A slewing motor was sent for repair from Associated British Ports (ABP) dockside crane at Immingham, who normally purchase new motors from Gotwald (Crane MAnufacturer) costing around £8,000 per motor. The engineer at Immingham asked if ERIKS could assess the motor and quote for repair, bearing in mind that all cranes on the dockside have this style of motor.
The winding machine bolts directly to the frame and is directly mounted over the shoe to be rewound
Generally when the pole shoes can be removed a simple insulation and rewind would be cost effective, however, on this particular design we were unable to remove the pole shoes and the coils would need to be wound manually directly onto the pole.
Some scale and accuracy were the initial concerns as the turns per coil were very high and the room for overlapping the interpoles & main fields was critical.
A simple tube for threading the winding wire was first used to manually go around the pole piece, this gave us very little tension and counting the turns and logging every 100 was becoming monotonous and timely.
We decided to try and change the manual handling to a mechanical device which would carry out the same function but be able to give some tension and count automatically every sing turn / revolution around the pole.
After various designs on paper we decided on a rectangle profile, which basically came into the field frame, came horizontal across the coil end and back down the opposing side of the field frame. Although this was a rectangle movement the end result was an elliptical finish.
The drive motor was controlled by inverter supply to give us slow ramp up until the tension on the shoes was satisfactory, at which point the frequency was risen to around 30Hz (4pole drive motor) this gave us optimum speed without damaging the copper conductor.
After the winding machine was fully functional and had successfully run a coil trial we guarded the entire unit to ensure entrapment from moving parts was eliminated.
A simple trip counter was fitted to ensure the correct turns were carried out per coil.
After completing the guarding and re assembling to the field frame the four poles were rewound at a fraction of the speed and accuracy as would normally be expected on this style of motor.
Each individual coil was wound within 45 minutes as opposed to previous repairs, which were around 4 hours per coil due to the manual counting and applying of each single turn. Also eliminating the need for extreme concentration and counting errors, this proved to be a great success.
The final cost of building the machine was £1.5K, this was agreed to be funded by the customer with the final repair price being £5K. A saving of £3K was achieved to ABP, with potentially 10 other machines to be repaired in the future.
ABP will now send these repairs to ERIKS Grimsby as opposed to automatically purchasing new.