Fully Variable Speed Control Unit for Lasko 2155A Window Fan

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Hello,
I have a Lasko 2155A window fan with integrated 3 speed control unit (links at the end of this post). I want to be able to fine tune the speed so I want a fully variable speed control unit that I would attach to the power cord, and control the speed from there instead.
The operator's manual states that the fan must not be used with a solid state speed control device. I understand that to mean that I must not simply attempt to vary the voltage, i.e. from 120VAC to 90VAC for example. I understand that this may cause the amperage to rise, and all sorts of nasty things may occur after that.
I read a little about the problem and I believe that the integrated speed control unit controls the speed by varying the AC frequency while maintaining the same voltage, i.e. from 120VAC 60hz to 120VAC 50hz and so forth. Though I don't actually know.
I sent a request for information on how to do what I want but I got the standard "don't do it" reply. As if by some magical mysterious way, I'm going to change my mind. So no luck from the manufacturer.
I've looked at the Air King 9155 model and I believe it's the same as the Lasko 2155A. Somebody correct me if I'm wrong. I also believe Lasko doesn't actually manufacture that model, they only sell it. So that might explain why I got the standard "don't to it" reply from them. I'll ask Air King next to see if I have better luck with them.
If any of you have experience with this kind of thing, please advise me on how to proceed. If there's already a device that I can buy and just plug in, that would be best. If there's some tinkering to do, it would depend on the depth and complexity of that tinkering.
Actually what would be best is if I found a similar window fan with an integrated fully variable speed control unit. Alas, the available choice of window fans pretty much stops at Air King. Though I understand that there's a slew of window fans that are not made anymore, like the Vornado for example, so that might be an option. However, my primary consideration of any window fan remains a fully variable speed control unit.
Thank you
Martin Levac
http://www.laskoproducts.com/fans/model_2155a.html http://www.airkinglimited.com/pages/industrial/window1.html
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"Martin Levac" wrote in message
Hello,
I have a Lasko 2155A window fan with integrated 3 speed control unit (links at the end of this post). I want to be able to fine tune the speed so I want a fully variable speed control unit that I would attach to the power cord, and control the speed from there instead.
The operator's manual states that the fan must not be used with a solid state speed control device. I understand that to mean that I must not simply attempt to vary the voltage, i.e. from 120VAC to 90VAC for example. I understand that this may cause the amperage to rise, and all sorts of nasty things may occur after that.
That's not what it means. It means they don't want any speed control devices on their fan.
I read a little about the problem and I believe that the integrated speed control unit controls the speed by varying the AC frequency while maintaining the same voltage, i.e. from 120VAC 60hz to 120VAC 50hz and so forth. Though I don't actually know.
That may be so. But it's their design and I don't know what they are doing.
I sent a request for information on how to do what I want but I got the standard "don't do it" reply. As if by some magical mysterious way, I'm going to change my mind. So no luck from the manufacturer.
Expected.
I've looked at the Air King 9155 model and I believe it's the same as the Lasko 2155A. Somebody correct me if I'm wrong. I also believe Lasko doesn't actually manufacture that model, they only sell it. So that might explain why I got the standard "don't to it" reply from them. I'll ask Air King next to see if I have better luck with them.
If any of you have experience with this kind of thing, please advise me on how to proceed. If there's already a device that I can buy and just plug in, that would be best. If there's some tinkering to do, it would depend on the depth and complexity of that tinkering.
Don't do it. Unless you don't mind the consequences.
Actually what would be best is if I found a similar window fan with an integrated fully variable speed control unit. Alas, the available choice of window fans pretty much stops at Air King. Though I understand that there's a slew of window fans that are not made anymore, like the Vornado for example, so that might be an option. However, my primary consideration of any window fan remains a fully variable speed control unit.
Thank you
Martin Levac
http://www.laskoproducts.com/fans/model_2155a.html http://www.airkinglimited.com/pages/industrial/window1.html
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On 6/20/2011 10:22 PM, Tom Biasi wrote:

Had nothing better to do tonight huh, Tom?
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"Martin Levac" wrote in message
On 6/20/2011 10:22 PM, Tom Biasi wrote:

Had nothing better to do tonight huh, Tom?
You are not obligated to consider anything that I say.
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I don't know the details. It would be mighty peculiar controller that would change frequency without changing voltage. As a general rule, you should be able to run typical induction motors below synchronous speed by changing the frequency to less than line frequency. BUT you have to lower the voltage in proportion to the frequency so as not to get excessive no load current.
If you do that, the only consequence is lower maximum torque. For a fan, that should not be a problem.
This assumes that between your own controller and the actual motor itself there is no other controller or circuitry that does not like yours.
--

