Wheel Slip or Creep control of EMD locomotives

Superior AC traction system of EMD's WDG-4 locos wheel slip or creep control on display here on a mountain section in India called Braganza Ghat with 1 in 37 (2.7%) gradient. 4500hp WDG-4 (GT46MAC) comes with 16-710G3B prime mover and IGBT technology similar to SD70MAC locos. It was found that if the wheels are made to slip on purpose slightly more then ground speed, maximum tractive effort is achieved. This is made possible with the aid of computer controlled wheel slip or creep control by interpolating ground speed determined by ultrasonic doppler radar and the motor RPM input from the loco controls. Twin WDG-4 locos lead a heavy coal train assisted by triple WDG-4 bankers(helpers) at the rear.