Pune's WDS 6 # 36115 being tested on the 'load box' at the home shed. The loco is notched up or down with a remote throttle via the MU cable rather than the physical controls in the cab. The output of the generator is loaded with a set of electrodes immersed in a large water tank. The newer generation locomotives (WDG4/WDP4 and perhaps the WDM3Ds) have dynamic brake grids large enough to act as a full sized loading resistor during tests - thus not need this facility while testing the loco output.
A loco sounds wonderful during these tests. From the train or from the track side, a fully loaded loco can be heard only for a few fleeting seconds. However at the load box, one can stand and listen to the beast, running all out, for a long, long time. 12th April 2007