All of the DC brushless Spal fans (and most other brushless DC [BLDC] fans) have a built in motor controller. This is required because you can't just PWM the power to a BLDC motor - you need to control each coil in order to start the motor and control the motor speed and then you need to monitor the feedback in a sensorless motor to know speed (or have a separate speed sensor).
Spal offers temperature sensors that output the frequency and duty cycle signals the BLDC Spal fan is expecting to see. NOTE -
two different control logic configurations exist in the Spal aftermarket and OEM BLDC fans. Spal makes two different versions of the temperature sensors for this reason. Make sure you get the correct sensor for your fan type.
Other companies also make devices that can read a conventional temperature sensor (and in some cases other sensor signals) and then output the PWM and duty cycle signal the BLDC Spal (and other) fans are looking for.
Some heavy duty truck and industrial brushless motor fans require an external brushless motor controller. I am not aware of any current OEM passenger light duty vehicles that use this type of brushless fan control configuration though.
The Spal brushless DC fans are looking for a PWM signal that is a low level speed control signal. You are not actually connecting directly to the motor on these fans - you are connecting to the motor controller that is built into the motor assembly. These types of fans usually have 3 or 4 pins. Two small terminals and two much larger terminals. One small terminal is the speed control signal input, the two larger terminals are the high current power and ground and the fourth (if it exists) is a diagnostic signal wire. In most systems you do not have to connect anything to that fourth wire for the fan to operate correctly.
Because this speed control signal is a PWM signal people often confuse this with PWM control of a conventional brush type fan which is not at all the same. In PWM controlled brush type DC fans you are turning on and off the power to the motor at fairly high frequency so the device performing the PWM of the power has to be able to handle high current loads.
In the BLDC fans the PWM speed control signal is a low level speed control signal so it is very low current. All of the motor drive current is on the main two power wires that are connected directly to the battery (usually with a fuse but without a relay).
Originally Posted by dhutton
Spal fans with built in PWM controller? Could you post a part number and/or some details?