wp3 high availability drives electrical machines and drives research group university of sheffield...
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WP3 High Availability Drives
Electrical Machines and Drives Research Group
University of Sheffield
Dr. Georges El Murr
Introduction• Electrical drives benefits over Mechanical, Hydraulic and Pneumatic
systems:– More economical– Environmental friendly– Higher efficiency– Less maintenance– More flexible in compact places
• Electrical drives system should be fault tolerant and reliable to be applied in safety critical applications:– Appropriate fault tolerant drive design (power module)– Appropriate Fault tolerant machine design (motor) – Health monitoring of machine and drive to detect early stage defects
allowing maintenance with minimal downtime
Power Module Faults• Potential faults in the power module may lead to:
– Instability of the drive– Loss of power complete drive shut down– Power reduction performance can be dramatically reduced– Excessive power input (voltage/current) leading to catastrophic
deterioration of the drive
How Does a Machine Fail ?Groundwall – winding
fault
Phase – phase fault Leakage current flutes
Bearing current discharge pits
Focus on Electrical
Phenomena
Fault Tolerant Inverter Designs
• Appropriate inverter topologies can be designed to tolerate open-circuit and short-circuit faults
• Faults should be detected• Remedial strategies should be used to control the inverter
Open winding converter topology
Multiple independent phases topology
Inverter with Redundancy Leg and Triacs
Fault Tolerant Machine Designs
Switched Flux PM Machine
PM Assisted Sync Reluctance Machine
Fractional Slot Concentrated Winding PM Machine
• Avoid complete damage of the machine• Keep producing the appropriate level of performance when fault occurs • Reduce the possible damaging effects of the faults ( torque ripple, demagnetization, thermal,
etc.)
Health Monitoring• Zero Sequence Model of Machine and Drive
– Indicator of insulation impedance– Detecting bearing current– Potential for cable/drive leakage
monitoring– Difficult to measure to required accuracy
• Temperature– Model based prediction of lifetime– Real-Time thermal model– How does load variation affect life?– Cancelling temperature dependence in
monitored parameter variation• Partial Discharge
– Standard online indicator for high voltage– Potential for increased problems with fast
switching drives
Leakage Paths in a Machine
Equivalent circuit for leakage
High Availability
Drives
• Healthy and Faulty conditions
• Overall all cost of the drive
• Amount of additional components• Overload capability of
components
• Life time estimation under healthy and faulty
conditions