120v vfd or

Anyone know who makes a 120v single phase ac motor drive that is very compact (and hopefully cheap and available on ebay)?
It's intended purpose will be for a pellet stove. The motor is a small open frame induction motor @1/5 hp max. The drive will be controlled with an analog input. I plan on setting up a plc (keyence, fanuc micro, etc, whatever is cheap on ebay)and using it to control the heat output by controlling the auger feed and setting it so the exhaust blower is proportional to the btu input. I have setup a friends stove with a timer for the auger that allows delay on and delay off to be set independantly. He claims almost 2x the heat output and 1/3 less pellets used. Would like to see if plc could increase efficiency even further.
Thanks

Try Automation Direct
http://web4.automationdirect.com/adc/Shopping/Catalog/AC_Drives_-z-_Motors/GS1_(120_-z-_230_VAC_V-z-Hz_Control)
or EBay

http://cgi.ebay.com/PowerFlex-4-AC-motor-drive-by-Rockwell-Automation-NEW_W0QQitemZ150110432622QQihZ005QQcategoryZ42894QQrdZ1QQcmdZViewItem

It appears that all the Automation Direct motor drives are 3-phase, with lowest voltage a 230 volt 3-phase output.

One of the Bardac drives (Model OD1-11050, 0.5 HP, 120 volts output) would work, but there are other cheaper otpions.
http://www.bardac.com/pages/products/ac_optidrive7.html


There is a simple motor drive-on-circuit-board for small 120 volt 1-phase motors. I can't think of who makes it right now. I thought of it! KB Electronics makes electronic fan speed controllers and cheap 1-phase AC drives:

http://www.kbelectronics.com/catalog_fan_dist_panel.htm

My error, thanks for the correction Lancie1

Thanks

Seems as though most are 3 ph out. And the ones that aren't have built in pots or rheostats. I guess I could always solder a fixed resistor as a shunt and vary voltage or current through that.

Thanks for the tips and info so far.

We use a lot of Leeson AC Drives where I work. I know they can use 120V single phase inputs.

http://www.leeson.com/products/stock_drives.htm

Hello todster;

One plant I used to work for used AC Tech drives, I seem to remember they would correspond to your specs, very cheap also.
http://www.actechdrives.com/actech/product.htm
Hope this helps,
Daniel Chartier

Careful about cheap...

Make sure that this "inexpensive" system is failsafe.

A number of years ago someone in this area "played with fire" and upgraded their woodburning stove with a homemade enhancement. Worked great the first season and then the next year, the fan stopped, heat continued, house burnt down (all were safe), and the insurance company would not pay the claim because it had non approved/ tested heating equipment.

Single phase AC motors do not lend themselves much to variable speed. That's why, even with a 120VAC single phase input, the output is 230VAC three phase with the intention that a 230V three phase motor be used.

The earlier posts have given you a few leads on companies that make speed controls for single phase motors (Franklin has one for their submersible pumps too) but you will want to read the specs closely. Probably the speed range is quite narrow and the torque diminishes quickly as speed goes down.

Much better to use a three phase motor, in my opinion.

I agree with DdickDV. I would suggest looking for a permanent magnet DC motor and requisite DC drive. They are plentyful and cheap at that HP level. They are also commonly used with a 120V supply.

These motors are designed to work at varying speeds, a typical single phase AC motor of this size really isn't.

KB electronics makes nice small DC drives

Todster,
The model that I was thinking of is the KBLC-120. You may not have noticed the KBLC-120 at KB Electronics. It is a chasis only, no enclosure, will work with 120 Volts AC universal motors, and has non-isolated 0-7VDC signal input terminals and an optional Signal Isolator. You might have to swap out your fan motor, if it is not the universal motor type.

http://www.kbelectronics.com/kboemsearch/s_list.php?from=6&col_1=2&col_2=11&col_3=15&col_4=&col_5=30&col_6=&res=15#

http://www.kbelectronics.com/data_sheets/kblc_data_sheet.pdf

The KBLC-120 is a 115 VAC rated 9 Amps RMS @ 45C. The control is designed for 90 VDC PM, Shunt and AC/DC motors. It will control motors between 1/100-1/2 HP (1.0 HP w/aux. Heat sink) by inserting the proper Plug-in Horsepower Resistor®. Speed range is 50:1 with load regulation of 1%. Features include Auto Inhibit®, Voltage Following, MOV transient protection, 5K speed pot and trimpot adjustments for Min, Max, Accel, IR and CL. Options include Auxiliary heat sink, AC Line and Armature Fuse Kit, Barrier Terminal Board, RFI/EMI filters and Signal Isolation (model SI-5). This control is intended for high volume OEM applications. This control is available worldwide from stocking KB distributors. UL, CSA, CE, RoHS available (C-tick and CCC pending) Patented. Dimensions: 4.30” x 3.60” x 1.30”.

Click to expand...

KB Penta Power drives are probably the best choice for 120 V variable speed fractional HP motor control.

If you do not have a universal AC motor then look to get a permanent magnet DC motor.

Thanks for all the leads. Will check out as I get time. The motor is a universal open frame. similar to whats found on cheap swimming pool filters. The stove has numerous redundant features for safety shut down built in and they will be set up on interrupts similar to emergency stop.
Again thanks for the input.

I have a little Minarik VFD that takes a 120V single phase input and outputs VF 3 phase at up to ~200V (v/hz). Its driving a 1/2 hp 3 phase motor on a small conveyor. It works great for this application.

todster wrote:

He claims almost 2x the heat output and 1/3 less pellets used. Would like to see if plc could increase efficiency even further.

Click to expand...

Uh... are you overcomplicating this? I had the same type of stove, back in the day. It actually ran on corn, and it worked pretty well except that the motor was tied directly to the timer and it kept blowing timers. After the second one, I put in an interposing relay. But I digress.

"2x the heat output" confuses me. BTUs are BTUs. Your house loses heat based on outside temp, your stove puts it back in based on fuel burned. Now, the configurable ON/OFF is a great idea- that gives you more flexibility in fuel burned over a unit period. But it isn't going to make the furnace any more efficient.

If you used a nano PLC with a setback thermostat tied to an input, you would do as well as with the more complicated analog setup I think. Setback T-stats save you money by running the furnace less often when you're not home. Not an option with a stove; but you can set a base auger cycle to keep the flame burning. Then, when the T-stat calls for heat, you ramp up the base cycle. Do this slowly so as not to suffocate the flame, of course. Time-proportioning the motor using the variable on/off could be done with a table, or maybe a simple algorithm. You'd get the fuel savings, which I think is going to be most of any increase in "efficiency" with a stove.

Have fun, and like people said be safe!