adccommunitymod (AutomationDirect) asked a question.
Created Date: October 23,2008
Created By: jondecker76
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Now that my Wind Turbine PLC program is finished and running, I want to start a new project.. A control system to replace the stock system in my Magnum Countryside 3500 Biomass stove (corn/pellet stove). The current stock controller has 2 knobs - a Heat setting and a speed setting for a stirring rod. Draft of the stove is controlled manually. I would like to use a DL05/CMore micro and build a robust, customizable control system. The stove already uses snap-disk thermostats to control some functions, so they will be easy to use as digital inputs. This brings me to the combustion blower. By making this variable speed, I can adjust draft of the unit, instead up using a manual valve. The problem is that I have absolutely no experience with variable speed drives. I see that AD has some for about $99. My questions are: - It appears that the output is always at 230v. Are there any drives that keep the incoming 115VAC? - Can I use the existing combustion air blower with a VFD, or would I have to replace it with a 3 phase motor? - What are my options for controlling a VFD from a DL05? (I am looking at thte GS1 series drives) - Any other general advice that anyone can give me regarding VFDs? thanks Jon
Created Date: October 23,2008
Created by: milldrone
jondecker76,
The single phase output question is asked quite often by VFD newbies. This can be done if (this is a big IF ) you are willing to spend 3 or more times what a conventional VFD will cost. Another drawback is the turn down ratio may only be 2 to 1 meaning you can only go half speed at the slowest. Also it will only work on certain types of single phase motors. Most users who research what is necessary end up going with a 3 phase motor. Because the total price (controller and motor) is less by going to 3 phase.
Here is a link to a single phase output VFD. http://www.invertek.co.uk/product_optidrive_e21.aspx
So if you want to use one of the AD VFD's yes you will need to use a 3 phase motor. Then at that point you will want the 230 volt output.
There are a couple of ways to control a VFD from a DL05
1. Discreet outputs and analog outs. The analog out is for controlling the speed infinitely.
2. Discrete outputs only. The VFD has preset speeds that are defined in the VFD programming. You access them by binary control to the VFD inputs
001 = preset speed#1
010 = preset speed #2
011 = preset speed #3
There is only three preset speeds plus a jog speed available (plus what ever you have set by the key pad) in the GS1
For the GS2 there are 7 jog speeds available
100 = preset speed #4
101 = preset speed #5
110 = preset speed #6
111 = preset speed #7
It is also possible to use the MOP (motor operated potentiometer) command and access this by digital inputs. When the up input is on the speed will increase until the input is off. When the down input is on the speed will decrease until the input is off.
3. Serial or Ethernet comms. You get access to everything if you want it, command speed, stop, start, accell decell ramps, motor loading, buss voltage, reset minor faults, kitchen sink :D
Created Date: October 24,2008
Created by: jondecker76
Thanks for your time in responding... Now I only have a few more questions:
-Regarding #3 - can I use the extra serial port of the DL05 to interface a GS1 VFD?
- Can a single phase motor be "converted " to a 3-phase motor by re-wiring the leads of the windings in the stator? (assuming of course you know which leads to use)
Created Date: October 24,2008
Created by: DonHill
PID Loop for fan
Tried a VFD on a wood stove. Worked ok but not worth the effort.
On a new stove a tried using a PID loop with the fan as the output.
Overall it does not seem to change the efficiency or heat output enough to
bother. If the "burn " is not hot enough you also build up excess kreosote in
the chimney flue.
Created Date: October 24,2008
Created by: milldrone
-Regarding #3 - can I use the extra serial port of the DL05 to interface a GS1 VFD?
Yes. See page 5-6 of the GS1 manual. http://web6.automationdirect.com/static/manuals/gs1m/gs1m.html . Side note: the GS1 does rs485 only and the DL05 does rs232 only so a FA isonet is required. This makes a DL06 or a GS2 more attractive (one or the other). Both the DL06 and the GS2 do both (rs485 and rs232)
- Can a single phase motor be "converted " to a 3-phase motor by re-wiring the leads of the windings in the stator? (assuming of course you know which leads to use)
If you mean "By re arraigning the leads in the peckerhead ". No. If you mean "to have the motor rewound by a motor rewinder ". Yes. But the rub is that it will cost way too much.
