A 3-wire fan can be controlled using the same kind of drive as for 2-wire fans—variable dc or low-frequency PWM. The difference between 2-wire fans and 3-wire fans is the availability of feedback from the fan for closed-loop speed control.
3-pin fans can only be controlled by adjusting the voltage that they are supplied with. Many motherboards can control fans both ways, by setting the fan mode to “DC/ Voltage” or “PWM”. It is also possible to control 4-pin PWM fans by adjusting the supply voltage.
A 3-wire DC fan is driven in the same way as a 2-wire DC fan, but the fan includes a tachometer line that provides the fan's rotational speed measurement. An external gate drive controller or some logic could then be used to set the PWM frequency based on the fan's speed measurement.
The three positions provide 230 VAC to each of the three outputs. This allows you to adjust the fan speed from low to high in 3 steps. With the version without Off position your fan will always be running at a predetermined low speed. It can never be completely switched off.
Conventional models rely on electrical resistance. They contain a wired controller circuit attached to an adjustable dial or toggle for changing the speed of the attached fans. These devices contain wire spools - conductors - with varying amounts of resistance to electrical current.
Capacitor Control:
A variable capacitance in series (usually few capacitors connected together with some tapping corresponding to each step) is used in this regulator. As we turn the knob the capacitance changes and it varied the voltage available to the fan. This will change the fan speed.
Brushless DC motors have 3 wires because they typically have 3-phase windings inside the motor. These 3 phases are used to control the rotation of the motor and generate a magnetic field to make the motor turn. The 3 wires provide a connection to each of these phases, allowing them to be powered and controlled.
You can access the BIOS by pressing a certain key, such as F2, F10, or DEL, when you boot up your PC. In the BIOS, you can find the fan settings under the hardware monitor, fan control, or thermal menu. You can adjust the fan speed based on the temperature, preset modes, or manual input.
Capacitors are used to control the fan's speed by varying the amount of capacitance in the circuit. The capacitor stores and releases electrical energy in a controlled manner, which affects the timing and phase of the voltage applied to the fan's motor windings. This, in turn, determines the fan's speed.
The connector plug is usually wired so that the Red wire accepts +12VDC input, the Black wire is Ground, and the Yellow wire outputs the Tachometer signal. The Tachometer signal is derived from a Hall-Effect sensor that senses the rotating magnetic fields generated by the rotating rotor.
The AC fan's speed depends on the line frequency and partially on the amplitude of the AC Voltage source.
A 3-wire fan can be controlled using the same kind of drive as for 2-wire fans—variable dc or low-frequency PWM. The difference between 2-wire fans and 3-wire fans is the availability of feedback from the fan for closed-loop speed control. The tach signal indicates whether the fan is running and its rate of speed.
Pins: The leads in a 3-pin connector are designated for power, signal, and ground. In a four-pin variant, the fourth lead is a control lead; in a fan application, it would control the speed of the fan. These connectors are often available in low halogen or halogen-free versions, especially those used in appliances.
These fans are also called 3-pin fans, as they come with 3 pins: a supply pin (usually 12 V DC), a ground pin, and a signal pin. PWM fans are DC fans with an extra wire for PWM. PWM fans are 4-pin fans, where the fourth wire sends a PWM signal to the fan motor. The PWM signal is the control input of the PWM fan.
Linear voltage regulation. A standard cooling fan is a DC motor with blades attached. By varying the voltage input across the acceptable range for a fan, the speed of the fan will increase (to added voltage) and decrease (to reduced voltage); a faster fan means more air moved and thus a higher heat exchange rate.
Brief Overview of DC Fan Sensors
Run at full speed with no speed control or tach output. Three-wire: Power, ground, and add a tach pulse/lock sensor output to monitor RPMs but no speed control. Four-wire: Power, ground, tach pulse/lock sensor output, and a PWM input control for varying fan speed.
If you can find the main power line into the motor, you can add a diode to cut the voltage in half. This will reduce voltage to all speeds on your fan.
3 SPEED FAN CONTROLLER
This controller employs the use of capacitors to achieve linear speed control of the fans. This method of control overcomes the annoying motor growl sometimes experienced in electronic controllers ensuring quiet operation of the fan motor. The mechanism is coloured BLACK.
In order for the light to be controlled by its own switch, the wiring between the switch and the fan unit needs a fourth wire, a red wire, to carry power to the light kit.
You will have 2 hot wires (usually black or red) and a neutral wire (usually white). When you measure the voltage between the 2 hot wires you will get 240 volts, when you measure from either hot to neutral you will get 120 volts.
A 3-pin case fan can easily be connected to a 4-pin connector on the motherboard. The fourth pin is simply left blank in this configuration. In most cases, it will then run unregulated at a fixed speed.
Three Wire DC Distribution Systems: It consists of two outer wires and a middle or neutral wire which is earthed at the substation. Availability of two voltages in a 3-wire system is preferred over the 2-wire system for d.c. distribution.