True. I would like to add some points.
I think the reason why WAP5 has high wheel slip risk is GTO traction converter which results in bogie isolation very often. The microprocessor control aids wheel slip rather than preventing it by reducing the current supply to the bogie whose axle is slipping.
click here
^ RDSO has cleared the operation of 26-coach...
more... trains in the SCR zone with a single WAP5 loco. However this is not followed due to reliability issues.
In WAP4, all motors are connected in parallel which means an axle is independently powered. However, it does not have computerized wheel slip control mechanism, unlike three phase locomotives.It suffers in bad weather conditions.
On the contrary, EMD locos (only WDP4B/4D and WDG4) have IGBT based traction converter which allows axle control. That results in better utilization of the available adhesion and thus, the tractive effort increases. These locos have creep control system (
click here which results in controlled slipping and eventually, the loco generates maximum tractive effort.
Now, CLW has already started providing IGBT traction converter and creep control with doppler radar to WAG9, 9H and WAP7 locos. WAP5 with IGBT is under development. Track the development here :
click here^ The three WAP5 locos in the list have IGBT based auxiliary converters. But the main traction converter is still GTO.