A lot 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 chosen. Others are employing epicyclic gears with a hydrodynamic superimposition drive.
Taking benefit of the condition of the art 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) engine and an Active Front-End Cycle Converter. So – E means Electric.
This is a high-speed gear drive system incorporating components 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. Often 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 liquid couplings producing slippage with results very little 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 expense 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.
Taking benefit of the state of the artwork in electric motors and frequency converters, the driving system for the superimposition of the planet carrier is based on a Long term Magnet Synchronous Superimposition (SI) engine and an Active Front-End Cycle Converter. Therefore – E means 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 existing to the electric motor. In a normal situation, the vibration will be Variable Speed Gearbox monitored and kept on a periodic basis. If the 360 Hz signal exists in the vibration spectrum, it isn’t normally of any concern. If, however, additional unexplained frequencies come in the vibration spectra, after that it might be advisable to check out both current waveform and the existing spectrum. In the pages that follow, a few examples of problems found out in DC drives and motors are offered.”
It started with hydraulic fluid 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.
Variable Frequency Drives (VFD) were developed and, simultaneously, the cost of the shaft trains increased, and so did efficiency. The problem of THD (Total Harmonic grid Distortion) rose and kept VFD out of many applications.