topPower Converter Characteristics

COMBO COMmercial Based cOnverter
Converters 03 COMBO-TDK Power Racks
06 COMBO-TDK [2000 A; 10 V] - HCRPABR
Converter Type 1 Quadrant
Control type FGC3 / Ethernet+
Current Accuracy 100 ppm

topDesign & Operation Responsibles

Yves THUREL Yves THUREL CERN Project manager
Edwin ROHRICH Edwin ROHRICH Electrical / Mechanical Designer

topPower Converter Architecture

A COMBO Power Converter is mainly used for Experiences or Test Labs to power warm or cold Magnets (or other type of load), for DC or slow cycling machine/use. Power Converter can be divided in 3 main parts:

  • Power Part:
    • COMBO Power Rack (incl. COMBO elements like: AC & DC panels, Aux-DC power supplies box).
    • A commercial Power Source (single, series or parrallel configuration)
    • A COMBO Config Panel, interfacing CERN FGC Controller with commercial power source interface.
    • Some additional sensors (Voltage, Current) to add CERN required functionalities.

  • CERN Digital Controller (FGC3):
    • The high level control from and to the Cern Control Room (using Ethernet+ bus)
    • 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.
    • Located inside a standard COMBO Crate (up to 3x controllers in one single crate).

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

Power Converter simplified Architecture .vsdx

topMagnet / Load Protection

Power Converter is part of magnet protection scheme, even if not directly fully responsible of the monitoring and diagnostic of the load. Dedicated systems like QPS - Quench Protection System (on superconductive magnet), or cooling system monitoring or thermoswitch (on warm magnet) can interlock Power Converter if magnet safety requires it, and through PIC/WIC (Power/Warm Interlock Controller) system, directly interfaced with the converter.

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 AC 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 Safe Paths, being a Crowbar for 4-quadrant converters). This system based on different paths using several free-wheeling diodes in the rack provide a safe discharge path for magnet current.
  • Monitor Earth current of the total circuit: converter + load (magnet and its DC cables), and take the correct action if threshold reached.

topFast Abort Interface

  • Machine Interlock system can request a Fast Abort to the converter, requiring it to stop providing energy to the load. Since some commercial power sources cannot be disconnected from AC-Mains throught their available control interface, this vital interface is re-designed entirely, involving AC contactors in charge of ensuring the converter cannot provide energy anymore to the load in any condition.

    Simplified Schematic

    Fast Abort Interface simplified schematic .vsd

topFree Wheeling Diode Safe Paths

  • The system is based on a Diode-based safe path for magnet current, designed on purpose for the application.

    Simplified Schematic

    Free Wheeling Diode Safe Path simplified schematic .vsd

topEarthing Leakage Current System

  • Detection system is an active system, since relying on a 100mA current source powering a 100Ohms resistor connected between earth and negative polarity of the Power Converter. A common mode voltage is then created, (100mA x 100Ohms) making possible to detect an earth fault even with converter being OFF. (OFF, not condamned).

    Earthing System Connected

    Earthing System simplified schematic .vsd

Typical Curves / Measurements

Output Voltage Ripple .txt [  5A     50mV  ] V 150MHz: 10us / 1ms - 30MHz: 2ms - I [9; 150] kHz / [150 kHz; 30 MHz]
[ 700A    3.6V ] V 150MHz: 10us / 1ms - 30MHz: 2ms - I IAB: std, FFT
Output Currrent Ripple .txt [ 700A    3.6V ] I Spy: Ripple / FFT
Output Currrent Tracking .txt 600A → 700A, di/dt = 5A/s I Spy: End of ramp
EMC: AC Conducted Noise .txt 2x (700 A; 4 V) [9; 150] kHz / [150 kHz; 30 MHz]
EMC: AC Burst Effect on I.out .txt 2x (700 A; 4 V) [0,1,2,4] kV applied on AC 3Ph-Side (.xls)
Earth to DC Neg Pol. FFT .txt 5ADC Floating , 700ADC Floating
Voltage source bandwidth Vout/Vref Voltage Bandwidth
Voltage Source Efficiency vs Output Power Efficiency Graph, (.xls)

Rack Thermal Characterization

topMachine Installation

Use SM18 6 Power Converters / 3 Racks
FREIA 2 Power Converters / 1 Rack
SM18 Use 6 Power Converters + 1
Building Bat 2173 (SM18)

topConverter Circuits