It will let all motors of all kinds work more efficiently, and allow a smaller motor to do the work of a bigger one, at little or no added cost.
Our industrial civilization utilizes countless motors to perform an almost infinite variety of jobs. Each one can be viewed as a three-part system comprising a motor, an energy source and the job of work it is doing, which we call the load.
In the case of an electric motor, the energy source would be a battery pack or the electrical grid; for a gasoline motor the fuel in the tank.
The load might be the driving wheels of a car or perhaps a pump or a fan or other type of industrial machinery.
The work being done has two components: the speed of rotation and the torque, or turning power. By means of the torque multiplication capability of mechanical gearing a relatively low power but fast spinning motor can be made to deliver a slow but powerful output. This is the function of a transmission.
Motors are typically internal combustion, (gasoline, diesel engines, turbines), external combustion (steam engines) or electric (AC and DC motors.) Some applications, particularly moving vehicles, require fine control over the speed with which the load is driven, and must be able to vary the power being delivered in response to changing circumstances.
Very few loads are stable and predictable. Even applications such as large industrial fans in HVAC systems, or the pumps that move our sewage do not deal with static loads, but vary widely according to circumstances. For many applications the ability to operate through a wide range of speeds is essential. The problem that has constrained the design of mechanical systems from the beginning is that no practical purely mechanical means of smooth speed control has hitherto been found. Instead we are forced to use inefficient and inelegant methods to achieve this necessary function. The particular workaround varies according to what kind of motor is involved.
Electric motors are either AC or DC; AC motors are locked to the frequency of the power supply, DC motors to the voltage. Varying either the frequency or the voltage of an electrical supply requires a hi-tech electronic device called a motor speed controller (MSC). MSCs are complex, expensive (second only in cost to the battery pack in an electric car) and wasteful. In addition at high power levels they become exponentially larger and more expensive. They are by far the most fault prone component of the motor system, and need advanced industrial capabilities to manufacture. In addition while they can vary the speed of the motor, they cannot vary its torque. The amount of torque delivered by an electric motor driven by an electronic Motor Speed Controller is the same no matter what the speed of the motor. A mechanical gear-based infinitely variable transmission, on the other hand, delivers increased torque at slow speeds, which is highly desirable in motor driven systems.
In the case of internal combustion engines, most of the complexity of a modern car engine is caused by the need to finely vary the speed of the motor gracefully through a huge variety of conditions. If the engine only had to run at one of two or three predefined speeds, it could be made vastly simpler.
Turbine engines, the most efficient of all internal combustion engines, cannot be used at all in most applications because it is not practicable to vary their speeds.
Clearly, then, a robust and inexpensive mechanical means of finely and controllably varying the speed of a motor driven system is of great potential value.