Custom, intelligent fan trays were designed for military defense applications. The 19-in. rack-mounted 1U trays have six fans, located within the tray to maximize the cooling of critical electronic elements. The key issues for the fan tray design were noise levels, current consumption and reliability. It uses a custom control board to sequentially power up each of the fans in order of importance to minimize the initial inrush current. The fans are over-specified and produce the required airflow when running at 70% of full speed.
The fans use an embedded microprocessor to control fan speed with PWM technology. A warning signal is triggered if power is lost to the fan tray, if the controller board develops a fault or if the speed of any fan falls below 20% of maximum. The fan design features a custom input air ducting system that brings air in from the front of the rack into the bottom of the fan tray.
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