 Newer versions of the WAG-9 feature full Insulated-gate bipolar transistor (IGBT) traction control; the debut model was the "WAG-9 31248".The class as a whole is denoted by the WAG-9i prefix in its model number, although there is a technical variant of this class named WAG-9H, with the "H" meaning "Heavy".The WAG-9H/9Hi locomotives are the second heaviest in regular service in India, the only freight-dedicated three-phase AC locomotives in the country, and the only electric locomotives in India fitted with IGBT.