Speed control for 120vac fan that does not add noise

[noviygera]

I have a 120vac window blower that I need to quiet down.
What type of speed control should I use (need at least 3 speeds) so that I am NOT adding any noise to my power lines?
Source?

Blower fan is 35watts, 120vac

thanks,
Herman

 

[vacuphile]

Variac

 

[nigelwright7557]

Switched resistors.

 

[noviygera]

Anything chaper/more basic than Variac that will work? I need three speeds only...

 

[noviygera]

>>Switched resistors

can you recommend a ready to use box that has that?

 

[vacuphile]

>>Switched resistors

can you recommend a ready to use box that has that?

Use a light bulb in series. Different wattages will provide different speeds.

 

[tauro0221]

Hi,
By a ceiling fan controller in the fan selling store. They have different sizes depending the fan.

 

[noviygera]

ceiling fan controller:
does it use switched resistors or transformer?

 

[vacuphile]

ceiling fan controller:
does it use switched resistors or transformer?

It puts hash on the line. The only el cheapo solution that doesn't do this light bulbs. It's a resistor, and part of a system of components that can handle high voltages safely.

 

[tauro0221]

Hi,
I have 4 fans that I used the fan controller to adjust the speed fan. I do not have any noise problems and the controller it is the one used a slide switch to adjust the speed of the fan. I bought them in Lowes. To install just remove the light switch for the fan and install the controller.

 

[AndrewT]

using a ordinary AC motor with a low supply voltage whether by Variac or high source impedance could lead to severe overheating.

The rotational speed generates a back emf.
This back emf opposes the drive voltage.

The difference between the drive voltage and the back emf is what drives the current through the motor and motor current equals torque. Some torque is used in overcoming friction.

If you reduce the back emf by reducing the speed, you potentially increase the risk of some operational conditions drawing massive overload current. The slower motor does not cool as well and you end up with a blown motor.

Some motor types are designed to tolerate speed control. You need to check if your motor is this tolerant type.

 

[noviygera]

AndrewT,

I checked with the manufacturer, the motor does tolerate speed control. In fact they make one for it but for the $100 I will not get it of course.
1. how does the basic 3 speed room fan work for $20 including the fan!?
2. I came up with this solution and it seems to work: 70v autoformer speaker volume control. Atlas 34watts.... 10 steps for fan speeds! Do you think this is safe?

thanks!
Herman

 

[AndrewT]

For a speed control tolerant motor, using a low source impedance voltage, rather than a resistively dropped voltage is better.
A tapped transformer is an excellent way to control the voltage with minimal losses.

 

[vacuphile]

Noviygera, so you are back to the variac, but now you are looking ar one specifically made for 70v speaker volume control. THIS WILL NOT BE SAFE.

There are plenty cheap variacs on Ebay that will be safe such as Powerstate Type 21 Variac 0 140V 4 5A with Knob Bezel Hardware | eBay

 

[Max Headroom]

Older style ceiling fan controllers are switched/tapped inductor....worth a try if you can find one.

Dan.

 

[noviygera]

Noviygera, so you are back to the variac, but now you are looking ar one specifically made for 70v speaker volume control. THIS WILL NOT BE SAFE.

There are plenty cheap variacs on Ebay that will be safe such as Powerstate Type 21 Variac 0 140V 4 5A with Knob Bezel Hardware | eBay

Thanks, that's a nice one you point out. But back to my 70v autoformer, why is it not safe?

Been using it for a few days now. Heats up very slightly, but not very much at all...

 

[Aucosticraft]

Well would recommend Fan controller that is capacitor based. where Xc is used to control the speed. you can make yours too and can get precise speed in the required steps.

 

[vacuphile]

It is not safe because the voltage rating is insufficient for use on the electricity net.

 

[noviygera]

Well would recommend Fan controller that is capacitor based. where Xc is used to control the speed. you can make yours too and can get precise speed in the required steps.

Can you please go into more detail how capacitor can control the speed of motor? would this be a phase speed control? This sounds very interesting.
thanks,
Herman

 

[noviygera]

It is not safe because the voltage rating is insufficient for use on the electricity net.

vacufile,
I am looking at the power rating: 35 watt attenuator vs 32 watt fan. Do you believe this still not a safe solution -- I know the voltage is 70 vs 115, but isn't heat = watts, so far I am under the watts limit of this attenuator.
Herman