Budweiser13
Active member
Hey guys get one of these I tossed my variac and these are different form the speedster's http://www.kb-controls.com/product....5F14.qscstrfrnt02?productId=114&categoryId=25 ...
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Can I lower the CFM of an inline fan through use of a speed control?
- Thread starter ThePizzaMan
- Start date
The controller you show is a motor slip type controller. KB controls has several inverter type controllers available.
Take a look at the AC Controller NEMA 1 for a frequency inverter type.
Take a look at the AC Controller NEMA 1 for a frequency inverter type.
For what it's worth, I have a six inch Vortex connected to a good quality ceiling fan dimmer and, when I turn down the fan, all it does is go slower and run more quietly - no screeching or anything else from the motor. While this may not be ideal for the fan motor, consider that if it reduced the life of the motor by 50%, that means it might last for 10 years instead of 20 years. All things considered, wearing out your fan a little faster doesn't add squat to your cost of growing.
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guest 77721
Here's my 2 cents for what it's worth. There are many styles of electric motors and several ways to control them.
The most common AC motor you will come across is a Universal AC Motor. This is a Series DC motor with a commutator and brushes for the Armature. It just so happens that when the current reverses in the field, it is matched by the commutation so the motor works on AC just like it was fed DC. You don't need to rectify AC to make DC for this motor to run. For speed regulation, the control is done through voltage control either by a Variac or a light dimmer which switches the AC to produce a chopped waveform. The Variac will provide smooth control with no motor noise while the dimmer will provide good control, the motor will buzz as the speed is reduced.
When you get into more powerful AC motors, there are more motor designs and different ways to control them. A shaded pole motor is found in fan applications because it is lightly loaded and doesn't need a starting capacitor like other split phase AC motors. It only has one pole and creates a simulated rotating magnetic field which the rotor will follow with some slip. This motor will follow the frequency with some slip so the best way to control it is with a variable frequency controller which manufactures a AC waveform with pulses. Speed control with a Variac or a Light Dimmer are methods of power reduction which will control the speed by creating more slip and high current draws. Running the motor hot will cook the insulation in the wiring and lead to early failure.
When you get into real AC motors, the polyphase induction motor is widely used in industry. A real VFD will produce a Volts/Hertz curve where the speed is controlled by the frequency and the torque is controlled by the voltage all at the same time.
The most common AC motor you will come across is a Universal AC Motor. This is a Series DC motor with a commutator and brushes for the Armature. It just so happens that when the current reverses in the field, it is matched by the commutation so the motor works on AC just like it was fed DC. You don't need to rectify AC to make DC for this motor to run. For speed regulation, the control is done through voltage control either by a Variac or a light dimmer which switches the AC to produce a chopped waveform. The Variac will provide smooth control with no motor noise while the dimmer will provide good control, the motor will buzz as the speed is reduced.
When you get into more powerful AC motors, there are more motor designs and different ways to control them. A shaded pole motor is found in fan applications because it is lightly loaded and doesn't need a starting capacitor like other split phase AC motors. It only has one pole and creates a simulated rotating magnetic field which the rotor will follow with some slip. This motor will follow the frequency with some slip so the best way to control it is with a variable frequency controller which manufactures a AC waveform with pulses. Speed control with a Variac or a Light Dimmer are methods of power reduction which will control the speed by creating more slip and high current draws. Running the motor hot will cook the insulation in the wiring and lead to early failure.
When you get into real AC motors, the polyphase induction motor is widely used in industry. A real VFD will produce a Volts/Hertz curve where the speed is controlled by the frequency and the torque is controlled by the voltage all at the same time.
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medi-useA
hoosierdaddy...wh@ would a fan speed controller for a roof mounted evap air con be motor slip or pulse modulation?
muA
WOW you all are making this way too complicated...
I've been controlling my 8" vortex for over a year now, with a $10 sliding dimmer-switch that you use on reading-lamps, etc...
all you need is a 3-prong outlet converter ($2), cuz the slider only takes 2-prongs.
pretty simple.
the fan is doing just fine btw, as good as new. and now it's so quiet i can sleep next to it.
I've been controlling my 8" vortex for over a year now, with a $10 sliding dimmer-switch that you use on reading-lamps, etc...
all you need is a 3-prong outlet converter ($2), cuz the slider only takes 2-prongs.
pretty simple.
the fan is doing just fine btw, as good as new. and now it's so quiet i can sleep next to it.
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medi-useA
I might be making it too complicated, but I have to make do with wh@ I have...wh@ I have is a Tekelek cooler control from a roof mounted evap air con.
muA
muA
agreed, also if you use silencers, and has silencing for your fan, you can't hear much of anything from a inline,
I have the speedster, and not sure if it makes it louder?
Cmon now..
Cmon now..
I agree - why does this need to be complicated. I have 4 house fans, ALL with variable speeds, hmmm, and the house fans didn't cost even close to what a good Variac costs.
So I took apart my smallest fan, and guess what, it has a 120 volt, 3 amp switch. Looks like it would cost about 20 cents a piece in bulk. I imagine my box fans might even have 5 or 6 amp switches.
I have tried fan 'dimmer' switches and I know the hum some people complain about. It puts the motor out of phase or something which causes the hum.
FYI: I use a fan that looks like it is from a dryer. It runs 120 volt using 80 watts at full speed, and that sucker pushes air... It looks like a blue UFO on it's side.
I would love to have the cheapest solution to this speed problem. Are inline fans really so different that I couldn't just use the switch from a standard box fan?
..
Cmon now..
I agree - why does this need to be complicated. I have 4 house fans, ALL with variable speeds, hmmm, and the house fans didn't cost even close to what a good Variac costs.
So I took apart my smallest fan, and guess what, it has a 120 volt, 3 amp switch. Looks like it would cost about 20 cents a piece in bulk. I imagine my box fans might even have 5 or 6 amp switches.
I have tried fan 'dimmer' switches and I know the hum some people complain about. It puts the motor out of phase or something which causes the hum.
FYI: I use a fan that looks like it is from a dryer. It runs 120 volt using 80 watts at full speed, and that sucker pushes air... It looks like a blue UFO on it's side.
I would love to have the cheapest solution to this speed problem. Are inline fans really so different that I couldn't just use the switch from a standard box fan?
..
