Enhancing the I/O Capability of VFDs to Remove the Dependency on External PLC

Abstract

Variable frequency drives are backbone of an industrial process. Their effective control and protection adds reliability to an industrial process. The present work is focused on enhancing the fault detection mechanism of Variable frequency drives installed at Coastal Gujarat Power Limited (CGPL). Coastal Gujarat Power Ltd (CGPL) MUNDRA is having total 12 Nos of VFDs having application of Coal Vessel Unloading at External Coal Handling Plant (ECHS) and that Coal transferred to Internal Coal Handling Plant (ICHS) for 4000MW Unit Generation, which is continuous running to transfer the coal to Main Plant. There are in total five plants each plant is generating 800MW. The distance for feeding the coal for generation purpose is 15 km away from ECHS Plant. Installed Variable Frequency Drives having limitation of inputs and outputs capability so, with the help of LOGO PLC installed in the drive which is useful for extending the input and output capability of the drive as well as it is cost effective compare to the VFDs having extended input/output capability. Installed drive is having two PLC one is SIEMENS basic LOGO PLC the other is expansion LOGO PLC module which are resulting in frequent failures faults of LOGO PLC modules that hampers coal transfer for plant generation. The limitation of this LOGO PLC is that it unable to detect fault, no monitoring, no control and it is not user friendly as well the fault rectification time is more. For removing the dependency of LOGO PLC on variable frequency drives, firstly this LOGO PLC is removed by initializing the new control unit in the drive which used to handle the entire task which was earlier performed by the LOGO PLC. Secondly it was removed by transferring all the logic of LOGO PLC in the main Allen Bradley panel which is used to instruct the drive, so that we can overcome these limitations. This helps to reduce the maintenance cost and improve the process control. This Enhancement of the input/output capability of variable frequency drives to remove the dependency on external programmable logic controller help in reduction of downtime, equipment efficiency, improved critical equipment availability and system reliability. The effective fault detection proposed by the ladder logics of LOGO PLC and Allen Bradley PLC are verified by the experimental results.