How to convert 2hp AC blower motor to variable speed

[rickr]

I have a 2HP 240V blower motor for which I would like to vary the speed from my plc. The motor is a standard HVAC type blower which is belt-driven from a motor.

Any inexpensive suggestions as to how I may use this motor or do I have to replace it with another type.

I'm in the process of upgrading the controls on this piece of equipment (Dectron Dry-0-Tron). It controls the environment in a swimming pool room.

 

[jraef]

rickr,
I hate to tell you this, but from your description it does appear that you have a permanent split capacitor 1 phase motor and you will not be able to use an electronic soft start device with it. The soft start components would be damaged by the capacitors in the motor. This will also prevent you from using a VFD as well, even if you found one that works on 1 phase motors. I have in the past used a soft start on a temporary fan with full knowledge that it would not last long, but it made the problem go away for a few months anyway. Baldor makes a cheap 1 phase soft start controller that you can simply mount and wire downstream from whatever is controlling your motor now. It may only last a few months, or you might get lucky and it will last a year or so, you never know. Your only alternative electrically is to change out the motor to 3 phase and add a VFD which will convert your 240V 1 phase power to 3 phase for the motor. FDigure $300-500 plus labor minimum.

Another approach would be a "mechanical soft start" clutch device such as a Torque Tamer, shot coupling or fluid coupling that will slowly allow the blower to accelerate even though the motor is started at full speed rapidly. Contact a Power Transmission distributor such as Motion Industries or Kaman Industrial for advice.

That pop you here is probably the sheet metal or even the fiberglass duct "oil canning" as busbar suggested, so another option may be to solve the problem mechanically, perhapse with spray-on sound dampening material or something like that.

Good luck. Subvert the dominant paradigm... Think first, then act!

 

[jbartos]

Suggestion: There may be something suitable related to your application available on web. If there happen to be some proven similar application, then it shall get serious consideration. Visit

http://www.toad.net/~jsmeenen/motor.html

http://www.achrnews.com/CDA/ArticleInformation/features/BNP__Features__Item/0,1338,26558,00.html

http://www.braschmfg.com/Download/cabinet.pdf

http://www.lsicsi.com/appnotes_files/body_application_notes.html

etc. for some interesting ideas, perhaps some higher power rated dimmer could perform the motor controls.

 

[jeffreal]

Take a look at this link for a way to do HVAC speed control of a PSC motor:

http://www.varidigm.com/pdf/Approved Final VSM-CP2 Data Sheet 15-1003A.pdf

I'm a chemist, not an EE, but this product looks good to me.

~Jeff

 

[CHDean]

If you can get away from a capacitor start motor there are small soft starts called torque limiters available for single phase. They are used in conjunction with existing starter. Cost is < $200US in small quantity. It will give you a time band of .5-5S and torque adjustment of 0-85%. Size is 2&quot;Wx4&quot;Hx5&quot;D, mostly heatsink. It's really designed for conveyer applications but may be the best cost item available.