More than 50% of the compression and pumping systems over 3 MW require a variable-speed drive. Often medium-voltage Variable Speed Gearbox motors fed by frequency converters and parallel shaft gears are chosen. Others are employing epicyclic gears with a hydrodynamic superimposition drive.
Taking benefit of the state of the art in electrical motors and frequency converters, the driving program 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 means Electric.
This 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.
More than 50% of the compression and pumping systems over 3 MW need a variable-speed drive. Often 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 generating 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, simultaneously, the cost of the shaft trains improved, therefore did efficiency. The issue of THD (Total Harmonic grid Distortion) rose and kept VFD out of several applications.
Taking advantage of the state of the artwork in electrical motors and frequency converters, the driving program for the superimposition of the planet carrier is founded on a Long term Magnet Synchronous Superimposition (SI) electric 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 over plots were taken by analyzing the current to the electric motor. In a normal situation, the vibration will be 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 come in the vibration spectra, after that it would be advisable to take a look at both the current waveform and the existing spectrum. In the pages that follow, some examples of problems found out in DC drives and motors are shown.”
It started with hydraulic liquid couplings generating slippage with results very little 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 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.