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 using epicyclic gears with a hydrodynamic superimposition drive.
Taking benefit of the condition of the artwork in electric powered motors and frequency converters, the driving program for the superimposition of the planet carrier is founded on a Permanent Magnet Synchronous Superimposition (SI) engine and an Active Front-End Cycle Converter. Therefore – E means Electric.
That 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.
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 using epicyclic gears with a hydrodynamic superimposition drive.
It started with hydraulic liquid couplings making 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.
Variable Frequency Variator Gearbox Drives (VFD) were developed and, at the same time, the cost of the shaft trains improved, and so did efficiency. The problem of THD (Total Harmonic grid Distortion) rose and held VFD out of many applications.
Taking benefit of the condition of the art in electrical motors and frequency converters, the driving system for the superimposition of the earth carrier is based on a Permanent Magnet Synchronous Superimposition (SI) motor and a dynamic 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 above plots were taken by analyzing the current to the motor. In a normal situation, 
the vibration will end up being 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, various other 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 web pages that follow, some examples of problems discovered in DC drives and motors are provided.”
It started with hydraulic fluid 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, simultaneously, the expense of the shaft trains increased, and so did efficiency. The problem of THD (Total Harmonic grid Distortion) rose and held VFD out of many applications.