A lot more than 50% of the compression and pumping systems over 3 MW need a variable-speed drive. Frequently medium-voltage motors fed by frequency converters and parallel shaft gears are selected. Others are using epicyclic gears with a hydrodynamic superimposition drive.
Taking advantage of the condition of the art in electrical motors and frequency converters, the driving system for the superimposition of the planet carrier is founded on a Long lasting Magnet Synchronous Superimposition (SI) engine and an Active Front-End Cycle Converter. So – E stands for Electric.
This is a high-speed gear drive system incorporating parts that allow the use of a low-cost constant-speed (electric) driver for a variable-speed application.
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 selected. Others are using epicyclic gears with a hydrodynamic superimposition drive.
It started with hydraulic fluid couplings generating slippage with results not much 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, simultaneously, the price of the shaft trains increased, therefore did efficiency. The problem of THD (Total Variable Speed Gearbox Harmonic grid Distortion) rose and kept VFD out of many applications.
Taking advantage of the state of the artwork in electric motors and frequency converters, the driving program for the superimposition of the planet carrier is based on a Long lasting Magnet Synchronous Superimposition (SI) electric 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 utilization of a low-cost constant-speed (electric) driver for a variable-speed application.
All of the over plots were taken by analyzing the existing to the electric motor. In a normal situation, the vibration will be monitored and kept on a periodic basis. If the 360 Hz signal exists in the vibration spectrum, it is not normally of any concern. If, however, other unexplained frequencies appear in the vibration spectra, then it might be advisable to take a look at both the current waveform and the current spectrum. In the webpages that follow, a few examples of problems 
uncovered in DC drives and motors are offered.”
It started with hydraulic fluid couplings producing slippage with results not much 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 cost of the shaft trains increased, and so did efficiency. The problem of THD (Total Harmonic grid Distortion) rose and held VFD out of several applications.