The ID.3 from Volkswagen, a compact (C-segment) electric car, features the company’s APP310 e-drive unit, which transmits power to the driven wheels using a compact two-stage single-speed gearbox.

It is designed to cope with all driving situations and is manufactured by Volkswagen Group Components at its plant in Kassel (Germany).

With a combustion-engined vehicle, the torque increases along with the engine speed and then falls. With an electric drive system, the maximum torque is available immediately and remains constant over a wide range of speeds.

The use of a multi-speed gearbox to achieve the desired speed or the necessary torque ‘along the speed curve’ is therefore not necessary; and when reversing the car, the direction of the electric-drive system is simply reversed. One gear accommodates every situation.

However, in order to achieve the maximum power of 150kW, the electric-drive unit (motor) must rotate at high speeds; and in order to provide a high level of torque, a ‘10-times’ transmission ratio is used.

Furthermore, to save space, the gearbox has a two-stage reduction, with two small cogs instead of one large one.

As a result, the electric-drive motor in the ID.3 provides the maximum torque of 310Nm constantly over a wide range of speeds.

The maximum speed of 160kph is reached at a maximum motor speed of 16,000rev/min.

Volkswagen (www.volkswagenag.com) says that because an electric drive system is very quiet and even ‘the tiniest sources of noise can be heard’, parts for the single-speed gearbox must be manufactured to high levels of precision.