Design, Manufacture, Transport and Integration on-site in Chile of ALMA Antennas

1. Design, Manufacture, Transport and Integration on-site in Chile of ALMA Antennas • ANTENNA DESIGN PRESENTATION • PM#04- 17-18 May 2006

2. Metrology System Panel Adjusters System New Support Legs Apex Structure Subreflector Mechanism Subreflector Receiver Cabin Panel System EL Bearing System Feed Shutter HVAC System Yoke Structure Backup Structure Antenna Control System Az. & El Encoder System Az & El Brake System Drive System Az & El Cable Wrap New Azimuth Bearing Az & El Stow Pins Az & El hard Stops Access platform Base Structure • Technical Description Cabling and Piping

3. Technical Description Azimuth and Elevation Drives • ACTIVITY STATUS • AZIMUTH: • The baseline (base external magnet ring with dual gap motors) continues to remain valid; • Continuation of interactions with possible suppliers; • A possible alternative with linear motors, with distributed power electronics, started the internal technical discussion and evaluation process; • Traditional alternative (pinion/rack) are under evaluation in particular concerning power budget; • Various possible suppliers have been contacted and meet; • Request for Offer processes started.

4. Technical Description:Azimuth and Elevation Drives • ELEVATION: • The main issue remains the maximum required torque for the stowing with snow (see specific point); • The baseline (cabin magnet ring with dual gap motors) continues to remain valid with the need of auxiliary drive; • Continuation of interactions with possible suppliers; • Traditional alternative (pinion/rack) are under evaluation in particular concerning maximum torque requirement; • Various possible suppliers have been contacted and meet; • Request for Offer processes started.

5. Critical Performance Characteristics Ability to bring the antennas to stow with wind up to 30 m/s with half of the torque provided by the system (one faulty drive in case of gear and pinion drive, half of the linear motors in case of a linear direct drives). It shall be possible to drive the antennas to stow in a rainfall rate of 2 cm/hr, with a snow accumulation of 50 kg/m2 in the reflector or with an ice load of 1 cm radial ice on all exposed surfaces, and…

9. ALTERNATIVE HYPOTHESIS UNDER EVALUATION

13. For the cases here above indicated, at the moment, the EL auxiliary drive is foreseen. The previous configuration is not possible so a new draft solution has been studied.

14. PREVIOUS SOLUTION

15. ACTUAL Hypothesis

16. AUXILIARY MOTOR CALCULATION SUMMARY TABLE Snow Moment (50 kg/m2) = 168433 Nm; Rack Radius= 2670 mm; Pinion Diameter = 255 mm; Pinion Teeth number = 17 mm; Wind Moment (30 m/sec) = 68306 Nm; Elevation Motor Torque = 2 x Wind Moment = 136612 Nm; Snow load = 50*136612/ 168433 = 40.6 kg/m2;

17. HARDWARE BASELINE • AZIMUTH DRIVE • N° 2 electronic drives • N° 16 Magnet segments, 30 poles – N. and poles TBR in function of the new diametre • N° 20 Drive segments forks (2 segments each) – TBR in function of the new diametre • ALTITUDE DRIVE • N° 2 electronic drives • N° 13 Magnet segments, 30 poles – N. and poles TBR in function of the reduced motion angle • N° 6 Drive arcs (6 arcs each side) • N° 1 Auxiliary drive system for critical conditions • Or: N° 2 Brushless Motors with pinion/rack coupling and integral rotor position control (encoder or resolver) • CABINET HARDWARE • N° 1 Insulation transformer • N° 1 Mains filter • N° 4 Filters between drives and motors • N° 2 Braking resistors (3kw) • N° 2 Hall effect sensor set (for the linear motor only)

18. INVESTIGATIONS POINTS • Thermal Dissipation for AZIMUTH • Interface with the encoders for phasing: still via ACU or direct in order to perform movement also in case of ACU failure? • User friendly interface for motion without ACU (implementation of PCU?) • Optimisation for power transients on fast motions • PTC / KTY electrical insulation reinforcement • Hall effect sensors mounting repeatability

19. ABB Proposal: AZIMUTH

20. ABB Proposal: ELEVATION

21. Technical Description: Antenna Control System ACU - Antenna Control Unit • ACTIVITY STATUS • The hardware configuration is under discussion, based on the prototype experience, new requirements, technical evolution and production phase peculiarities (e.g. interfaces with subassemblies). • Specific discussion over the internal CAN bus interfaces are on going. Analyses over Profibus and othe field buses are under evaluation in order to be prepared for any possibility (drives, encoders, metrology, HVAC, PCU display, etc.). • Specific analysis for the PCU display is under preparation – LCD with low frequency refresh seems a reasonable solution – to be discussed with ESO. • Analyses, in order to well define all the requirements for the servo performances (in particular inputs/requirements for drives and encoders), are on going.

22. Technical Description: Antenna Control System ACU - Antenna Control Unit • Openbrick Linux confirmed with some integrations/improvement such as the BIOS flashed instead of battery supply. This give easy remote control access and has been demonstrated good performances on the prototype. Boot routines shall be revised for “high altitude” work. • VT100 actually considered the baseline as a “user friendly” interface for people working at 5000m asl (high altitude analysis) – possibly bigger characters can be used. The alternative of a browser seems not the best solution for Chajnantor. • Interfaces more robust (digital) with the tiltmeters are under evaluation. • The configuration interface for the thermal metrology is confirmed. • From the S/W point of view, the “porting” of the actual ACU S/W under RT Linux is not jet started. • Interactions with possible suppliers and Request for Offer processes started.

