VFD Technology for Running High Speed Turbo Machineries

High-speed motor/generator applications are demanding. Control instabilities and imperfections that are masked at low speeds can become critical at high speeds. CastNX developing drives for running high-speed asynchronous and synchronous generators.

The turbo machinery used in energy recovery processes typically use specialty high-speed generators. The generators are usually equipped with special magnetic bearings or airfoil bearings and can spin in excess of 100,000 rpm.

The advantage of using high-speed generators is that they are extremely compact, efficient, and have high power density.

First off, what do we mean by “High Speed”? The best definition is the one that is used by the US Department of Commerce. Outlined in regulation ECCN 3A225, drives operating 600Hz and above are considered high speed. The general purpose VFD’s available in market operates up to 400 HZ

High-speed applications are very demanding applications for VFDs. They require extremely stable motor control algorithms with very fast control loops.

Here at CastNX, we like difficult applications because this is where we excel and where our technology and application engineering differentiate us from our competitors.

These applications could require multiple axes of coordinated motion control or be located in challenging environmental conditions. Operating a high-speed motor/generator is one example of a difficult drive application.

However, if you were to put me on a steep hill and I were to go very fast, the end result would not be good. I would likely begin to lose control, and then try to correct myself, overcorrect, and crash. This is like a high-speed motor application – there is less room for error on the control stability. Any small load transient acts like the crack in the road or the rough pavement and can cause the control system to become unstable.

A company cannot develop high-speed motor control algorithms overnight. CastNX high-speed drive products represent decades of motor control engineering.

The VFD power stages used in high-speed applications are also unique, especially at high power (100Hp+). The IGBTs must be capable of switching at a very high frequency – usually 8kHz and above. The higher switching frequency causes more heating and the power stages must be designed specifically for that use.

Air cooling these large IGBTs with high frequency can be challenging if not impossible.

So CastNX also offers liquid-cooled drives which are particularly effective at cooling the large high-speed VFDs.

The solution available is 415/440V 10 HP and offers high-speed outputs (up to 2000Hz) for running high-frequency motors.

CastNX high-speed motor technology brings precision control to high-speed, high-frequency applications, reducing vibration and motor heating. Limiting motor heating plays a significant role in optimizing system efficiency and maximizing the service life of bearings and motors in turbo compressors and blowers.

CASTNX’s Energy Recovery Systems are interesting to highlight because they combine a lot of our unique leading-edge technology. The systems also highlight the breadth of CASTNX products and our ability to integrate them together to provide a comprehensive solution.

An Energy Recovery System (ERS) or Energy Conversion System (ECS) is an electronic system that controls turbo machinery and converts energy from some process.