topPower Converter Characteristics

Picture of the converter

Power In 3 ~ 230 V/ xx A
Power Out [+18 kA; +/-10 V]
Converter Type 2 Quadrant
Control type FGCx / Ethernet / WorldFip
Current Accuracy ?? ppm@ 30 mn
?? ppm@ 24 h
??? ppm@ 1 year
(1 ppm=18 mA)

topInvolved Peoples

Serge PITTET Serge PITTET CERN Project Leader
Maxime SARDANO Maxime SARDANO Mechanical intergation

topPower Converter Architecture

This Power Converter is used for powering HL-LHC Superconductive Magnets, and for DC applications.

Different parts were designed and produced separately, with the option of a Power Converter being finally integrated in a housing rack, with 3 main parts:

  • Power Part:
    • Power Rack (AC & DC distribution, interconnections)
    • Ideally Removable Power Modules, including redundancy as much as possible.

  • CERN Digital Controller (FGCx?):
    • The high level control from and to the Cern Control Room (using fieldbus to be defined)
    • The high precision digital current loop (when a voltage source is controlled)
    • Collecting and reporting all status, faults, and measurements from all the different parts to the remote services, for diagnostic and operation purposes.

  • High Precision Current sensor(s) (DCCTs)
    • Measuring DC current at the required precision.
Simplified Schematic

Power Converter simplified Architecture .ppt


topPower Part

Voltage Source is based on a full bridge phase shifted topology followed by a 4 quadrant switching stage to allow the 4 quadrant operation.

One DCCT is used for the high precision current loop (FGC), and is located directly in the voltage source, even if not used by it to operate as a pure voltage source.

Power In 3 x 400V with Neutral / xxA
Power Out 180 kW max (±18 kA ±10 V)
Cooling type Water cooling and Fans
Converter Weight Power Module ............ xx kg
Simplified Schematic

Power Part simplified Architecture / Topology .vsd


Typical Curves

Output Voltage Ripple TBD

topControl Part

Control & regulation principles are summarized in a detailled schematics representating only the part involved in the output current regulation scheme.

Control & regulation principles are summarized in a detailled schematic representating only the part involved in the output current regulation scheme.

FGCx regulation detail.

Regulation Control simplified schematic .vsd

High precision current control loop is managed by the digital controller called FGC (Function Generator Controller). This unit includes a high precision Sigma Delta Analog to Digital Converter which digitalize the analog current measurement coming from 1 or 2 Current sensors (DCCTs: DC current Transducer). Precision is then directly relying on sensor precision: current sensors, the ADCs, and the algorithm being used for the regulation loop. Voltage source is then used as a power amplifier, powering the load through a high bandwidth voltage loop.


topMagnet Protection

Power Converter is part of magnet protection scheme, even if not directly fully responsible of the monitoring and diagnostic of the superconductive magnet status. Dedicated systems QPS (Quench Protection System) + PIC (Power Interlock Controller) can interlock Power Converter if magnet safety requires it.

Power Converter is then expected to:

  • Always ensure that external protection system can stop the Power Converter through a safe signal called Fast Abort. This redundant signal uses 2 paths to interlock and stop the converter and its redundancy is checked each time it acts. It directly acts on DC Contactor bobbin, ensuring its opening as required.
  • Stop powering the load in safe way (handling the magnet energy even when stopping, through dedicated system called free-wheeling diode). This passive system based on different paths using several free-wheeling diodes in the rack provide a safe discharge path for magnet current (energy).
  • Monitor Earth current of the total circuit: converter + load (magnet and its DC cables), and take the right action if threshold reached.


  • Fast Abort Interface

    Machine Interlock system can request a Fast Abort to the converter, in case a quench is detected. Converter is then assumed to react as soon and as quick as possible, stopping providing energy to the load. This signal being part of the magnet safety scheme, it is acting redundantely at the level of Converter DC Mains Contactor. 2 paths are used and monitored to stop the contactor. The schematic is described below:

    Simplified Schematic

    Fast Abort Interface .vsd

  • Free-wheeling diode

    The system is based on 3 different paths provided by Free-Wheeling Diodes providing a safe path for magnet current.

    Simplified Schematic

    free-wheeling Diode System simplified schematic .vsd

  • Earth System

    The circuit injects a 100 mA DC current on a grounded resistive branch, resulting in a common mode voltage at the output circuit easing the earthing fault detection. Output circuit Common mode voltage is, without any earth fault, around 10V (=100 mA x 100 Ohms), and is not relying on load operation, making possible to detect an earth fault even with converter being OFF. (OFF, not condamned).

    If an earth fault occurs on the output circuit, a faulty current will be deviated from the initial path back to earth by using the shunt 10 Ohms resistor path (monitored for detecting this fault).

    Overcurrent protection is achieved through a 1A-100V fast fuse in series in the path provided for the earthing fault current.

    Simplified Schematic

    Earthing System simplified schematic .vsd

topPower Converter Components .vsd


A power converter is actually a sum of different equipments under several different sections in the SY-EPC group. The modularity is a key factor for easier maintenance with regards to LHC tunnel access conditions.

Power Converter is built through two Power Racks. One contains the six Sub-Converter Power Modules, when the second one includes the converter crowbar and DC-contactor systems, the converter power part control electronic, the FGC complete Electronic Chassis, the two DCCTs head and their electronics.


topMagnet Types

to be defined xxxxxx


topMachine Installation

HL-LHC Use xx Power Converters


topProduction Contract & Contact History

Developped Designed/CERN
Manufactured Contry(s)
Production xxx Pc
Responsibles: Serge PITTET Serge PITTET

topConverter Circuit Names


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