Automated GTO Measurement Validation and Stack Selection System

Automated GTO Measurement, Validation and Stack Selection System T. Stadlbauer, V. Senaj 10/04/2018

GTO like Thyristors A special semiconductor switch. GTO (left), GTO wafer (right) • Peak off state voltage 4. 5 k. V • Peak current 80 k. A 10/04/2018

GTO Stack • 10 series connected GTOs • Static voltage sharing resistor: 5 MΩ resistor parallel to each GTO • Dynamic voltage sharing snubber capacitors: 250 n. F in parallel to each GTO 10/04/2018

LHC Beam Dumping System (LBDS) • • Both extraction and dilution generators employ similar stacks with 10 series connected GTO like thyristors as the main switches To detect a failure of an individual GTO the GTO stacks are continuously monitored. 10/04/2018

LBDS Stack Monitoring • The monitoring system compares: the full stack voltage Uf to the lowest potential GTO voltage U 1. • It generates an alarm/interlock in case of abnormal behaviour. Uf U 1 10/04/2018

LBDS Stack Monitoring • Uf x 10 U 1 10/04/2018

LBDS Stack Monitoring • Uf x 10 • U 1 10/04/2018

GTO Measurements GTO Leakage Current Over Voltage. • 2. 5 • Individual GTOs can differ more than 50%. • A good selection for a stack is required. Current [u. A] 2 1. 5 KV 109. 27 KV 133. 28 1 KV 133. 16 0. 5 0 0 500 1000 1500 2000 2500 3000 3500 Voltage [V] 10/04/2018

LBDS Stack Monitoring • • The accuracy of the voltage surveillance system can be compromised by individual GTO leakage current variations if the latter is too high, compared to the current in the voltage sharing resistors. Uf U 1 10/04/2018

GTO Measurements GTO Leakage Current Dependence on Temperature. • Relative increase of ILeak between 19. 5°C and 27°C 100 Relative increase [%] 90 4667 80 4682 4905 70 4906 5009 60 5011 50 40 0 500 1000 1500 2000 2500 3000 Forward-blocking voltage [V] Leakage current increases with temperature. → Sensitive to temperature. Measurements have to be done at the correct operating temperature. 10/04/2018 3500

GTO Measurements GTO Leakage Current Over Time. Deviation of GTO resistance over time at 3 k. V. 3000 V 3. 5 3 2. 5 Deviation [%] • 2 1. 5 R 1 0. 5 0 0 100 200 300 400 500 600 Time [s] → Take settling time into account. 10/04/2018 700 800 900

GTO Measurements • Old Measurement System: • • Temperature regulation with potentiometer as reference ~30 minutes Manually carried out with 2 DMM and HV PS Required manpower for 1 GTO ~30 minutes Settling time only limited taken into account 10/04/2018

GTO Measurements • New Automated Measurement System: • Required manpower for 5 GTOs ~2 minutes • User-friendly temperature setting 10/04/2018 • Logging of all relevant data • Automatically generated test protocols for each GTO

GTO Measurements HV PS HV Divider Shunt Resistor 5 x Leakage current PT 100, 4 wire Heater controlled by MOSFET GTO Measurement Box Temperature control Data Logger DB on Demand (IT-DB) Excel Data Viewer (Web Interface) Control Software (Virtual Machine) 10/04/2018

GTO Measurements 10/04/2018 • Predefined measurement procedures and GTO types • Precise temperature regulation • Location and serial number are stored

GTO Measurements 10/04/2018

GTO Test Protocols • Online available • For all measured GTOs • Automatically generated: saves ~20 min compared to manual process http: //fps-seb. web. cern. ch/gto. php? GTOserial=KV 133. 28 10/04/2018

GTO Stack Selection Selects automatically a set of 10 GTOs with best fitting parameters for one stack with very similar behaviour over the whole voltage range at our operational temperature by: • • • removing unacceptable high settling times removing GTOs with too high or low absolute resistance assuring a specified maximum relative GTO resistance spread searching the optimum combination of GTOs especially for the low potential position saves ~20 min compared to manual process 10/04/2018

GTO Stack Selection • Automatically a test protocol is generated which can be used for the identification and assembly of the stacks. http: //fps-seb. web. cern. ch/gto/stack. php? Stack. Serial=MKD_WEST_20170227_3 10/04/2018

Conclusion • • • The measurement procedure and accuracy has been improved. The automated stack selection significantly reduced the deviation of GTOs in one stack. Temperature setting and regulation has been improved. Automatic measurement protocols have been introduced. More than 900 GTOs have been measured. More than 57 stacks have been selected. The automated GTO measurement system saved up to now more than ~90 man-days. 10/04/2018

Database Normalization • The following tables have been used. 10/04/2018