Power Converter Characteristics
Design & Operation Responsibles
Gilles Le Godec - Jean-Luc Blanc - Emilien Coulot - Stéphane Reignier
Power Converter Topology
For the main brick (APOLO), a 50 Hz transformer (galvanic isolation – voltage adaptation – phase shift), a diode rectifier, and a DC-Link filter are used for the AC/DC conversion. An IGBT bridge (4 quadrant operation) with an output filter are used for DC/DC conversion.The energy of the magnet is:
• Recovered in a capacitors bank on the DC-Link during cycling mode of operation,
• Dissipated in a brake chopper in case of too small energy storage on the DC-Link,
• Dissipated In a bipolar crowbar in case of fault,
One module APOLO:
APOLO topology .vsd
Two modules APOLO are assembled in parallel to increase the current capability (APOLO_2p):
APOLO_2p topology .vsd
Two modules APOLO are assembled in series to increase the voltage capability (APOLO_2s):
APOLO_2s topology .vsd
Four modules APOLO are assembled in parallel to increase the current capability (APOLO_4p):
APOLO_4p topology .vsd
Power Converter is part of magnet protection scheme, even if not directly fully responsible of the monitoring and diagnostic of the magnet status. PIC/WIC (Power/Warm 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.
• Stop powering the load in safe way (handling the magnet energy even when stopping, through dedicated system called Crowbar). This active system provides a safe resistive 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.
► Active Crowbar
Each APOLO module is equipped with its own active crowbar.The system is based on a 2.2 Ω power resistor connected to two thyristors which are triggered when there is a faulty condition on the converter or when the voltage Vmeas goes beyond a predefined threshold (BOD protection).
APOLO Crowbar System simplified schematic .vsd
►Earth fault detection
The Detection system is a passive system which is composed of a resistor connected between:
• Negative polarity and the earth for APOLO, APOLO_2p and APOLO_4p,
• Mid-point of the converter and the earth for APOLO_2s,
The voltage threshold VEARTH is set to 0.5V (fault current of 5mA) and the the resistor REARTH is able to withstand the nominal converter voltage during 1 second.
APOLO Earth System simplified schematic .vsd
APOLO_2s Earth System simplified schematic .vsd