How do fans control speed?

Asked By: Lanying Mimiague | Last Updated: 31st May, 2020
Category: home and garden indoor environmental quality
4.2/5 (44 Views . 14 Votes)
In a capacitive type fan regulator, various combinations of capacitors is used to control the speed of the fan. (or voltage across capacitor is inversely proportional to the capacitance). Hence, if capacitance is increased then the voltage across the capacitor decreases allowing more voltage across the fan motor.

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Regarding this, how does a capacitor control fan speed?

The idea behind a capacitor regulator remains the same, which is to adjust the voltage across the motor of the fan. Now, when you increase the capacitance, the voltage across the capacitor decreases but that across the fan motor increases. Accordingly, the speed of the fan increases.

Beside above, how does a 3 speed fan work? With 3-speed motor, Hot voltage connects to main winding at 3 different points. Only 1 point at a time receives power. That's what the fan switch does. When voltage is applied to each point, the main winding is energized as voltage from Black Hot wire completes circuit with White neutral wire.

In this regard, how do I control the speed of a 3 wire fan?

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.

Does changing capacitor increase fan speed?

You can change the capacitor and restore the rated speed of fan. However, that will not make it go any faster than its rated speed. The only case it might make the fan faster is if the capacitor used were smaller than ideal to begin with.

29 Related Question Answers Found

Which capacitor is used in fan?

In ceiling fans, 2.2 mfd / 250V non-polarized electrolytic AC capacitor is used. You are welcome to read more Important Interview Questions and MCQs. Fixed capacitors are used in fans.As you can see on the capacitor by yourself. its capacitance is generally from 4-6 micro farad.

What happens if fan capacitor fails?

However, two things happen in case a fan capacitors fails, or is not connected. Speed of this rotation will be quite slow, as in the absence of capacitor, it will not get required running torque. The running winding is likely to get damaged soon due to heavy current.

Why the ceiling fan is slow?

Answer: A faulty capacitor may cause a ceiling fan to run slowly or quit running altogether. The capacitor should be replaced by an electrician: There are three screws that hold the light kit or switch or housing cap to the bottom of the fan.

What is inside a fan regulator?

When we switch on a fan, the voltage difference causes the current to pass through the motor and the fan rotates. The regulator controls the voltage that makes the current flow less or more. Lower the voltage lower the speed of the fan. So a regulator controls the voltage levels for the fan.

Can you replace a capacitor with a higher UF?


You can almost always replace a capacitor with one of a higher voltage. This is the limiting factor of a capacitor due to dielectric breakdown voltages that the manufacturer chose. Varying capacitance gets a little trickier.

Why do brushless motors have 3 wires?

There are three wires going to the motor instead of two. The wiring between the ESC and the Arduino consists if the same 5 wires. The three wires give the brushless motors more pulling power. The two wires of the brushed dc motor can be thought of as forward and reverse.

How do I control my 12v fan speed?

Simple Fan Speed Control
Here is a simple mod to allow the speed of any 12V fan to be varied. All we need to do is insert a rheostat or variable resistor in the 12V wire to the fan. The rheostat should be rated at least 3 Watt, (for fans up to 10Watt), and have a resistance of 20 – 50 Ohms.

How do I slow down my cooling fan?

To slow the fan speed, locate the slider next to "CPU Processing Speed" and slide it down by moving across to the left. To speed up the fan, move the slider to the right.

What is PWM fan speed control?

Pulse-width modulation (PWM) is a common method of controlling computer fans. A PWM-capable fan is usually connected to a 4-pin connector (pinout: Ground, +12 V, sense, control). Typically a fan can be driven between about 30% and 100% of the rated fan speed, using a signal with up to 100% duty cycle.

How do PWM fans work?


In short, PWM operates like a switch which constantly cycles on and off, thereby regulating the amount of power the fan or pump motor gains. The PWM system that is used for controlling fans and pumps works with the motor, either getting +12V (full power) or 0V (no power). So, the motor is being fed impulses of power.

How do you wire a fan speed controller?

Connect the second black wire of the controller to the black wire from the fan motor. Connect the white wire from the supply line to the white wire of the fan motor. Make sure that the wire strands are straight and secure the wire leads of the control to the circuit wires by twisting them together.

Can you control PWM fans with voltage?

Yes, the power delivered to the fan is the same. The inefficiency of non PWM fans comes from the fact that they are controlled with a linear voltage regulator. If the linear regulator is outputting anything less than the 12V (full speed) input, it will dissipate the excess power as waste heat.

Does reducing fan speed save electricity?

Capacitors regulate the fan speed by regulating the waveform of power supply. These do not get heated up and thus save electricity when the fan is running at lower speeds (at higher speeds electricity consumption of fan is the same with both regulators).

Can I use a rheostat with a fan?

Use a fan control (dimmer designed specifically for fans) on the power supply to the fan. Any kind of dimmer--rheostat, variable transformer, solid state control--will reduce the voltage supplied to the motor.

Why does my ceiling fan only go one speed?


The fan is stuck on one speed
This is another common problem, and 95% of the time is due to a blown capacitor. The capacitor determines how much power is delivered to the fan motor. If the capacitor burns out, only a small amount of electricity will make it to the motor, and the fan will be stuck on a low speed.

Can you use a light dimmer to control fan speed?

Standard dimmer switches should never be used to control the fan motor on a ceiling fan because the dimmer could damage the fan motor, or overheat and start a fire. A safe repair can be as simple as replacing the dimmer switch with a standard toggle switch, but you also lose the ability to dim the light.

Why does fan speed reduce?

once power was given, capacitor will create a RMF(Rotating Magnetic Field) in motor. if capacitor is not connected or damaged fan just produce humming noise and start heating and damage the windings also. once capacitor losses its capacitance value torque will be reduced resulting in slowing the fan speed.