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 chosen. Others are using epicyclic gears with a hydrodynamic superimposition drive.
Taking advantage of the state of the artwork in electric motors and frequency converters, the driving program for the superimposition of the earth carrier is based on a Permanent Magnet Synchronous Superimposition (SI) engine and an Active Front-End Cycle Converter. So – E means Electric.
That is a high-speed gear drive system incorporating parts that allow the utilization 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 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 creating 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, at the same time, the cost of the shaft trains increased, and so did efficiency. The issue of THD (Total Harmonic grid Distortion) rose and held VFD out of many applications.
Taking advantage of the state of the artwork in electric powered motors and frequency converters, the driving program for the superimposition of the planet carrier is based on a Permanent Magnet Synchronous Superimposition (SI) motor and an Active Front-End Cycle Converter. Therefore – E means Electric.
This 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 current to the motor. In a normal situation, the Variable Speed Gearbox vibration will become monitored and kept on a periodic basis. If the 360 Hz signal is present 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 the current waveform and the existing spectrum. In the web pages that follow, some examples of problems discovered in DC drives and motors are shown.”
It started with hydraulic fluid couplings generating 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.
Variable Frequency Drives (VFD) were developed and, at the same time, the cost of the shaft trains improved, therefore did efficiency. The problem of THD (Total Harmonic grid Distortion) rose and held VFD out of many applications.