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Annex A12: Availability of Critical Functions

The critical functions concerning availability are:

1. Support and guidance of a cabin

2. Motoring a cabin

Topic 1: It is assumed that the cabin has the following architecture: Four mutually independent air gap control systems. Levitation and guidance is still possible if at least two system are operational. MTTF (Mean Time to Failure) for one of these systems is:

  MTTF Failure rate
30,000 h
gap probe
85,720 h
current supply
500,000 h
1,000,000 h
coil wire
500,000 h
total per system
20,000 h
per cabin (4 systems)
5,000 h
0.0002 1/h

Actions taken on failure are:
1. A cabin with one failed air gap control system must not enter commercial service.
2. On failure of an air gap control system during commercial service the cabin may finish its current trip.
3. On failure of a second air gap control system during commercial service the vehicle must exit at the next station, unload the road vehicle and be repaired.

Calculation of failure frequency for the sample line Duisburg-Cologne according to Annex A10. Changeover rate be 75%.

number of cabins
line exploitation (road vehicles per day)
averaged operational hours per cabin and day   
at 40 km (total 16 min) averaged trip length
12 h
the total system has a failure of type 1 or 2 each
0.1 d
and a failure of type 3 each 
168 a

Concluding, no appreciable non-availability result by failure of the air-gap-control system.

For topic 2 it is assumed that the inverters may be switched to three long stator sections each. On failure of a stator supply system a neighbouring system takes over. MTTF of the long stator supply is:

  MTTF failure rate
100,000 h
power supply
200,000 h
1,000,000 h
62,500 h
0.000016 1/h

On failure of three neighbouring supply systems the motorising function of a long stator section fails only. In this case the cabins may pass this motor section non motorised only. Delays of typically a few seconds result. The line Duisburg-Cologne has approximately 10,000 motor sections. 4h averaged repair time.

Frequency of an inverter failure: a failure each
6.25 h
Frequency of a failure of three neighbouring inverters: each 

No appreciable non-availability due to failure of the stator power supply result.