More than 50% of the compression and pumping systems above 3 MW require 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 benefit of the state of the artwork in electric motors and frequency converters, the driving system for the superimposition of the earth carrier is based on a Long term Magnet Synchronous Superimposition (SI) engine and a dynamic Front-End Cycle Converter. Therefore – E stands for 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.
A lot more than 50% of the compression and pumping systems above 3 MW require a variable-speed drive. Frequently medium-voltage motors fed by frequency converters and parallel shaft gears are selected. Others are employing epicyclic gears with a hydrodynamic superimposition drive.
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 Variator Gearbox converter and a superimposed epicyclic drive.
Adjustable Frequency Drives (VFD) were developed and, simultaneously, the expense of the shaft trains improved, and so did efficiency. The issue of THD (Total Harmonic grid Distortion) rose and kept VFD out of several applications.
Taking benefit 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) motor and an Active Front-End Cycle Converter. So – E means Electric.
That 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 above plots were taken by analyzing the existing to the motor. In a normal scenario, the vibration will end up being 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, additional unexplained frequencies appear in the vibration spectra, then it would be advisable to have a look at both current waveform and the current spectrum. In the webpages that follow, some examples of problems uncovered in DC drives and motors are shown.”
It started with hydraulic liquid 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.
Adjustable 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 held VFD out of several applications.