Sam

Conservatives are against Darwinism but for natural selection.
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The motor is an induction motor, as far as you are concerned this means the speed is locked to the frequency of the AC line. There are some tricks in rearranging some connections to the stator winding to get some different speeds but 3 different speeds are about the limit. I haven't looked but I bet if you google variable speed induction motors you will get a lot more info. Jimmie
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On 6/20/2011 10:55 PM, JIMMIE wrote:

Since the speed of the motor is locked to the AC frequency, and since I'm not about to fiddle around the insides of that motor, then it means I want a device that controls the AC frequency at the power cord. Any idea how to proceed, Jimmie?
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The problem is that you can't simply continue to lower the frequency as the lower the frequency the less effective the induction is. Also you will find that variable frequency controllers are pricey.
Your best bet is to find a motor with brushes that you can vary the speed of with common speed controllers.
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On 6/21/2011 7:52 AM, jamesgangnc wrote:

I did find that. Cheapest VFD at a glance was $325. Although I don't see why they should be. Maybe these things are too specialized to be made cheaply.
It's a fan and there's little I can do about its design. It must be quiet and that is partly why I want full control over the speed.
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That's part of it. There is not a high demand. Theoretetically an inverter design could be adapted to a variable frequency output. But you still have to convert to dc, then convert back to ac with a variable frequency switching supply of some sort. And you are still limited by the ability of the induction motor to operate at lower frequencies. Even 30hz, which is just half, is far worse at induction.
Practically all small fans will be built with an induction motor and speed control will be done via multiple sets of windings. Brushed motors are more costly and have issues with brush wear and electrical noise. They are seldom found in home appliances. I have seen them in blenders though. Probably because blenders have a lot of speeds.
Your most effective solution, barring finding a fan with a non induction motor, would be to replace the motor. That will probably involve some minor fabrication unless you are really lucky. Another option would be a DC motor and a variable output dc power supply.
But as you have found, there is no simple plug in solution for your problem.
Perhaps a smaller fan. Or put the fan in a window further away from you. If you leave the nearby window open you will still be in the cross breeze.
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+1 to this...
A DC motor in a fan will be easier to control in the manner you desire and wish to control your fan in for whatever unknown and insane reasons.you have yet to disclose...
~~ Evan
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On 6/21/2011 8:38 AM, jamesgangnc wrote:

I just want to say thanks for the reply and effort. I appreciate it. That goes for the other useful posters too.
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There's little you can do? Come on, Sparky! Design and build one yourself. It's not magic. Build a bank of 12v computer fans - they're quiet enough. Or spring for a fan that does what you want without 'fixing it'.
BTW, I'd never tell someone not to do something that has the potential of keeping me entertained.
R
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On 6/21/2011 8:55 AM, RicodJour wrote:

We all know what you did. It wasn't your smartest move.
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"Martin Levac" wrote in message
On 6/21/2011 7:52 AM, jamesgangnc wrote:

I did find that. Cheapest VFD at a glance was $325. Although I don't see why they should be. Maybe these things are too specialized to be made cheaply.
It's a fan and there's little I can do about its design. It must be quiet and that is partly why I want full control over the speed. ------------------------------------ One problem with using a solid state voltage controller (fairly cheap in small sizes) is that you have to set the minimum possible speed to some reasonable value in order to avoid stalling/overheating. It may not be quiet enough at that setting. Depending on the nature of the controller that is built in , there could be a problem if the built in controller was set to its lowest setting and the external controller limit was set for the case of the built in controller at a higher setting. in any case using an external controller, might not give you any advantage over the lowest speed setting built in.
There is also the possibility that the manufacturer is covering its legal ass.
Don Kelly cross out to reply
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Variable Frequency power inverter. The basic idea would be like taking a UPS and making the output frequency variable.. The real problem doing thiss is that the design of the motor is such that if you get very far away from 60 Hz with a cheap fan motor it is going to start to heat up. To get around this problem you will need a motor designed for it. We use such motors at work and they are expensive.
Jimmie
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Just set your internal fan switch to high and use one of these: http://www.harborfreight.com/router-speed-control-43060.html
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It's very unlikely that this speed controller works with induction motors. Most hand tool motors have brushes.
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wrote:

or wire an incandescent lamp dimmer to a duplex outlet,then plug in the fan(on high range). That's how I speed control my fixed speed model 270 Dremel Mototool.
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Jim Yanik
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Again. Your dremel is a brushed motor, not an induction motor. What works for a motor with brushes doesn't work on induction motors.
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