Different operating requirements

Readers letters

Mr Padgett queried reconciling manufacturing of Harrier continuously variable transmissions with disapproving of them for traction

In his letter of the July edition Mr Padgett queried reconciling manufacturing of Harrier continuously variable transmissions with disapproving of them for traction. The valid reason lies in the completely different operating requirements. With a jet engine the input speed is variable but the output has to be at a fixed (400 Hz) speed so there was no choice but to tolerate the weight and efficiency penalties of infinitely variable mechanical drive. In contrast, for standard traction, the output speed varies but the input Diesel is extremely flexible and stays efficient over a 3 to 1 speed range, so all the range needed can be supplied by a standard gearbox with the Diesel.

Nowadays the same problem arises with “renewable” energy if a varying speed turbine is to drive 50 Hz mains but with modern power electronics there is the solution of 3 phase generating followed by inverting.