Mitsubishi revitalize aging oil–cooled drives
A novel approach to refurbishment has brought a number of old variable-speed drives up to state-of-the-art specification at a cement works in Warrington. Factory automation specialists Newton Tesla were called in to carry out a major overhaul of the oil-cooled drives, which began operating 25 years ago, as they were underperforming and inefficient by today’s standards.
The company’s brief was to bring each drive’s performance up to a modern standard, without making them difficult to refit back into their original installations. George Newton, an engineer for Newton Tesla, recalled: ‘The units were so ruggedly built that, from the outside, they looked rather like nuclear containment flasks. They were covered in cast cooling fins and huge, compared to today’s drives of similar capacity.
‘At first we were thinking about putting a modern Mitsubishi E540 drive into a new sheet steel cabinet and making bespoke interfaces so that they could be reinstalled back on site. But then I had a brain wave and wondered about stripping out the original electronics and putting a Mitsubishi inverter in the oil-filled case. Doing so would maintain the same external appearance and connections, making it possible to refit on site in a matter of minutes.’
The drives were opened up and all internal components, heat-sinks, reactors and printed circuits were discarded, leaving an internal steel frame that the new Mitsubishi E540 fitted into quite conveniently.
The E540 inputs and outputs are connected to the original socket giving the same control functions as before. The inverter is mounted in such a way that when the steel frame is lowered back into the oil tank, it is completely submerged in a high grade insulating oil that is widely used in high voltage switchgear.
An FR-PU04 parameter keypad is mounted under the outer lid to allow setting of the drive in the oil tank. ‘This was such a radical solution and, as far as we know, the first time it had been done that we did extensive load testing before returning the drives to the cement works,’ explained Mr Newton.
‘They ran perfectly no matter how we loaded them. In fact, the oil cooling proved very effective; the outer tank surface topped out at only 31°C, with a load of 5.5kW for 8h, whereas with air cooling the heat sink reached 60-75°C.’
Running tests have shown that the Mitsubishi drives have improved overall plant performance by a considerable margin. Newton Tesla are now presenting their refurbishment idea to other companies who have aging oil-cooled drives in critical roles.
Mitsubishi Electric Europe, Travellers Lane, Hatfield, Herts AL10 8XB; tel: (01707) 276100; fax: (01707) 278695.
The company’s brief was to bring each drive’s performance up to a modern standard, without making them difficult to refit back into their original installations. George Newton, an engineer for Newton Tesla, recalled: ‘The units were so ruggedly built that, from the outside, they looked rather like nuclear containment flasks. They were covered in cast cooling fins and huge, compared to today’s drives of similar capacity.
‘At first we were thinking about putting a modern Mitsubishi E540 drive into a new sheet steel cabinet and making bespoke interfaces so that they could be reinstalled back on site. But then I had a brain wave and wondered about stripping out the original electronics and putting a Mitsubishi inverter in the oil-filled case. Doing so would maintain the same external appearance and connections, making it possible to refit on site in a matter of minutes.’
The drives were opened up and all internal components, heat-sinks, reactors and printed circuits were discarded, leaving an internal steel frame that the new Mitsubishi E540 fitted into quite conveniently.
The E540 inputs and outputs are connected to the original socket giving the same control functions as before. The inverter is mounted in such a way that when the steel frame is lowered back into the oil tank, it is completely submerged in a high grade insulating oil that is widely used in high voltage switchgear.
An FR-PU04 parameter keypad is mounted under the outer lid to allow setting of the drive in the oil tank. ‘This was such a radical solution and, as far as we know, the first time it had been done that we did extensive load testing before returning the drives to the cement works,’ explained Mr Newton.
‘They ran perfectly no matter how we loaded them. In fact, the oil cooling proved very effective; the outer tank surface topped out at only 31°C, with a load of 5.5kW for 8h, whereas with air cooling the heat sink reached 60-75°C.’
Running tests have shown that the Mitsubishi drives have improved overall plant performance by a considerable margin. Newton Tesla are now presenting their refurbishment idea to other companies who have aging oil-cooled drives in critical roles.
Mitsubishi Electric Europe, Travellers Lane, Hatfield, Herts AL10 8XB; tel: (01707) 276100; fax: (01707) 278695.
