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 selected. Others are using epicyclic gears with a hydrodynamic superimposition drive.
Taking advantage of the state of 
the art in electric motors and frequency converters, the driving system for the superimposition of the planet carrier is founded on a Permanent Magnet Synchronous Superimposition (SI) electric motor and an Active Front-End Cycle Converter. So – E stands for Electric.
This is a high-speed gear drive system incorporating elements that allow the usage 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. Frequently medium-voltage motors fed by frequency converters and parallel shaft gears are chosen. Others are employing epicyclic gears with a hydrodynamic superimposition drive.
It started with hydraulic fluid couplings making slippage with results not much better than the throttle.
The look of hydraulic clutches then improved and included a Variable Speed Gearbox torque converter and a superimposed epicyclic drive.
Variable Frequency Drives (VFD) were developed and, simultaneously, the price of the shaft trains improved, and so did efficiency. The issue of THD (Total Harmonic grid Distortion) rose and held VFD out of several applications.
Taking advantage of the condition of the artwork in electric motors and frequency converters, the driving system for the superimposition of the planet carrier is founded on a Long lasting Magnet Synchronous Superimposition (SI) electric motor 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.
All of the over plots were taken by analyzing the current to the electric motor. In a normal scenario, the vibration will become monitored and kept on a periodic basis. If the 360 Hz signal is present in the vibration spectrum, it isn’t normally of any concern. If, however, additional unexplained frequencies appear in the vibration spectra, then it would be advisable to check out both the current waveform and the current spectrum. In the pages that follow, a few examples of problems discovered in DC drives and motors are provided.”
It started with hydraulic fluid couplings generating 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, simultaneously, the price of the shaft trains improved, and so did efficiency. The issue of THD (Total Harmonic grid Distortion) rose and kept VFD out of many applications.