A lot more than 50% of the compression and pumping systems above 3 MW need a variable-speed drive. Often medium-voltage motors fed by frequency converters and parallel shaft gears are chosen. Others are employing epicyclic gears with a hydrodynamic superimposition drive.
Taking advantage of the condition of the artwork in electrical motors and frequency converters, the driving system for the superimposition of the Variable Speed Gearbox planet carrier is based on a Permanent Magnet Synchronous Superimposition (SI) motor and a dynamic Front-End Cycle Converter. Therefore – E means Electric.
That is a high-speed gear drive system incorporating components that allow the use of a low-cost constant-speed (electric) driver for a variable-speed application.
A lot more than 50% of the compression and pumping systems over 3 MW require a variable-speed drive. Often medium-voltage motors fed by frequency converters and parallel shaft gears are chosen. Others are using epicyclic gears with a hydrodynamic superimposition drive.
It started with hydraulic fluid couplings creating slippage with results very little better than the throttle.
The look of hydraulic clutches then improved and included a torque converter and a superimposed epicyclic drive.
Variable Frequency Drives (VFD) were developed and, at the same time, the price of the shaft trains improved, therefore did efficiency. The issue of THD (Total Harmonic grid Distortion) rose and kept VFD out of many applications.
Taking advantage of the condition of the art in electric powered motors and frequency converters, the driving system for the superimposition of the planet carrier is based on a Long term Magnet Synchronous Superimposition (SI) engine and a dynamic Front-End Cycle Converter. So – E stands for Electric.
This is a high-speed gear drive system incorporating elements that allow the use of a low-cost constant-speed (electric) driver for a variable-speed application.
All of 
the over plots were taken by analyzing the current to the engine. In a normal scenario, the vibration will become monitored and stored on a periodic basis. If the 360 Hz signal exists in the vibration spectrum, it is not normally of any concern. If, however, additional unexplained frequencies appear in the vibration spectra, then it might be advisable to have a look at both current waveform and the current spectrum. In the pages that follow, some examples of problems discovered in DC drives and motors are presented.”
It started with hydraulic liquid couplings making slippage with results very little much better than the throttle.
The design of hydraulic clutches then improved and included a torque converter and a superimposed epicyclic drive.
Adjustable Frequency Drives (VFD) were developed and, at the same time, the cost of the shaft trains increased, and so did efficiency. The issue of THD (Total Harmonic grid Distortion) rose and kept VFD out of several applications.