Electronic Motor Controllers for Cooling Fan Modules
April 2006
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Engineers have developed two new controllers for adjusting the speed of cooling fan module (cfm) motors. The cfm controllers are versatile, economical, have a high degree of reliability, and are easy to assemble.

The W2 controller was designed to control one or two brush motors in parallel. It has a maximum power rating of 400 W at 13 V, and can operate in an ambient temperature of 110°C.

The controller has an operating voltage range of between 9 V and 16 V, with a fully variable speed managed with just one signal wire. It is designed to meet the EMC specification detailed in CISPR 25 level 5. It also has an open loop.

Additionally, the controller provides protection against accidental destruction as follows: preventing damage due to “blocked rotor” defects with a programmable re-start strategy, surviving open-load conditions, tolerating over-voltages of 18 V for 1 hour and 24 V for 1 minute, tolerating short periods of excessive temperatures, and tolerating a reverse battery condition for 1 minute with the fan running in reverse.

It is also possible to implement diagnostic feedback, according to the OEM’s specifications, by using either “pull-down” or “coded error messages” protocol. The controller has a variation on inter-connectors for power, signal, and motor output/inputs that will suit the system makers’ own standard designs.

The main characteristics of the W3 controller include: 800 W maximum power at 13 V, 110°C maximum ambient temperature for full operation, 9 V to 16 V operating voltage range, total management with 1 to 3 signal wires, up to 20 KHz output pulse width modulation signal, EMC to CISPR 25 level 5, closed loop architecture with separate speed control strategies, and complete separation between power and signal circuit.

Programmable strategies for protection against fault and diagnostic features are similar to those of the W2.

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