Now that I have tried to inform you of your options and because I think you are an intelligent guy. I'm going to give you a link to a discussion about single phase and VFD's. I have not tried this and I do not know if it will work. but in theory I can see how it would. Please note all the warnings and how all the posters tried persuade the original poster to reconsider.
http://www.plctalk.net/qanda/showthread.php?t=18541&highlight=vfd
In post #36 Sparkz shows what he did. Note that it has problems at low speed
Created Date: October 24,2008
Created by: KPrice
jondecker76, "Can a single phase motor be "converted " to a 3-phase motor by re-wiring the leads of the windings in the stator? " No. By "leads of the windings ", you mean the wires in the motor junction box on the side or end of the motor. These leads are to be connected per the motor connection diagram, and are for changing voltage, changing direction, and/or changing speed for the single-phase motor. The windings in the stator slots are placed in a different configuration, number, size, etc. for 3-phase versus 1-phase. Also, 1-phase motors use a start winding, where a 3-phase motor does not. Hope this helps.
Created Date: October 24,2008
Created by: KPrice
Here's a source for technical books in general.
http://www.omega.com/bobi/
Here's a link for electric motor books in particular.
http://www.omega.com/search/esearch_bob.asp?start=0&perPage=10&summary=yes&sort=rank&search=electric+motors&submit=Search
Created Date: October 24,2008
Created by: jondecker76
Thanks a lot everyone, this was all very useful information - I'll read up on the links provided and get a better understanding of what will be involved.
Also, it might help to include a broad overview of my control idea to see where and how the VFD would fit in...
On nicer (expensive) corn stoves (Like the Bixby Maxfire), draft is controlled via blower speed. On cheaper ones like mine (a Magnum Countryside 3500), the blower speed is constant, and draft is adjusted by a manual valve.
What I would like to do is design a control system where the user can save "profiles ". For example, I may make a "Field Corn " profile to use when I am burning field corn, which usually has a moisture content around 17%. I may have a different profile for burning my favorite brand of wood pellets, and yet another profile for burning wheat. So once the project is finished, I won't have to re-adjust my stove manually for the new characteristics of the new fuel. I can simply load my "Wheat " profile for example.
Under each profile, you can save presets. For example, I may make a "Low Fire " preset that will be used when the thermostat is not calling for High Fire. I would likely also make "High ", "Medium " and "Low " presets for each profile.
Now, for each preset for each profile, I can have setpoints for auger feed on and off times, combustion blower speed (draft), room blower speed, stirring rod speed, etc.
As you can see from above, a PID loop would not be needed at all, it will be a simple user setpoint that the user can dial in once, then recall it whenever it is needed. Manually adjusting draft for maximum performance takes a bit of time, and each time fuel is switched you must do the process over again - as finding the same spot with a manual draft valve isn't really easy.
In all, I just want to build the Cadillac of stove controls.
thanks again for all the useful advice
Created Date: October 24,2008
Created by: stimpsonjcat
Fascinating!
Created Date: October 31,2008
Created by: jondecker76
Still looking for a suitable 3-phase motor...
The current motor is a small (about 3 1/3 " diameter) 120V 0.95A (0.12 HP) 3000 RPM motor.
I need to find something equivalent, a 240v 3-Phase 0.12-0.15 HP and 3000 - 3600 RPM should be close enough - I 've just had no luck finding any motors in that range. I even called FASCO (the manufacturer of the current motor) to see if they have a 3-phase equivalent with no luck.
Anyone have any ideas where I can get a 3-phase motor around these specs?
thanks
Jon
Created Date: November 10,2008
Created by: JeffB
Corn burner
Johndecker76. Instead of going to the expense of a vfd, how about using a small electric damper actuator to vary your air intake. Many are available from Grainger or even Ebay. There are 120 volt units as well as 24 vac units available. It would probably be slightly less efficient than a variable speed motor but we 're talking relatively small hp here so the gain in efficiency would be negligable. You can probably get all the parts you need for about $150 or less.