Reproduction interdite © ALMA EUROPEAN CONSORTIUM Reproduction forbidden Design, Manufacture, Transport and Integration in Chile of ALMA Antennas Page 1

Reproduction interdite © ALMA EUROPEAN CONSORTIUM Reproduction forbidden Design, Manufacture, Transport and Integration in Chile of ALMA Antennas Page 2

Reproduction interdite © ALMA EUROPEAN CONSORTIUM Reproduction forbidden Design, Manufacture, Transport and Integration in Chile of ALMA Antennas Page 3 Power Distribution DESIGN BASELINES  Interface with ALMA low-voltage Power Distribution Systems : Icc = 10 kA (TBC by ESO – if > 10kA CRE required)  3 BUS distribution system (as for specification)  Optimized loads distribution (respect to the Prototype network) and in particular:  FE loads - dedicated distribution in RC switchboard  BE loads - dedicated distribution in RC switchboard  HVAC portion - dedicated distribution in RC switchboard  SDU separated supply line  Use of Miniature circuit-breakers (MCBs) with time-current characteristic "K"

Reproduction interdite © ALMA EUROPEAN CONSORTIUM Reproduction forbidden Design, Manufacture, Transport and Integration in Chile of ALMA Antennas Page 4 ALTITUDE PROBLEMS EFFECTS  Reduced cooling capacity of air  Lower dielectric strength ELECTRICAL DEVICES INVOLVED  Circuit breakers, contactors, disconnectors, residual current relays, cables  Electronics cards

Reproduction interdite © ALMA EUROPEAN CONSORTIUM Reproduction forbidden Design, Manufacture, Transport and Integration in Chile of ALMA Antennas Page 5 CONTACTORS THERMAL RELAY For the TORs there is no variation in their rating depending on the altitude. The only variation is related to the limited capacity of dissipating temperature. This imply the following deratings:

Reproduction interdite © ALMA EUROPEAN CONSORTIUM Reproduction forbidden Design, Manufacture, Transport and Integration in Chile of ALMA Antennas Page 6 MOTOR OVERLOAD DEVICES There is no current derating necessary. What it must be checked is the lower insulation level of the air. This means a probable choice of devices assuring a nominal working voltage of 690V. Analyses of market apparatuses on going. The mechanical functions are not an issue. MINIATURE CIRCUIT BREAKER De-rating of performances ALTITUDE[m] Dielectric capacity Uimp [V] Maximum Voltage Ub max [V] Rated current In at 40°C [A]1xIn0,96xIn0,93xIn0,90xIn