Power Converter Characteristics Design & Operation Responsibles Power Converter Architecture Power Part Control Part

Magnet Protection Power Converter Components Magnet Types Machine Installation Production Contract & Contact History

Power Converter Characteristics

Involved Peoples

Serge PITTET	CERN Project Leader
Maxime SARDANO	Mechanical intergation

Power 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.

Power Converter simplified Architecture .ppt

Power 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 Part simplified Architecture / Topology .vsd

Typical Curves

Control 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.

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.

Magnet 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:

  

  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.

  

  free-wheeling Diode System simplified schematic .vsd

• Earth System

  This system is based on a two modes detection system: Active (by default) and Passive (configurable). In Active mode, the load is polarized to +10 V versus earth on its output mid-point (common mode). This allows detecting any earthing leakage faulty condition, without the need to energise the circuit for allowing the detection system to operate. A 100 Ohms earthing resistor in series with a 0.1 A fuse connects the mid-point to earth, with this resistance being used as a current sensor (shunt) sensing the circuit earthing leakage current. The system monitors the earthing leakage current to a value of 5 mA maximum allowed. The fuse (0.1 A fast) is provided to limit damage risk on the circuit side in any case and mode (active / passive).

  

  Earthing System simplified schematic .pptx

Power Converter Components

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.

Magnet Types

Machine Installation

Production Contract & Contact History

Developped	Designed/CERN
	2017-2023
Manufactured	Contry(s)
	Manufacture
Production	xxx Pc
Responsibles:	Serge PITTET

Converter Circuit Names

 RPxxx