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topPower Converter Characteristics

R41 cubicle
R41 CLEMESSY
Power In 3 ~ 18KV/7200A
Power Out 6000A/600V
Converter Type Thyristors 12P
Control type Front end VME

topOperation Responsibles

1st Intervention Piquet Area icon Piquet TE-EPC Experimental Areas(163668)
Responsibles: Yves GAILLARD Yves GAILLARD
Xavier GENILLON Xavier GENILLON

topPower Converter Architecture

The R41 Power Converter is used in North experimental area to power SM2 spectrometer magnet, for DC application.

This power converter is composed of 2 main parts:

The Power part contains the thyristor bridges, the DCCT, the polarity reversal switch, the LC filter and auxiliary circuitry.

The control electronics is integrated in a control rack installed close to the Power Converter. Its function is to provide the local interface between the Power part and the Control part.

The Converter Crate is also installed in the control rack. Its function is to achieve with two loops the regulation of the output current and voltage and interface to a common data bus which is daisy chained externally to other Power Converters and to the VME front end with the Data Bus.

R41 General Control architecture

R41 power converter architecture

topPower Part

The primaries of both transformers are connected together on one set of 18kV 3 phase terminals (no neutral). They are wound in the same way and connected according to an extended delta, with a phase shift of 15 degree.

The secondaries are wound in a star-connection mode and each feeds a 3 phases thyristor bridge assembly A and B connected in parallel.

The secondary circuits are protected against negative voltage with two Free Wheeling diodes.The DC output is connected to a polarity reversal switch via a DC ripple filter, allowing the output voltage to be connected normally or inverted from the load.

Power In 3 ~ 18KV/7200A
Power Out 6000A/600V
Cooling type Demineralized water
Converter Weight ?
Converter Size width: 4000mm 
depth: 2250mm
height: 2000mm

R41 power part

Power Part simplified Architecture / Topology .pdf

topControl & Regulation Part

Control: The new VME crate is in operation since 2006 and replaced the old junction crate. It's the heart of the control system, there is one crate installed per building.

Control system

Control system simplified schematic

Software architecture

Software architecture simplified schematic

Software used to control North power converters:

Regulation: Regulation of the output current and voltage is achieved with one current loop which ensures stabilisation for low frequency perturbations. The current loop is driven by a remote controlled precision reference source (DAC). A precision current transducer (DCCT) measures the output current and produces a voltage developed across high precision and stability resistors (burden). A precision comparator amplifier with very high gain, compares the DAC and DCCT signals and produces a voltage to drive the firing of the thyristor bridges, which is synchronised with the 50 Hz incoming supply, occurs at a 300 Hz frequency. During operation such as Polarity Switch change and under fault circumstances, the Blocking signal acts directly on the Thyristor trigger drivers to inhibit the output firing circuits.

Regulation principle  12P

Regulation Control simplified schematic

topMagnet Protection

Each magnet connected to a North Area Power Converter can have a number of bits of feedback data for monitoring its status.

These can be as follows depending on the magnet involved:

  • Water Pressure: This is a pressure sensor installed at the input of the cooling loop, integrated in the magnet. This alarm can also be triggered by a water flow sensor installed on some “Eletta” water cooled cables, which is wired in series with the magnet alarm. There is no separate alarm given.
  • Water Temperature: This is a temperature sensor located at the exhaust side of the cooling loop.
  • Coil Temperature: This is a series of temperature thermostats selected to protect the appropriate magnet against excessive coil temperature.
  • Rheostat: This is no longer used, except to indicate a fault on the “Eletta” water cooled cables on GOLIATH magnet.
  • Red Button: This is an “Emergency Off” switch located on the magnet to allow shut down of the associated Power Converter(s) in the event that someone working in the vicinity detects a fault. The Red Button alarm can also come, for selected Power Converters, from a contact on the Access System which is in series with the Red Button of the magnet.
  • Terminal Box: This is a door interlock switch located on the second terminal box, installed between the Power Converter and the magnet. This interlock can be bypassed on the Power Control Crate by inserting a jumper on the front panel.(Safety procedures are affected by this action).
  • Earth Fault: Monitor Earth current of the total circuit: converter + load (magnet and its DC cables), and take the right action if threshold reached. All four positive output points before the Polarity Switch are strapped together and connected to the Earth Leakage Protection sensor relay. Activation of the Earth Leakage sensor relay for either Power Converter will be indicated in the status data

Activation of any of the above signals automatically causes the “Stop” signal to be generated, causing the Reference Current value to go to zero, followed 30 seconds later with the switch off of the MCB, if the Polarity switch is not in the Stop position. This is initiated by the MCB Release signal.

topMagnet connection

  • Terminal Box (TB): Only two terminal boxes in the experimental area are installed between the power converter and the magnet. There are no terminal boxes installed in BA82.

Magnet connection

SM2 Magnet connection simplified schematic


Terminal Box

EHN2 Terminal boxes

topMagnet Types

R41 power converters supplies the following loads:

  • Spectrometer Magnet (SM2)

topMachine Installation

Number of R41 power converters installed in North area:

topProduction Contract & Contract History

  • Manufacturer: CLEMESSY
  • Production year: 1980