I am making a cotton candy machine and I need to be able to slow down the motor a little bit. Its 115 volts and 3000 rpms. I was told that I might need a special kind but Im almost positive I could use a regular house light dimmer. Which kind should I use?
Dimmer For Motor Speed Control
There are several kinds of 115 VAC motors out there. The universal motor found in many home appliances will run slower if dimmed, but in reducing RPMs you also reduce power because you are basically choking off the motor's source of energy. Because the motor is running near its stall point it will have very little torque available (but since you're using it to make cotton candy, you shouldn't have any trouble there). Any light dimmer will work for this, but if you can find a cheap variac of the same current rating as your motor, you'll get better results. The majority of single-phase AC motors run at a speed that is determined by the windings and the AC line frequency, though, so a true AC motor will not run slower if you use a dimmer; it will only get hotter and produce less usable torque. The only way to slow down a motor of this type is to use a variable frequency drive (VFD) or inverter, which can actually change the frequency of the power supplied to the motor. But here you have to be careful, because unlike a three-phase motor, a single-phase motor cannot start at just any speed. If you get an inexpensive (under $200) drive with a keypad programming interface, you can set it up to start the motor at full speed and then slow to a preset RPM. Again, these motors are designed for a specific speed so you will lose efficiency when slowing them down, but your application doesn't need a lot of torque. eBay is a good source of cheap VFDs, but check to make sure that you select one compatible with single-phase output (and that your motor is also compatible).
Use one that is rated for motor use. Usually you will see the phrase fan motor. But you need the max current drawn by the motor, and the dimmer should be rated for that current or higher. The one in the reference is rated for motors up to 1.5 amps. That is about 180 watts. If it is always going to be running at the reduced speed, you may be better off with a transformer or a power resistor. For example, a stepdown transformer with an output of 12 volts at 5 amps can be wired to provide 115–12 = 103 volts at 5 amps. .
