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Hot-pluggable fan trays for telecom applications eliminate downtime

Papst has introduced fan trays where the individual fans are mounted in removable cassettes, providing the first truly hot-pluggable units. This eliminates maintenance downtime because fans can be changed without equipment being shut down.

The new fan cassettes also have easily removable dust filters that can also be changed without removing all power to the tray. The trays can be provided in any size and with a variety of fan combinations to suit the application. All have integral microcontrollers that optimise fan speed over a wide range to save energy and minimise noise. The precise control and monitoring parameters are user-specific and can be programmed during manufacture.

A typical unit for telecommunications applications is a 300mm ETSI specification tray containing three 120mm diameter fans. This has a standard 2SU (50mm) height. The assembly delivers 700 cubic metres per hour airflow in free space and operates from a nominal -48Vdc (-30 to -75Vdc) supply. Dual power inputs are provided so that the unit can work as part of a parallel redundancy system. An integral DC/DC converter produces the 24 volt supply for the fans. Comprehensive control and alarm circuits are built into the assembly allowing designers to define high/low temperature limits. A Green/Amber/Red light system on the front panel of the unit indicates normal operation, over-temperature, and major fault conditions. All inputs and outputs, including power supply rails and alarm signals, are linked via front panel mounted D-subminiature connectors.

An external thermistor can be used for temperature measurement, at start up the microprocessor will assess whether an external thermistor is attached, if not the system will then default to thermal operation based on a pre-fitted internal sensor.

Papst 120mm fans use either high precision ball or Sintec sleeve bearings for long-life, low noise operation. They feature electronically commutated, external rotor motors and electronic protection against reverse polarity, blocking and overloading.