Power Converter, definition from Wikipedia A power converter is an electrical or electro-mechanical device for converting electrical energy. It may be converting AC to or from DC, or the voltage or frequency, or some combination of these. One way of classifying power conversion systems is according to whether the input and output are alternating current (AC) or direct current (DC):
- AC to DC
- DC to AC
- DC to DC
- AC to AC
However, modern power converters are made with many conversion stages. For example, an UPS (uninterruptible power supply) is made with two stages, first an AC to DC conversion to make a DC voltage, where the batteries are connected, followed by a DC to AC conversion, which supplies the load. Amongst the many devices that are used for this purpose are:
- Switched-mode power supply
- Motor generator set
- DC-DC Converter
Electrical power conversion is a special field of electrical engineering. Power electronics is the application of solid-state electronics for the control and conversion of electric power. It is even more restrictive as it excludes rotating machines (electrical motor and generator).
Power converter or power supply?
In the early 80's the term "power supply" was dominant at CERN. Then, it became attractive to differentiate the terminology between the mains power supply, a laboratory power supply and the so-called magnet power supply. The trend, also in industry, was to treat the domain of power conversion as a special field, due to the increasing use of power solid-state electronics. Today at CERN, the term of power converter is used for the accelerators but the experiments prefer the term of power supply. Worldwide, the term of power supply stays the most widely used.
Where do we find power converters in particle accelerators?
Everywhere! Particle accelerators are powered by electricity, which requires power conversion. Power supplies are used for computers, control systems, electronics …These widely used devices are industrial products. Special power supplies are needed for magnet, radiofrequency, particle source, kicker, speta,…
Why the magnet power converters are so specials?
Particle accelerators required high accuracy power converter for magnets. The magnets drive the beam and they need a very stable DC current. The input of the power converter is usually AC (from electrical network) and the output is a DC voltage applied to the magnet. As in most of the case, the magnetic field of the magnet can’t be measured in real-time, the output current of the power converter is used to control the beam. The current is measured with a highly accurate current transducer. This transducer employs zero-flux compensation techniques and is called a DCCT (Direct Current Current transformer).
What are the most important parameters for accelerator magnet operation?
- Output DC current
- Output DC voltage
- Output voltage ripple
- Output current stability
- Output current accuracy
- Output current setting resolution...
Special CERN Accelerator School on the subject of ‘power converters’: Power converters for particle accelerators, CERN Accelerator School 2004, Warrington, UK (CAS)
Specialized course on power convertors, CERN Accelerator School CAS 1990, Montreux, Switzerland
Some books on power electronics:
Mohan, Undeland, Robbins, “Power Electronics: Converters, Applications and Design” ISBN: 978-0-471-22693-2
M. H. Rashid, "Power Electronics : Circuits, devices and Applications" ISBN 978-0131011403
B.M. Bird, K.G. King, D.A.G. Pedder, "An Introduction to Power Electronics”ISBN 978-0471926177