (i.e. speed
reference) and control modes (i.e. droop) are performed in the drive Logic
Control. In addition to controlling the state of the drive, the drive Logic
Control monitors the present operating condition of the drive and provides
this information as available feedback to external control devices. The
drive Logic Control also monitors fault sensing.
Speed Reference Selection
There are five preset speeds stored in parameters in the drive.
Additionally, an External Speed Reference and one of two Jog inputs may
be selected as the velocity reference input to the drive. The Speed
Reference Select block uses information provided from the drive Logic
Control to determine which of the available references will be used as the
input to the Velocity Control. The selected reference is sent to a ramp
before being sent as the velocity reference input to the Velocity Control.
Velocity Feedback Select
The drive has been designed for normal operation using one of three
possible means of velocity feedback. Hardware for interfacing the drive to
a digital encoder is provided as standard in the drive. Armature voltage is
constantly monitored by the drive and can be used for velocity feedback. If
a DC tachometer is used for speed feedback, the drive must be equipped
with a Discrete Adapter Board connected to Port A of the Microbus.
IMPORTANT: An external voltage divider for the DC Tach will be
needed to obtain the correct voltage for the Discrete Adapter Board analog
input circuit.
Feedback in the form of an analog signal from the DC tach is sent to the
Discrete Board, converted to a digital signal and scaled for input to the
Velocity Feedback Select block. The Velocity Feedback Select block uses
information stored in a drive setup parameter to determine which of the
feedback signals is to be sent to the Velocity Control.