Electrical Configuration and System Protection Focus Coil Electrical Configuration and System Protection

Circuit Configuration – Normal Operation AMI 430 Controller (SS use AMI 420) AMI regulates the output current Ramp rate is set via the AMI to <30ma/s DC contactor AMI 430 Power Supply Focus Coil Energy Absorber Dump Circuit Sorensen 250A power converter Energy absorber is needed during ramp down due to unipolar PSU

Circuit Configuration – Magnet Quench DC contactor AMI 430 Power Supply Focus Coil 3 ohms Energy Absorber Dump Circuit If a Quench is detected the DC contactor will opened The magnet energy is then discharged into the dump circuit Voltages of up to 700V can be generated across magnet Earth connection at centre of resistors reduces voltage to earth

Power Converter Rack Thermal Test Fans Activate

FC#1– Current Stability Measurement AMI Controller – Stability Specification = 100ppm Drift over 12.5 hours < 10mA Tested with FC#1

RR2 Layout – rack allocation QD System racks Oxygen Depletion System Auxiliary rack (Tracker & Diffuser) FC & SS Control & Instrumentation racks SS Ground Fault Protection rack FC & SS Power Supply racks

Power Supply and Instrumentation Racks Power supply system is air cooled and housed in single rack Instrumentation is housed in a single rack including temperature monitors, heater controller and helium level indicator The equipment provides monitoring and protection for the magnet SS and FC racks in RR2

Control System Philosophy VME system downloads the system configuration via the Ethernet connection. Ethernet also provides the communication with the high levels of the control system Allow parameters to be monitored / controlled via a GUI interface The VME provides analogues to the plant via a serial interface CANBus interfaces up to 30 status modules Each status module contains relay outputs for control and opto isolated inputs for the interlocks

Standardised Control System with Plant equipment Controls Interface Super Conducting Magnet compressors Power Supply racks Standardised Control System with Plant equipment All control interfaces are standardised. A number of control racks are located inside the MICE Hall and rack rooms. Each rack consists of VME crates, Canbus modules and ADC/DACs. These racks control - vacuum, compressors, power supplies, tracker equipment, etc. All controls equipment is modular and can easily be replaced – spares are available. DL Control System Quench data logger

Control Interface – Ramp Enable Interlocks Ramp Enable - Command AMI 430 Controller Insulating-Vacuum PPS Guardline A PPS Guardline B PSU Rack Temperature Earth Fault Helium Level Low PSU s/D Fault Fast Ramp Down SSD/SSU Turbo pumps All interlocks are latched into the Control System Volt free contact activates ramp enable Any interlock will activate the ramp enable Current automatically ramped down to Zero Once activated controller is locked DC Contactor will remain closed

Control Interface - DC Contactor Interlocks DC Contactor Quench Detected Activated by Volt free contact DC Contactor - Command Volt free contact sent directly to DC Contactor Opening DC contactors at nominal current is highly likely to cause a quench DC Contacts are latched closed Volt free contact also sent to Control System Can only be opened by Quench interlock A Control system failure will not open DC contacts

Quench Protection – System operation Voltage Tap Input 3 Voltage taps Resistive measurement Amplified Central tap amplified Outer voltage taps to provide reference Isolated Signal is isolated from the magnet Compared Window comparator used to compare signal Relay de-energised If signal is outside of the specified range System Latched in the quenched state Quench Triggered Relay chain open circuit Magnet Circuit breakers opened Quench Detection Card Quench Detection Crate

Quench Protection – System Operation (cont.) System currently has two methods of setting the trip point. Through a fixed resistor which currently sets the tripping threshold at 20mV Through a variable resistor which can set the tripping threshold between 10mV and 600mV. This function is switch selectable and is mounted on each card. When a quench is detected several actions happen at once. A signal is sent to activate the dump circuit A signal is sent to control system to alert the operators A signal is also sent to magnet power supplies and other equipment that may be affected by the quench to power down

Voltage Taps - Configuration The voltage tap tripping voltages are set to 20mV for all of the HTS and LTS comparisons and approximately 600mV for the coil comparisons. Four quench detection channels are connected across the HTS and LTS leads Two channels are connected across the two coils of the magnet as this was required to achieve an overlap

QP System – Operating Characteristics

Data Logging Each channel is connected differentially to each of the voltage taps Each input channel is rated for >1kV There are 16 channels with one allocated for the quench signal 2 of the channels will be used to record quench triggers from the SS magnets The remaining 13 channels are used to monitor the coils, LTS and HTS leads The processor stores 2 sets of triggered data and is automatically set via the ramp enable. Currently only 1 minute of data is recorded at 1ms intervals. Will be soon updated to 8 minutes DC contactors open 600mV threshold Quench signal activated

QP System – Key Operating Parameters Quench detection circuit is based on a proven and reliable 30 year old design concept from the Paul Scherrer Institute (PSI). Each QD channel uses 3 voltage taps to monitor the voltage differences progressively across the SC magnet. Each QD channel is rated for 1.5kV galvanic isolation between channel and earth and 1.5kV channel to channel. The power supply crate contains commercially available power supplies with built-in n+1 redundancy The Quench detector system has been used with the decay solenoid and focus coil since early 2013 and has successfully sensed over 20 quenches whilst training both FC’s during training in R9 and finally in the Mice Hall.

Protection Against Transient Overvoltage MICE Hall main Sub-station Transient Suppression also installed on UPS board Transient Suppression installed on main distribution board. Preventing lightning strikes and disturbances on the supply network damaging equipment. Transient suppression also being fitted on UPS board due to isolated double conversion technology.

(short duration – unlikely to cause quench) Power Converters and Controllers susceptibility to network disturbances FC - AMI 430 Controller – AC supply threshold measured at 159V (spec -176V). Once AC supply lost the AMI resets and output is set to ZERO. This will cause a fast ramp (circuit components limited) – likely to cause a quench – tested and verified. DCCT supply failure is also likely to cause a quench. FC – Sorensen 250A PSU – if AC supply is lost then a fast ramp will be initiated until power returns. Again likely to cause a quench. Some of the recorded network disturbances could have affected the FC power converter. (short duration – unlikely to cause quench) FC – AMI 430 Controller (SS use AMI 420) FC - Sorensen 250A power converter (main) 230 Vac (operating range 176 - 264 Vac) – 76% of 230Vac 400 Vac (operating range 342 - 440 Vac) – 85% of 400Vac

Rack Room 2 – UPS Inverter and Batteries Two 30kVA UPS (inverter) have been installed and support Control, Power Supplies, Vacuum and Instrumentation in RR2. UPS for Critical Load Batteries The 2 x 30kVA UPS operate in parallel and share a common battery pack.

Emergency - Ramp Down A Ramp Down button is installed on the FC power supply racks This button interface directly with the AMI 430 controller It will ramp the current to zero at the programmed ramp rate. (between 10 and 30ma/s) Once activated the AMI controller is locked until the current reaches zero Note – this is not a Fast Ramp Down as installed on the SS magnets If the DC contactor was opened it would probably quench the magnet A risk assessment concluded that quenching the magnet should be avoided even during an emergency Note - Emergency Ramp Down on the SS opens the DC contacts and ramps the current to Zero quickly Racks installed in RR2

Questions?