WP3 High Availability Drives
Electrical Machines and Drives Research Group
University of Sheffield
Dr. Georges El Murr
g.elmurr@sheffield.ac.uk
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
Groundwall – winding
Fail ?
Bearing current discharge
fault
pits
Leakage current
flutes
Phase – phase fault
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
Multiple independent phases
topology
Open winding converter
topology
Inverter with Redundancy
Leg and Triacs
Fault Tolerant Machine
Designs
•
•
•
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.)
Switched Flux PM
Machine
PM Assisted Sync
Reluctance Machine
Fractional Slot Concentrated
Winding PM Machine
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
• Healthy and Faulty
conditions
Performance
• Life time estimation
under healthy and faulty
conditions
Reliability
Cost
• Overall all cost
of the drive
High
Availability
Drives
• Overload capability of
components
Overrating
• Amount of additional
components
Redundancy
Factor