23. Technical Description: Antenna Control System Controls – general overview

24. INVESTIGATIONS POINTS for ACU • Interface with the encoders: • IK320V as per prototype • Ethernet for the new proposed interpolation boards (Heidenhain) • Fast Digital for Seiki solution • Implementation of accessibility to the connectors (change of layout) • Interface with the drives (internal CAN and relevant communication protocol) • New ICD with ABM (still draft – not applicable) • High altitude analysis for the electronics • Grounding / Cables Shielding management • Local / Remote selector on AZ platform?

25. Technical Description HVAC System • General: • Continuation of analyses for possible solutions: • a) Coolant liquid – mono-ethylenic glycol - Zitrec MC • (produced by Arteco – Belgium) - Freezing point –33°C

26. Technical Description HVAC System • General: • Continuation of analyses for possible solutions: b) Coolant liquid – mono-ethylenic glycol 50% - Freezing point –33°C

27. Technical Description HVAC System • General: • Continuation of analyses for possible solutions: c) Coolant liquid – Coolant liquid used in the prototype – hycool 40% Freezing point -40°C

28. Technical Description HVAC System • General: • Continuation of analyses for possible solutions: d) Gas • Continuation of interaction with possible suppliers. • Volume above receiver flange: • Calculation of the thermal scenario on this area; • Analysis and definition of the real requirements; • Possible technical solutions in terms of heat exchange and relevant implementations.

29. Winter: ext T= -20°C

30. Summer: ext T= +30°C

31. INVESTIGATIONS POINTS • Type of refrigerant in case of liquid (baseline solution) • Gas solution (direct expansion) now possible with 90° only of EL motion • Dedicated Thermal analysis on the area above Receiver Flange (condensation risk?) • Analysis if the Free-cooling implementation is still a valid solution • Accessibility to the HVAC power and control cabinet • High altitude analysis vs. performances • Area above receiver flange

32. Technical Description: Encoders • ACTIVITY STATUS • Continuation of the interactions with Heidenhain in order to speed-up the process of receiving a first draft information over the new interpolation board. • Joint analysis with Heidenhain for the protection of both AZ and EL encoders. • Analysis and collection of the detailed specification, in order to verify the AZ minimum reading heads numbers, on going. • Technical discussion with other possible suppliers and relevant analysis of the impacts on the baseline system configuration (in particular issues related to ACU and drives interfaces, timing, etc.).

33. INVESTIGATIONS POINTS FOR AZ • Correct budgeting w.r.t. AZ bearing performances • Optimisation of the reading heads number • Moisture / icing conditions: qualification tests possible • Correct budgeting w.r.t. 1.5deg “on the sky” • Analysis of the mechanical machining tolerances for AZ bearing • Thermal coefficients of the matched surfaces • EMC analysis for the common path of the cables (AZ cable chain) • Alternative Interpolation electronics

40. INVESTIGATIONS POINTS FOR BEI SOLUTION • Slip-Stick effects to be investigated • Interface with ACU to be investigated • Interface with base / AZ cable wrap / Yoke to be investigated • Good environmental protection • Electrical robustness • EMC to be investigated • No feedback data on performances on ALMA VERTEX prototype available

41. Technical Description: High Altitude Analysis • COOLING ISSUES: • The derating value of 30% is commonly adopted by the electrical users suppliers. The AEM 35% remains more than reasonable. • Reference Document: ALMA memorandum n°203 and standard engineering thermal calculations; • Data from suppliers of electrical and electronics equipment: derating of 5% every 1.000 m of altitude increments (derating of 25% at 5.000 m a.s.l.); • a value equal to 35% for the electrical equipments, continuously working at the nominal power, should be considered conservative; • For users such as the Feed Shutter or Stow Pins, no derating can be applied; • In any case, the power derating factor of 35% should be taken as the basis for the electrical dimensioning of the equipment working at the nominal power; • Different deratings can be applied with a dedicated duty-cycle calculation vs. thermal dissipation (when in air); • Exceptions to reduction factor are possible were the cooling of the equipment is made by refrigerating liquids. • ELECTRICAL INSULATION ISSUES: • Reference Document: IEC 60664; • Evaluation of the “pollution degree”; • Over-voltage categories identification; • Analysis on the electrical/electronic apparatuses w.r.t. they working voltages; • Corrective Factors for altitudes above 2000m

42. Technical Description: High Altitude Analysis • UV / HOZONE: • For the Production, all the criteria adopted for the Prototype will be used, in particular the material selection and direct light protection wherever possible. • HUMAN BEHAVIOUR: • Discussion needed with respect to oxygen enrichment/bottles availability; • User friendly interfaces; • Very basic messages; • Analysis of the inspection and maintenance on condition procedures.

43. The general effect of electrical and environmental factors on creepage distance and clearance: • pollution degree, • overvoltage category, • working voltage, • the previous factors cumulatively, • comparative tracking index (applies to creepage distance only), • altitude (applies to clearance distance only). • For elevations above 2000 m, the required clearance is increased by the following factors: to 3000 m, 1.14; from 3000 to 4000 m, 1.29; and from 4000 to 5000 m, 1.48

44. Thermal Derating w.r.t. Power: source IEC 60034-1 (issue 11) - table 11

46. ALMA Memo n. 203 Table 4: Equipment size increase to achieve sea level output