ZLT Automation | Case Studies | DC to AC
Drives
Overview
The leading kitchen components supplier MFI Manufacturing
Ltd approached ZLT Automation to provide a turnkey solution
to upgrade their front line, board lamination process
machine. Degradation over a period of time in the speed
holding capability and problems of torque mismatch on
the original DC drives systems continued to cause quality
and downtime problems. The decision was taken by MFI
management and senior engineers to replace all existing
DC controls, motors and gearboxes with AC drive systems
capable of providing reliability, speed holding and
dynamic speed control performance. ZLT Automation, a
technical partner for the award nominated range of SIEI
inverter drives provided their own state of the art
Avy closed loop, field orientated vector inverter drives
to meet the customers stringent performance demands.
In addition to the performance requirements demanded
from the new drives, the project necessitated detailed
ZLT project management control to complete the machine
strip down, drives installation , re wiring and on site
commissioning of the machine to be carried out during
a finite shutdown period of only seventeen days.
Scope of Supply
Main items:
a) 5 off closed loop field orientated vector inverters.
b) 5 off AC drive motors and gearboxes with encoders.
c) New AC drives panel integrated into existing control
panel suite to replace existing DC drives cabinet.
d) 5 off HMI operator display units and mimic diagram
incorporated into existing operator control console.
e) Electrical refurbishment and rewiring of the complete
machine to MFI standards.
f) Provision of new electrical documentation including
Autocad drawings of complete machine
Technical
Dynamic speed control and speed matching of each of
the five drive systems was necessary to keep the boards
at the same constant separation distance and at the
synchronised speed when being processed through each
of the cleaning, glueing, drying, chemical catalyst
and lamination stations. From the control position a
“master” speed reference signal was provided
to each drive. To achieve the close speed matching characteristic
required to be maintained during dynamic load torque
changes imposed by some of the treatment stations, each
drive motor was fitted with absolute encoder feedback
which combined with the performance characteristic of
the Avy vector drives provided speed regulation performance
of 10,000:1. Each drive system was fed with the digital
master speed reference signal from the master HMI with
individual HMI speed adjustment of each drive available
to the operator for start up and trimming adjustments
from the control console. Additional benefits to operational
and maintenance personnel were provided by utilising
the full digital capability of each drive in the provision
of a data link between each drive and its associated
HMI display. Motor data and drive status information
was made available from each inverter to each drive
HMI through standard software links providing full operational
drive status information at the operator position.
Summary
Previous quality and downtime issues have been resolved.
The performance and reliability of the drives has provided
MFI with full operational capacity for their lamination
process. The project was successfully completed and
commissioned on time during the specified shutdown period.
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