Whitelegg equipment aids traction motor repairs

Whitelegg Machines

Baker D65R surge tester

Key equipment supplied by Whitelegg Machines is enabling the Anstee and Ware Group to repair and service traction motors.

The Anstee and Ware Group provides electrical and mechanical engineering services and can service the needs of industries such as steel, aerospace, oil and gas, utilities, paper and quarrying.

Recently, however, the company identified a market opportunity to specialise in the servicing and repair of traction motors for the rail and mass transit industry.

Anstee and Ware agreed to commit GBP300,000 to the latest technology to enable rapid and high-quality repairs to traction motors, with the focus of the investment to be at its Castle Donnington site adjacent to the motor-racing circuit.

The company prepared specification documents for open tendering and, based on a competitive quote, Whitelegg was asked to supply key pieces of equipment to realise the project.

Anstee and Ware specified that certain key pieces of equipment were essential to its new Traction Motor servicing cell, which needed to be in place to win major rail contracts.

The items specified were a Baker D65R surge tester and Rimac of Italy TIG Welder and Undercutter machines, all sourced through Whitelegg, along with a test panel capable of 0-1,200VDC.

At Anstee and Ware, the normal process for DC traction motor servicing - following on from motor receipt at its works - is dismantling, cleaning, stoving and inspection, with a preliminary bar-to-bar surge test leading to go or no-go.

If no-go, the armature is completely rewound with new coils.

A second surge test is then carried out, followed by the TIG welding of the coils to the commutator risers.

The sequence continues with vacuum impregnation, lathe skimming and concentric and dynamic balancing.

Another bar-to-bar test is followed by undercutting and a final bar-to-bar test.

The whole motor is then run on a test bed at up to 1,200VDC.

From start to finish, a five-day turnaround is the norm.

Electrical testing plays a major part in this programme and the Baker D65R resistance, Hipot, surge and bar-to-bar tester was chosen for its advanced capabilities, which were designed to maximise testing accuracy in a lightweight, sturdy format with additional predictive testing.

The Baker D65R digital winding tester can perform winding resistance, Hipot and surge tests.

It can also digitise and store data for future use.

Surge testing detects faults in inter-turn, winding and phase-to-phase insulation systems.

Using advanced analogue-to-digital conversion hardware, the D series captures the surge test waveform, remembers it, displays it indefinitely and outputs to a printer.

Of particular relevance to Anstee and Ware was the fact that the lower impedance of series-wound armatures, as found in traction motors, makes accurate surge testing of these coils difficult through normal equipment.

The D65R, however, allows the user to safely test these coils using higher currents.

When testing these coils, a specific voltage is applied on adjacent commutator bars, reducing the need for an excessively high voltage, which could potentially damage the coil.

The traditional manual welding of new coils to commutator bars can be haphazard, lengthy and inaccurate.

The need for high accuracy and rapid TIG welding at this stage of motor servicing was vital.

The Rimac machine, specified by Whitelegg, can handle core diameters from 100mm to 1,500mm and up to 999 bars.

The welder torch automatically moves on to a new weld until the riser is complete.

Bar indexing is via a stepper motor.

The time taken for a standard traction motor has been reduced to four hours.

Another traditionally time-consuming process was undercutting.

Now, with the Rimac in place, the time taken for working a typical Class 66 traction motor has been reduced from six hours to 45 minutes.

This servo-controlled machine is said to be simple to set up.

A camera with 10x magnification and a 15in (38cm) LCD screen simplifies the observation of the cutting area.

Laser positioning is said to ensure high accuracy.

Anstee and Ware has won contracts for rewinding both alternators and traction motors for the Ex BR HST power cars, as well as Class 66 freight locos traction motor overhauls.

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