Changing the Hz on the power supply to a motor will change the speed with little or no adverse effects. They do not change current, voltage, magnetic field, or any other factor other than frequency. There is currently only one way to control the speed of a single speed AC motor. At the very least, it would severely shorten the life of the motor. This usually isn't as harsh as holding a fan blade, but it can be disastrous. You are essentially weakening the magnetic resistance and allowing a current rush outside the operating parameters of the motor. The same can be said of reducing the voltage across the fan with some sort of outside variable resistor. Holding the fan blade eliminates the magnetic field and creates a rush of current. If you stopped a motor from spinning (like holding onto a fan blade), the motor would smoke, then burn up. This is called inductive impedance, or sort of a magnetic resistance.
#Dimmer switch for fan series#
But when you wind it in a series of coils (like inside a motor), you create a dense magnetic field when current is running thru it, casing the motor to spin, and do work. The inside of a motor is nothing but wire. Wire has almost no resistance, which is why we use it to take our current to our devices. But increased current with shorten the life of the bulb, or burn it out immediately. You would affect the current running thru it, which if you lower(as with dimming) there are no bad side effects. You can lower or raise the voltage but the resistance will stay the same. The filament in a light bulb is a good example. All devices have a resistance to current. When to much current goes thru it will burn up the device, wiring, etc. * Now I will attempt to explain the science behind it all.Īn electrical device operates when current runs thru it. Best case scenario, your replacing fans like they are going out of style.
Remember, the knob is a switch, not a speed controller. They would each have their own parameters. Each set of windings are almost like a separate motor. The speed knob on a fan is a switch that switches current to a different set of windings. Multi speed motors have more than one set of windings. Why do ceiling fans have different speeds if you can't control speeds of an AC motor? Second, you could purchase a variable frequency drive, but these usually cost more than the fan itself.Ħ. First, buy a fan that runs at your desired speed.
What's the best way to run my fan at my desired speed? Sometimes they trip for no reason, then your fan would be off when your on vacation and that can be disastrous for your crop.ĥ. Can I use a rheostat if I also use some type of thermal protection device? Thermostats are on/off switches that turn on/off at a desired temperature.Ĥ. Can I use a thermostat to act as a rheostat? AC motors need to run at preset voltage, motor speed, and current draw. While they can be used to adjust the speed of a DC motor, its a big no-no on AC motors. Rheostats, like potentiometers are glorified variable resistors. I have heard of rheostat's being used to adjust the speed of a fan, why wont this work?
They are to replace the controllers that are already on a multi-speed fan.Ģ. Why do they sell fan controllers at hardware stores? I will explain how this works, but first I want to dispel the reasoning behind this misunderstanding.ġ. These windings are fixed and unchangeable, and wired to be operated at a certain voltage, with a fixed amount of amp draw. There is a growing misconception that this is safe to do, but the logic behind it is flawed.Ī fan that has no speed control when manufactured has copper windings inside that determine speed and horsepower. You cannot use a light dimmer to control a fan.
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